Biological sensor

Abstract

To provide a biological sensor which is capable of detecting a motion of each muscle and is easy to attach and constitute.SOLUTION: A biological sensor (100), in use, is mounted on a living body as a subject. The biological sensor includes: a light emitting unit (11) for irradiating a living body with light; a light receiving unit (12) for receiving return light from a muscle of at least a part of the living body; and an output unit (13) for outputting information on the deformation of the muscle of the part on the basis of a detection signal from the light receiving unit corresponding to the received return light.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] As an example of this type of device, a device has been proposed that exerts muscle strength corresponding to the minimum estimated oxygen saturation in the blood of the subject's muscles based on a correlation table showing the correlation between oxygen saturation and exerted muscle strength (see Patent Document 1).

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

[0004] [Patent Document 1] JP 2001-70289 A [Patent Document 2] Japanese Patent Application Publication No. 5-068675 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology described in Patent Document 1 monitors oxygen saturation, which decreases (i.e., changes occur) due to muscle contraction over a certain period of time, and therefore has the technical problem of being unable to detect instantaneous muscle contraction.The technology described in Patent Document 2 has the technical problem of being unable to detect individual muscle contractions, as the attachment band is wrapped around the subject's arm, and therefore only detects contractions that combine agonist and antagonist muscle movements, for example.

[0006] Furthermore, electromyographs that measure the electrical potential of the body surface have the technical problem that attachment of the sensor requires time and care, and also requires a highly accurate detection circuit to detect weak electrical potentials.

[0007] The present invention has been made in view of, for example, the above-mentioned problems, and has an object 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] In order to solve the above-mentioned problems, the biosensor of the present invention is a biosensor that is attached to a living organism as a subject, and comprises: a light-emitting unit that irradiates light to the living organism; a light-receiving unit that receives return light from at least one muscle part of the living organism; and an output unit that outputs information regarding deformation of the muscle part based on a detection signal from the light-receiving unit in response to the received return light.

[0009] The functions and other advantages of the present invention will become apparent from the following detailed description of the preferred embodiments. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an overview of a biosensor according to an embodiment; [Diagram 2] 1A and 1B are diagrams for explaining the measurement principle of a biosensor according to an embodiment. [Diagram 3] 1 is an example of a biological signal. [Figure 4] 1 is an example of a detection signal before and after filtering. [Diagram 5] 4 is an example of an output of a biosensor according to an embodiment. [Figure 6] 13 is an example of measurement results for each of a plurality of muscles. [Figure 7] 11 is a diagram comparing the output of a biosensor according to an embodiment with the output of an electromyogram. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of a biosensor according to the present invention will be described.

[0012] The biosensor of the embodiment is a biosensor that is 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 return light from at least one muscle part of the living body; and an output unit that outputs information regarding deformation of the muscle part based on a detection signal from the light-receiving unit in response to the received return light.

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

[0014] The light emitting unit emits light having 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, for example, the measurement target. The light receiving unit receives return light from at least one muscle part of the living body.

[0015] The output unit, which may include, for example, a memory, a processor, etc., outputs information regarding deformation of a muscle in a certain area based on a detection signal from the light receiving unit.

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

[0017] Therefore, the output section outputs, for example, information indicating the signal level of the detection signal as information regarding the deformation of the muscle at one site.

[0018] According to the biosensor of this embodiment, information on the deformation of a muscle in a certain area is output based on the return light from the muscle, so that instantaneous changes in the muscle in a certain area can be detected. In addition, since the light receiving unit receives the most return light from the muscle closest to the biosensor (here, the muscle in the certain area), the detection signal from the light receiving unit is dominated by the effect of the deformation of the muscle closest to the biosensor. In other words, according to the biosensor, it is possible to detect only the deformation of the muscle in a certain area.

[0019] Furthermore, since the biosensor optically detects muscle deformation, it can be made simpler in configuration and easier to handle than an electromyograph that measures weak electrical potentials on the body surface.

[0020] In one aspect of the biosensor according to this embodiment, the output section determines an increase in the signal level of the detection signal as a contraction of a muscle at a certain site.

[0021] According to this embodiment, deformation of a muscle in a certain area can be detected relatively easily, which is extremely advantageous in practical use.

[0022] In another aspect of the biosensor according to the present embodiment, the light emitting section and the light receiving section are disposed on a flexible member.

[0023] According to this aspect, the distance between the light-emitting unit and the light-receiving unit on the component can be kept constant, thereby making it possible to make the measurement results obtained by the biosensor reproducible and to easily attach the biosensor to a living body.

[0024] In another aspect of the biosensor according to the present embodiment, the biosensor further comprises an attenuation means for attenuating a signal component having a period longer than the predetermined period, which is included in the detection signal.

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

[0026] In the present embodiment, therefore, the attenuation means attenuates signal components having a period longer than a predetermined period that are included in the detection signal. Therefore, according to this aspect, deformation of the muscle at a certain site can be suitably detected. 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 a subject is pedaling a bicycle.

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

[0029] In FIG. 1(a), a biosensor 100 includes a light-emitting unit 11, a light-receiving unit 12, a calculation unit 13, and a display unit .

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

[0031] The light receiving unit 12 has a light receiving element such as a PD (Photodiode). The light emitting unit 12 receives at least return light from a muscle of a living body to be measured as a subject. Here, "return light" typically means light scattered or reflected by the living body. The light receiving unit 12 outputs a biosignal as a "detection signal according to the received return light" according to the present invention.

[0032] 1(b), the calculation unit 13 includes a band-pass filter 131 and a normalization unit 132. The operation of the calculation unit 13 will be described in detail later.

[0033] Here, the measurement principle of the biosensor 100 will be described with reference to Fig. 2. Fig. 2 is a diagram for explaining the measurement principle of the biosensor according to the embodiment.

[0034] 2, first, the light-emitting unit 11 and the light-receiving unit 12 of the biosensor 100 are attached to a part of the subject's body that includes the muscle to be measured. Note that the light-emitting unit 11 and the light-receiving unit 12 do not have to be attached to the subject's skin directly or via gel or cream, and may be attached over clothing that shows the movement of the muscle to be measured, such as clothing that fits closely to the skin.

[0035] It is desirable that each of the light-emitting unit 11 and the light-receiving unit 12 is arranged on a flexible member as shown in FIG. 2(a) (note that for ease of explanation, the flexible member is not shown in FIG. 2(b)). However, each of the light-emitting unit 11 and the light-receiving unit 12 does not have to be arranged on a flexible member. Note that the "flexible member" in the embodiment is an example of the "flexible member" according to the present invention.

[0036] When a muscle contracts, the myosin filaments pull the actin filaments closer to the center, and the myosin and actin filaments overlap deeply with each other. As a result, the muscle fibers become more densely packed together and the muscle as a whole changes to a rounder shape compared to when the muscle is relaxed (see Figure 2(b)).

[0037] When the muscle contracts, as shown in FIG. 2, the light-emitting unit 11 and the light-receiving unit 12 approach 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 FIG. 2, the angle is indicated as "θ 1 " to "θ 2"). As a result, the optical distance from the light-emitting unit 11 to the light-receiving unit 12 is shortened. Therefore, of the light emitted from the light-emitting unit 11 and scattered or reflected by the muscle being measured, the amount of light that is incident on the light-receiving unit 12 increases.

[0038] In addition, when a muscle contracts, 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, and therefore the amount of light scattered or reflected by the muscle being measured increases when the muscle contracts.

[0039] That is, there is a correlation between the amount of light detected by the light receiving section 12 (i.e., the signal level of the outputted biosignal) and the change in the muscle to be measured.

[0040] When a subject is pedaling a bicycle, the muscles in the subject's legs periodically contract and relax. When the biosensor 100 is attached to the subject's legs, the biosignal output from the light receiving unit 12 has a period synchronized with the pedaling, as shown in FIG.

[0041] Incidentally, the biosignal includes the influence of physiological reactions such as changes in cardiac output. Specifically, as shown in Fig. 4(a), the entire biosignal fluctuates up and down in a relatively long period due to the physiological reactions. The biosignal shown in Fig. 4 shows fluctuations over about 10 minutes.

[0042] Therefore, in this embodiment, the components caused by the physiological reaction included in the biosignal are attenuated by the bandpass filter 131 (see FIG. 1(b)) of the calculation unit 13. As a result, the signal output from the bandpass filter 131 becomes as shown in FIG. 4(b).

[0043] The filtered signal output from the band-pass filter 131 is normalized by the normalization unit 132 (see FIG. 1(b)). Specifically, the normalization unit 132 normalizes the filtered signal by defining the maximum value of the signal amplitude of the filtered signal as the maximum contraction state of the muscle and the minimum value of the 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 a muscle contraction rate of 100% and the minimum value of the normalized signal as a muscle contraction rate of 0%. Note that the "information indicating the time variation of the muscle contraction rate" according to the embodiment is an example of the "information regarding the deformation of a muscle at a site" according to the present invention.

[0045] In this embodiment, the crank angle of the bicycle on which the subject is pedaling is detected by a crank angle sensor 20 (e.g., 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 indicating the time variation of the muscle contraction rate output from the calculation unit 13 in association with the crank angle (see FIG. 5).

[0046] Displaying the data in this manner allows the subject to know the transition of the muscle contraction rate during pedaling, which is extremely advantageous in practical terms.

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

[0048] As a result, it is possible to, for example, evaluate how muscles are used when pedaling, detect unintentional eccentric contractions (elongational muscle contractions), etc., which is extremely advantageous in practical use.

[0049] (Effects of this embodiment) Among the techniques capable of evaluating the state of muscle movement, the most practical is the electromyograph. Therefore, the measurement results of the biosensor 100 according to this embodiment and the measurement results of the electromyograph are compared with each other with reference to Fig. 7. The graphs shown in Fig. 7 each show the variation of the muscle contraction rate for one cycle (i.e., 360 degrees of crank angle).

[0050] Although the explanation of the principle of the electromyograph is omitted, the electromyograph detects an action potential caused by a command from the brain to contract a muscle. In contrast, the biosensor 100 optically detects changes in the muscle as described above. In other words, the biosensor 100 detects the results of changes in the muscle. Thus, although the measurement principles of the electromyograph and the biosensor 100 are different, as shown in FIG. 7, the measurement results for each muscle are very similar.

[0051] Therefore, it can be said that the measurement results obtained by the biosensor 100 are valid and have the same level of measurement accuracy as 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 an electromyograph measures the action potential of a muscle, it can also measure muscle contraction that does not involve muscle deformation, such as isometric contraction. On the other hand, the biosensor 100 measures muscle contraction from a change in the amount of received light caused by muscle changes, and therefore cannot measure muscle contraction that does not involve muscle deformation.

[0053] Here, in particular, if the light emitting unit 11 and the light receiving unit 12 of the biosensor 100 can be physically fixed to a part including the muscle to be measured, the biosensor 100 can measure changes in the muscle, and is very easy to handle. In addition, since the biosensor 100 only needs to be able to detect signals at a speed of about the subject's movement (for example, 10 Hz or less), it is possible to simplify, for example, the circuit configuration, and to achieve miniaturization. Therefore, the biosensor 100 can suitably measure the state of muscles in fields where muscles are actively moved, such as in the field of sports.

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

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

[0056] The present invention is not limited to the above-described embodiments, but can be modified as appropriate within the scope that does not contradict the gist or concept of the invention that can be read from the claims and the entire specification, and 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: biosensor, 131: band pass filter, 132: normalization unit

Claims

[Claim 1] A biosensor to be attached to a living body as a subject, A light emitting unit that irradiates light onto the living body; A light receiving unit that receives return light from at least one muscle of the living body; an output unit that outputs information regarding the deformation of the muscle at the one site based on a detection signal from the light receiving unit corresponding to the received return light; A biosensor comprising:

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