Prolonged Static Stretching Improves the Steadiness of Medium-Intensity Sustained Submaximal Contractions

Static stretching (SS) is often used as a common technique to improve flexibility before exercise and athletic competitions. However, less is known regarding its influence on force steadiness during submaximal isometric contractions. PURPOSE: To examine the acute effects of a bout of prolonged SS on force steadiness of medium- to high-intensity sustained submaximal isometric contractions. METHODS: Fourteen young men (mean ± SD: age = 24 ± 5 yr; height = 178 ± 8 cm; weight = 84 ± 11 kg) performed 12 sets of passive SS on their forearm flexors. Each stretch lasted 100 s, and 20 s of rest between consecutive stretches was provided. Before (Pre) and immediately after (Post) the SS intervention, isometric maximal voluntary contractions (MVCs) were tested for quantifying the strength of the forearm flexor. In addition, subjects also performed submaximal isometric contractions at 30%, 50%, and 70% of their pre-determined MVCs. To quantify force steadiness, the standard deviation (SD) of the force output from the flat portion of each submaximal contraction was calculated. A paired-samples t-test was used to examine the isometric strength before and after the SS. In addition, a two-way [contraction intensity (30% vs. 50% vs. 70% MVC) × time (Pre vs. Post)] repeated measures analysis of variance (ANOVA) was used to examine the possible changes in force steadiness at three different contraction intensities after the SS intervention. When appropriate, follow-up tests included one-way repeated measures ANOVAs and paired-samples t-tests. RESULTS: The isometric strength of the forearm flexor significantly decreased (mean ± SD: PreMVC = 323 ± 62 N, PostMVC = 289 ± 75 N; p < 0.001) following the SS intervention. The results from the two-way repeated measures ANOVA indicated that there was a significant interaction (p = 0.02). When compared Pre-force SD to Post-force SD at each intensity, force SDs significantly decreased for both 30% (p = 0.015) and 50% MVC (p = 0.043), but remained unchanged for 70% MVC. CONCLUSION: The decreased force SDs suggested that the subjects’ ability to maintain a steady force at medium intensity was better following the SS intervention. Therefore, static stretching prior to athletic events may be helpful for improving sports performance that requires extremely high levels of movement accuracy.