No abstract

No abstract

BACKGROUND: Due to physical and psychosocial issues associated with long-term sitting in a wheelchair, devising new ways to facilitate upright mobility is a key issue in rehabilitation medicine. Wearable Power-Assist Locomotor (WPAL) is a motorized orthosis and is developed for providing independent and comfortable walking for paraplegic patients. METHODS:The WPAL consists of a wearable robotic orthosis and custom walker. To facilitate alternate usage with a wheelchair, the wearable robotic orthosis is based on a medial system with motors located at the bilateral hip, knee and ankle joints to reduce the increase in heart rate during gait. The gait parameters include stride length, toe clearance height, swing time, double support time, etc. (gait speed: up to 1.3 km/h). Independent gait with the walker can be learned through a five-stage gait exercise sequence. The first two stages are stepping and gait exercises with parallel bars. The third stage is gait exercise on treadmill. The subsequent two stages are gait exercise with walker. RESULTS: Seven motor-complete paraplegic patients (spinal cord functional levels: T6-T12) participated. Through a series of exercises, all users achieved independent gait on a level floor (Functional Ambulation Categories: 4). The mean duration and distance of consecutively walking were 14.1 ± 11.4 minutes and 165.6 ± 202.6 m, respectively. The most competent user was able to walk continuously for as long as 40 minutes and 640 m whereas only for 6 minutes and 107 m with a conventional orthosis. CONCLUSIONS: These results suggest that WPAL might be useful device for supporting upright walking in persons with paraplegia.

To investigate the effects of aging on coordination of plantar flexor muscles during bipedal and unipedal stances, we examined a relationship between the center of pressure sway and electromyographic activity of these muscles, and also the common neural input, using a coherence analysis. Healthy young and elderly adults were asked to perform bipedal and unipedal standing. The electromyograms were recorded unilaterally from the medial and lateral gastrocnemius (MG and LG) and soleus (SL) muscles, and the common input was analyzed for MG-LG, MG-SL, and LG-SL pairs in two frequency bands: a delta band, that is associated with force variability, and a beta band, that could reflect the corticospinal drive. Main results indicated that the MG and SL muscles worked for lateral sway, while the LG muscle worked for medial sway during the unipedal stance. The delta-band coherence for the MG-SL pair and the beta-band coherences for all the pairs were larger during the unipedal than bipedal stance for both groups. The delta-band coherence for the MG-SL pair was larger for the elderly than young adults during the unipedal stance. In addition, the beta-band coherence for the MG-SL pair was larger than the other pairs during the unipedal stance for the elderly. These findings suggest that the oscillatory activity between the MG and SL muscles is strongly involved in the control of unipedal stance, and aging would increase the cortical drive to these muscles to deal with the postural sway that could be affected by forces generated cooperatively by them.