Objective: To examine the acute effects of static stretching and its duration on maximal muscular performance.
Data Sources: PRISMA guidelines for reviews were followed. MetaLib was used to search 4 databases (MEDLINE, ScienceDirect, SPORTDiscus, and Zetocup) to February 2011, for article titles containing words including static and acute stretch (exploded), and its effects on force, power, and speed. Further searches were conducted on the first authors and reference lists of relevant articles.
Study Selection: Inclusion criteria were original peer-reviewed studies evaluating a stretching intervention, in humans, on maximal voluntary muscular performance in strength-, power-, and speed-dependent tasks. Studies were required to compare ≥2 interventions or prestretch and poststretch data. One reviewer excluded articles by title and then abstract, which were then verified by a second reviewer. The remaining full-text articles were assessed by 2 reviewers, and consensus on exclusions was reached. Study methods were evaluated on the 11-point PEDro scale by 2 reviewers. From 4559 titles identified, 123 full-text articles were screened and 106 were included.
Data Extraction: The extracted data included stretch duration (<30 seconds, 30-45 seconds, 1-2 minutes, and >2 minutes), muscle group stretched, and maximal muscular performance recorded and its relation to the stretching intervention. One analysis included all studies, and the second included only studies with appropriate control or reliability statistics. Because the interventions and outcome measures were heterogeneous, the authors provided pooled summary effects in subgroups categorized by duration of stretches.
Main Results: Examining the 149 findings within the 106 articles, 44% showed significant reductions in strength-, power-, and speed-dependent tasks after acute stretching (pooled estimate of reductions, −3.7% ± 4.9%). Among the 104 findings in the 74 studies with appropriate controls, 50% showed significant reductions in performance (pooled estimate of reductions, −4.5% ± 5.2%). Ten studies examined the effects of stretches of <30 seconds duration on tests of 20-m sprint time, vertical jump, medicine-ball throw; isometric hand and knee strength, jump distance, and peak cycling power. Overall, <30 seconds of stretching resulted in a pooled estimate of −1.1% ± 1.8% reduction. Fifteen studies examined the effects of stretches of 30-seconds to 45-seconds duration on tests of vertical jump height, 10-m or 30-m sprint time, throwing velocity, bench press, overhead throws, or leg extension power. Overall, 30 to 45 seconds of stretching resulted in a pooled estimate of −0.6% ± 3.1% reduction in speed-dependent or powerdependent tasks. Eleven studies examined the effects of 30 to 45 seconds of stretching on handgrip strength, concentric knee flexor muscular voluntary contraction (MVC), isometric and concentric knee extensor strength, concentric plantar flexor MVC. chest press strength, and isometric knee flexor MVC. The pooled estimate of the effect of 30-second to 45-second stretches on strength was a reduction of −4.2% ± 2.7%. When stretch durations were >60 seconds, the mean reduction across tests of performance was −4.2% ± 5.0%. Study quality was moderate (range, 3–7/11 points; mean, 5.4) with infrequent blinding; 11 studies had no control group or reliability analyses and 21 studies used the control condition inappropriately.
Conclusions: Short durations of acute static stretch did not result in a meaningful reduction in muscular performance. Stretches of 30 to 45 seconds may reduce strength but not power, and stretches longer than 60 seconds reduced maximal performance on strength-, power-, and speed-dependent tasks.
Clin J Sport Med. 2012;22(5):450-451. © 2012 Lippincott Williams & Wilkins