Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
A METHOD AND A MEASURING DEVICE FOR THE IDENTIFICATION OF THE LACTIC-ACID THRESHOLD
Document Type and Number:
WIPO Patent Application WO/2006/078207
Kind Code:
A1
Abstract:
The invention relates to a method for the identification of the lactic-acid threshold, which comprises the steps of non-invasively measuring changes in the arterial carbon-dioxide content of a living creature, subjecting said living creature to work at different workloads, measuring, as well as varying in a controllable way, the above-mentioned workload of the same living creature, determining the workload at the point of inflection where the carbon-dioxide content of the arterial blood begins to decrease as a consequence of increased workload, by measuring changes in the above-mentioned arterial carbon-dioxide content and said workload, and of relating said point of inflection to the lactic-acid threshold. The invention relates furthermore to a measuring device for the identification of the lactic-acid threshold, which comprises a first measuring unit (1) for the non-invasive measurement of changes in the arterial carbon-dioxide content of a living creature under workload and a second measuring unit (2) for the measurement of said workload.

Inventors:
Folke, Mia (. Solrosgatan 63, Västerås, Västerås, S-722 45, SE)
Application Number:
PCT/SE2006/000057
Publication Date:
July 27, 2006
Filing Date:
January 16, 2006
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
Folke, Mia (. Solrosgatan 63, Västerås, Västerås, S-722 45, SE)
International Classes:
A61B5/00
Domestic Patent References:
2004-08-19
Foreign References:
US6554776B12003-04-29
US6176241B12001-01-23
DE10248500A12004-05-19
Attorney, Agent or Firm:
Mattsson, Mikael (Groth & Co KB, Box 6107, Stockholm, S-102 32, SE)
Download PDF:
Claims:
CLAIMS
1. Method for the identification of the lacticacid threshold, characterized in that it comprises the steps of: noninvasively measuring changes in the arterial carbondioxide content of a living creature, subjecting said living creature to work at different workloads, measuring, as well as varying in a controllable way, the abovementioned workload of said living creature, determining the workload at the point of inflection where the carbon dioxide content of the arterial blood begins to decrease as a consequence of increased workload, by measuring changes in the abovementioned arterial carbondioxide content and said workload, and relating said point of inflection to the lacticacid threshold.
2. Method for the measurement of the lacticacid threshold according to claim 1 , characterized in that the noninvasive measurement is made in the exhalation air.
3. Method for the measurement of the lacticacid threshold according to claim 2, characterized in that the noninvasive measurement in the exhalation air measures changes in the endtidal carbondioxide content.
4. Method for the measurement of the lacticacid threshold according to claim 2, characterized in that the noninvasive measurement in the exhalation air measures changes in the molecular weight of the exhalation air.
5. Method for the measurement of the lacticacid threshold according to claim 1, characterized in that the noninvasive measurement is made transcuta neously.
6. Measuring device for the identification of the lacticacid threshold, characterized in that it comprises a first measuring unit for the noninvasive measure 9 ment of changes in the arterial carbondioxide content of a living creature under workload and a second measuring unit for the measurement of said workload.
7. Measuring device according to claim 6, characterized in that it comprises an analysis unit that communicates with said first and second measuring unit and is arranged to be able to determine and indicate the point of inflection where the carbondioxide content of the arterial blood begins to decrease in a living creature, as a consequence of increased workload, and to determine and indicate the workload at said point of inflection.
8. Measuring device according to claim 6, characterized in that said first measuring unit is arranged to measure changes in the carbondioxide content of the exhalation air.
9. Measuring device according to claim 8, characterized in that said first measuring unit is arranged to measure changes in the endtidal carbondioxide content.
10. Measuring device according to claim 7, characterized in that said first measuring unit is arranged to measure changes in the transcutaneous carbon dioxide content.
11. Measuring device according to claim 8, characterized in that said first measuring unit is arranged to measure changes in the molecular weight of the exhalation air.
Description:
2 prise a plurality of steps of preparations before sampling, sampling and analysis of the samples.

The lactic-acid threshold test is a steady-state test of increasing workload. Frequently, the test takes place in special laboratories, but may also be made during the sport activity in question on the arena. Each workload lasts for some minutes, so that, among other things, the heart rate and the lactic-acid content are stabilized (steady state). In the end of each workload, the lactic-acid level in the blood is measured.

There are different definitions of the lactic-acid threshold. One definition is the workload where the lactic-acid concentration in the blood is 4 mmol/l. This level is called OBLA, Onset of Blood Lactate Accumulation, but also other absolute lactic-acid levels are used. The lactic-acid concentration in the blood is constant or increases slowly in the beginning of the lactic-acid threshold test and thereafter it increases strongly. The point of inflection where the lactic-acid concentration begins to increase strongly is called "the individual anaerobic threshold", IAT, and corresponds to the maximal workload where the production of lactic acid and the disposal of the same are in equilibrium. Exactly how this point of inflection should be read is a subject of dispute, and it is difficult to see it clearly in certain persons. Said point of inflection, IAT, may occur at workloads both above and below the lactic-acid level of 4 mmol/l. Frequently, well-trained persons have their IAT at low lactic-acid concentrations. Studies have shown that athletes can work on levels that correspond to IAT for a long time. This is not possible at said threshold OBLA unless the point of inflection, IAT, occurs at lactic-acid concentrations of 4 mmol/l or more. This shows that it is IAT that is of interest for an athlete and that the absolute value of the lactic-acid level is of secondary importance to the individual athlete. Thereby, IAT is another definition of the lactic-acid threshold and the definition of the lactic-acid threshold that is used in the present invention.

The lactic-acid threshold is correlated to workload. The athlete uses the knowledge of the workload at the lactic-acid threshold to control his or her work- load during training and competition in order to avoid to "overtax one's strength" by too much lactic acid or training and competing at too low a workload, whereby maximum result is not attained.

The lactic-acid threshold may also be used to evaluate different methods of training. The lactic-acid threshold changes when training, but it also matters

3

which groups of muscles that are involved, quantity of glucose and free fatty acids in the blood and on which altitude the athlete makes his or her performance. This makes it interesting to verify the lactic-acid threshold in the kind of sport in question, on the day in question. Therefore, it is desirable to use a method and a measuring device that give secure and stable measurements and that can be carried out fast and easily in any environment.

WO 2004012577 discloses a respiratory analyzer, which by means of the measurement of respiratory gases and flows can calculate the lactic-acid threshold of a living creature. WO 9522929 discloses a method and a device for the determination of the lactic-acid threshold of a living creature. By establishing a relation comprising the variables of the respiratory minute volume, as well as the oxygen and carbon- dioxide contents of the respiratory minute volume in the exhalation and inhalation air, respectively, a curve can be plotted. The value of the lactic-acid threshold for a living creature is then obtained on the point of the curve where the derivative is equal to zero.

US 6387053 discloses a respiratory analyzer, which by means of the oxygen and carbon-dioxide concentration can determine the lactic-acid threshold by means of a mathematical model. However, there are a number of disadvantages of the methods and the devices mentioned above. Since a plurality of parameters are required to establish the lactic-acid threshold of a living creature and the value of the lactic-acid threshold has to be calculated, the risk that the calculated value deviates from the actual value increases. In order to measure the requisite parameters, a plurality of sen- sors are in addition required, which involves a complicated procedure and an expensive and bulky construction.

Object of the Invention

The object of the present invention is to provide a method and a device that solve the problems mentioned above and accordingly suggests an improved method and a measuring device for the measurement of the lactic-acid threshold of the kind described.

4

Summary of the Invention

The above object is attained by the present invention such as it is defined in the independent claims 1 and 6. Suitable embodiments of the invention are defined in the dependent claims. Thus, in claim 1 , according to the present invention, there is defined a method for the identification of the lactic-acid threshold, the method comprising the steps of non-invasively measuring changes in the arterial carbon-dioxide content of a living creature, said living creature carrying out work at different workloads, measuring, as well as varying in a controllable way, the above-mentioned work- load of said living creature, determining the workload at the point of inflection where the carbon-dioxide content of the arterial blood begins to decrease as a consequence of increased workload, by measuring changes in the above-mentioned arterial carbon-dioxide content and said workload, and of relating said point of inflection to the lactic-acid threshold. In accordance with the invention, the advantage is gained to be able to relate the lactic-acid threshold to the point of inflection where the carbon-dioxide content of the blood decreases because of increased workload, whereby said lactic-acid threshold can be verified clearly and certainly. Since the measurements are made non-invasively, no handling of blood is required, which is favourable from a point of view of the risk of infection. Furthermore, the method gives the possibility of making measurements during work, without stopping for the sampling, whereby a user directly can get feedback of the measured values. The denomination user refers to the person that is using the equipment to make the measurements on himself or herself, or on said living creature. In addition, the method is simple and requires no previous knowledge to be effected, which also allows a person to carry out the lactic-acid threshold test by himself or herself. Furthermore, there is the possibility of carrying out the lactic-acid threshold test on an animal that is subjected to a certain work on, for instance, a running belt. Since the method only requires a point of inflection and not a correct measured value, the measuring unit to measure changes in the arterial carbon-dioxide content of a living creature does not need to be calibrated before use.

According to an advantageous embodiment of the invention, the non-invasive measurement can be carried out in the exhalation air. By the fact that only one parameter, the carbon-dioxide content of the exhalation air, is required in

5 order to identify the lactic-acid threshold, economical advantages are gained because only one sensor is required to measure changes in said carbon-dioxide content of the exhalation air. According to an alternative, the non-invasive measurement in the exhalation air can measure changes in the end-tidal carbon-dioxide content. According to an additional alternative, the non-invasive measurement in the exhalation air can measure changes in the molecular weight of the exhalation air.

According to an additional advantageous embodiment, the non-invasive measurement can be carried out transcutaneous^. Thereby, said living creature does not need to breathe in a mouthpiece or another type of collection unit for the collection of exhalation air.

In claim 6 according to the present invention, there is defined a measuring device for the identification of the lactic-acid threshold, characterized in that it comprises a first measuring unit for the non-invasive measurement of changes in the arterial carbon-dioxide content of a living creature under workload and a second measuring unit for the measurement of said workload.

In accordance with the invention, the advantages explained above are gained.

According to an advantageous embodiment of the invention, the measur- ing device can comprise an analysis unit that communicates with said first and second measuring unit and is arranged to be able to determine and indicate the point of inflection where the carbon-dioxide content of the blood begins to decrease in a living creature, as a consequence of increased workload, and to determine and indicate the workload at said point of inflection. Thereby, the lactic- acid threshold can be related directly to the workload. This also means that the device becomes more user-friendly, as the point of inflection does not need to be found manually.

Brief Description of the Drawings The invention will now be described closer by means of embodiment examples and reference being made to the accompanying drawings, where:

Fig. 1 shows a block diagram of the measuring device according to the present invention, and

6

Fig. 2 shows, in a graph, an example of the relationship between arterial carbon-dioxide content, in this case the end-tidal carbon-dioxide content, and the workload, in this case the heart rate of a living creature.

Detailed Description of the Drawings

In Figs. 1-2, there are shown a first embodiment of the present invention applied to a measuring device for the identification of the lactic-acid threshold. However, it should be directly emphasized that even if several embodiments have been shown and described, it should be appreciated that many more modifications can made, without departing from the scope of the present invention.

The measuring device in Fig. 1 comprises a first measuring unit 1 and a second measuring unit 2. In this embodiment, changes in the molecular weight of the exhalation air is measured directly in the air flow of the exhalation air from a living creature by said first measuring unit 1. In order to avoid moisture and tem- perature variations in said measuring unit 1 , the exhalation and inhalation air, respectively, pass a moisture filter 5 and a heat exchanger 6, respectively. The moisture filter 5 and the heat exchanger 6 may be a common unit or two separate units. Said second measuring unit 2 measures the workload of said living creature. In this embodiment, the workload in the form of the heart rate is measured, but of course the workload can be measured in many different ways, for instance, in generated power, velocity, lap time, or as perceived exertion or speed.

Furthermore, the measuring device comprises an analysis unit 3 connected to the measuring units 1 , 2 mentioned above, as well as to a display 4, either via cable or wireless. Said analysis unit 3 is arranged to be able to deter- mine and indicate the point of inflection where the carbon-dioxide content of the blood decreases because of increased workload of the living creature, by means of values measured by said first measuring unit 1 , as well as possibly determine and indicate the workload, which is measured by said second measuring unit 2, at said point of inflection. The result is transferred from the analysis unit 3 to said display 4. On the display 4, said point of inflection and said measured workload becomes visible to a user, who thereby can control the training or the competition according to the same values. The display 4 may of course also show, for instance, an index of the arterial carbon-dioxide content or the measured point of inflection in a graph, so that direct feedback is obtained. Said first measuring unit 1

7 may of course be used separately and give direct feedback to the user. When the point of inflection takes place, i.e., when the carbon-dioxide content of the arterial blood decreases because of increased workload, said analysis unit 3 may give a signal to the user. The analysis unit 3 stores the results so that they can be proc- essed afterwards directly in said analysis unit 3 or in a computer that is connected to said analysis unit 3, either via cable or wireless.

Fig. 2 shows a graph of how the arterial carbon-dioxide content varies with the workload of a living creature. By measuring the arterial carbon-dioxide content during work, the lactic-acid threshold can be verified as the workload where the arterial carbon-dioxide content begins to decrease because of increased workload. In Fig. 2, the X-axis indicates the heart rate as the current workload, but of course the workload may also be related to other measurands, such as, for instance, generated power, velocity, lap time or as perceived exertion or speed, dependent on what is desired to be used to verify optimum workload. The Y-axis in Fig. 2 indicates the arterial carbon-dioxide content measured as the end-tidal carbon- dioxide content of the exhalation air. The arterial carbon-dioxide content, which can be measured breath by breath or continuously, may of course also be related to other measurands such as, e.g., the molecular weight in the exhalation air. This is possible when the amount of carbon dioxide increases in the exhalation air upon anaerobic work. The lactic-acid threshold, i.e., the point of inflection where the carbon-dioxide content of the blood begins to decrease because of increased workload, is marked in Fig. 2 by a dashed line.

In order to be able to measure the lactic-acid threshold, a living creature is subjected to a steady-state test starting at a low load, which is increased until the living creature passes said point of inflection. The workload may of course be varied in another way than intensification, e.g., be raised and lowered iteratively in order to find the workload where the arterial carbon-dioxide content begins to fall because of increased workload. In order to get exact values, each workload preferably lasts for some minutes until steady state appears. In order to obtain a value as accurate as possible of the workload at the lactic-acid threshold, it is important to measure at several different workloads.