Acute Effects Of Passive Stretching On The Electromechanical Delay and Evoked Twitch Properties.

Studies have shown passive stretching may transiently decrease force and alter twitch-related properties. However, the effects of passive stretching on the electromechanical delay (EMD) are still unknown. To examine the acute effects of passive stretching on the EMD, peak twitch force (PTF), rate of force development (RFD), and peak-to-peak M-wave (PPM) for the soleus muscle during evoked isometric plantar flexion muscle actions. Fourteen men (mean ± SD age = 21.2 ± 2.4 yrs; body mass = 80.0 ± 14.9 kg; height = 176.9 ± 7.2 cm) volunteered for the study. Five transcutaneous electrical stimuli (each separated by 5 seconds) were delivered to the tibial nerve before and after passive stretching. The stretching protocol consisted of nine repetitions of passive assisted stretching designed to stretch the calf muscles. Each repetition was held for 135 seconds with 5-10 seconds of rest between each passive stretching repetition. An average of three pre- and post-stretching twitches were used to analyze each variable. Dependent-samples t-tests (pre- vs. post-stretching) were used to analyze the EMD, PTF, RFD, and PPM data. There were no significant changes (p > 0.05) from pre-to post-stretching for any of the variables, including EMD (pre- and post-stretching mean ± SE = 29.9 ± 1.1 and 28.8 ± 1.4 ms), PTF (14.5 ± 1.1 and 14.7 ±1.1), RFD (225.1 ± 15.7 and 211.6 ± 19.1), or PPM (3.7 ± 0.5 and 3.4 ± 0.5), Our findings indicated no significant stretching-related changes in EMD, PTF, RFD, or PPM. These findings suggested that passive stretching of the calf muscles did not affect the mechanical aspects of force production from the onset of the electrically-evoked twitch to the peak twitch force. These results may help to explain the mechanisms underlying the stretching-induced force deficit that has been reported as either “mechanical” or “electrical” in origin. These findings suggested that if there is a stretch ing-related decrease in muscle force production, it may be more related to decreases in neural drive (i.e., electrical) than alterations in the mechanical components of muscle contraction. These findings may also be useful for strength and conditioning professionals who are concerned with the potential for performance decreases associated with acute passive stretching. [ABSTRACT FROM AUTHOR]