Abstract
This study was aimed to examine the impact of acute stretching on the rate of force development (RFD) of the plantar flexors (PF). Eleven physically active female subjects participated in the study. The right calf muscle-tendon unit was stretched during five passive cyclic slow stretches(5°/s) that consisted of a dynamic ascending stretch phase to a pre-determined final joint angle (80% of maximal dorsiflexion angle) and a 15∼s hold phase. Maximal isometric torque (MVC) of PF and dorsiflexors (DF) and the RFD of PF were determined before, immediately and 30min following stretching. Changes in passive stiffness, passive resistive torque and torque relaxation of PF were computed during stretching. Passive characteristics decreased significantly during stretching (−11 to −27%, P<0.01). DF MVC did not change following stretching but there was a significant decrease in PF MVC immediately and after 30 min of recovery (−10%, P< 0.001). In contrast, PF RFD remained unaltered following stretching (P>0.05). These results indicate that passive stretching (< 5 min) can be applied without altering the capacity to develop torque rapidly under isometric condition up to 75% of MVC despite significant MVC impairment. These findings may have practical implications for stretching undertaken during rehabilitation or sport training.