JP2017035374A - Lower limb muscular strength measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lower limb muscular strength measuring system which can remarkably cut the measurement time compared to the conventional method in which a relation between each muscle group strength and output at the tip of the lower limb is analyzed based on a notion of cosine tuning and it is essential to complete a hexagonal output distribution map through a new output distribution drawing method which exposes inclination of each side of the output distribution.SOLUTION: Two muscle group strengths are the greatest in each side in an output distribution in the functionally effective muscle theory, but a muscle group strength is the largest because sum of squares of the muscular strength becomes the smallest in an output distribution of the cosine tuning. Just one side of the output distribution is measured and the muscular strength of the corresponding muscle group is derived by using the characteristics.SELECTED DRAWING: Figure 5

Description

The present invention relates to a system for measuring muscle strength of the lower limbs as an output distribution map and further calculating muscle strength of each muscle group.

A muscle strength evaluation method using a joint torque measuring device is a simple method that only measures torque generated around a joint, but has high reproducibility of measurement results and is generally used. However, since joint torque is the resultant force of a plurality of muscles around the joint, it is difficult to classify and evaluate individual muscle forces.

As a method of introducing a musculoskeletal model for the evaluation of maximum muscle strength, there is an effective muscle theory by function proposed by Kumamoto et al. In this method, a model in which a plurality of muscles are classified into six muscle groups according to their functions is used by limiting the movement of the limbs to a two-dimensional plane motion. In this model, the range of the maximum force exerted at the limb tip, called output distribution, is defined by a hexagon having geometric features, and individual maximum muscle strength can be evaluated from the measured output distribution chart. Patent Document 1 discloses an invention for measuring an output distribution chart and an invention for obtaining the muscle strength of each muscle group from the output distribution chart. Patent Document 2 discloses an invention that improves the reliability of measurement of an output distribution diagram.

Patent Document 2 also discloses a method for calculating each muscle group force based on cosine tuning from an oval output distribution. Although the output distribution is represented by a hexagon, the actual output has rounded vertices, and there is an error between the measured value and the output distribution. Therefore, the maximum force of each side obtained by output distribution measurement and a method of drawing an oval output distribution by rounding the vertex using a Bezier curve from the vertex of the output distribution have been proposed. In addition, a method for calculating each muscle group force based on cosine rhythm from an oval force distribution in which an error from an actual measurement value is reduced has been proposed. Here, each muscle is based on a so-called cosine rhythm in which the activity is reduced in a cosine shape from the direction in which the muscle activity is maximized, which is called the optimal direction. A method to calculate the combination of muscle strength and optimal direction was proposed.

JP 2000-210272 “Muscle Strength Evaluation Method and System” Japanese Patent Application Laid-Open No. 2015-077397 “Measurement System for Output Distribution of Lower Limb and Muscle Strength Calculation System”

D. Nozaki, et al: "Muscle activity determined by cosine tuning with a non-trivial preferred direction during isometric force exertion by lower limb", J. Neurophysiol, Vol. 93, pp. 2614-2624, 2005

In the conventional effective theory for each function, the maximum force at the lower extremity tip in 4-6 directions is measured, the output distribution is plotted so as to satisfy the geometric characteristics, and an appropriate value is set for the ratio of the paired antagonistic muscle strength. The effective muscular strength by function is obtained using the assumptions such as. Therefore, if there is even one side that is difficult to measure, the whole muscular strength is affected.

In Patent Document 1, each muscle group force is derived from the measured output distribution using an assumption that there is as little error between living bodies as possible, but a deviation from the assumption of the subject is an error of the muscle group force. Furthermore, since the measurement result of one side of the output distribution affects the results of all muscle group forces, if there is even one side of the output distribution that does not measure well, the calculation result of the muscle group force will be affected as a whole. Arise.

The invention described in claim 1 is a lower limb muscle strength measurement system that outputs a hexagonal output distribution map using a 3 to 6 muscle group model for the force exerted at the lower extremity tip.
In the hexagonal output distribution diagram obtained by this lower limb muscle strength measurement system, the inclination of each side of the hexagonal output distribution diagram is based on the minimum sum of the squares of the muscular strength obtained from the concept of cosine tuning, and at each muscle group strength and lower extremity tip. It is obtained from a pseudo matrix indicating the relationship with the output.
In addition, each side of the hexagonal output distribution map is obtained from the measured measured values of the lower extremity tip force and the inclination, and is obtained from the obtained lower extremity tip maximum force of each side by cosine tuning based on the minimization of the sum of the squares of the muscular strength. The maximum strength of the muscle strength is determined.

The invention according to claim 2 is the leg muscular strength measuring device according to claim 1, wherein a back bed and a belt which is fixed to the bed and into which the ankle can be inserted are provided, and the ankle is placed inside the belt. A sensor that senses the force in the biaxial direction exerted by the foot in contact is disposed. The lower limb strength measuring device of the present invention is provided with a controller for guiding the measurement procedure while collecting and processing the output data of the sensor, and a monitor for displaying the data processing result and the measurement procedure. Therefore, even a person unfamiliar with the lower limb strength measurement apparatus of the present invention can be guided to the next measurement procedure sequentially while confirming the progress of the measurement, and can easily complete the measurement.

In the hexagonal output distribution chart of the lower limb tip in the prior art, the opposite side of the hexagon is parallel to each other and has the same length, and the maximum force at the lower limb tip is measured in at least four directions to plot the output distribution. . On each side of the output distribution created by this method, the two muscle group forces are maximum. Moreover, in order to derive the muscular strength of each muscle group, it is necessary to complete the measurement of the output distribution, and if one side of the output distribution is not accurately measured, the entire muscular strength is affected. Furthermore, since some assumption is required when deriving the muscle strength, the muscle strength value depends on the assumption.
However, in the drawing of the present invention, the above assumption is not necessary for deriving each muscle group force. That is, in the present invention, the measurement is performed independently for each side of the hexagonal output distribution, and the maximum value is determined for each side to derive the muscle group force. Therefore, the measurement result at one side does not affect the muscle group strength at the other side. If the measurement objective is achieved by measuring only some muscle group forces, the measurement can be limited to only the required muscle group forces, so it was essential to complete the hexagonal output distribution map. Compared to, measurement time can be greatly reduced.

It is a 3 to 6 muscle model diagram of the two-joint link mechanism of the lower limbs. It is the figure showing the output distribution map based on cosine tuning, and the muscle where the muscular strength becomes the maximum. It is a figure which shows the edge measurement method in output distribution map preparation. It is an output distribution map used by this system, and a flow chart of an effective muscular strength calculation algorithm. Represents a measurement system. It is a figure of a measurement posture. It is a flowchart of a measurement procedure.

The effective muscles by function and the effective muscle strength by function will be described with reference to FIG. For 2 joint movements in the sagittal plane of the lower limb, 3 to 6 muscles classified according to the function for the muscle joint are defined as effective muscles by function. Specifically, one joint muscle group contributing to the first joint 4, one joint muscle group contributing to the second joint 5, and two joint muscle groups contributing to both the first joint 4 and the second joint 5 The torque expressed by each function effective muscle is called the effective muscle strength by function.

The arrows at the lower extremity tip 6 in FIG. 1 indicate the magnitude and direction of the force exerted by the functionally classified muscle groups at the tip, the line segment connecting the knee joint 5 and the tip 6, the hip joint 4 and the knee joint 5. And a line segment connecting the hip joint 4 and the tip 6 are parallel to each other.

Knee and hip joints torque T = [Thip, ^Tknee] the relationship and functional summarizing ^T and the antagonist muscle in a single muscle effective strength _{Tfem = [T 1, T 2} , T 3] T
It expresses. Where G is
It becomes.

Next, the expression force F = [Fx, Fy] ^T , the joint torque T = [Thip, Tknee] ^T and the Jacobian matrix J which is a function of the lower limb posture are expressed by the following equations.

In the cosine tuning by the central nervous system, the muscle strength is distributed so that the sum of the squares of the muscle strength is minimized. Therefore, the effective muscle strength by function Tfem = [T that combines the tip force F = [Fx, Fy] ^T and the antagonist muscle by one muscle. ₁ , T ₂ , T ₃ ] The pseudo-inverse matrix in the relational expression of ^T
Apply. Here, + represents a pseudo inverse matrix. As a result, the sum of squares of muscle strength Tfem ^T Tfem is minimized.

Next, an output distribution based on the cosine tuning shown in FIG. 2 is obtained.
This maximizes the magnitude | F | of the exertion force 7 while satisfying the upper and lower limits of each muscle group force while minimizing the sum of squares of the muscle force due to equality constraints. The side 8 in FIG. 2 is a side obtained by maximizing the display force 7 in a certain direction. Further, if the direction θ of the exerting force is set to 0 to 360 ° and the calculation is performed for all directions, the maximum value of the exerting force in the remaining five directions is obtained, and a hexagon is created. When a certain muscle group reaches the maximum force, the magnitude of the exertion force | F | becomes the upper limit | Fmax |, so that one muscle group force is maximum on each side.

Here, we describe a method for measuring the output distribution from the tip exertion force of the lower limbs and a method for deriving unknown muscle group forces from the results. The name of each side of the output distribution is made to correspond to the name of the muscle having the maximum strength. Slope a _S of s side of the power distribution is = force on the side Fmax_s [| Fmax_s | cosθ, | Fmax_s | sinθ] can be defined by small displacement with respect to the angle θ of.

Next, Fmax_s necessary for calculating a _S is defined. First, the pseudo inverse matrix of [Equation 4] is defined by the following equation.
At this time, the relationship between the force Fmax_s on the output distribution side based on the cosine tuning and the maximum value Tmax_s of the effective muscular strength by function is expressed by the following equation.
Here, the same muscle number is assigned to i of Zx_i and Zy_i (e.g., i = 1 if s = e1 and i = 3 if s = f3).

From the above equation, the magnitude of the force on the output distribution side based on the cosine tuning is as follows.
Accordingly, the minute displacement is expressed by the following equation.
Substituting [Equation 10] into [Equation 6],
Since the slope a _S of the s side of the output distribution based on the cosine rhythm is determined only by the elements of the Jacobian matrices J and G, it depends on the posture of the lower limb but does not depend on the muscle strength. Also, the sides of the antagonistic muscles have the same slope.

A method of determining each side of the output distribution from the measured lower limb tip force F using the slope a _S of the s side of the output distribution determined by the above equation will be described. In this method, as shown in FIG. 3, when a certain side 11 is measured, a straight line having the same inclination as the side 11 with respect to the force measurement point 9 is drawn, and a distance 10 from the center of the straight line is calculated.

When the distance from the center is the largest, it means that the maximum measurement point is on that side of the output distribution map, so the maximum measurement point 12 and the straight line 11 are stored. From these, when the subject exhibits the lower limb tip force, the measurement point Fmax_s on the side of the output distribution farthest from the origin can be determined. And this is implemented with six sides, and a hexagonal output distribution map can be drawn by using the intersection of each straight line as a vertex.

As shown in FIG. 2, the s side of the output distribution based on the cosine tuning is the maximum force Fmax_s at the tip when Ts reaches the upper limit Tmax_s. Therefore, the maximum force Fmax_s by function is obtained by substituting the maximum force Fmax_s constituting the s side into [Equation 8].

In addition, this system has an output distribution drawing program that allows measurement while drawing an output distribution map in real time. The algorithm of the program is as shown in FIG. 4, and first, the value of the force on the two-dimensional plane exhibited at the tip of the lower limb is measured (step S1).

A straight line having three kinds of inclinations is drawn from the side inclination a _S of the output distribution of [Expression 11] through the measurement point. (Step S2) Here, the distance from the center is calculated in order to compare the three straight lines with the sides of the output distribution chart having the same inclination. (Step S3) The distances from the respective origins are compared (Step S4). If the distance is large, a straight line and the maximum measurement point for forming the straight line are stored for use as a new side (Step S5). Otherwise, keep it as before. However, since there are two sides with the same inclination for each straight line, only the side on the same side with respect to the origin is used.

The corresponding effective muscle strength is calculated from [Equation 8] from the maximum measurement point.
An output distribution map can be calculated from the six stored straight lines (step S6). Then, the obtained output distribution map and effective muscle strength are displayed on the monitor screen (step S7), and by repeating this, it is possible to draw the maximum output distribution map and display the maximum effective muscle strength in real time. In this program, if the test subject exerts the maximum force again and becomes larger than the side of the output distribution, a new side is constituted by the value of the force, so that the measurement can always be performed while the program is operating.

An apparatus for drawing an output distribution map and calculating a muscle strength based on the sum of squares of the muscular strength is a device that can measure the tip exertion force by fixing the tip of a lower limb in an arbitrary posture as shown in FIG. It consists of a computer 27 for processing the output distribution drawing program from the value of the sensor 26 and a monitor 27 for displaying the measurement result. A method of displaying the processing result of the computer on the monitor screen is performed using a graphic program interface OpenGL.

The force at the tip of the lower limb needs to be measured with the subject fixed in one posture, but the force sensor 26 is used for the subject to perform measurement in the target posture (the hip joint angle θ1 and the knee joint angle θ2 in FIG. 6). The apparatus which can fix the part which connects the leg leg which has (2) in arbitrary positions in a two-dimensional plane is used.

The apparatus having two degrees of freedom as shown in FIG. 5 fixes the position of the lower limb connection portion at a predetermined position, thereby causing the subject to take a target posture.

In order to facilitate the measurement, the subject displays the magnitude and direction of the force at the tip of the lower limb as an arrow in real time as shown in the monitor screen 25 of FIG. 5 so that the force value can be visually recognized. The current output distribution map obtained in step (6) and the six effective muscle strengths obtained in [Equation 8] are also displayed.

As a result, the subject displays the power distribution map measured so far, along with the magnitude and direction of the force at the tip of the lower limb that he is currently demonstrating, so he exerts the force toward the specified target side It becomes possible.

The flow of measurement is as shown in the flowchart of FIG. First, L1 and L2 of the thigh and crus are measured (step S8), and the posture of the apparatus is adjusted so as to be the target joint angles θ1 and θ2 of the subject (step S9). The subject is fixed in a target posture (step S10), and the force applied to the force sensor is read by making the subject in a weak state. Since it is desired to measure only the exertion force at the tip of the lower limb of the subject, the value of the weak force sensor is read to compensate for gravity in order to remove the weight of the lower limb (step S11).

When this processing is completed, the slope of the side of the output distribution is calculated using [Equation 11], and measurement of the output distribution of the subject is started (step S13). Then, it is confirmed whether or not the subject exerts the maximum force toward the side (step S14), and the measurement is finished (step S15).

In the conventional functional effective theory, the maximum force at the tip of the lower limb in 4-6 directions is measured, the output distribution is drawn so as to satisfy the geometric characteristics, and the effective muscle strength by function is obtained using some assumptions. Therefore, if there is even one side that does not measure well, it affects the overall muscle strength. On the other hand, the method of the present invention does not require an assumption such as setting an appropriate numerical value for the ratio of a pair of antagonistic muscle forces, which was essential in the prior art, and the muscle strength is obtained independently for each side, and one muscle strength is targeted. If so, it is only necessary to measure the maximum force in one direction. Therefore, it is possible to end the measurement only by measuring the maximum force for the side corresponding to the muscle to be measured without measuring all six sides.

This device can be applied to epidemiological studies that require a large number of measurement monitors because it can be measured in a shorter time and with less burden on the subject than conventional measurement devices. This can be used for research to clarify the relationship between For example, it is possible to quantitatively solve problems by performing evaluation and diagnosis based on the results of epidemiological surveys, and effective use can be expected when considering measures such as fall prevention.

DESCRIPTION OF SYMBOLS 1 Lower leg thigh 2 Lower leg lower leg 3 Feet 25 Trunk 28 Slider 29 for moving footrest Slider rotating shaft 30 Measuring device backrest 31 Trunk fixing belt 32 Lower abdominal fixing belt 33 Measuring device seat 34 Handrail

Claims (2)

A lower limb muscle strength measurement system that outputs the force exerted at the lower limb tip in a hexagonal output distribution map of a 3 to 6 muscle group model,
The slope of each side of the hexagonal output distribution map is obtained from a pseudo matrix indicating the relationship between each muscle group force and the output at the tip of the lower limb, based on the minimum sum of squared strengths obtained from the concept of cosine tuning,
Each side of the hexagonal output distribution map is obtained from the measured measurement value of the lower extremity tip force and the inclination, and from each obtained upper extremity force of the lower extremity, the cosine rhythm based on the minimization of the sum of the squares of the muscular strength is used. A lower limb strength measurement system characterized by determining the maximum strength of muscle group strength. The lower limb muscle strength measuring device is a back bed,
A belt fixed to the bed and capable of inserting an ankle,
A sensor that is disposed inside the belt and senses a biaxial force exerted by the foot in contact with the ankle;
A controller for guiding the measurement procedure while collecting and processing the output data of the sensor;
The lower limb muscle strength measurement system according to claim 1, further comprising a monitor that displays the data processing result and the measurement procedure.