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Muscle moment arm defines the function of the muscle. To date, moment arms of the arm muscles at the glenohumeral joint using the tendon excursion method have not been reported. As the functions of these muscles at the shoulder joint are controversial, this study was undertaken to determine the moment arms of the long and short heads of the biceps (LHB, SHB), the coracobrachialis, and the long head of the triceps muscles. The moment arms were determined in 10 cadaveric shoulders by measuring the tendon excursion when the arm was rotated by 1 radian (57.3°) in 22 different motions. The LHB was a flexor, horizontal flexor, and abductor. The SHB and coracobrachialis were flexors, horizontal flexors, and adductors. The long head of the triceps was an extensor and adductor. Arm rotation significantly affected the function of the LHB only: it was an internal rotator in flexion and an external rotator in abduction. This study clarifies the individual function of the arm muscles at the glenohumeral joint.

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Muscle architectural changes, induced by changes in joint position, can influence the amplitude distribution of surface electromyograms (EMGs). By combining grids of electrodes, ultra sound (US) imaging and three-dimensional (3D) kinematics, the relative contribution of different anatomical factors (e.g., pinnation angle, muscle thickness) on EMG features may be quantified. The aim of this paper was to explore the potentiality of this technique in the analysis of how much muscle architectural changes, induced by changes in joint position, can influence the EMG amplitude distribution. While provided with EMG visual-feedback, a participant was asked to recruit a single motor unit of the right tibialis anterior (TA) muscle at two different ankle positions. Surface EMGs, kinematic data and US images were acquired. The spatial distribution of the amplitude of motor unit action potentials was assessed from EMGs. Ankle angles were obtained from 3D kinematics. TA width and thickness variations between the two ankle positions were obtained through the segmentation of US images reconstructed in 3D space. When compared with ankle at plantar flexion, ankle at neutral position resulted in greater TA width and thickness, as well as, in more widely distributed EMG amplitude. These results suggest TA architecture may markedly affect the amplitude distribution of surface EMGs.

The purpose of this study was to investigate an effective recovery method on muscle function and blood of lactate level after maximal isotonic exercise. This study was conducted in 36 adult males. The group was divided into three groups. Sling therapy group (SG, $n=12$), sling therapy group with whole body vibration continuous (SAVG, $n=12$) and sling therapy group with whole body vibration in intermittent (SIVG, $n=12$) were randomly composed. Sling exercise therapy using supine position and whole-body vibration of 10Hz, 5mm were performed. Lactate level and muscle function during the rest, fatigue and recovery period were measured and then maximal exercise using back extension was performed to induce fatigue. After 15min, sling with whole body vibration was conducted in two groups, respectively. Blood lactate was measured a few hours before and after of vibration. Also, muscle function between only sling exercise therapy condition, sling with whole body vibration condition in all time and sling with whole body vibration condition in intermittent time were analyzed. Lactate level was recorded by lactate measurement device. Isokinetic of lumber joint extension and flexion Peak torque/body weight, total work (J), average power (W) and acceleration time (m/s²) were measured using isokinetic dynamometer. The recovery method of sling with whole body vibration showed positive changes in physical characteristics. Isokinetic contraction of peak torque/body weight (N$\cdot$m), average power (Watts) and total work (J) were significantly increased in the recovery step for SIVG. Lactate level was significantly decreased for SIVG as compared with SG and SAVG. This study demonstrated that sling exercise therapy with intermittent time whole body vibration could provide a positive effect on the efficient recovery of muscle function and higher reduction of lactate after maximal isotonic exercise.