Abstract. Essential tremor is an involuntary trembling of body limbs in people without tremor-related disease. In previous study, suppression of tremor by sensory electrical stimulation was confirmed on the index finger. This study investigates the effect of sensory stimulation on multiple segments and joints of the upper limb. It denotes the observation regarding the effect's continuity after halting the stimulation. 18 patients with essential tremor (8 men and 10 women) participated in this study. The task, "arms stretched forward", was performed and sensory electrical stimulation was applied on four muscles of the upper limb (Flexor Carpi Radialis, Extensor Carpi Radialis, Biceps Brachii, and Triceps Brachii) for 15 seconds. Three 3-D gyro sensors were used to measure the angular velocities of segments (finger, hand, and forearm) and joints (metacarpophalangeal and wrist joints) for three phases of pre-stimulation (Pre), during-stimulation (On), and 5 minute poststimulation (P5). Three characteristic variables of root-mean-squared angular velocity, peak power, and peak power frequency were derived from the vector sum of the sensor signals. At On phase, RMS velocity was reduced from Pre in all segments and joints while peak power was reduced from Pre in all segments and joints except for forearm segment. Sensory stimulation showed no effect on peak power frequency. All variables at P5 were similar to those at On at all segments and joints. The decrease of peak power of the index finger was noted by 90% during stimulation from that of On phase, which was maintained even after 5 min. The results indicate that sensory stimulation may be an effective clinical method to treat the essential tremor.

BACKGROUND: The sitting in an awkward posture for a prolonged time may lead to spinal or musculoskeletal disease. It is important to investigate the joint loads at spine while sitting.OBJECTIVE: The purpose of this study was to investigate the joint moment and antero-posterior (AP) reaction force at cervico-thoracic and lumbosacral joint for various sitting postures.METHODS: Twenty healthy males participated in this study. Six sitting postures were defined from three spinal curvatures (slump, flat, and lordosis) and two arm postures (arms-on-chest and arms-forward). Kinematic and kinetic data were measured in six sitting postures from which joint moment and AP reaction force were calculated by inverse dynamics.RESULTS: In the cervico-thoracic joint, joint moment and AP reaction force were greater in slump than the flat and lordosis postures (p< 0.001) and also in arms-forward posture compared to arms-on-chest posture. In the lumbosacral joint, joint moment and AP reaction force were greater in slump than flat and lordotic posture (p< 0.001) but there was no difference between different arm postures. The joint loads (moment and AP reaction force) at the cervico-thoriacic joint were closely related to the head flexion angle (r> 0.86) while those at the lumbosacral joint were correlated to the trunk flexion angle (r> 0.77). In slump posture, the joint moments were close to or over the extreme of the daily life such as sit-to-stand and walking. Consequently, if the slump is continued for a long time, it may cause pain and diseases at the cervico-thoracic and lumbosacral joints.CONCLUSIONS:The results of the study indicated that the lordosis or flat would be better spinal postures. Also, keeping arms close to body would be desirable to reduce joint loads.

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Gait modification strategies are effective in reducing knee joint loads, which are associated with the development and progression of knee osteoarthritis (OA). However, the effect of modification of the initial foot contact method in high-loading descending task was not investigated. Here, we show that the initial foot contact strategy significantly alters knee joint moments during descending tasks. We found that the second peak flexion moment was lower for the forefoot strike (FFS) than for the rearfoot strike (RFS) in both stair and ramp descent. As for the peak adduction moment, the second peak was lower for the FFS in stair descent, but two peaks were inconsistent in ramp descent. Our results demonstrate that the knee joint loads can be reduced by simple modification of the initial foot contact strategy. In both descending modalities, the FFS may benefit people with early OA in the patellofemoral joint, whose progression is associated with the peak flexion moment. Likewise, the FFS during stair descent may benefit people with early OA in the medial knee, whose progression is associated with the peak adduction moment. The results would be helpful for prevention and rehabilitation programmes of knee OA.

Aim: The purpose of this study is to measure the acceleration of upper body (pelvis, shoulder and head) during walking and to investigate whether the acceleration patterns differ among age groups and genders. Methods: Twenty-nine old subjects and thirty young subjects participated in this study. Tri-axial accelerations were measured on the back of upper body (head, shoulder and pelvis). Subjects performed two trials of walking on a treadmill in their own comfortable speeds. Three-way ANOVA (repeated measures) was carried out for the root mean square of each directional acceleration with age, gender and sensor position as independent factors. Results: Age effect was significant on the RMS accelerations of the transverse plane. In the anteroposterior direction, the pelvis acceleration was greater in the younger group, while the head acceleration was greater in the older group ([Formula: see text]). In the mediolateral direction, the pelvis acceleration was comparable between age groups but the shoulder and head accelerations were greater in the older group ([Formula: see text]). The overall accelerations were greater in men than in women ([Formula: see text]). The phase-delay and attenuation of shoulder acceleration relative to the pelvis acceleration was smaller for the elderly in AP and ML directions ([Formula: see text]). Normalization of RMS accelerations by height, weight and leg length did not affect the age differences but negated the gender differences. Discussion: Greater head acceleration in older subjects were related to less attenuation of acceleration in the upper body, which may affect the sensory systems in the head and deteriorate balance control during locomotion.