Oxygen consumption, oxygen cost and physiological cost index in polio survivors: a comparison of walking without orthosis, with an ordinary or a carbon-fibre reinforced plastic knee-ankle-foot orthosis.

OBJECTIVE To examine, for polio survivors, whether walking with a carbon-fibre reinforced plastic knee-ankle-foot orthosis (carbon KAFO) is more efficient than walking with an ordinary KAFO or without an orthosis. DESIGN Consecutive sample. SETTING Post-polio clinic, University Hospital of Occupational and Environmental Health, Kitakyushu, Fukuoka, Japan. PARTICIPANTS Eleven polio survivors who had a carbon KAFO prescribed at the post-polio clinic. INTERVENTIONS A carbon KAFO was prescribed, fabricated and inspected. MAIN OUTCOME MEASURES Oxygen consumption, oxygen cost and physiological cost index. RESULTS An ordinary KAFO weighed 1403 g (standard deviation(SD) 157 g), whereas a carbon KAFO weighed 992 g (SD 168 g). Subjects walking with a carbon KAFO showed a tendency to increase step length, and to increase speed significantly compared with walking without an orthosis and with an ordinary KAFO (paired t-test, p < 0.05). Oxygen consumption per body weight, oxygen cost (O2 consumption for 1-m walk divided by body weight) and physiological cost index ((heart rate at 3-min walk - heart rate at rest) /speed) were significantly lower than those walking without an orthosis (-16%, -35%, -33%; paired t-test, p < 0.05) and were lower than those walking with an ordinary KAFO (-9%, -14%, -15%; paired t-test, p < 0.05). CONCLUSION The gait efficiency of polio survivors with a carbon KAFO was objectively better than those without an orthosis or with an ordinary KAFO.