Biosensors

Abstract

This provides a biosensor that can detect the movement of individual muscles and is easy to install and configure. [Solution] The biosensor (100) is attached to a living body as a test subject when in use. The biosensor comprises a light-emitting unit (11) that irradiates light onto the living body, a light-receiving unit (12) that receives reflected light from the muscles of at least one part of the living body, and an output unit (13) that outputs information regarding the deformation of the muscles of one part based on a detection signal from the light-receiving unit corresponding to the received reflected light.

Description

Technical Field

[0001] The present invention relates to a biosensor, and particularly to the technical field of biosensors that measure the state of a living body using optical technology.

Background Art

[0002] As this type of device, for example, a device that exhibits the muscle strength corresponding to the minimum value of the oxygen saturation in the blood of the muscle of a subject estimated from a correlation table showing the correlation between oxygen saturation and the exerted muscle strength has been proposed (see Patent Document 1).

[0003] Alternatively, a device that is fixed to the arm of a subject by a wearing band, has a pressing member that changes according to the contraction state of a muscle, and outputs a detection signal corresponding to the movement displacement of the pressing member has been proposed (see Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in Patent Document 1, since the oxygen saturation that decreases (i.e., a change appears) due to muscle contraction for a certain period is monitored, there is a technical problem that instantaneous muscle contraction cannot be detected. In the technology described in Patent Document 2, since the wearing band is wound around the arm of the subject, for example, a contraction combining the movement of the prime mover and the movement of the antagonist muscle is detected, and there is a technical problem that the contraction of each individual muscle cannot be detected.

[0006] Furthermore, electromyographs, which measure the electrical potential of the body surface, have technical problems such as requiring time and care to attach the sensors, and needing a high-precision detection circuit to detect weak electrical potentials.

[0007] This invention has been made, for example, in view of the above-mentioned problems, and aims to provide a biosensor that can detect the movement of individual muscles and is easy to attach and configure. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a biosensor that is attached to a living body and comprises: a plurality of light-emitting units that irradiate the living body with light; a plurality of light-receiving units paired with each of the plurality of light-emitting units to receive reflected light from a plurality of muscles of the living body; and an output unit that outputs information regarding the deformation of the plurality of muscles due to contraction and extension of the muscles based on detection signals from the plurality of light-receiving units corresponding to the amount of reflected light, wherein the plurality of light-emitting units and the plurality of light-receiving units are arranged on a flexible member.

[0009] The effects and other benefits of the present invention will be revealed from the embodiments described below. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing an overview of the biosensor related to the example. [Figure 2] This is a diagram illustrating the measurement principle of the biosensor according to the embodiment. [Figure 3] This is an example of a biological signal. [Figure 4] This is an example of the detection signal before and after filtering. [Figure 5] This is an example of the output of the biosensor according to the embodiment. [Figure 6] This is an example of measurement results for each of several muscles. [Figure 7] This figure compares the output of the biosensor according to the embodiment with the output of the electromyogram. [Modes for carrying out the invention]

[0011] Embodiments relating to the biosensor of the present invention will be described.

[0012] The biosensor according to this embodiment is a biosensor attached to a living body as a subject, and comprises a light-emitting unit that irradiates light onto the living body, a light-receiving unit that receives reflected light from the muscles of at least one part of the living body, and an output unit that outputs information regarding the deformation of the muscles of one part based on a detection signal from the light-receiving unit corresponding to the received reflected light.

[0013] The biosensor is attached to a living body when in use. Here, the biosensor may be attached to the living body by a dedicated attachment member such as a band, or by medical paper tape, for example.

[0014] The light-emitting unit emits light with a wavelength of, for example, 660 μm to 940 μm (red light to infrared light). The wavelength of the light emitted from the light-emitting unit is not limited to the above wavelengths and may be set appropriately depending on the object being measured. The light-receiving unit receives reflected light from at least one muscle tissue in a living organism.

[0015] For example, an output unit equipped with memory, a processor, etc., outputs information regarding the deformation of a muscle in a particular area based on a detection signal from a light receiving unit.

[0016] Specifically, when a muscle in one area contracts, the physical distance between the light-emitting and light-receiving parts decreases and the muscle pressure increases compared to when the muscle is stretched (relaxed). As a result, when a muscle in one area contracts, the amount of reflected light received by the light-receiving part increases compared to when the muscle is stretched (i.e., the signal level of the detection signal increases).

[0017] Therefore, the output unit outputs information indicating the signal level of the detection signal, for example, as information regarding the deformation of a muscle in a particular area.

[0018] According to the biological sensor according to this embodiment, information regarding the deformation of a muscle is output based on the reflected light from the muscle at a certain site, so that even an instantaneous change in the muscle at a certain site can be detected. In addition, since the light receiving unit receives the most reflected light from the muscle closest to the biological sensor (here, the muscle at a certain site), the detection signal from the light receiving unit is dominated by the influence of the deformation of the muscle closest to the biological sensor. That is, according to the biological sensor, only the deformation of the muscle at a certain site can be detected.

[0019] Furthermore, since the biological sensor optically detects the deformation of the muscle, the structure can be simplified and the handling can be facilitated as compared with an electromyograph that measures the weak electric potential on the body surface.

[0020] In one aspect of the biological sensor according to this embodiment, the output unit determines that an increase in the signal level of the detection signal is the contraction of the muscle at a certain site.

[0021] According to this aspect, the deformation of the muscle at a certain site can be detected relatively easily, which is very advantageous in practical use.

[0022] In another aspect of the biological sensor according to this embodiment, the light emitting unit and the light receiving unit are arranged on a flexible member.

[0023] According to this aspect, the distance between the light emitting unit and the light receiving unit on the member can be kept constant, so that the measurement result by the biological sensor can be made reproducible and the biological sensor can be easily attached to the living body.

[0024] In another aspect of the biological sensor according to this embodiment, it further includes attenuation means for attenuating a signal component having a period longer than a predetermined period included in the detection signal.

[0025] Research by the present inventor has revealed that the detection signal includes the influence of physiological responses, such as changes in cardiac output. The influence of physiological responses included in the detection signal (i.e., the component of the signal related to physiological responses) is longer than the fluctuation period of the detection signal caused by changes in muscle.

[0026] Therefore, in this embodiment, the attenuation means attenuates signal components with a period longer than a predetermined period included in the detection signal. Accordingly, this embodiment allows for the effective detection of muscle deformation in a single area. [Examples]

[0027] An embodiment of the biosensor of the present invention will be described with reference to the drawings. In the following embodiment, it is assumed that the subject is pedaling a bicycle.

[0028] The configuration of the biosensor according to the embodiment will be described with reference to Figure 1. Figure 1 is a block diagram showing an overview of the biosensor according to the embodiment.

[0029] In Figure 1(a), the biosensor 100 is configured to include a light-emitting unit 11, a light-receiving unit 12, a calculation unit 13, and a display unit 14.

[0030] The light-emitting unit 11 has a light-emitting element such as an LED (Light Emitting Diode). The wavelength of the light emitted from the light-emitting unit 11 may be set appropriately, for example, depending on the object to be measured.

[0031] The light-receiving unit 12 has a light-receiving element such as a PD (photodioe). The light-emitting unit 12 receives at least reflected light from the muscle of the living organism being measured. Here, "reflected light" typically refers to light scattered or reflected by the living organism. The light-receiving unit 12 outputs a biological signal, which is a "detection signal corresponding to the received reflected light" according to the present invention.

[0032] As shown in Figure 1(b), the calculation unit 13 is configured to include a bandpass filter 131 and a normalization unit 132. Details of the operation of the calculation unit 13 will be described later.

[0033] Here, the measurement principle of the biosensor 100 will be explained with reference to Figure 2. Figure 2 is a diagram illustrating the measurement principle of the biosensor according to the embodiment.

[0034] In Figure 2, first, the light-emitting unit 11 and the light-receiving unit 12 of the biosensor 100 are attached to the part of the subject that includes the muscle to be measured. Note that the light-emitting unit 11 and the light-receiving unit 12 do not necessarily have to be attached directly to the subject's skin or via a gel or cream; they may be attached over clothing, such as skin-hugging clothing, as long as it allows the movement of the muscle to be measured to be visible.

[0035] It is preferable that the light-emitting unit 11 and the light-receiving unit 12 are arranged on a flexible member, as shown in Figure 2(a) (Note that the flexible member is not shown in Figure 2(b) for the sake of explanation). However, the light-emitting unit 11 and the light-receiving unit 12 do not necessarily have to be arranged on a flexible member. The "flexible member" in the embodiment is an example of a "flexible member" according to the present invention.

[0036] When a muscle contracts, myosin filaments pull actin filaments towards the center, causing the myosin and actin filaments to overlap deeply. Compared to the relaxed state of the muscle, the muscle fibers become denser and the entire muscle takes on a more rounded shape (see Figure 2(b)).

[0037] When a muscle contracts, as shown in Figure 2, the light-emitting unit 11 and the light-receiving unit 12 move closer to each other, and the angle between the normal to the light-emitting surface of the light-emitting unit 11 and the normal to the light-receiving surface of the light-receiving unit 12 changes (in Figure 2, it changes from "θ1" to "θ2"). As a result, the optical distance from the light-emitting unit 11 to the light-receiving unit 12 decreases. Therefore, the amount of light emitted from the light-emitting unit 11 and scattered or reflected by the muscle being measured that enters the light-receiving unit 12 increases.

[0038] In addition, during muscle contraction, intramuscular pressure increases and blood flow to the active muscle is restricted, so the amount of light absorbed by the blood is reduced compared to when the muscle is relaxed. Therefore, during muscle contraction, the amount of light scattered or reflected by the muscle being measured increases.

[0039] In other words, there is a correlation between the amount of light detected by the light-receiving unit 12 (i.e., the signal level of the output biological signal) and the changes in the muscle being measured.

[0040] When a subject is pedaling a bicycle, the muscles in the subject's legs contract and relax periodically. When the biosensor 100 is attached to the subject's leg, the biosignal output from the light-receiving unit 12 will have a period synchronized with pedaling, as shown in Figure 3, for example.

[0041] Incidentally, biosignals include the influence of physiological responses, such as changes in cardiac output. Specifically, as shown in Figure 4(a), the entire biosignal fluctuates up and down with a relatively long period due to physiological responses. Note that the biosignal shown in Figure 4 shows fluctuations over a period of approximately 10 minutes.

[0042] Therefore, in this embodiment, the bandpass filter 131 of the calculation unit 13 (see Figure 1(b)) attenuates components caused by physiological responses included in the biological signal. As a result, the signal output from the bandpass filter 131 is as shown in Figure 4(b).

[0043] The filtered signal output from the bandpass filter 131 is normalized by the normalization unit 132 (see Figure 1(b)). Specifically, the normalization unit 132 normalizes the filtered signal by setting the maximum signal amplitude of the filtered signal as the maximum muscle contraction state and the minimum signal amplitude as the non-contraction state of the muscle.

[0044] Next, the normalization unit 132 outputs information indicating the time variation of the muscle contraction rate, for example, by setting the maximum value of the normalized signal as 100% muscle contraction rate and the minimum value of the normalized signal as 0% muscle contraction rate. The "information indicating the time variation of the muscle contraction rate" in this embodiment is an example of "information regarding the deformation of a muscle in a single area" according to the present invention.

[0045] In this embodiment, the crank angle of the bicycle being pedaled by the subject is detected by the crank angle sensor 20 (for example, a pedaling monitor). The display unit 14 of the biosensor 100 uses the crank angle detected by the crank angle sensor 20 to display, for example, information showing the time variation of the muscle contraction rate output from the calculation unit 13, in correspondence with the crank angle (see Figure 5).

[0046] Displaying the data in this way allows subjects to understand the changes in muscle contraction rate during pedaling, which is highly advantageous in practical terms.

[0047] Furthermore, the biosensor 100 is not limited to a pair of light-emitting units 11 and light-receiving units 12, but may also include multiple pairs of light-emitting units and light-receiving units. With this configuration, it is possible to detect the changes in the contraction rate of each of several muscles used in the pedaling motion of a bicycle, such as the rectus femoris (front of the thigh), biceps femoris (outer hamstrings), gluteus maximus (buttocks), semitendinosus (medial hamstrings), tibialis anterior (front of the calf), and gastrocnemius (posterior of the calf) (see Figure 6).

[0048] As a result, it is possible to perform tasks such as evaluating the differentiation of muscle use during pedaling and detecting unintended eccentric contractions (lengthening muscle contractions), which is highly advantageous in practical applications.

[0049] (Effects of this embodiment) Among the technologies capable of evaluating the state of muscle movement, electromyography (EMG) is considered the most practical. Therefore, the measurement results of the biosensor 100 according to this embodiment and the measurement results of an EMG are compared with reference to Figure 7. The graphs shown in Figure 7 all show the fluctuation in muscle contraction rate for one cycle (i.e., 360 degrees of crank angle).

[0050] While I will omit a detailed explanation of the principle of electromyography (EMG), EMG detects action potentials resulting from commands from the brain to contract muscles. In contrast, the biosensor 100, as described above, optically detects changes in muscles. In other words, the biosensor 100 detects the results of changes in muscles. Thus, although the measurement principles of EMG and the biosensor 100 are different, as shown in Figure 7, the measurement results for each muscle are very similar.

[0051] Therefore, the measurement results obtained by the biosensor 100 are reasonable and can be said to have a measurement accuracy comparable to that of an electromyograph. In other words, the biosensor 100 can measure instantaneous muscle changes for each muscle with high accuracy, just like an electromyograph.

[0052] However, since electromyographs measure the action potential of muscles, they can measure muscle contractions that do not involve muscle deformation, such as isometric contractions. On the other hand, the biosensor 100 measures muscle contraction from changes in the amount of light received due to changes in the muscle, and therefore cannot measure muscle contractions that do not involve muscle deformation.

[0053] In particular, the biosensor 100 can measure changes in the muscle if the light-emitting unit 11 and the light-receiving unit 12 can be physically fixed to the area including the muscle to be measured, and it is very easy to handle. In addition, the biosensor 100 only needs to be able to detect a signal at a speed similar to that of the subject's movement (e.g., 10 Hz or less), so the circuit configuration and other aspects can be simplified and miniaturized. For this reason, the biosensor 100 can suitably measure the state of muscles in fields where muscles are actively moved, such as in sports.

[0054] In this embodiment, bicycle pedaling was used as an example, but for relatively simple periodic movements such as jogging or running, the biosensor 100 can display measurement results as shown in Figures 5 to 7.

[0055] The "calculation unit 13" and "bandpass filter 131" in this embodiment are examples of the "output unit" and "attenuation means" according to the present invention, respectively.

[0056] The present invention is not limited to the embodiments described above, and can be modified as appropriate without contradicting the gist or idea of ​​the invention as can be inferred from the claims and the specification as a whole. Biosensors with such modifications are also included in the technical scope of the present invention. [Explanation of Symbols]

[0057] 11...Light-emitting unit, 12...Light-receiving unit, 13...Calculation unit, 14...Display unit, 20...Crank angle sensor, 100...Biometric sensor, 131...Bandpass filter, 132...Normalization unit

Claims

[Claim 1] A biosensor that is attached to a living body as a test subject, A light-emitting unit that irradiates light onto the living organism, A light-receiving unit that receives reflected light from at least one part of the muscle of the living organism, An output unit that outputs information regarding the deformation of the muscle of the one part based on a detection signal from the light receiving unit corresponding to the reflected light received, A biosensor characterized by having the following features.

Images