研究者詳細 - 内山　孝憲

© 2020 The Author(s). Medial gastrocnemius muscle stiffness was estimated using a system identification technique. The medial gastrocnemius muscle was electrically stimulated using surface Ag-AgCl electrodes and the center of pressure fluctuation in the forward-backward direction was measured with a force plate. Electrically induced fluctuation of the center of pressure was classified according to the displacement and velocity of the center of pressure. The classified steps of displacement and velocity were 0.2 cm and 0.2 cm/s, respectively. The ranges of the classes were ±0.15 cm and ±0.15 cm/s. The classified fluctuations were synchronously averaged and the averaged fluctuation was regarded as an output signal of the transfer function from the electrical stimulation to the fluctuation. The transfer function was identified as an estimate of muscle stiffness using a singular value de-composition method. The average muscle stiffness of eight young male participants ranged from 56.7 to 75.9 N/m. Muscle stiffness was high when the displacement of the center of pressure was positive and the velocity was negative. These characteristics resembled the preceding 0.3 s of the electromyogram. This preceding high muscle activity probably contributed to muscle stiffness. Muscle stiffness was well approximated with a multiple linear regression plane, in which the explanatory variables were the displacement and velocity of the center of pressure.

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Relationship between medial gastrocnemius muscle stiffness and the angle between the rearfoot and floor

Uchiyama T., Hamada E.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS 6860 - 6863 2019年07月

研究論文（国際会議プロシーディングス）, 筆頭著者, 責任著者, 査読有り

© 2019 IEEE. The present study examined the stiffness in the medial gastrocnemius muscle at various angles between the rearfoot and the floor. Six healthy young men participated in the study. A triangle support was attached to the force plate. Each participant placed their forefoot and rearfoot onto the force plate and the triangle support, respectively. Electrical stimulation was applied to the medial gastrocnemius muscle using Ag-AgCl surface electrodes. The center of pressure was measured with the force plate, and electrically-induced fluctuation of the center of pressure was extracted using a Kalman filter. Measurements were performed at 10°, 20°, and 30°angles of the triangle support. The transfer function from the stimulation to the fluctuation was identified, and the poles of the transfer function were used to estimate the medial gastrocnemius muscle and ankle stiffness. The muscle stiffness increased as the angle of the triangle support increased.

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Optimum displacement of muscle in relation to thickness for biceps brachii hardness measurement using a push-in meter

Murayama M., Inami T., Shima N., Nosaka K., Uchiyama T., Yoneda T.

Biomedical Physics and Engineering Express （Biomedical Physics and Engineering Express） 5 （ 1 ） 017001 2018年11月

研究論文（学術雑誌）, 共著, 査読有り

Objective: Muscle hardness measured by a push-in meter is calculated from a force-displacement curve (FDC) based on a two-layer spring model. Since a FDC is not linear, how to set a linear range in the FDC largely affects muscle hardness calculation. The present study investigated the linearity of the FDC to find the best portion relative to muscle thickness (MT) for muscle hardness measurement based on a two-layer spring model. Approach: Forty-seven men (age: 28 ±10 years, height: 176 ±7 cm, body mass: 73 ±11 kg) participated in the present study. Hardness of the biceps brachii muscle was measured at the mid-belly using a push-in meter. The FDC was obtained every 5% up to 50% of the MT, and linear regression equations of ten different portions within the FDC were calculated. The coefficient of determination (R 2 ) of each regression line was compared by ANOVA, and a piecewise linear regression analysis was performed by dividing the identified FDC into three linear segments. Results: One-way ANOVA showed a significant (p < 0.01) main effect in R 2 values of ten regression equations. Post-hoc analyses showed no significant differences in R 2 between 0%-15% MT and 0%-40% MT. While the linearity of the FDC was high between 0%-15% and 0%-40% MT, the highest R 2 value was found at 0%-25% and 0%-30% MT. According to the analysis of three linear segments in the FDC, the mean value of the point between the second and third segments was 28.5 ±4.3% MT. Significance: These results suggested that muscle hardness assessment using a push-in meter should be performed close to 30% MT depth for biceps brachii muscle.

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Stiffness and viscosity of the vastus lateralis muscle in cycling exercises at low constant power output

内山孝憲/斉藤海仁

Advanced Biomedical Engineering 7 124 - 130 2018年06月

研究論文（学術雑誌）, 共著, 筆頭著者, 責任著者, 査読有り

We examined muscle stiffness at various pedaling rates under conditions of constant power output. Eight healthy young participants pedaled a cycle ergometer at a power output of 47 W. The combinations of pedaling rate and workload were 40 revolutions per min (rpm) and 11.7 N, 60 rpm and 7.8 N, and 80 rpm and 5.9 N, respectively. One electrical stimulus per two pedal rotations was applied to the vastus lateralis muscle at a crank angle of 30° in the down phase. Mechanomyograms (MMGs) were measured using a capacitor microphone, and the evoked MMG was extracted. An evoked MMG system was identified, and the coefficients of the denominator of the transfer function were used to estimate stiffness and viscous coefficient of the muscle. Muscle stiffness was 236–705 Nm−1, and was proportional to the pedaling rate when power output was held constant, while the viscous coefficient did not change from approximately 15 Nm−1s. In conclusion, our findings demonstrate that stiffness of the vastus lateralis muscle increases with increasing pedaling rate under conditions of constant power output, while the viscous coefficient does not change.

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Muscle stiffness estimation using center of pressure fluctuations induced by electrical stimulation

内山孝憲/杉山綾菜

IFMBE Proceedings 68 （ 2 ） 569 - 572 2018年06月

研究論文（国際会議プロシーディングス）, 共著, 筆頭著者, 責任著者, 査読有り, ISSN 16800737

We proposed a novel technique to estimate muscle stiffness using center of pressure (COP) fluctuations induced by electrical stimulation. Six participants stood on a force plate and the COP displacement was measured with and without electrical stimulation applied to the gastrocnemius muscle. The displacement measured in the stimulated condition involved both intrinsic and electrically induced fluctuations. To obtain the intrinsic fluctuation, the measured displacement was smoothed using a Kalman filter constructed by approximating the displacement measured in the non-stimulated condition with an autoregressive model. The intrinsic fluctuation was subtracted from the measured displacement to obtain the electrically induced fluctuation. The fourth-order transfer function from the electrical stimulation to induced fluctuation was identified using a singular value decomposition method. The transfer function had natural frequencies of approximately 2 and 0.3 Hz. The former was close to the natural frequency of the gastrocnemius muscle, and the latter was close to the resonance frequency around the ankle joint. The proposed method can provide muscle and ankle joint stiffness in a standing posture.

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System identification of velocity mechanomyogram measured with a capacitor microphone for muscle stiffness estimation

内山孝憲/朝重大喜

Journal of Electromyography and Kinesiology 33 （ 2 ） 57 - 63 2017年03月

研究論文（学術雑誌）, 共著, 筆頭著者, 責任著者, 査読有り

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System identification of evoked mechanomyogram to clarify lower limb muscle stiffness in treadmill walking

府川友彦/内山孝憲

Advanced Biomedical Engineering 5 1 - 6 2016年02月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

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Muscle stiffness estimation using a system identification technique applied to evoked mechanomyogram during cycling exercise

内山孝憲/斉藤海仁/新庄克也

Journal of Electromyography and Kinesiology 25 （ 6 ） 847 - 852 2015年12月

研究論文（学術雑誌）, 共著, 筆頭著者, 責任著者, 査読有り

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トレッドミル歩行中における前脛骨筋の弾性推定

府川友彦，内山孝憲

計測自動制御学会論文集 51 （ 8 ） 542 - 544 2015年08月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

等尺性随意収縮時の誘発筋音図のシステム同定

品田泰洋，内山孝憲

生体医工学 53 （ 2 ） 69 - 75 2015年04月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

ダブルパルス刺激による筋音図のシステム同定

川端航内山孝憲

生体医工学（日本生体医工学会） 53 （ 1 ） 8 - 13 2015年02月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

System identification of mechanomyogram at various levels of motor unit recruitment

内山孝憲，田村昂広

SICE Journal of Control, Measurement, and System Integration 7 （ 6 ） 321 - 326 2014年11月

研究論文（学術雑誌）, 共著, 査読有り

System identification of evoked mechanomyogram from abductor pollicis brevis muscle in isometric contraction

内山孝憲，酒井弘章

Medical & Biological Engineering & Computing 51 （ 12 ） 1349-1355 2013年11月

研究論文（学術雑誌）, 共著, 査読有り

Comparison of displacement and acceleration transducers for the characterization of mechanics of muscle and subcutaneous tissues by system identification of a mechanomyogram

篠原啓太，内山孝憲

Medical & Biological Engineering & Computing 51 （ 1-2 ） 165-173 2013年02月

研究論文（学術雑誌）, 共著, 筆頭著者, 責任著者, 査読有り

機械刺激による筋・皮下組織・皮膚の力学特性の解析

有岡征志郎，内山孝憲

生体医工学 50 （ 6 ） 613-619 2012年12月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

誘発筋音図のシステム同定と伝達関数の刺激頻度依存性の解析

宇佐美洋佑，宮原佐和，内山孝憲

バイオメカニズム（バイオメカニズム学会） 21 195-205 2012年08月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

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