Static stretching increases muscle fatigue during submaximal sustained isometric contractions

The purpose of this study was to examine the acute effects of a static stretching protocol on neuromuscular fatigue of the flexor carpi radialis (FC) and flexor digitorum (FD).

Twenty-six healthy and right-handed men with a mean (SD) age of 27.1 (2.9) years volunteered for this study. The fatigue test was performed before (Pre) and after three sets of 50 s stretching (Post) applied to the right hand, and twice (T1 and T2) without stretching to the left hand as a control condition. Isometric handgrip fatigue exercise was maintained for 30s within the range 50-60% of the maximal voluntary contraction. From the electromyography (EMG), root mean squares (RMS) values and mean frequency (MF) were obtained for each 2s consecutive windows of test and normalized by the MVC obtained in 6s tests. From time series, coefficients of linear regression were determined used to compare Pre with Post and T1 with T2 by paired samples t-tests.

Higher rate of increase in EMG on Post compared to Pre was found in both FC (P=0.015) and FD (P=0.006). A higher rate of decrease of MF for FC (P=0.004) and FD (P=0.005) was observed with Post compared to Pre. Conversely, the differences between T1 and T2 were not significant (P>0.05).

These findings indicate that static stretching performed immediately before submaximal isometric muscle actions may increase neuromuscular fatigue assessed by EMG, suggesting that could reduce muscle's endurance capacity.