Published papers

長母指屈筋の等尺性収縮について、筋電図、粘弾性および収縮力の関係を調べた。粘弾性が張力に先行して調節されていることを報告した。（4頁）

© 2018 IOP Publishing Ltd. 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.

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.

© 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.

LPZAR法によって31P-NMRスペクトルを推定することにより，Mg負荷時の細胞内の無機リン酸，ATP，Mgイオン濃度を求めて報告した．（8頁）