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In this study, we investigated the changes in the muscle activities of the brachialis (BR) and biceps brachii (BB) during dynamic elbow flexion under different movement velocity and load conditions. Twenty healthy adult males performed isotonic elbow flexions in the full range of motion (0–140^∘) under angular velocities of 30^∘/s and 60^∘/s, and with (30% maximum torque) and without load conditions. Muscle activity was measured using surface electromyography (EMG). The muscle activity of the BR and BB was compared to their response to different angle phases, angular velocity and load conditions. Both muscle activities of the BR and BB significantly increased in the initial angle phases of the elbow flexion. Muscle activity of the BR progressively increased with increasing elbow flexion, whereas that of the BB plateaued regardless of the velocity and load conditions. Specifically, BB muscle activity plateaued after an initial increase in the earliest phase at 60^∘/s with load conditions. It was suggested that BR and BB contributed to the control of the movement in a different way during dynamic elbow flexion.

The motion of the skeletal estimated from skin attached marker-based motion capture(MOCAP) systems is known to be affected by significant bias caused by anatomical landmarks mislocation but especially by soft tissue artifacts (such as skin deformation and sliding, inertial effects and muscle contraction). As a consequence, the error associated with this bias can propagate to joint kinematics and kinetics data, particularly in small rodents. The purpose of this study was to perform a segmental kinematic analysis of the rat hindlimb during locomotion, using both global optimization as well as segmental optimization methods. Eight rats were evaluated for natural overground walking and motion of the right hindlimb was captured with an optoeletronic system while the animals walked in the track. Three-dimensional (3D) biomechanical analyses were carried out and hip, knee and ankle joint angular displacements and velocities were calculated. Comparison between both methods demonstrated that the magnitude of the kinematic error due to skin movement increases in the segmental optimization when compared with the global optimization method. The kinematic results assessed with the global optimization method matches more closely to the joint angles and ranges of motion calculated from bone-derived kinematics, being the knee and hip joints with more significant differences.