The effects of muscle activation on postural stability in diabetes mellitus patients with cutaneous sensory deficit in the foot.

Activity of the lower leg muscles in response to an unexpected disturbance to upright standing was studied in diabetic patients and non-diabetic matched controls. The diabetic individuals were classified into two groups: diabetic patients with normal cutaneous sensitivity in the foot (n=27) and patients with cutaneous sensory deficit (n=23). All participants completed twenty trials standing on a force platform that rotated upward 8 deg at 50 deg/s. This movement produced short-latency and medium-latency responses in the gastrocnemius muscle and a single long-latency response in the anterior tibialis. All muscle activity was assessed using electromyography techniques. Results indicated that the average delay of the short-, medium- and long-latency responses produced by the diabetic groups was comparable to control group values. However, the within subject variability associated with activating the anterior tibialis was found to be statistically greater for the cutaneous deficit diabetic group. Additionally, fifty percent of the CD group failed to produce an observable stretch reflex response. The results suggest that the inability to generate a neuromuscular response with consistent temporal patterning is a contributing factor to greater postural sway observed in diabetic patients with cutaneous sensory deficit in the foot.