With progress of modern technology, manually-propelled wheelchairs are still of importance for individuals with mobility impairments. The repeated wheelchair propulsion and strenuous daily activities cause high loads and thus injuries on the upper extremity joints. Over the past few years, a considerable number of studies have been made on biomechanical analysis of wheelchair propulsion and wheelchair-related activities. Thorough investigation of biomechanics during wheelchair propulsion enhances comprehension of mechanism of injuries and provides information to improve wheelchair design and fitting. Numerous investigations have been made to demonstrate factors which cause low effectiveness of force application and inefficiency of movements. Emphasis was also placed on developing analytical models to simulate wheelchair propulsion.
The goal of this study was to investigate the movement coordination among the hip, knee, and ankle joints during solo performance of the Tai Chi (TC) basic movements in order to understand its dynamic postural control. Nine male community-dwelling adults with experienced TC pushing hands participated in this cross-sectional study. The Eagle ® motion analysis system with eight cameras was used to collect the trajectories of all reflective markers at sampling rate 100 Hz while the subject performed the ward-off, rollback, press, and push movements. Motion among the hip, knee, and ankle joints was highly coupled. Coupled joint motion, hip flexion-knee flexion-ankle dorsiflexion or reverse, existed in ward-off, rollback, and press phases for the front leg. However, in the push phase, the hip joint angle was kept almost constant with coupled knee and ankle motions. For the rear leg, coupled motion existed between the hip and the knee joints only. The ankle joint motion differed between the front and the rear legs during the basic movements of TC (p < 0.05). Basic characteristics were documented such as the forward knee never extending further than forward toe and both legs maintaining flexion during the full exercise cycle with hip and knee of front and rear legs having synchronized movements in opposite directions. The forward and backward shifts of TC basic movements have considerable contributions to the posture control in terms of the fine coordination of three lower extremity joints. This information could improve training protocol design for TC Chuan teaching and help beginners make an efficient and less damaging movement.
This study aims toward an investigation and comparison of the digital force control and the brain activities of older adults and young groups during digital pressing tasks. A total of 15 young and 15 older adults were asked to perform force ramp tasks at different force levels with a custom pressing system. Near-infrared spectroscopy was used to collect the brain activities in the prefrontal cortex and primary motor area. The results showed that the force independence and hand function of the older adults were worse than that of the young adults. The cortical activations in the older adults were higher than those in the young group during the tasks. A significant hemodynamic between-group response and mild negative correlations between brain activation and force independence ability were found. Older adults showed poor force independence ability and manual dexterity and required additional brain activity to compensate for the degeneration.
The purpose of this study was to examine the correlation between the foot arch volume measured from static positions and the plantar pressure distribution during walking.A total of 27 children, two to six years of age, were included in this study. Measurements of static foot posture were obtained, including navicular height and foot arch volume in sitting and standing positions. Plantar pressure, force and contact areas under ten different regions of the foot were obtained during walking.The foot arch index was correlated (r = 0.32) with the pressure difference under the midfoot during the foot flat phase. The navicular heights and foot arch volumes in sitting and standing positions were correlated with the mean forces and pressures under the first (r = -0.296∼-0.355) and second metatarsals (r = -0.335∼-0.504) and midfoot (r = -0.331∼-0.496) during the stance phase of walking. The contact areas under the foot were correlated with the foot arch parameters, except for the area under the midfoot.The foot arch index measured in a static position could be a functional index to predict the dynamic foot functions when walking. The foot arch is a factor which will influence the pressure distribution under the foot. Children with a lower foot arch demonstrated higher mean pressure and force under the medial forefoot and midfoot, and lower contact areas under the foot, except for the midfoot region. Therefore, children with flatfoot may shift their body weight to a more medial foot position when walking, and could be at a higher risk of soft tissue injury in this area.
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