MUSCLE FATIGUE DETERMINATION METHOD AND SYSTEM

Abstract

A method for determining a muscle fatigue of a muscle includes a first step of electrostimulating the muscle at different frequencies. A second step of the method includes determining forces developed by the muscle in response to the electrostimulations of the first step. A third step includes determining a muscle fatigue on basis of the forces determined in the second step.

Claims

1. A method of determining a muscle fatigue of a muscle, comprising the steps of: (i) electrostimulating the muscle at different frequencies; (ii) determining forces developed by the muscle in response to the electrostimulations of step (i); and (iii) determining a muscle fatigue on basis of the forces determined at step (ii).

2. The method according to claim 1, wherein the frequencies of step (i) are between 0 and 1000 Hz.

3. The method according to claim 1, wherein: the frequencies of step (i) comprise a first frequency, and a second frequency greater than the first frequency, the first frequency differing from at least 10% of the second frequency; and the forces comprise a first force developed by the muscle in response to the electrostimulation of step (i) at the first frequency, and a second force developed by the muscle in response to the electrostimulation of step (i) at the second frequency.

4. The method according to claim 3, wherein the first frequency is between 0 and 50 Hz and/or the second frequency is between 50 and 200 Hz.

5. The method according to claim 4, wherein the first frequency is about 20 Hz and/or the second frequency is about 100 Hz.

6. The method according to claim 1, wherein step (iii) comprises a comparison of the forces determined at step (ii), and a determination of the muscle fatigue based on this comparison of the forces.

7. The method according to claim 3, wherein step (iii) comprises a computation of a ratio of the first force to the second force, a comparison of the computed ratio to a threshold, and a determination of the muscle fatigue based on this comparison of the computed ratio to the threshold.

8. Determination method according to claim 7, the threshold being defined by F(μ)/F(μ′), wherein: F is a human independent increasing regular function expressing a force developed by a non-fatigued muscle in response to an electrostimulation as a function of a frequency of this electrostimulation; and μ and μ′ are respectively the first and the second frequencies.

9. The method according to claim 7, wherein: the first frequency is between 10 and 40 Hz; the second frequency is between 90 and 120 Hz; and the threshold is between 40 and 90%.

10. The method according to claim 1, wherein: the frequencies are a minimal frequency smaller than 50 Hz; the frequencies comprise a family of frequencies smaller than 200 Hz and integer multiple of the minimal frequency; and step (iii) comprises: a computation of a discrete integral of a function associating, to each frequency of the family, a force determined at step (ii) developed by the muscle in response to the electrostimulation of step (i) at this frequency; and a determination of the muscle fatigue based on the computed discrete integral.

11. The method according to claim 1, wherein the forces are determined in steps (ii) by direct force measurements by means of a strain gauge or a dynamometer.

12. The method according to claim 1, wherein the muscle fatigue determined at step (iii) consists in a long-lasting peripheral muscle fatigue.

13. The method according to claim 1, wherein the muscle is at least a portion of a muscle of a lower limb of a human.

14. The method according to claim 13, comprising, before step (i), the steps of: (a) providing a device comprising: a seat for receiving the human in a seated position, and adapted for being positioned on a horizontal support; a leg support element mechanically coupled to the seat, and adapted for receiving at least part of a leg of the lower limb; and an instrument for measuring the forces at level of the leg support element; (b) positioning the seat on a horizontal support; (c) positioning the human on the seat, in a seated position; and (d) positioning at least part of the leg on the leg support element, wherein the forces are determined at step (ii) by means of the instrument, and wherein the device remains substantially stationary with respect to the horizontal support during an execution of steps (i) and (ii) thanks to a weight of the human exerted at level of the seat.

15. The method according to claim 14, wherein steps (c) and (d) are such that: a foot of lower limb hangs in an air; a whole thigh of the lower limb lies on the seat; and a back of a knee of the lower limb is in contact with a lateral side of the seat.

16. A system for determining a muscle fatigue of a muscle, the system comprising: an apparatus configured to generate an electrostimulation of the muscle at a range of frequencies, the apparatus comprising a controller configured to select any frequency of electrostimulation in the range of frequencies; a device configured to determine a force developed by the muscle in response to an electrostimulation generated by the apparatus; and a logical unit connected to the device and configured to determine a muscle fatigue on basis of forces determined by the device as forces developed by the muscle in response to electrostimulations generated by the apparatus at different frequencies of the range of frequencies.

17. The system according to claim 16, wherein the range of frequencies extends from 0 to 200 Hz, and the logical unit is configured for: carrying out a computation on at least some of the forces, among which: a first force determined by the device as a force developed by the muscle in response to a first electrostimulation generated by the apparatus at a first frequency of the range of frequencies; and a second force determined by the device as a force developed by the muscle in response to a second electrostimulation generated by the apparatus at a second frequency of the range of frequencies, the first frequency being smaller than the second frequency and differing from at least 10% of the latter; and determining the muscle fatigue based on this computation.

18. The system according to claim 16, wherein the device further comprises one of a strain gauge and a dynamometer configured to directly measure the force developed by the muscle in response to an electrostimulation generated by the apparatus.

19. The system according to claim 16, wherein the muscle is at least a portion of a muscle of a lower limb of a human, wherein the device comprises: a seat for receiving the human in a seated position and adapted for being positioned on an horizontal support; a leg support element mechanically coupled to the seat and adapted for receiving at least part of a leg of the lower limb; and an instrument for measuring a force developed by the muscle at level of the leg support element, in response to an electrostimulation generated by the apparatus; and wherein the device is configured for remaining substantially stationary with respect to the horizontal support when forces are developed by the muscle at level of the leg support element, in response to electrostimulations generated by the apparatus at the different frequencies, in response to a weight of the human exerted at level of the seat.

20. The system according to claim 19, wherein the device further comprises at least one of: a mechanical arm or a mechanical frame coupling together the seat and the leg support element, and comprising a connecting member to the instrument either at level of the seat or at level of the leg support element; and at least a position adjustment element for modifying at least one among: one of a position and an orientation of the mechanical arm or the mechanical frame with respect to the seat, and one of a position and an orientation of the leg support element with respect to the mechanical arm or the mechanical frame.

21. The system according to claim 20, wherein the device is in one of: the seat, the leg support element, the instrument, the mechanical arm or the mechanical frame, and the position adjustment element; and the seat, the leg support element, the instrument, and the mechanical arm or the mechanical frame.

Description

DESCRIPTION OF THE DRAWINGS

[0068] The foregoing aspects and many of the attendant advantages of this disclosed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0069] FIG. 1 shows a flow chart of the determination method according to an embodiment of the disclosed subject matter;

[0070] FIG. 2 shows curves of the force developed by a muscle in response to an electrostimulation at a given frequency as a function of this frequency; and

[0071] FIG. 3 shows a device of a system for determining a muscle fatigue of a muscle according to an embodiment of the disclosed subject matter.

[0072] The drawings in the figures are not scaled. Similar elements can be assigned by similar references in the figures. In the framework of the present document, identical or analogous elements may have the same references. The presence of reference numbers in the drawings cannot be considered to be limiting, in particular if these numbers are indicated in the claims.

DETAILED DESCRIPTION

[0073] Description of embodiments of the disclosed subject matter are hereafter described with references to figures, but the disclosed subject matter is not limited by these references. In particular, the drawings or figures described below are only schematic and are not limiting in any way.

[0074] As illustrated in FIG. 1, the muscle fatigue determination method of the disclosed subject matter proposes to shortly electrostimulate the muscle at at least two different frequencies μ.sub.1, μ.sub.2, μ.sub.3, . . . , μ.sub.n, for a number of electrostimulations n≥2, to determine, preferably to measure, the forces F.sub.1, F.sub.2, F.sub.3, . . . , F.sub.n developed by the muscle in response to each of the electrostimulations respectively at each frequencies μ.sub.1, μ.sub.2, μ.sub.3, . . . , μ.sub.n, and to determine a muscle fatigue of the muscle based on the so determined forces F.sub.1, F.sub.2, F.sub.3, . . . , F.sub.n. Such a determination can be performed for example by ratio computation of two forces and/or discrete integral computation, and comparison of at least one of these computations to at least one expected value, as fully explained in any of the embodiments of paragraph [0014] to [0024].

[0075] FIG. 2 illustrates graphs of the force developed by the muscle in response to the electrostimulations as a function of the frequency. The force is read on the vertical axis 82 (in Newton), and the frequency is read on the horizontal axis 81 (in Hertz). The curve 61 corresponds to the graph of a theoretical expected function F expressing a force developed by a non-fatigued muscle in response to such electrostimulations as a function of the electrostimulation frequencies. The curve 62 represents a continuous and regular extension of dots cloud corresponding to the points (μ.sub.1, F.sub.1), (μ.sub.2, F.sub.2), (μ.sub.3, F.sub.3), . . . , (μ.sub.n, F.sub.n) as measured for a fatigued muscle. It is noticed that the space between the two curves 61 and 62 is greater for low frequencies (e.g. between 10 and 40 Hz), than for high frequencies (e.g. greater than 90 Hz). This space corresponds to differences 71 and 72 between measured forces for the muscle and expected forces from function F for a non-fatigued muscle respectively at low and high frequencies. In particular, the difference 72 is so small that it can be assumed that the two curves 61 and 62 are substantially the same for high frequencies. If it is assumed that the ratio F(20)/F(100) is known to be about 65%, it is then sufficient to measure the forces F.sub.1 and F.sub.2 developed by the muscle in response to electrostimulations at μ.sub.1=20 Hz and μ.sub.2=100 Hz respectively for determining the muscle fatigue, advantageously without the need for knowing a specific human dependent curve for the same muscle but non-fatigued. Indeed, as F.sub.2 corresponds substantially to F(100), the measure of F.sub.2 corresponds in some sense to a reference measure while the measure of F.sub.1 allows to highlight a divergence with expected value in term of ratio to F.sub.2. In particular, when the ratio F.sub.1/F.sub.2 differs significantly from 65%, a muscle fatigue is deemed to be determined according to the method and can be quantified. This value of about 65% for the ratio is indicative and not limitative. Other values such as about 60%, or about 70% or about 80% can be convenient depending on the considered function F.

[0076] An advantageous device 1 for measuring the forces F.sub.1, F.sub.2, F.sub.3, . . . , F.sub.n for a lower limb muscle is illustrated in FIG. 3. It is part of the muscle fatigue determination system according to various embodiments of the disclosed subject matter. The device 1 comprises a seat 10 comprising a smooth portion 11 for receiving the human in a seated position, a rigidity frame 12 for the smooth portion 11, and positioning lower members 13 for removable positioning the seat on a horizontal support. The rigidity frame 12 contribute to the rigidity of the seat, in particular at level of the smooth portion 11 which can be made of a flexible and/or padded material for the human comfort. The positioning lower members 13 can be adjustable in height from 0 to 1/20 meter below the smooth portion 11 for improving the stability of the seat 10 on the horizontal support. They can be suction cups. They can have protected extremities. They are not arranged for being placed on a ground because another part of the device 1 extend much lower than them. The device 1 comprises a leg support element 3 fixed to the seat 10 by means of a mechanical frame 2 as illustrated. The leg support element 3 includes a semi-cylindrical hollow portion for receiving and at least partially immobilizing a lower part of the lower limb leg. It integrates an instrument 4 for measuring a force developed by the muscle at level of the leg support element 3, in particular in response to the electrostimulations. The mechanical frame 2 comprises a connecting member 5 to the instrument 4 at level of the leg support element. In particular, in the illustrated configuration of FIG. 3, the instrument 4 is a strain gauge fixed along a first direction in sandwich between the leg support element 3 and the connecting member 5. The strain gauge comprises a connecting extremity 41 for connecting the device 1 with a non-represented logical unit of the determination system of the disclosed subject matter. The latter is configured for determining a muscle fatigue on basis of at least some of the forces F.sub.1, F.sub.2, F.sub.3, . . . , F.sub.n determined by the device 1 in response to the electrostimulations at each of the frequencies μ.sub.1, μ.sub.2, μ.sub.3, . . . , μ.sub.n. The connecting member 5 also comprises a position adjustment element 51 for changing the position the leg support element 3 and the instrument 4 with respect to the mechanical frame 2, along a second direction d which is perpendicular to the above-mentioned first direction.

[0077] In other words, the disclosed subject matter relates to a determination method of a muscle fatigue based on information arising from forces developed by the muscle in response to electrostimulations of the latter at different frequencies. The disclosed subject matter also relates to a system for implementing the method.

[0078] The present disclosure has been described in relation to the specific embodiments which have a value that is purely illustrative and should not be considered to be limiting. The skilled person will notice that the disclosed subject matter is not limited to the examples that are illustrated and/or described here above. The disclosed subject matter comprises each of the new technical characteristics described in the present document, and their combinations.

[0079] While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosed subject matter.