Effect of plantar flexion resistance of ankle-foot orthosis on tendon length during gait

This study investigates the effect of the plantar flexion resistance (PFR) of an ankle-foot orthosis (AFO) on the plantar flexor tendon length during gait. We measured and estimated the knee flexion angle, plantar flexion angle, and plantar flexor tendon length in healthy male adults. The results showed that the knee flexion and plantar flexion angle were significantly different in the strong PFR (s-PFR) compared with the no-AFO condition. In addition, the change in the gastrocnemius tendon length significantly decreased in the s-PFR condition compared to the no-AFO condition. These results suggest that over PFR prevents the gait improvement because the extension of the gastrocnemius tendon in the late stance is very important for the forward propulsion during gait.