The present invention relates to a method for carrying out muscle exercises and, when appropriate, for measuring exercising conditions.

The invention also relates to equipment for carrying out the method.

The work performed by muscles can be divided into two categories. Concentric work, also referred to as positive work, in which the muscle is shortening (contracting) under an applied load, and eccentric work, also referred to as negative work, during which the muscle is lengthening during muscle work. For instance, concentric work is performed predominantly when lifting a barbell, whereas eccentric work is performed predominantly when lowering the weight. The force or power developed by skeletal muscle for a given rate of shortening or lengthening, often expressed as joint angular velocity, is always greater in the case of eccentric work than in the case of concentric work. The force is often expressed as the torque prevailing in the joint concerned.

The well-known movement of lifting a dumbbell with the vertically hanging arm, by bending the elbow (so-called biceps curl) will be used hereinafter to illustrate the conditions that prevail during muscle training exercises.

Similar to the majority of the joints of the body, maximum strength, or torque, is achieved in the elbow joint during the mid phase, when the arm is bent at right angles. When performing the above-mentioned dumbbell training, a relatively favourable loading is obtained during said movement, since the gravitational force exerted by the dumbbell will exert maximum resistance to the concentric training or exercise movement in the position in which the force or power in the elbow joint reaches its maximum. The minor lever arm of the gravitational force will result in a relatively light load, both at the beginning and at the end of the movement. The mid phase of the movement, however, is the most difficult to pass, and hence the speed of the movement will fall and the muscle will not be loaded to a maximum throughout

the whole movement.

In strength-training exercises, it is necessary to achieve constant, maximum voluntary muscle tension and a constant shortening and lengthening rate during the whole movement, in order to achieve maximum effect in training. It is not suitable to use conventional springs in such muscle-training exercises, since said movement is retarded progressively by the increasing load.

When exercising or training muscles with the aid of conventional equipment, such as barbells and dumbbells, difficulties are experienced in maintaining maximum muscle tension throughout the whole movement concerned, and in maintaining isokinecy * constant change rate in muscle length, since linear inertia forces, primarily at high movement speedB, e.g. ballistic movements; throwing movements, are highly influential. Complicated transmission devices can be used in thiε respect, although such devices are specific for each movement to be carried out and are normally both expensive and bulky and are further¬ more limited by the anatomical differences between individuals con- cerned. Furthermore, heavy weights are required when large groups of muscles are to be exercised or trained. Many kinds of training machines provided with weight stacks are to be found as a replacement for training with free weights. These machines, however, are restricted by significant energy losses in the form of friction. Consequently, the eccentric training phase is far less demanding than the concentric training phase. Since the excentric muscle strength is greater, it will be evident that much of the training effect is lost in this training phase.

Several different types of training equipment employ friction to obtain a desired load profile, although normally it is only possible to carry out concentric training.

The present invention relates to a novel training method and training equipment capable of creating a well-defined speed profile during both concentrical and eccentrical muscle work in the absence of significant energy losβes. The equipment is light in weight and requires only small space in comparison with conventional

strength-training equipment, which enables the equipment to be used in the home and in the hospital bed for training or exercising a number of muscle-groups in the body.

The invention thus relates to a method for exercising or training muscles with the aid of training equipment and, when appropriate, for measuring and determining training conditions. The method is par¬ ticularly characterized in that the training person loads the relevant muscles, by increasing or decreasing the rotational energy (E(kin)), kinetic energy, of a rotatable flywheel.

The invention also relates to training equipment for training or exercising muscles and, when appropriate, for measuring training conditions. The equipment is mainly characterized by a rotatable flywheel which functions to load the relevant muscles of the training person, by increasing or decreasing the rotational energy (E(kin)), kinetic energy, of the flywheel, and the equipment further includes flywheel-activating means operable by the training person.

The invention will now be described in more detail with reference to exemplifying embodiments thereof illustrated in the accompanying drawings, in which

- Figure 1 illustrates schematically a first embodiment of inventive equipment, seen at right angles to the plane of the flywheel;

- Figure 2 illustrates the equipment of Figure 1 from the left in said figure;

- Figure 3 is a graph which illustrates pull-off speed aε an often preferred function of the extended lengt ;

- Figure 4 is a sketch of the inventive equipment intended for explaining the measuring of reference signs;

Figure 5 illustrates schematically a pull-device, a pull belt or strap, seen transversely to its longitudinal direction and its thickness direction;

- Figure 6 is a schematic side view of a flywheel operative to vary., inertia forces by varying weight distribution;

- Figure 7 is a schematic side view of a leg training device for use in a horizontal position, particularly in a weightless environment;

- Figure 8 is a schematic side view of part of another horizontal leg-training device;

- Figure 9 illustrates schematically a safety release device provided in handle means and operative to break the connection between said handle means and said pull-device under given conditions;

- Figure 10 illustrates part of a safety release device according to Figure 9, with the device in its released state;

- Figure 11 is a longitudinal section through a safety brake arrange¬ ment operative to retard or brake the flywheel the medium of a pull-belt;

- Figure 12 is a schematic side view of an arrangement substantially in accordance with Figure 7, although with the flywheel activated indirectly via a lever arm;

- Figure 13 illustrates schematically part of an arrangement sub¬ stantially according to Figure 12, arranged for knee-extension with the training person in a sitting position;

- Figure 14 illustrates schematically the arrangement of Figure 13 intended for leg-curl training with the training person in a sitting position;

- Figure 15 illustrates schematically the arrangement of Figure 13 intended for arm-curl training with the training person in a sitting position; and

- Figure 16 illustrates schematically the various positions of the flywheel in relation to the free, loaded end of the lever arm in the case of an arrangement substantially according to Figures 12-15.

The equipment illustrated in Figures 1 and 2 includes a rotatable flywheel 1, which is rotatable about an axle 2. The reference numeral 3 identifies a bracket structure by means of which the flywheel 1 can be mounted on a wall 4 or like support structure. The rotational energy (E(kin)), kinetic energy, of the flywheel, can be increased or decreased for loading the relevant muscles of a training person 5,

Figures 7 and B. In the case of the embodiment illustrated in Figures 1 and 2, said energy is influenced by a pull-device 6 in the form of a belt, strap or like device 6, said pull-device being wound around a hub part 7 of the flywheel 1 and provided with a handle part 8 which is intended to be gripped by the training person, who as part of the training procedure can pull the belt 6, when coiled-up on the hub, wherewith the belt is unwound from the hub and said energy increased, or else pull the belt 6, hold the belt, when the belt has been unwound and the wheel set in rotation, therewith to retard rotation of the wheel.

As before mentioned, it is often desired to train or exercise with both constant and maximum muscle tension and with well-controlled speed of muscle shortening or lengthening. Constant shortening or lengthening speed in the muscle is corresponded here by a given pull- off speed, which is contingent on the joint anatomy concerned and the position of the flywheel. The desired pull-off speed v, Figures 1 and 4, is often near constant, however, as described hereinafter.

A desired movement pattern is illustrated in Figure 3, and comprises essentially two mutually different phases.

Phase 1 constitutes an acceleration phase, during which the pull-off speed v obtainβ a desired constant level as quickly as possible.

Phase 2 constitutes an isokinetic phase, during which, when v is constant, the angle velocity of the joints concerned, and primarily the shortening (contraction) rate of the group of muscles trained are held

relatively constant. Provided, inter alia, that the pulling force is constant, the following approximative relationships apply in the muscle-loading situation illustrated schematically in Figure 4:

E(kin) -= J Fds = F . s = J " (1)

where

F = Pulling force s = The path travelled under the influence of the pulling force F J = Moment of inertia of the flywheel w = The angular velocity obtained subsequent to s

The influence of, inter alia, friction and kinetic energy stored in joints and muscles has been ignored. The following relationship also applies:

v = w • r (2) where r = the radius

Provided that v is constant, the following expression is obtained from (1) and (2):

r = k (3)

where k = a constant (4)

In order for v to be made constant or substantially constant, the geometry, thickness, of the pull-belt 6, the pull-device, can be varied so as to fulfill or substantially fulfill the expression (3). This is achieved by means of an elongated pull-device whose shape narrows or tapers from its free end, provided with said handle means

8, i.e. the thickness of the belt decreases from said end. During phase 2, w will increase in accordance with

Calculations are more difficult to carry out with regard to phase 1. A tapering pull-belt with great thickness nearest the handle means, provides a desired rapid increase in speed. A thick pull-belt of substantially constant thickness is also able to provide a considerable effect during phase 1.

In the case of the pull-belt embodiment illustrated in Figure 5, the rate of reduction in thickness of the belt decreases in a direction away from the handle means. Thus, Figure 5 illustrates a method of varying the decrease in lever arm as opposed to the flywheel for influencing the relationship between the force exerted and the rate of muscle shortening or muscle lengthening.

In the case of the Figure 6 embodiment, the moment of inertia of the flywheel is varied by varying weight distribution during flywheel rotation, so as to influence the relationship between the force exerted and the rate of muscle shortening or muscle lengthenin . In the case of the illustrated embodiment, the flywheel includes at least one weight 9 which can be moved radially and which is intended to be displaced for redistribution of the weight in response to the rotational forces, centripetal forces, that occur. The moment of inertia increases when the weight is moved outwardly. The weight is preferably displaced against the action of a spring force, for example against the action of a helical spring 10 located inwardly in relation to the weight and tensioned when the weight is displaced outwards. The reference numeral 11 identifies a powerful limit spring positioned externally in relation to the weight. The extreme change in pull- belt thickness required for achieving a substantially constant pull-off speed v, cannot be suitably applied in practice during phase 1, in which acceleration shall take place. In this respect, it is appropriate to employ redistribution of the weight in order to change the moment of inertia J. In this respect, the characteristics of the pull spring

10 can be used to control the change of J in response, inter alia, to the angular speed w. The flywheel may have several weights, as indi¬ cated by the broken-line weight 9 in Figure 6, the various weights 9 conceivably having mutually different springs 10, so as to achieve a high degree of flexibility with regard to changes of J. Movement of the weight concerned is stopped by means of the limit spring 11, whereupon the change in J originating from this weight ceases. It is also conceivable to fixate the weights in the radial direction, both beneath and above given rotational speeds.

A combination of varying moments of inertia and pull-belt configura¬ tions is an example of the flexibility permitting the characteristics of the equipment to be changed.

Calculations of the total moment of inertia as a function, for in¬ stance, of s can be carried out by specifying spring characteristics and employing equilibrium between spring force and centripetal force.

The following expression is obtained with designations, inter alia, according to Figure 6:

where

Jtβ-t = The moment of inertia of flywheel plus weight (s) Ji = The moment of inertia of the flywheel

Ja = The moment of inertia of weight(s)

J _a = mR ^a (7) where m = Mass of the weight R = The instantaneous radial position of the weight

R can be calculated from equilibrium between spring force of springs having linear characteristics and centripetal force:

F* = k _Δ 1 = k ^• (R - R«_) (8) where

F* = spring force k = spring constant

1 = length difference R _β = weight starting position

Fc mv v (9) where

F _β = centripetal force

V _v = circumferential weight speed

(10)

1 - mw ^a

K

From the work (F - s) and E(kin) carried out, there is obtained:

F ^• s = J w ^a = (Ji + Ja) w ³ = i w ³ + mR ^{3 •} w ^a (11)

2 2 2 2

Jtot can be calculated as a function of s from equation (12).

The equipment illustrated in Figure 7 is intended for use in a weight¬ less environment, and includes a bed-part 12 provided with a foot-end 13 and intended to support the training person 5. The illustrated embodiment also includes a slide 14 which is movable along said bed- part and on which the training person is intended to lie and to which a flywheel 1 is connected. The bed-part 12 iε anchored detachably to adjacent walls or like support structures, with the aid of spring devices 15. The flywheel 1 is connected to a carriage 15 by means of a pull-belt said carriage being movable along the foot-end of said bed-part and said flywheel being activated by the legs 13' of the training person; via said carriage and said pull-belt. Also shown is an embodiment in which the flywheel is located beneath a reclining surface on the bed-part, wherewith the pull-belt extends, for instance, between the flywheel and the carriage via a central recess (not shown) in said bed-part. The reference 16 identifies a shoulder support and the reference 17 identifies a handle gripped by the

training person. The movable mass has been minimized with the illu¬ strated arrangement, in .that it is not necessary to move the flywheel.. relative to the training person.

In the case of the equipment illustrated in Figure 8, a flywheel is mounted adjacent a bed of more conventional design. In this embodiment, the flywheel is mounted adjacent the foot of the bed, so that the pull-belt can be drawn-out in a direction towards the head of the bed. This embodiment also includes a carriage for supporting the feet of the training person. As will be understood, embodiments are con¬ ceivable in which the flywheel, as illustrated in Figure 7, is located beneath the bed. Because of the low movable mass concerned, the equipment illustrated in Figure 7 and 8 can be used for advanced strength-training with high movement speeds.

Figure 9 illustrates an embodiment comprising devices by means of which the training person activates the flywheel or brings influence to bear thereon, these devices preferably being located in the region of the handle part 8 for gripping by the training person and include a safety release arrangement 18 constructed so as to break the con¬ nection between the training person and the flywheel when a given pulling force is exceeded.

The release arrangement of the embodiment illustrated in Figures 9 and 10 includes a spring connection 19 between the training person and the flywheel, wherein a release pin 20 in its non-release position, shown in Figure 9, adopts a latching position in a latching space 21 and, when the pulling force F increases sufficiently, iβ withdrawn successively from said latching space against a spring force, such as to be removed from the latching space when a given pulling force is exceeded, Figure 10, wherein said connection is broken by removal of the spring 19' and pin from the handle part by means of a pull-belt connection 22.

The release pin 20 and the latching space 21 are preferably provided in the handle part.

The reference 23 identifies a manual safety-release catch, shown in

broken lines, operative to open the latch space to an extent such as to enable the release pin to leave the latching space, so as to break said connection.

In Figure 11, the reference 24 identifies a brake arrangement which is operative to retard or stop the flywheel when coiling-in the pull-device 6, the pull-belt 6, with the aid of flywheel energy, said coiling of the belt resulting in an increase in the rotational energy of the flywheel, as a result of pulling-out said pull-device. A stop device 25 is mounted adjacent the pull-device and is intended to be braked/stopped against a damping device 26, therewith distancing the gripping or attachment means, etc. of the training person from the flywheel and restricting coiling of the pull-belt. Also shown is an embodiment in which said braking action is achieved by means of one or more springs 27 and a piston-like part 28 intended for co- action with said springs. In addition to having a safety function, the brake arrangement also functions to enable solely concentric training to be carried out by drawing-out the pull-device.

It is often desired to measure or estimate training or training performance quantitatively and qualitatively, not least for research purposes. The reference 29 in Figure 9 identifies a force or power transducer arranged in the handle part, and more specifically in the seat 30 of the spring 19'.. Although not shown, the equipment will also preferably include a rotation speedometer and pull-off speed transducer, preferably placed close to the flywheel. Although not shown, the equipment will also preferably include devices for register¬ ing, processing and monitoring the training or performance concerned. A number of functions are conceivable in this regard. For instance, the devices for registering, processing, etc. may be constructed to deliver a signal when the speed at which the pull-device is pulled-off (the pull-off speed) varies in an undesirable manner, or when the pulling force falls beneath a predetermined value. The registering devices may alβo be constructed to record work performed (^F« _. ds) and therewith the instantaneous kinetic energy.

The embodiment illustrated in Figure 12 is essentially the same as that illustrated in Figure 7, and has a lever arm 32 pivotally

suspended at its upper end 31. The lower end 33 of the lever arm is connected to the pull-device and is intended to be activated by the training person, preferably between said ends 31, 33. The lever arm is operative to reduce the pulling force on the flywheel in comparison with an arrangement according, for instance, to Figure 7, at sub¬ stantially the same force exerted by the training person.

Figures 13-15 illustrate the use of a combined lever arm and flywheel for different types of training. The joint 34 concerned is placed adjacent the pivoted end 31 of the lever arm. As will be seen from the Figures, this arrangement provides a wide variation in training procedures. Figure 16 illustrates further possibilities of varying the characteristics of the equipment. For instance, the rotational axle of the flywheel, and. therewith the point at which the pulling force F engages the flywheel via the pull-device, can take different positions in relation to the end 33 of the lever arm where the pull- device is mounted adjacent said lever arm 32. The system, according to Figure 16, is determined geometrically by the height h of the rotational axle above or beneath a horizontal line passing through the end 33, and the horizontal distance a of the rotational axel from said end 33.

The length of the lever arm and the prevailing moment arm with which the pull-device attacks the flywheel shall be known. The various characteristics of a training sequence can be determined, with the aid of relatively simple trigonometrical deliberations.

The inventive method and the modus operandi of the inventive equipment will be understood in all essentials from the aforegoing. The muscles concerned are subjected to load by increasing or decreasing the kinetic energy of a flywheel, losses due to friction being very small. The possibility is provided of influencing, inter alia, the pull-off speed, which has a known relationship with muscle contraction speed, by means of the prevailing moment arm through the thickness of the pull-device and/or by varying the moment of inertia. Thus, a belt coil-on phase will immediately follow a belt pull-off phase, since the rotation of the flywheel will continue with the rotational force imparted thereto during the belt pull-off phase.

The characteristics of the equipment can thus be varied in several ways. For instance, the moment of inertia and/or the geometry of the pull-device can be utilized to vary the relationship between the force exerted and the speed of muscle shortening/muscle lengthening, and the positioning of the flywheel can be utilized, inter alia, to the same end. A constant pull-off speed has been considered in the described exemplifying embodiment. A selected speed profile can be predetermined, predescribed, however. According to one embodiment, preferred in many instances, the relationship between the force exerted and the pull-off and coil-on speed v of the pull-device respectively can be influenced to such an extent that the speed of muscle contraction or muscle extension will be substantially constant or follow another conservative speed profile during a substantial part of a training sequence. By conservative is meant here a "speed maintaining" characteristic. Other magnitudes, such as pulling force in the pull-device, can also be predetermined with regard to their profile. In the light of known data with regard to joint movements, such data often specifying the torque occurring in said joints, it is possible to determine, for instance, corresponding pulling forces in the pull-device and training can be adapted to what is known, by predetermining the training conditions with the aid of the possiblities of effecting variations with respect to the characteristics of the equipment.

It will be evident from.the aforegoing that the inventive method and inventive equipment afford considerable advantages of the nature mentioned in the introduction. Important advantages include the possibilities of influencing the muscle-loading characteristics concerned and the relatively small weight and size of said equipment.

The invention has been described in the aforegoing with reference to a number of exemplifying embodiments. It will be understood, however, that other embodiments and minor modifications are conceivable without departing from the concept of the invention.

With regard to the possibiities of changing characteristics by varying the position of the flywheel, it will be understood that this does

not only apply when a lever arm is provided, but also when the pull- device is activated directly by the training person.

Thus, wide variations with respect to belt thickness are conceivable, for instance an alternating increased and decreased thickness along the belt.

With regard to equipment intended for training in a weightless en¬ vironment, such equipment can, in principle, also be used in normal environments where gravity prevails. In this case, the equipment is erected on a floor or like support structure. The arrangements il¬ lustrated in Figures 13-15 need not, in themselves, be configured substantially similar to arrangements according to Figure 12, but may be configured in some other suitable manner. It can be said generally that the manner of arranging the flywheel for different purposes can be varied within wide limits.

The invention is therefore not restricted to the aforedescribed and illustrated embodiments, since variations can be made within the scope of the following Claims.