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2 Acta of Bioengineering and Biomechanics

2 Ohta Y.

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The relationship between changes in joint kinematics parameters and mechanomyographic signals during non-isometric contraction in human skeletal muscle

Ohta Y.

Acta of Bioengineering and Biomechanics

2013

Vol. 15, no. 2

97--104

The present study determines the effects of summation of contraction on joint kinematics in human ankle and mechanomyography (MMG) signals during non-isometric contraction. The excursion and angular velocity of dorsiflexion and eversion were measured during several summation profiles during non-isometric contractions. The joint kinematics parameters and MMG responses to 1–8 pulses at a constant interval of 10 ms were recorded to investigate the effects of different numbers of stimuli. In an examination of two-pulse trains with different inter-pulse intervals, the joint kinematics parameters and MMG responses to inter-pulse intervals of 10–100 ms were recorded from the tibialis anterior muscle. The main finding was that facilitating effects of subsequent stimulation were limited to angular velocity of eversion during the contribution of a second stimulus, suggesting that facilitating effects of second stimulus reflect angular velocity but not joint angle excursion. A comparison with MMG signals clarified that MMG signals poorly correlate with changes in the joint kinematics parameters (excursion and angular velocity) when the inter-pulse intervals or numbers of stimuli are increased. These findings will provide useful information for assessing the muscle contractile properties with evoked MMG signals during non-isometric contraction.

Effects of tendinous tissue properties on force output evoked by 2-pulse trains at different inter-pulse intervals in the human tibialis anterior muscle

Ohta Y.

Acta of Bioengineering and Biomechanics

2012

Vol. 14, no. 4

45-52

The aim of this study was to clarify the effects of tendinous tissue properties on origin of greater force output at short inter-pulse intervals in the 2-pulse trains compared to those at longer inter-pulse intervals. Thus, this study investigated the contributions of the second stimulus (C2) in 2-pulse trains with different inter-pulse intervals on the torque response and tendinous tissue properties of human skeletal muscle in vivo. The torque response and tendinous tissue elongation following single pulses and 2-pulse trains at different inter-pulse intervals (5, 10, 20, 30, 40, 50, 80, 100, 150, and 200 ms) were recorded in the tibialis anterior muscle using real-time ultrasonography. C2 with inter-pulse intervals of 5-100 ms invoked significantly greater torque responses than single pulses. In contrast, the elongation and compliance of tendinous tissue for C2 with inter-pulse intervals from 5-80 ms were significantly lower than those of the single-pulse response. A significant negative relationship between torque response and tendinous tissue compliance was observed in C2 with different inter-pulse intervals. The torque response as a result of C2 is greater at short inter-pulse intervals in which the force summation due to second stimulus coincides with the period of decreased tendinous tissue compliance due to the first stimulus.