As used herein the expressions"exercising apparatus"and"exercising method"are to be given broad meanings and are not limited to apparatus for and methods of exercising per se. Rather the expressions refer to all apparatus and methods in which muscle exercises or does work and thus the expressions include assessment, measuring, testing, and therapeutic apparatus and methods.

This invention relates particularly to a method of assessing and facilitating muscle strength in resisting a force greater than the muscle itself can develop in muscle shortening contraction. The invention thus relates to an apparatus and method for assessing the strength of a user, the apparatus including a means for generating force external to and greater than the muscle being tested. As such it provides an alternative to the Jamar, Biodex and Cybex dynamometers.

This invention also relates to an exercising apparatus and method for isotonic and isokinetic muscle strengthening, either for therapy in the clinical circumstances of muscle weakness or for general muscle fitness, exercise and strengthening.

This invention also relates to exercising for eccentric muscle tensioning in a load range greater than maximum isometric force, and to a method for testing muscle strength in this load range.

Background of Invention Apparatus and methods of the type referred to above assess the force exerted and/or the work performed by muscle contraction, or facilitate muscular exercise obtained in muscle contraction. Such apparatus and methods include at their most basic level, an actuator that transforms the contraction of muscular exertion into force or pressure which acts against a resistance, such for example as the force exerted by a means for creating force or exerting pressure. This results in motion of the actuator against the resistance whereby work is

performed. The actuator and the means of resistance are coupled, for example by a mechanical, hydraulic or pneumatic linkage. The force or pressure exerted in the linkage conduit and the lineal or volumetric displacement of the actuator are measured.

To best understand the purpose and use of such apparatus and methods, reference will be made to the biological event and to the nature of muscular contraction, as well as reference to the apparatus and methods per se.

Muscular contraction is enabled over a range of action of a muscle fibre from a fully lengthened state to a fully shortened state, and enabled up to a maximum force that is dependent upon the contraction velocity of that fibre, the force being less for rapid contraction, greater for a lesser speed of contraction, and greatest when muscle acts to resist a greater force than it itself can exert.

The tensile force of maximal muscular contraction is also a function of the contractile length of the muscle fibre, being greatest in the mid-position of shortening/lengthening, and being substantially less at the extremes of shortening and lengthening. Profiles of maximum force exerted over the full range of lengthening to shortening can be created for varying contraction (shortening) velocities, and in the case of forced extension (lengthening) by a greater external force, the velocity is reasonably considered a negative dimension. There thus exists the limiting case of the null velocity, and a profile can be approximated for this by a test at very slow shortening or lengthening.

Muscle is able to develop significant additional internal force against external load over and above the force it can develop in shortening. This additional internal force is available to resist relengthening, or to enable controlled relengthening at loads greater than"maximum isometric force". This additional internal force does not enable muscle fibre shortening. Consequently the muscle does not do work in this load range.

This invention allows testing, and facilitates the ability, of muscle to develop force and resist external load in the load range in excess of"maximum isometric force". The invention also enables assessment of eccentric muscle contraction at the load range less than"maximum isometric force", and can provide therapy and muscle strengthening in this lesser load range.

Muscle fibres exist in muscles which are visibly discrete contractile

entities that invite specific names. Functionally these are part of larger systems of muscle groupings that act complexly across joints, and assist or oppose each other. Even in opposition, muscles act in coordination, creating a tonus or tension in the muscles about a joint that stabilises its rigid bony components as a precondition to useful muscular work.

In a complexly contracting muscular system acting as moment arms about an axis of a joint, the force is reasonably measured as torque, and the effect of contraction is angular displacement. In practical terms, both in clinical medical assessment and in exercise and sports physiology, it is desirable to assess or facilitate the action of these complexly contracting muscle systems functioning about a joint, or even over two or more adjacent joints.

The measurement of force exerted, and of work performed and power developed, by a group of muscles acting about a joint or in a complexly contracting musculo-skeletal system, requires actuators specifically and ergonomically designed for that musculo-skeletal system that may not include the means to measure lineal or volumetric displacement. Such an actuator may usefully act upon a specific deformable linear displacement or volumetric apparatus, facilitating the measurement of these parameters.

Thus apparatus and methods of the type described above have the capacity to create profiles of force generated at constant linear or angular contraction velocity for the range of muscle action in contraction, or profiles of linear or angular contraction velocity for constant force load exerted by force creation or pressurising means acting on the actuator.

The force and power profiles for a complex muscle system will be congruent with the profiles established for individual muscle fibre contraction, and will reflect the greater force able to be exerted within the midrange of muscle fibre contraction. They will reflect the particular geometric configuration and"moment arms"of the points of attachment of muscles, and the total force able to be exerted and linear extension and shortening of individual muscles able to be achieved. The profiles so obtained will be specific for each joint or complexly contracting muscular system, but broadly will have the same shape across the demographic range of human identity, except in circumstances of specific disability. Such profiles can then become a clinical tool in the

assessment of human muscle function and of human disability.

Exercising apparatus in which hydraulic circuits control the equipment is well known. US patents 5277681 to Holt, 5058887 and 5330406 to Patterson, 4979735 to Stewart, 4976426 to Szabo and 4846466 to Stima are examples of such known equipment.

Apparatus and methods for assessing the strength of a user are described in my international patent application PCT/AU98/00747. The content of the specification of this application is incorporated herein by reference.

The clinical and exercise physiology assessment of work and power is the subject of my copending applications referred to above. The invention described in some of the embodiments of this specification relates to an assessment with an apparatus assisted by an external power source. In other embodiments this present invention relates to apparatus which can be operated in a number of modes in which the actuator acts against an immovable force, against a moveable force and in accordance with the embodiment referred to above, against a variable force which can be"overcome"by the user to thereby facilitate the assessment of the ability of muscle to do work, and test"isometric strength"as a limiting state between concentric and eccentric muscle contraction.

Summary of Invention The present invention aims to provide an alternative to known apparatus and methods of the above type.

In one aspect this invention resides broadly in a method of assessing the force generated by muscle, the method including:- pressurising a fluid circuit by a controllable pressure source; operating actuator means by muscle against the pressure set in the fluid circuit, and measuring parameters indicative of the force generated by the muscle and of muscle lengthening; whereby the force generated by muscle is assessable at loads greater than maximal isometric muscle force.

The expression"pressurising a fluid circuit"is to be given a broad

meaning and includes pressurising elements within a fluid circuit or pressurising a discrete portion of a fluid circuit. Thus for example a pump may pressurise only that portion of a fluid circuit between the pump output and a downstream resistance valve. The expression"the pressure set in the fluid circuit"is to be understood to include reference to the pressure difference between the pressure in that portion of the circuit which is pressurised and the pressure in the portion of the circuit not so pressurised, ie the pressure drop over a resistance valve for example.

It is preferred that the fluid circuit is pressurised by a pressure source and the pressure is set by selectively variable pressure reduction valve means, the pressure source and the pressure reduction valve means being in the fluid circuit.

As used herein the expression"pressure reduction valve means"is to be given a broad meaning. The expression is to be taken to include a controllable or variable pressure release valve where the pressure is controlled largely independent of flow rate once the pressure threshold is reached; or a non regurgitating controllable or variable resistance valve, where pressure and flow rate vary synchronously; or the combination of both above valves in parallel and separately controlled. The expression"pressure reduction valve means"also includes the situation where there is null flow through any valve at any pressure.

It is also preferred that the pressure source and actuator means are operated to deform deformable fluid reservoir means to vary the volume thereof, the reservoir means being in fluid communication with the circuit.

It is further preferred that the degree of pressurisation is controlled by the pressure reduction valve means.

In another aspect this invention resides broadly in a method of exercising, the method including:- repeatedly pressurising a fluid circuit including a pressure source and selectively variable pressure reduction valve means for selectively varying the pressure in the circuit; controlling the pressure in the circuit by the pressure reduction valve means, and operating actuator means to deform deformable fluid reservoir means to

vary the volume thereof, the reservoir means being in fluid communication with the circuit; whereby operation of the actuator means occurs against a resistance or pressure set by the pressure reduction valve means.

In a preferred embodiment the method includes measuring parameters indicative of muscle force or strength of the user.

In one preferred embodiment operation of the actuator means provides for measurement of the lengthening or shortening of muscle.

In another preferred embodiment operation of the actuator means provides for measurement of the maximum muscle strength that can be exerted against a steady or an increasing load.

In another preferred embodiment operation of the actuator means provides for isotonic muscle strengthening.

In another preferred embodiment operation of the actuator means provides for isokinetic muscle strengthening.

In another preferred embodiment operation of the actuator means provides for therapeutic treatment of a patient having muscle weakness.

In another preferred embodiment operation of the actuator means provides for eccentric muscle tensioning.

In a further aspect this invention resides broadly in a method of measuring muscle strength, the method including:- pressurising a fluid circuit including a pressure source and a selectively variable pressure reduction valve means for selectively varying the pressure in the circuit; controlling the pressure in the circuit by the pressure reduction valve means; operating actuator means to resist deformation of deformable fluid reservoir means, the reservoir means being in fluid communication with the circuit whereby operation of the actuator means occurs against a resistance or pressure set by the pressure reduction valve means, and measuring parameters indicative of muscle force or strength of the user, or muscle length or musculoskeletal position.

In another aspect this invention resides broadly in a method of muscular

therapy, the method including:- pressurising a fluid circuit including a pressure source and selectively variable pressure reduction valve means for selectively varying the pressure in the circuit; controlling the pressure in the circuit by the pressure reduction valve means; operating actuator means to deform a deformable fluid reservoir means in fluid communication with the circuit whereby operation of the actuator means occurs against a resistance or pressure set by the pressure reduction valve means; allowing the deformed fluid reservoir means to reform under the action of the pressure source, and re-operating the actuator means to again deform the fluid reservoir means.

In a further aspect this invention resides broadly in a method of eccentric muscular tensioning, the method including:- pressurising a fluid circuit including a pressure source and selectively variable pressure reduction valve means for selectively varying the pressure in the circuit; increasing the pressure in the circuit by varying the setting of the pressure reduction valve means, and operating actuator means to resist deformation of deformable fluid reservoir means, the reservoir means being in fluid communication with the circuit whereby operation of the actuator means occurs against an increasing pressure set by the pressure reduction valve means.

In another aspect this invention resides broadly in a method of testing the muscle strength of a person, the method including:- (a) pressurising a fluid circuit including a pressure source and a selectively variable pressure reduction valve means for selectively varying the pressure in the circuit; (b) controlling the pressure in the circuit by the pressure reduction valve means; (c) operating actuator means to deform deformable fluid reservoir means to

vary the volume thereof, the reservoir means being in fluid communication with the circuit whereby operation of the actuator means occurs against a resistance or pressure set by the pressure reduction valve means; (d) measuring parameters indicative of muscle force or strength of the user, or muscle length or musculoskeletal position; (e) varying selected operating characteristics within the fluid circuit, the operating characteristics including the setting of the pressure reduction valve means and the rate of pressurising the circuit; (f) repeating steps (a) through to (d), and (g) comparing the indicative parameters measured in step (d) to thereby demonstrate anomalies indicative of feigned maximal contraction or deliberate under-performance of the person being tested.

In another aspect this invention resides broadly in an exercising apparatus including:- a fluid circuit including a pressure source for pressurising the fluid in the circuit and selectively variable pressure reduction valve means for selectively varying the pressure in the circuit; deformable fluid reservoir means, and actuator means operable by a user to deform the reservoir means to vary the volume thereof; wherein the circuit is in fluid communication with the reservoir means whereby operation of the actuator means occurs against a resistance or pressure set by the pressure reduction valve means.

In a preferred embodiment the fluid circuit includes a chamber in fluid communication with the reservoir means, and the pressure reduction valve means selectively varies the pressure in the chamber.

In a preferred embodiment the pressure source pressurises the circuit at a selectively variable rate.

In a preferred embodiment the exercising apparatus includes safety control means for limiting the pressure in the circuit.

It is preferred that the safety control means is responsive to the pressure in the reservoir means exceeding a predetermined level representative of the safe limit associated with the muscular condition of the user. The safety control

means can also be responsive to the pressure in the chamber exceeding a predetermined level representative of the pressure limit associated with safe operation of the apparatus. The safety control means can also be responsive to the lineal or volumetric configuration of the actuator and/or the deformable fluid reservoir means exceeding a predetermined limit representative of the safe limit associated with operation of the apparatus.

It is preferred that the safety control means is operable to stop the pressure source pressurising the circuit. The safety control means can also be operable to control the pressure reduction valve means.

In one embodiment the pressure reduction valve means is a variable resistance valve for selectively varying the pressure and fluid flow rate in the circuit.

Alternatively, in another preferred embodiment the pressure reduction valve means is a variable pressure release valve.

In another embodiment the pressure reduction valve means is a variable resistance valve in parallel with a variable pressure release valve.

In a preferred embodiment the exercising apparatus includes measuring means for measuring parameters indicative of muscle force or strength of a user.

It is preferred that the measuring means includes:- pressure measuring means for measuring the pressure in the circuit between the pressure source and the pressure reduction valve means, and length, angle or volumetric measuring means for measuring the flexion/extension arc excursion of a joint or for measuring the deformation of the deformable fluid reservoir means.

The measuring means preferably also includes time measuring means for measuring the time at the beginning and end of each deformation and the duration of each deformation and the interval between deformations.

It is preferred that the exercising apparatus also includes calculating means for calculating parameters indicative of strength and speed of muscle lengthening and/or shortening of the user.

In a preferred embodiment the exercising apparatus includes display means for displaying the above parameters.

In a preferred embodiment the pressure source is a pump. It is preferred that the exercising apparatus includes a fluid reserve for providing fluid to the pressure source.

In one preferred embodiment the fluid is a gas. The gas is preferably air.

Alternatively in another embodiment the fluid may be a liquid.

In a preferred embodiment the reservoir means is a resilient bladder adapted to resile from a deformed configuration after deformation to a reformed configuration for re-deformation. Alternatively the reservoir means can be a limp collapsible bladder.

In another preferred embodiment the reservoir means is a piston and cylinder and the actuator means is operable by a user to move the piston.

In a preferred embodiment the exercising apparatus includes valve control means for selectively varying the operating pressure of the pressure reduction valve means.

In a preferred embodiment the fluid circuit is a looped fluid circuit. As used herein the expression"looped fluid circuit"is to be given a broad meaning and includes all looped circuits wherein the pressure source and pressure reduction valve means are in fluid communication within the circuit loop.

In a preferred embodiment incorporating aspects of the invention described in my copending applications, the exercising apparatus may include an auxiliary fluid circuit which includes the pressure reduction valve means in common with the looped fluid circuit and further includes manually deformable fluid reservoir means. In this embodiment it is preferred that the apparatus also includes switching means for switching operation of the apparatus between the looped fluid circuit and the auxiliary fluid circuit. In this embodiment it is also preferred that the apparatus is adapted to switch between the circuits whereby the apparatus is operable in a plurality of modes.

In the embodiment including a resistance valve, where relevant, the work performed in an action cycle is summated as the mathematical integral of instantaneous flow rate and instantaneous pressure as a function of part or all of the excursion of a joint from flexion to extension (or extension to flexion), or of a specified linear distance of contraction of a complexly contracting muscle system. Power is calculated as the time derivative of this quantum.

In the embodiment including a pressure release valve, where relevant, work performed can be calculated as the product of the pressure measured in the chamber, and the volume change of the deformable fluid reservoir. Where relevant, the display means are adapted to display these calculated parameters of work and power.

Description of Drawings In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention, wherein:- FIG 1 is a graph of force versus range of movement derivable with known equipment such as that described in US patent 484644 (Stima); FIG 2 is the graph of tension versus shortening velocity for an isolated mammalian skeletal muscle fibre as derived by Katz in 1939; FIG 3 illustrates the profiles of maximum isokinetic concentric contraction and maximum isokinetic eccentric contraction; FIG 4 is a schematic diagram of the invention; FIG 5 illustrates possible profiles of the test of the flexors and the extensors in eccentric contraction about a joint; FIG 6 illustrates cyclically repeated tests of slow eccentric muscle contraction against an increasing load; FIG 7 is a graph of load versus range of motion depicting profiles obtained from different resistance settings of a resistance valve; FIG 8 is a graph of lengthening velocity versus range of motion depicting profiles obtained from different resistance settings of a resistance valve; FIG 9 is a graph of force versus range of motion using a pressure release valve to identify a point on the ascending limb of the profile of maximum eccentric contraction and a corresponding point on the ascending limb of maximum isometric contraction, for validating the force difference therebetween; FIG 10 is a graph of force versus range of motion using a pressure release valve to identify a point on the descending limb of the profile of maximum eccentric contraction and a corresponding point on the descending limb of maximum isometric contraction, for validating the force difference

therebetween; FIG 11 illustrates tests starting from null pressure utilising either a pressure release or a resistance valve to identify a reading of maximum isometric force at a location in the range of motion and in the corresponding point on the profile of maximum eccentric force; FIG 12 illustrates a test starting from null pressure assessing the ability of a subject to maintain constant force in eccentric muscle relengthening over a range of motion, and FIG 13 is a schematic diagram of an alternative embodiment of the invention including aspects of the invention described in my copending applications. This embodiment of the invention constitutes a fully featured muscle assessment and development apparatus with a pressure accumulating constant volume chamber and mirrored pressured fluid flow circuits.

FIGS 14-24 allow an appreciation to be gained of the relationship between the present invention and those described in my international patent application PCT/AU98/00747, wherein:- FIG 14 is a schematic diagram illustrating the basic configuration of a device to measure and facilitate the strength, work and power of human muscle; FIG 15 is a schematic diagram illustrating a hand-pump and pneumatic pressure accumulator assessing hand strength, work and power; FIG 16 is a schematic diagram illustrating a muscle-powered muscle strength, work and power assessment and development device utilising a pressure reduction valve; FIG 17 is a schematic diagram illustrating a muscle-powered muscle strength, work and power assessment and development device utilising a pressurised looped fluid circuit, and FIGS 18-24 are schematic diagrams illustrating several operating modes of the auxiliary or mirrored pressurised fluid flow circuit of the present invention and described with reference to the embodiment illustrated in FIG 13, in each case the active mechanical and pneumatic/hydraulic elements and fluid filled conduits being identified in bolded outline.

Description of Preferred Embodiment of Invention

Prior to describing the preferred embodiments of this invention in detail it will be useful for a better understanding of the purpose and use of such apparatus and methods to again refer in greater detail to the biological event and to the nature of muscular contraction with reference in general terms to the apparatus and methods of the invention.

The standard means of force creation in the assessment of the maximum torque exerted by a complex musculo-skeletal system acting about a single axis (the axis of the joint) is the force plate attached to a motorised action arm which rotates on an axis (or electro-mechanical derivatives of this concept), so providing a constant angular velocity against which the muscle system exerts force. This can provide known profiles which are already described in the literature. The test is described as"isokinetic".

Although there is angular displacement and force exerted, in a real sense no"work"is performed by muscle on the system as muscle exertion has absolutely no effect on the physical outcome of the event. The retardation of the motion of the action arm is infinitesimal.

Using hydraulic means, a similar circumstance to the force plate and rotating arm can be created. A hydraulic pump causes volumetric change of an actuating mechanism through an hydraulic linkage. As muscle resists the movement of that mechanism it will create a force which exerts pressure in the fluid.

In an embodiment of the present invention, the pressurising means is a controllable (variable flow) fluid pump that delivers fluid into the fluid conduit at a set constant rate for the test, which rate is not affected by any pressure exerted by muscle action against it. The fluid is delivered by the conduit into the actuator, or into a deformable fluid reservoir if such is interposed between it and the actuator. Measurement of the pressure so exerted at each point in the action movement of the muscle system (as measured in the muscle system, or as measured on the actuator, or as measured in some other volumetric apparatus) enables a profile to be obtained.

The profiles so created differ, depending on whether a profile is created in slow maximal concentric force (muscle shortening, resisting an external force) or slow maximal eccentric force (muscle relengthening, under a force greater

than it can itself develop). However neither of these profiles provides the limiting information for concentric contraction, which is the maximum force muscle can exert in a given anatomical length when neither shortening nor relengthening.

This is called the maximum isometric force.

The apparatus described in US patent 4846466 to Stima provides a means and a method to measure the value of maximum isometric strength of muscle flexors or extensors at any chosen static anatomic position of flexion/extension. The Stima method is to use a hydraulic circuit utilising a pressure release valve to bring a moment arm to a chosen position within the range of motion of the joint, and then lock the moment arm. Muscular force applied to the moment arm is then measured in the conventional manner. The points so obtained would lie close to the profile for maximum slow concentric force obtained in accordance with the present invention. By plotting numbers of points using this method, a profile such as that illustrated in FIG 1 could be developed.

However a complete profile of maximum isometric force cannot be derived from an event involving muscle shortening or lengthening. This is because, by definition, when measuring isometric force there must be no significant action of shortening or relengthening of muscle. Values of force obtained in a continuous act of normal muscle shortening (concentric contraction) will be less, while values obtained in the continuous act of normal muscle relengthening (maximum eccentric contraction) may be substantially greater, for reasons which follow.

A slow isokinetic concentric profile created with maximum exertion will approximate the theoretical profile of"maximum isometric force"across the range of motion of the contracting muscular system.

However the slow maximal eccentric isokinetic profile may demonstrate values of force up to 70 percent greater than the equivalent concentric isokinetic profile so obtained.

There is a substantial difference between the force a muscle fibre can exert in concentric contraction, and the tension it can resist in eccentric contraction. The difference arises because the substantial"elastic strength"of muscle in the load range beyond"maximum isometric force". This elastic

strength is critical to the function of muscle.

The phrase"elastic"is used to describe the ability of muscle while conserving energy to resist load within this range, but does not necessarily imply that muscle substantially stretches and elastically shortens as a result of increasing and diminishing loads within this range.

The graph illustrated in FIG 2 presents the standard graph of maximum force able to be developed as a function of normal muscle fibre shortening or lengthening. It is important to note that at maximum stimulation (at any chosen muscle fibre length) maximum (isometric) force is obtained when muscle fibre length is held constant. No greater force can be developed by the muscle due to any neural stimulus. The additional force-identified on the graph as force in excess of 100% maximum tetanic tension-is due to an externally applied force, against which the muscle cannot shorten. It can resist this force-maintaining length-or lengthen under precise control.

The graph of FIG 3 presents a representation of the two force profiles that can be obtained from a muscle in slow isokinetic contraction. The profile demonstrating lesser force across the range of motion of the joint (or complexly contracting muscle system) is obtained with muscle fibre shortening (concentric contraction). The profile demonstrating greater force across this range of motion is obtained with an external force, greater than muscle can develop in concentric contraction, obtaining muscle fibre lengthening against maximum exertion.

The difference between the force a muscle fibre can exert in concentric contraction, and the tension it can resist in eccentric contraction is presented in the literature as being 70% of maximal concentric contractile force. In other words, normal muscle being stretched by an external tension can develop 170% of its maximal concentric contractile force as eccentric tensile force. The quantum is largely independent of"lengthening velocity", as once maximum slow eccentric contractile force is attained more rapid relengthening does not provide for a greater contractile force.

There is thus a substantial range of force (which may be in excess of half of the range of force in which muscle can contract) in which a muscle system can resist extension, but cannot actively shorten-until the load is lessened to "maximum isometric force". In this load range muscle cannot"do work". At

loads exceeding this range, muscle ruptures.

The role of eccentric contraction is essentially different from that of concentric contraction. Its role-both as an internal role of a muscle unit acting against opposing muscles in a muscle system, and externally as an intrinsic capability of muscle open to conscious human use-is to"grasp, hold securely and release with precision".

The three phases of a task undertaken in eccentric contraction are:- positioning the muscular system at a certain position within the"range of motion"with the muscles in a set static state at less than"maximum isometric force" ; accepting a load of greater than"maximum isometric force"and maintaining constant muscle length, against a constant or varying load within the range from"maximum isometric force"to"maximum eccentric force"for that position in the"range of motion", and/or the controlled precise release of tension and/or length (the act of muscle relengthening) the muscle still resisting a load greater than"maximum isometric force".

The ability of muscle elasticly to accept and carry a static load substantially in excess of its ability to exert contractile force, and do so with less expenditure of energy, enables muscle safely, and without rupture, to resist transient excessive tensions-greater than maximum isometric force-that arise from sudden movement in the gravity field, for example, forces generated in safely recovering from a fall, and provides other bio-mechanical advantages.

One powerful muscle group (the agonist group) is all that is required to stabilise a joint.

The antagonist muscles can set their positions at low tension and then hold that position while the agonist muscles apply further tension by active contraction. The antagonist muscles move into a tension range greater than their respective values of"maximum isometric force", and can hold that position, or in a controlled manner release that position by precise relengthening under a load greater than"maximum isometric force" ; the only muscles doing"active work"being the agonists.

The criteria of competent eccentric contraction are threefold:-

a force range up to 170% of maximum isometric force is obtained; muscle can resist relengthening within this range, and muscle relengthening can be precisely controlled within this range.

Profiles obtained in the act of muscle shortening and relengthening are of intrinsic value in establishing these criteria-indeed provide more useful information than do isolated measures of"maximum isometric force"-both in the clinical assessment of muscle weakness, and in assessing and facilitating healthy muscle strength.

This invention, and that described in my co-pending applications, provide means and methods to obtain such profiles.

Also disclosed in this application are different means and methods to approach the values and specify the anatomical positions of"maximum isometric force"and"maximum eccentric force". Such methods may, by demonstrating major anomaly and inconsistency in a comparison of results, confound an attempt to feign disability.

It will be appreciated that a range of significant and relevant physiologic measurements are able to be obtained using the means and methodology of the present invention which are not disclosed in the prior art referred to above.

The use of a pressure release valve as pressure reduction valve means, without any external power source (as described in my co-pending patent), provides for a continuous profile of contraction velocity at fixed load. At any setting of the pressure release valve less than"maximum isometric force", the graph of the instantaneous flow rate across the"range of motion"of the joint obtained from an act of maximal muscle shortening provides the profile of contraction velocity for the specified load. As the specified load is increased, the available range of motion of the muscular system may diminish, as muscle contraction in the outer ends of the range becomes too weak to overcome the set load.

By incrementing the setting of a pressure release valve, a family of profiles of contraction velocity for incremented loads can be obtained in the course of a test of reciprocating muscle action.

As already described, test apparatus incorporating an externally powered looped fluid circuit-without pressure reduction valve means-provides for the

creation of isokinetic profiles of concentric and eccentric contraction.

For concentric contraction the pump is enabled in reverse, i. e. it extracts fluid from the high pressure segment of the looped circuit, while maximum muscular force is being exerted. For both concentric and eccentric contraction the subject is instructed to exert maximum force on the actuator for the duration of its physical movement, but is informed that the actuator will feel completely resistant to human effort, and will not"give"in response to the muscular pressure applied. The test begins with the muscle to be tested in a shortened (eccentric test) or lengthened (concentric test) state. The resistance valve is closed, its resistance effectively infinite, and the muscle is made to maximally contract concentrically or eccentrically against the movement of the actuator.

The use of a resistance valve as pressure reduction means (a) provides for greater facility in creating components of"isokinetic"profiles of maximum eccentric contraction; (b) enables tests that move in"vertical profile"-in either direction-from zero load, through maximum isometric force (quantifying its value in the process) to maximum eccentric force (for any anatomical position in the range of motion of the joint or complex contracting muscle system); and (c) provides for tests of accuracy and precision in maintaining constant eccentric force during muscle lengthening, at selected quanta of force between maximum isometric and maximum eccentric force, through a chosen range of muscle lengthening.

Specific protocols are described for the safe use of embodiments of this invention in muscle strengthening eccentric exercise.

The use of a pressure release valve provides a significant safety element in a comprehensive safety plan of procedure, design and specification for this equipment.

Turning now to a detailed description of the invention with reference to FIG 4 which is a schematic diagram of the invention with mechanical and pneumatic/hydraulic parts of the apparatus indicated by black bolded lines and outlines, information links by grey dotted lines. Exercising apparatus 10 includes a looped fluid circuit 11, deformable fluid reservoir means 12 and actuator means 13 operable by a user to deform the reservoir means to vary the volume thereof.

Looped fluid circuit 11 includes a chamber 14, a pressure source in the form of pump 15 and an external power source 16 for pressurising the chamber at a selectively variable rate and a valve 17 to selectively vary the pressure in the chamber. Chamber 14, pump 15 and valve 17 are in fluid communication within looped fluid circuit 11.

Deformable fluid reservoir means 12 is in fluid communication with chamber 14 by means of piping 18 or the like.

A fluid reserve 19 is included in looped fluid circuit 11 for providing fluid to pump 15. As indicated previously, the system may operate either hydraulically or pneumatically. If the operating fluid is air, the atmosphere may effectively constitute fluid reserve 19.

Fluid bypass line 20 provides for the return of fluid from deformable fluid reservoir 12 to fluid reserve 19, or from fluid reserve 19 to deformable fluid reservoir 12, without having to alter or reset pressure reduction valve means 17, at the conclusion of each test of eccentric muscle contraction. This line is closed during the creation of a force profile or a test of force, but provides for the easy return of actuator 13 to the initial state of a test, using low pressure flow means (which may be muscle powered).

Alternatively, with the flow enabled out of the fluid reserve, the configuration also provides for a muscle powered mirrored second circuit 21 with one pressure measurement means and one pressure reduction valve common to both circuits. With this configuration, using the second embodiment of PCT/AU98/00747, one single apparatus can be used to assess concentric work performance and power output, create isokinetic force profiles, perform tests of eccentric and isometric muscle strength, and of eccentric muscle lengthening precision.

This configuration is depicted in FIG 13.

As seen in FIG 4, exercising apparatus 10 includes safety control means 22 for limiting the pressure in the chamber. Safety control means 22 is responsive to the pressure in reservoir means 12 (as indicated schematically by grey dotted line 23) exceeding a predetermined level representative of the safe limit associated with the muscular condition of the user. Safety control means 22 is also responsive to the pressure in chamber 14 (also indicated

schematically by grey dotted line 23) exceeding a predetermined level representative of the pressure limit associated with safe operation of the apparatus.

Safety control means 22 is operable (as indicated schematically by grey dotted line 24) to stop the action of pump 15 pressurising chamber 14. Safety control means 22 is also operable (as indicated schematically by grey dotted line 25) to control variable valve 17. Safety means 26 dumps pressure from chamber 14 in the pressurised segment of the circuit. Valve control means 27 are provided to selectively vary the operating pressure of a pressure release valve and/or to vary the operating resistance of a variable resistance valve.

Exercising apparatus 10 also includes measuring and control means 28 for measuring parameters indicative of muscle force or strength of the user.

Measuring and control means 28 includes manometer 29 for measuring the pressure in chamber 14, and volume or flow measuring means 30. Measuring and control means 28 also includes time measuring means 31 for measuring the time at the beginning and end of each deformation and the duration of each deformation and the interval between deformations. It may also measure sequentially at short time intervals the pressure and the fluid flow rate to allow for mathematical integration of pressure and flow rate with respect to time, or to a measure of muscle contraction, joint or actuator movement, or reservoir deformation.

Measuring and control means 28 also incorporates pressuring pump control means 32 that controls its action and flow rate, and also communicates (not shown) with pressure reduction valve control means 27.

Exercising apparatus 10 also includes calculating means 33 for calculating parameters indicative of strength, work, work rate and speed of muscle contraction of the user. Exercising apparatus 10 also includes display means 34 for displaying the indicative parameters. The indicative parameters can also be printed as reports by printer 35.

As will be appreciated from the foregoing, the apparatus of the present invention may be utilised in a number of applications.

In use, the present invention provides a method of exercising in which chamber 14 is pressurised by pump 15 and the pressure in the chamber is

controlled or modulated by variable pressure reduction valve 17. By operating actuator means 13 to deform deformable fluid reservoir means 12, the volume of the reservoir is varied and because reservoir 12 is in fluid communication with chamber 14, a user of the exercising assembly operates against a pressure set or affecte by variable valve 17.

Measurement of parameters indicative of muscle force or strength of the user provide the user with a range of indicators for therapeutic treatment, comparative analysis and general muscle conditioning and development. These include measurement or testing of muscle strength, isotonic muscle strengthening, isokinetic muscle strengthening, therapeutic treatment of a patient having muscle weakness, and eccentric muscle tensioning.

Thus in use, the present invention provides a method of measuring muscle strength in which chamber 14 is pressurised and the pressure in the chamber controlled or modulated by variable valve 17. Actuator means 13 are operated by a user to resist deformation of deformable fluid reservoir means 12 by holding the actuator means steady against a pressure or resistance set by variable valve 17. Parameters are generated which are indicative of strength.

Alternatively in another use, the present invention provides a method of muscular therapy in which chamber 14 is pressurised and the pressure in the chamber controlled or modulated by variable valve 17. Actuator means 13 are operated by a user to deform deformable fluid reservoir 12 and the deformed fluid reservoir then reforms under the action of pump 15. Actuator means 13 are then reoperated by the user to again deform fluid reservoir 12.

In a further use, the present invention provides a method of eccentric muscular tensioning in which chamber 14 is pressurised and the pressure in the chamber controlled or modulated by variable valve 17, the pressure in the chamber being increased by increasing the pressure setting of variable pressure release valve means and or by varying the resistance of variable resistance valve means by means of valve control 27. Actuator means 13 are operated by a user to resist deformation of deformable fluid reservoir means 12 by holding the actuator means steady against increasing pressure.

In another use, the present invention provides a method of testing the muscle strength of a person in which chamber 14 is repeatedly pressurised and

the pressure in the chamber controlled or modulated by variable valve 17.

Actuator means 13 are repeatedly operated by a user and in the manner outlined above, parameters indicative of muscle force or strength of the user are provided. Selected operating characteristics within looped fluid circuit 11, such as for example the setting of variable valve 17 or the rate at which pump 15 pressures chamber 14, are then varied. The person being tested then repeats the repetitive operation of actuator means 13 and another set of indicative parameters for the different operating conditions is obtained. A comparison of these sets of results can demonstrate anomalies indicative of feigned maximal contraction or deliberate under-performance of the person being tested.

FIG 5 profiles strength directly as a function of the angle of the flexion or extension of the joint, or indirectly as a function of a length, angle or volumetric measurement of the actuator, as it responds to that muscle action.

FIG 6 profiles maximum eccentric strength as a function of time. The operator can manually control the pressure setting of the pressure reduction valve means to visually maintain the anatomical position of the joint under test in its most advantageous midrange flexion/extension position, while the subject continues to maximally exert force. Alternatively a computer control algorithm can perform the same task by negative feedback from actuator, position (or the conformation of the deformable reservoir), and the fluid pressure sensor. In either case the task is to'hunt'the position of maximum force by imposing on the muscular system a state of slow eccentric contraction, terminated by a significant reduction in the pressure setting of the pressure reduction valve means once a measurement of maximum force has been obtained, or once a certain state of flexion/extension of the joint has been achieved. For example, the resistance of a resistance valve acting as the pressure reduction valve means can then be reduced. At this point the muscular force overcomes the pressure set in the pressure chamber, causing immediate concentric contraction of the muscle system and a return to the joint conformation close to the initial position of the test. At this point, the pressure and/or resistance settings of the valve means at the beginning of the initial action cycle, or found on its 'ascending limb'are re-invoked.

This process can be repeated as many times as desired to test for

consistency, and also to assess stamina.

Portion"A"of the profile illustrates pressure and/or resistance settings of the valve means provided by a computer control algorithm. In the first stage of each cycle the resistance setting of the valve means increases to a pressure determined by the safety function of the equipment. At a set pressure above the pressure reading in the chamber, there is a reduction of the pressure setting of the pressure release valve (acting as a safety measure in parallel with the functioning resistance valve) of the valve means, its pressure setting reducing at a preset level above, but in step with, the pressure measured in the chamber.

At the same time, or prior, the resistance setting of a resistance valve acting as part of the valve means, does not further increase. The third stage is reached when a preset conformation of flexion/extension of the joint/muscle system, or the actuator, or the deformable reservoir, is reached, at which point lower settings of the valve means found at the beginning of the action cycle, or on its ascending limb, are reinstated. Continued maximal muscle force will then rapidly deform the deformable fluid reservoir by venting fluid through the valve means, until it returns to an anatomical conformation found at the beginning-or on the ascending limb-of the strength profile, where exerted muscle force can no longer overcome the pressure in the chamber. At that time, or at a time afterward, the increasing pressure and resistance settings of the pressure reduction valve means can be recommenced, and a new test cycle begun.

Portion"B"of the profile in FIG 6 illustrates the flexion/extension excursion of the joint/muscle system (or the change in length, arc, or volume of the actuator or the deformable fluid reservoir) as this cyclical process continues.

Portion"C"of the profile in FIG 6 illustrates the pressure readings in the chamber as cycles of this test continue.

The graphs in FIG 7 are of muscle force versus range of motion and depict profiles obtained from different resistance settings of a resistance valve, and those in FIG 8 are of lengthening velocity versus range of motion and depict profiles obtained from different resistance settings of a resistance valve. A description of these follows with reference to alphabetic characters"A"to"F".

As depicted by"A"and"Bl","B2"and"B3"in FIG 7, the range between "maximum isometric force"and"maximum eccentric force"for all positions

within the range of motion of the joint can be found by profiling the force curves created in slow maximal isokinetic concentric and eccentric contraction with the embodiment of the invention using a resistance valve. The eccentric force curve is first derived by assessing the isokinetic maximum force profile of a musculo-skeletal system at a slow constant angular rate of eccentric contraction.

As depicted by"B1","B2"and"B3", the resistance valve can then be opened by steps, and the test repeated at each lessened value of resistance.

The subject will find that with each such test their muscle exertion will appear to have"greater effect", and that each test takes a correspondingly longer time.

However the obtained profiles of force as a function of"range of motion"will be essentially the same, where the maximum eccentric force muscle can exert is largely independent of relengthening velocity (as is implied in FIG 2). Thus there appears on FIG 7 a bundle of curves"A","B1","B2","B3"broadly representing the profile of"maximum eccentric force".

With further stepped lowering of the resistance of the valve, a point"C"of the ascending limb of a profile is reached where eccentric relengthening stalls.

The fluid flow through the resistance valve equals the fluid flow from the pump.

If having arrived at that circumstance, maximal exertion is continued while the resistance of the valve is then manually reduced, the pressure profile at"D"will demonstrate a pressure reduction continuing in the absence of muscle shortening, until the level of"maximal isometric force"for that muscular system (in that position in the range of motion of flexion/extension) is reached at"E". At that point muscle shortening"F"will occur, evident to the subject and the analyst as the beginning of concentric contraction, and on the profile as a retrograde movement of the line of the profile.

Profiles can be derived of both the instantaneous force exerted and the instantaneous contraction velocity as functions of the chosen range of motion.

Force exerted will present as a"hill"curve as seen in FIG 7, with values of force higher at the midrange of the range of motion, successive curves being effectively collinear (as once maximum isokinetic force is attained, increased lengthening velocity does not result in increased force) while the lengthening velocity-constant in the isokinetic test-will increasingly reduce in the midrange

as resistance is diminished.

The graph of instantaneous contraction velocity given in FIG 8 presents a line"A"representing the constant isokinetic lengthening velocity of the initial test and then increasingly steep valley curves"B1","B2","B3", representing the reduction in lengthening velocity that occurs-expecially in the midrange of the range of motion-as the resistance of the resistance valve is successively reduced. A point"C"is reached where the profile reaches the zero line i. e. eccentric contraction has ceased. If then the resistance of the valve is then manually reduced and then varied, the line on the profile graph of force against range of motion in FIG 7, depicting the force exerted against muscle contraction will traverse, ie run down and/or up, in the range between the maximum slow eccentric force and the maximum isometric force which is approximated by the maximum slow concentric force. This is as depicted on the graph at that position of the range of motion. If the force exerted against muscle contraction falls below"maximum isometric force", the line depicted moves retrograde, as the muscle can now shorten. On the graph of"lengthening velocity"the position of the profile point remains fixed on the zero line until the pressure of "maximum isometric force"is reached, when the line of the profile then moves retrograde below the"zero line"at"F", signifying a reversed velocity. Thus letters"C","D", and"E"of FIG 8 all refer to the single point at zero lengthening velocity.

In performing this test, the resistance setting of the resistance valve can be varied within limits, varying the pressure in the range between maximum isometric and maximum eccentric force. In a simple competent contracting muscle system, this variation of load should not affect the ability of the subject to hold the linear position of the contracting muscle system.

The invention thus provides measures of"maximum isokinetic eccentric force"and"maximum isometric force"at a particular point of the"range of motion"of the musculo-skeletal system, and the competence of the muscular system to maintain constant linear length within this range can be tested. These values can be compared to the comparable values obtained from the profiles of maximum eccentric and concentric force across the range of motion.

Although prima facie appearing to be a more complex manner of deriving

the data indicated in FIG 1 than that available from known equipment, the present invention provides more data thereby enabling a greater understanding of normalcy or abnormalcy of muscle function. Moreover, the family of curves so obtained provides much greater validation of the results, as does the visual evidence of muscular lengthening and shortening.

In FIGS 9 to 12, two curves constant appear. The upper one is the profile, previously determined, of maximum slow isokinetic eccentric force, and the lower profile is of previously determined maximum slow isokinetic concentric force over the physiologic range of motion of the joint.

The graphs in FIG 9 illustrate maximum isokinetic eccentric and concentric force and the use of a pressure release valve to identify a point on the ascending limb of the profile of maximum eccentric contraction and a corresponding point on the ascending limb of maximum concentric contraction, for validating the force difference therebetween. The graphs in FIG 10 illustrate force versus range of motion and the use of a pressure release valve to identify a point on the descending limb of the profile of maximum eccentric contraction and a corresponding point on the descending limb of maximum isometric contraction, for validating the force difference therebetween.

As can be seen in FIGS 9 and 10 with reference to alphabetic characters "A1"to"A2"a (non-isokinetic) profile of"maximum slow eccentric force"can be obtained using either a pressure release or a resistance valve in a looped fluid circuit starting at low pressure. In FIG 9 and FIG 10 profile"A" (starting in limb "A1"and concluding in limb"A2") represents a profile so obtained. The test begins with the muscle system to be tested in a shortened state, the valve in a fully open state of no pressure or no resistance, and with fluid circulating in the loop under no pressure (A1). The pressure or resistance setting of the valve is then gradually and continuously increased, while maximum pressure is exerted by muscular system on the actuator. Both pressure and the position in the "range of motion"are continuously recorded. The graph of the force exerted as a function of the range of motion presents as the"ascending limb"of a profile of the maximum force exerted in slow eccentric contraction. The corresponding graph of contraction velocity as a function of range of motion will demonstrate a slowly ascending undulating curve to the point of maximum isometric force, at

which point (in time and in position) a pressure release valve will fully close.

With the use of a pressure release valve the graph of contraction velocity will at that point lift to a higher but level value, as muscle contraction from that point is effectively isokinetic. With the use of a resistance valve the resistance of the valve can at that point be locked, and the descending limb of the profile will be generated (A2), since as the eccentric force gradually diminishes, the flow through the valve will reduce as well. The generation of the profile will not stall.

With the use of a pressure release valve, a further test can be performed (see curve"C"in FIG 9). A pressure value that lies on the ascending limb of the already established"maximum isokinetic eccentric force profiles set on the pressure release valve. The test is begun from the position of full muscle shortening, and isokinetic eccentric contraction (muscle lengthening) continues until that point previously chosen on the profile is reached. Lengthening then abruptly ceases, as the muscle can eccentrically resist the force exerted against it by the actuator. At that point the assessor can again gradually reduce the pressure setting-and then further vary the setting-of the pressure release valve. Again, the muscle length should remain the same until, with pressure reduction, the pressure level of"maximal isometric force"is passed. At that point the muscle will shorten concentrically as the pressure setting of the valve continues to reduce.

With a slight variation, this technique can test for levels of"maximum isometric force"in the descending limb of the profile (see curve"B"in FIG 10).

At any stage of the generation of an isokinetic eccentric profile, the assessor can abruptly drop the pressure by reducing the resistance of a resistance valve or the pressure setting of a pressure release valve. Maximally contracting muscle will no longer be forced to lengthen, but will not be able to shorten, until the load falls to the level of"maximal isometric force"for that position in the"range of motion"of the contracting muscle system, when shortening will abruptly occur.

The graphs in FIG 11 show tests starting from null pressure utilising either a pressure release or a resistance valve to identify a reading of maximum isometric force at a location in the range of motion and in the corresponding point on the profile of maximum eccentric force. The graphs in FIG 12 show a test starting from null pressure assessing the ability of a subject to maintain

constant force in eccentric muscle relengthening over a range of motion.

As seen in the results in FIGS 11 and 12, the tests can also be performed from"the bottom up", using either valve. A subject is asked to oscillate muscular shortening and relengthening about a chosen position in the range of motion of a muscular system, while the load on the system is gradually increased. The subject will be able to maintain the oscillation-so doing work- until"maximal isometric load"is reached, at which point the subject will be able to hold position, or relengthen the muscle, but not shorten. The subject is then asked to hold position while the pressure is varied in the range above"maximal isometric load"so assessing the ability to hold the position in eccentric contraction, and testing to find the level of"maximal eccentric force"for that position.

Two tests of precision in the control of eccentric muscle contraction are identified. One is a test of precision in maintaining a prescribed force, and the other of maintaining a prescribed lengthening velocity. In each case the apparatus uses a resistance valve, and the subject is asked to view on a computer graph the instantaneous plot of applied force or of lengthening velocity as he or she maintains eccentric muscle force. Having initially increased the pressure to a force level in the eccentric range of muscle contraction, the observer can vary the resistance of the valve, and/or the flow rate of the pressurising means. The task of the subject is to maintain the prescribed force or lengthening velocity in this circumstance. The competence of the subject in performing this task is measured against the plots of pressuring means flow rate, pressure reduction valve resistance, force and lengthening velocity, measured against time and against range of motion.

This test can be conducted at differing pressure levels within the range of "maximum eccentric"force.

This task can also be assigned as a form of strengthening exercise, both for muscle conditioning, and in circumstances of muscle disability.

The above description of the biological function of muscle in the tension range from maximum eccentric force to maximum isometric force, and the diagrams of the profiles and traverses presented in this patent description, are based on a consideration of Katz's seminal study of eccentric muscle fibre

contraction in 1939, as illustrated in FIG 2. The following three biological factors add a degree of complexity.

"Vertical traverses"decreasing tension through the force range from maximum eccentric force to maximum isometric force (or increasing tension from maximum isometric to maximum eccentric force) may demonstrate the phenomenon of"drift"to a lesser or greater degree.

The length of the total musculo-tendinous segment may slowly increase with time. In part this is due to the tensile properties of tendon, which can slowly increase in length when placed under significant tension, and partially due to the properties of the sarcomere, which in the force range above maximum isometric force can resist lengthening tension either absolutely or partially, depending on the force exerted, the state of "freshness"or"fatigue"of the muscle segment, and its general health.

The shape of the profile of"slow concentric isokinetic tension"across the range of muscle shortening, and the shape of the profile of"slow eccentric isokinetic tension"across the range of muscle lengthening, may be different. Muscle can behave differently in shortening under load and in lengthening against a load it cannot resist, at different stages of the sarcomere length profile. Forceful isometric or concentric contraction from a starting position of extended sarcomere length can result in non-uniform sarcomere shortening, as may forceful eccentric contraction into the range of extended sarcomere length. Indeed some sarcomeres may become anomalously"over-extended"and non-contractile. This effect may affect the shape of the profile curves, especially in the range of long sarcomere length.

"Non-contractile sarcomeres"so created may not immediately correct themselves as muscle shortens, and subsequently performed"maximum muscle tension tests" (concentric, isometric, or eccentric) may demonstrate weakened contractility and altered profiles. This circumstance will affect the"repeatability"of strength tests, especially when tests are performed in the range of extended (long) sarcomere length, but such discrepancy can be considered to be an integral element of the overall phenomenon of"fatigue".

The tests performed by the methodology disclosed in this patent application will inevitably reflect and reveal the complexity of function of the musculo-tendinous segment in the tension range from maximum eccentric force to maximum isometric force. This is a purpose of this methodology, and such complex results do not detract from its validity and value. Such effects are an indication of muscle fatigue and dysfunction, or of the complex nature of complexly contracting musculoskeletal systems, and can be so interpreted.

The effects of"deliberate under-performance"and conscious fabrication of disability are different, and a testing methodology exists to make evident such behaviours.

It should be noted that provision of a pressure release valve in hydraulic exercise equipment set to open at a safe tension less than the observed maximum eccentric contractile force, will provide for safe eccentric muscle exercise. This pressure release valve can be in parallel with a resistance valve, where a resistance valve is needed for a test or exercise.

The present invention can be incorporated in a single apparatus with the inventions described in my international patent application PCT/AU98/00747.

The present invention and those described in my co-pending application can be regarded as constituting two mirrored circuits, one with fluid moving by muscle actuation, the other with fluid moving by the action of a pump powered by an external source. The external power source can be the muscle power of the tester, but is preferably a more constant source of power, and therefore of fluid flow. In a third process of testing, both circuits are immobilised.

This present invention and the second embodiment of PCT/AU98/00747 both utilise a valve. This valve can be common to both in a design which mirrors the two fluid circuits, and uses one valve and its controlling and safety mechanisms to provide for the measurement, calculation and assessment of work, power, contraction velocity and maximum exertable muscle force. Thus as seen schematically in FIG 13, an operator can switch between the external powered circuit and the muscle powered circuit by the use of conventional switching or valving mechanisms, such as for example isolating shutoff valves in the separate parts of each fluid circuit.

FIG 13 is a schematic diagram of an alternative embodiment of the

invention including aspects of the invention described in my copending applications. This embodiment of the invention constitutes a fully featured muscle assessment and development apparatus with pressure accumulator and mirrored pressured fluid flow circuits. The mechanical and pneumatic/hydraulic parts of the apparatus are indicated by black bolded lines and outlines, information links by grey dotted lines.

Apparatus 40 seen in FIG 13 is now described with reference to additional features to those shown in FIG 4, with like features similarly numerically referenced where appropriate or necessary for descriptive purposes. Apparatus 40 includes mirrored fluid circuits 41 and 42, with fluid circuit 41 constituting a primary looped fluid circuit and fluid circuit 42 constituting an auxiliary looped fluid circuit. Circuits 41 and 42 share chamber 14, valve 17 and fluid reserve 19. Pump 43 and external power source 44 in primary circuit 41 are equivalent to pump 15 and external power source 16 illustrated in FIG 4, whereas a muscle powered pump and actuator 45,46 in auxiliary circuit 42 can be used by a tester/operator to vary pressure parameters. Volumetric measuring means 47 measures volume change and/or fluid flow rates as indicated.

Chamber 48 accumulates pressure (in the first embodiment of PCT/AU98/00747), which pressure constitutes the load against which work is performed. Measurements are made of the initial and final pressures of each pump cycle, and of the time instants of these measurements. From this data the work performed, power generated and the"volumetric pump velocity"each pump cycle can be calculated.

By switching by conventional means between the circuits, operation of the equipment in one of several modes can be effected.

By shutting off both circuits 41 and 42, and opening a valve to a pressure accumulating constant volume chamber, the test of the first embodiment of PCT/AU98/00747 can be performed. By shutting off the looped fluid circuit 41, the test of the second embodiment of PCT/AU98/00747 can be performed.

FIGS 14-22 allow an appreciation to be gained of the relationship between the present invention and those described in my international patent application PCT/AU98/00747.

A basic configuration of apparatus for assessing the work performed by muscle contraction or to facilitate muscular exercise is illustrated schematically in FIG 14 with text annotations. In FIG 15 an annotated schematic diagram illustrates and describes the hand pump and pressure chamber pneumatic test device for assessing the work performed by muscle contraction or to facilitate muscular exercise described in my international patent application PCT/AU98/00747.

FIG 16 is a schematic diagram with annotations describing and illustrating a muscle powered pneumatic muscle strength, work and power assessment and development device utilising a pressure reduction valve.

Similarly FIG 17 is a schematic diagram with annotations describing and illustrating the muscle powered pressurised auxiliary fluid flow circuit for assessing the work performed by muscle contraction or to facilitate muscular exercise described with reference to the embodiment illustrated in FIG 13 of the present invention.

There is an intrinsic value in placing an externally powered pump circuit in parallel with the actuator circuit (see FIG 13) for the for the performance of tests of muscle shortening. In this embodiment, there is no closing physical deformation or lineal shortening of the actuator while the muscle force increases from the null level to that force sufficient to overcome the internal pressure of the twin fluid circuits. (There will be opening physical deformation or lineal lengthening unless the actuator has reached its mechanical state of maximum physical capacity or maximum lineal length.) With the actuator stopped at its state of maximum physical capacity or maximum lineal length, no external work is performed in the process of increasing the muscle force exerted from the null level to the quantum needed to overcome the internal pressure of the twin fluid circuits, and all the external work performed by the hand will be measured by this embodiment. (In the invention described in my international patent application PCT/AU98/00747, although the work performed in deforming or shortening the actuator while the pressure in the actuator is increased to the level set by a pressure accumulating constant volume chamber or pressure release valve is not measured by the device, it is a direct function of the work performed and the

pressure overcome, so it can be accurately allowed for in the computation of the derived parameters or work and power.) With an externally powered pump circuit in parallel with the actuator circuit, there is no range of movement of the actuator where the load exerted against the muscle is less than that set by the internal pressure of the parallel fluid circuits.

This arrangement permits the study of eccentric muscle contraction (muscle lengthening) at load ranges both above and below maximum isometric force.

The formal test of eccentric muscle contraction in any load range requires an external means to lengthen muscle.

With a resistance valve as pressure reduction valve means, pressure can be varied both by varying the valve resistance, and by changing the rate of flow of fluid through the pressurising means. With a pressure release valve as pressure reduction valve means, varying the fluid flow rate in the circuit will have minimal effect on the pressure reduction across the valve. These features may be of value as confounding measures where the analyst suspects a subject is feigning disability.

FIGS 18-24 schematically illustrate the mirrored pressurised fluid flow circuit of the present invention as described with reference to the embodiment illustrated in FIG 13, in respective ones of several operating modes. In each of FIGS 18-24, the active mechanical and pneumatic/hydraulic elements and operative fluid circuit (s) are highlighted in bold outline.

FIG 18 illustrates a mirrored pressurised fluid flow circuit device equipped with a pressure accumulating volume chamber enabled to measure an isokinetic eccentric or concentric force profile. FIG 18 thus illustrates the fluid pumped by external power with no pressure reduction valve and is for for developing isokinetic force profiles.

FIG 19 illustrates a mirrored pressurised fluid flow circuit device equipped with a pressure accumulating volume chamber enabled to utilise a pressure reduction valve to obtain traverses and other profiles of eccentric or concentric force. FIG 19 thus shows the fluid pumped by external power with a resistance and/or pressure release valve relieving pressure for testing eccentric muscle contraction and profiling force and power.

FIG 20 illustrates a mirrored pressurised fluid flow circuit device equipped with a pressure accumulating volume chamber configured to assess concentric muscle contraction, utilizing the pressure accumulating volume chamber and operated solely by muscle power, where the pressure in the volume chamber increases continuously under muscle action until muscle force is no longer able to deform the actuator. The device is enabled to obtain a profile of work and power in concentric muscle contraction, the work and power being assessed against incrementing load. FIG 20 thus illustrates the hand pump and pressure accumulating pneumatic volume chamber test of power output and maximum force.

FIG 21 illustrates a mirrored pressurised fluid flow circuit device equipped with a pressure accumulating volume chamber configured to assess concentric muscle contraction, utilizing a pressure release valve, and operated solely by muscle power, overcoming in each contraction the load provided by the pressure release valve. FIG 21 thus illustrates the fluid pumped by hand means through a pressure reduction valve for testing power output and maximum force.

FIG 22 illustrates a mirrored pressurised fluid flow circuit device equipped with a volume chamber configured to assess concentric muscle contraction, utilizing both the pressure accumulating volume chamber and a pressure release valve, and operated solely by muscle power, where the pressure in the volume chamber increases to a set level, and then remains at that level.

FIG 23 illustrates both circuits in use. In FIG 23 muscle power"assists" external power, and the pressure drop across the valve means is a function of flow rate in the pressurised circuit. This arrangement can test work done by muscle. The only use identified for this configuration is to assess strength and obtain profiles of work and power versus load, where it is necessary to confound a subject.

FIG 24 illustrates a minimum configuration that, once loaded with fluid, acts as a strain gauge. In the hydraulic embodiment it simulates the Jamar dynamometer, and in the pneumatic embodiment the Vigorometer, and enables direct comparisons between its own results and the norms established by these technologies.

Pneumatic and particularly hydraulically actuated exercising apparatus

have the potential to inflict serious and even fatal injury. In a preferred embodiment and in practical commercial use the present invention incorporates or provides a number of safety features and aspects, not all of which are necessarily incorporated in all embodiments and applications of the invention.

These safety features and aspects include the following:- Where there is a danger, there should always be present a guardian trained in the safe use of equipment.

Competent electrical grounding is provided for all electrically powered or connected equipment and components. Isolation circuits and ground fault circuit breakers are provided for components in electrical continuity with actuators.

Each test or exercise is set up under null pressure to limit the mechanical range of action of the equipment to safe limits.

The closed pressure chamber has an additional pressure release safety valve that will automatically release all pressure if a safe limit is exceeded.

The controllable valve means is so constructed that when not under direct control with the control means directly activated, the set pressure is null.

The operator/tester/guardian has always available a safety switch which (a) turns off the pump, and (b) releases all pressure in the closed pressure vessel. This safety switch is tested before the equipment is operated.

The subject has always available a safety switch which (a) turns off the pump, and (b) releases all pressure in the closed pressure vessel. This safety switch is tested before the equipment is operated.

A suitably constructed mechanical frame provides further protection by activating the third safety means listed above. Failing that, the test device can be caused to deform or fail, thereby preventing excessive range of motion and/or excessive force being applied to a body part.

This safety device is tested before the equipment is operated.

Weak links are designed into the equipment, and will rupture should the equipment exert pressure on the safety frame in the event that the safety

pressure release valve in the closed pressure chamber fails.

The setting of the variable valve means is linked to the actual pressure measured within the closed pressure chamber, so that from the point of maximal pressure measured (maximum muscular force applied), the setting of the pressure release valve does not continue to linearly increase with time, but varies, and indeed will diminish in degree, being continuously set at a predetermined difference above the pressure then continuously measured within the closed pressure chamber. This effect can be achieved if the pressure setting of the pressure release valve is initially set to increase linearly, but whenever the reading of the pressure measuring means falls to a preset difference below the instantaneous reading of the pressure release valve, the setting of the pressure release valve is thereafter controlled to remain at no more than this difference above the reading of the pressure measuring means as that pressure is continually monitored.

If the measured pressure in the closed pressure chamber falls more rapidly than a predetermined rate, or falls below a predetermined level, the system switches off. (The pump ceases and the pressure setting of the pressure release valve becomes null.) The test has ceased, at whatever the range of muscle relengthening that has been achieved, and a new test cycle (if needed) must be commenced.

As a safety measure a controllable pressure release valve, or rapidly openable stop valve, is provided in parallel with pressure reduction valve means to characterise eccentric muscle contraction. When there is no flow through a valve at any pressure, safety control means 22 enables an instantaneous reduction of pressure in an emergency.

The embodiments of the present invention thus allow for :- Measurement of a maximum force exerted by a musculo-skeletal system in slow eccentric contraction.

Derivation of a profile of exerted force plotted against the configuration of the musculo-skeletal system given as an angle, distance or volume.

Profiles can be created for different speeds of eccentric contraction.

Low load level reciprocating concentric muscle exercise with passive

return.

Single or successive high load level eccentric muscle exercises.

Testing the integrity of muscle in maximal eccentric contraction by quantifying the extent of the range of force in eccentric contraction, the ability of muscle in eccentric contraction to resist relengthening, and to relengthen muscle at a specified level of load and velocity in a controlled and precise manner.

It will be appreciated that the present invention has a number of advantages over known apparatus and methods.

The use and function of prior art arrangements can be far more complex than that of the present invention. Thus for example in comparison with Stima (US 4846466), the low load exercise or activity sequence of this invention involves no more than (a) the setting of the pressure release valve at low load, (b) the pump causing a passive movement of the body part to one limit of motion, and (c) the mechanism then continuing itself unchanged-while the muscles are used to do hydraulic work, lowering the volume of the hydraulic system at constant or controlled pressure until the other end of the range of motion is obtained. The cyclical process then begins again from (b).

The present invention also creates a range of strength profiles throughout the full extension/flexion range of eccentric contraction of the muscle system at different speeds of eccentric contraction.

The ability of eccentrically contacting muscle systems to exert force and controllably relengthen can be closely studied. Assessments derived from the strength profiles can be correlated with a. anatomical studies of muscle, and studies of the geometry of the moment arms of the various muscles acting across a joint, to study the varying contributions of different muscle elements to muscular torque exerted about a joint at different stages of flexion and extension. b. studies of the electromyographic activity of the various muscles acting across a joint as those muscles engage in maximal states of contraction- concentric, eccentric and isometric, and c. thermographic studies of muscle temperature, as normal muscle, and muscle with disability, attempts maximal exertion of force against load,

and maximal power output-both positive and negative.

The present invention also provides further security of results and conclusions against a claim of submaximal exertion. The ability to create an eccentric strength profile enables it to be compared with the norm, in shape, in the position of maximal force, and in variability within one test and between tests. The maximum strength so determined can be compared with the maximum strength found doing formal reciprocating work against an increasing load. These two different measurements can be made consecutively on the same test instrument and the results immediately compared. Different parameters of this test instrument can be varied-the choice of valve means, the initial pressure, the maximal pressure, the speed of increase of the pressure set for the pressure release valve, the flow rate of the pump.

The difference so found between concentric and eccentric force can then be closely studied by undertaking traverses between maximum eccentric force and isometric force at null lengthening velocity as already described in this methodology.

The present invention provides for the measurement of the maximum torque/force/pressure able to be exerted by muscles acting against an increasing force acting isotonically against them, in a process of resisted eccentric contraction.

The present invention provides for the creation of a profile of the maximum/torque/force/pressure able to be exerted by a muscle system, as it concentrically contracts first isotonically to maximum force, then isometrically as that force diminishes, throughout its range of muscle relengthening, plotted against the appropriate angular, linear or volumetric dimension that indicates flexion/extension angle, linear range of motion, or range of complex muscle action.

The present invention provides the basis for reciprocating concentric muscle contraction as exercise therapy, injured or weak muscles being made alternately to act against low torque/force/pressure exerted through the transformation means, and then being passively relengthened as the transformation means returns the connected musculo-skeletal parts to their initial extended position. This cycle of light concentric contraction and passive

relaxed relengthening may have the additional effect of gently extending the range of motion of a joint, where that range of motion is limited by muscle spasm, ligament or tendon contracture or joint stiffness.

The present invention provides the basis for reciprocating eccentric muscle contraction as forceful exercise, muscle strengthening, and athletic training. An increasing external force ultimately forces a flexed limb into extensions, against maximum exerted force. At the end of each cycle, the pressure in the pressure chamber is substantially reduced or returned to a null vale, permitting concentric muscle contraction to return the muscle system to a shorthened state. This cycle of exercise can be repeated as desired.

The present invention permits muscle to maximally exert against a lesser, an equal or a greater force. Rather than just have muscle exert force against the equivalent of a"brick wall", ie an immoveable strain gauge such as the Jamar dynamometer, the use of the pressure of a fluid in a restrained container to exert force against muscle, provides for variations in the resisting force being translated into observable muscle shortening and relengthening. This is seen and felt by the subject, is visible to a tester, and is quantifiable in an objective process of measurement.

The present invention tests muscle using a means that provides for shortening and relengthening-even for short distances, and over significant time spans-and thus provides a more physiological test than those of the prior art. The subject will consider the test more natural-and therefore do more naturally as there is an implicit promise of success. If sufficient energy is exerted, the device can be made to move unlike the Jamar dynamometer or equivalent apparatus.

The present invention provides that when strength alone is being evaluated in a quasi-isometric manner, the use of a variable resistance valve instead of a variable pressure release valve will create a subjective scenario midway between"isotonic force"and the equivalent of"the brick wall". This will not invalidate the test results and provides a circumstance where, when resistance is finite, any flexion against resistance will immediately increase the resisting force-whereas"giving in"to the external force will result in a reduction in that external force. The profile obtained should be essentially the same in

each case but the subjective feel of the test will be different. The difference has the potential to be a valuable testing tool.

A preferred embodiment of the present invention provides an apparatus which is adapted to operate in a number of modes including a so-called"brick wall"test, in which the valve is effectively eliminated by screwing the resistance valve into its seat, or setting the pressure of the pressure release valve at an excessively high value at the beginning. In another mode, in which a looped fluid circuit simply has pressurising means, pressure measurement means and a deformable fluid reservoir, muscle pressure exerted on the actuator should provide a similar profile, provided the person being tested maximally exerts against a"moving brick wall". The test of this mode is equivalent to known tests involving a moving arm with a pressure transducer plate. The apparatus of the present invention also, and principally, assesses the ability of muscle to do work and tests isometric strength as a limiting condition between concentric and eccentric muscle contraction. It does this in several different ways which facilitate an analysis of states of weakness of muscle contraction.

In a preferred embodiment of the present invention, the looped fluid circuit arrangement creates conditions to measure pressure and deformation or pressure and fluid flow, which can allow for the calculation of work performed, or the construction of a profile of force exerted over the range of movement of a joint, or the prescription of a measured quantum of work for muscle to perform.

Moreover, the looped fluid circuit creates a feeling in the muscles of the person being tested which gives the perception of an ability to overcome the mechanical force being exerted. The use of a pressure release valve simulates the function of muscle in a gravity field. The use of a resistance valve simulates the function of muscle in a fluid medium such as is experienced when swimming. The natural feel of the apparatus of this preferred embodiment of the invention is believed to be explained by the fact that the perceptions referred to above can be considered two of the"age old"functions of muscle, which together with the contractile qualities of muscle, the tensile and elastic qualities of tendon, the various forms of joint articulating bone, have all developed to facilitate a human doing work either on land in the gravity field or in water.

The apparatus and methods of the present invention thus provide for the

presenting of tests and the prescribing of work optimised to the biological function of muscle.

The apparatus and methods of the present invention and that of my earlier applications enable the study of reciprocating muscle function. The earlier invention enables the study of the concentric elements of reciprocating muscle function, and this invention the eccentric elements of reciprocating muscle function.

The use of hydraulic or pneumatic means in the present invention allows a design that provides for the conduction of heat away from the elements of the apparatus where work is being performed and heat is being generated.

Appropriate design allows for indefinite continuation of reciprocating muscle action without risk of damage to the apparatus from over heating.

With the apparatus and methods of inventions of the present and co- pending applications, muscle function of hand grasp can be closely studied and precisely defined and characterised, which the Cybex and Biodex apparatus do not allow.

With the apparatus and methods of the present invention, linear excursions of an actuator are as readily obtained as are rotatory excursions.

This may prove particularly useful in assessing antigravity muscle function.

The apparatus and methods of the present invention enable a close and quantitative assessment of the physiological dysfunction that occurs between the performance of slow isokinetic concentric and slow isokinetic eccentric contraction, including the difference in the maximal muscle force that is able to be exerted in each circumstance.

The present invention provides graphs plotted of maximum muscular force obtained for both slow isokinetic concentric and slow isokinetic eccentric contraction over the available range of motion of a muscle system. In these graphs profiles for maximum slow isokinetic eccentric force and maximum slow isokinetic concentric force can be plotted and then checked by traverses being conducted between these limits.

In accordance with the present invention the primary measured parameters of time, pressure, and of linear angular and/or volumetric displacement, and/or fluid flow rate, can be accurately measured with a

presently available and inexpensive technology. The apparatus and methods of the present invention enable these parameters to be used to derive measurements of eccentric and concentric muscle force as individual measurements and profiles over the range of motion of muscle action, together with calculations of work performed, force exerted, and shortening velocity related particularly to concentric muscle contraction. Thus equivalent assessments to what is provided by the Cybex and Biodex instrumentation can be provided at a significantly reduced cost. These price points fall within the practical reach of clinical medicine.

The concept and methodology and apparatus of the present invention lends to designs and construction of simple robust, compact and light exercise devices, but also provide for the measurement of work performed and power developed in standard Scientific Units. There is also the means, where relevant, to rapidly generate a graph of work and power as a function of load for each muscle system under exercise and test, as a measure of health, recovery from illness, and/or musculo-skeletal disability and injury, or to quantify athletic stamina and performance.

The provision of an external power source in the present invention can provide for forms of eccentric muscle strengthening and the specific assessment of muscle function in the range of eccentric muscle action.

The present invention brings into general clinical practice methodologies previously restricted to muscle function laboratories, together with understandings and insights in muscle physiology previously believed to have had only theoretical and experimental significance.

The methodologies for the apparatus of the present invention can reasonably detect feigned disability and deliberate submaximal performance, and conversely can reasonably validate a claim of maximal effort.

It will of course be realised that whilst the above has been given by way of an illustrative example of this invention, all such and other modifications and variations hereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of this invention as is herein set forth.