A systematic review of the effects of acute static stretch on maximal muscular performance

The benefits of pre-exercise muscle stretching have been recently questioned (Magnusson & Renström, 2006) following reports of significant post-stretch reductions in force and power production. However, methodological issues and equivocal research findings have prevented a clear consensus being reached. As no detailed systematic review exists, the literature describing responses to acute static muscle stretch was comprehensively examined. Medline, ScienceDirect, SPORTDiscus, Swetswise and Zetoc were searched with recursive reference list checking. Selection criteria included: randomised, quasi-randomised and intervention-based trials published in peer reviewed journals examining an acute static stretch intervention on maximal muscular strength, power or speed performance published before 2011. The search revealed 2634 possible articles; one-hundred met the inclusion criteria. Study design was often poor, with many studies not imposing a control condition/group or providing appropriate reliability statistics (31%). There is no evidence that short-duration acute static stretch (<30 s) has a detrimental effect (pooled estimate = -0.5%), with there being overwhelming evidence that stretch durations of 30-45 s also imparted no significant effect (pooled estimate = -2.7%). A clear dose-response effect was evident between stretch duration and both the likelihood and magnitude of significant decrements, with a significant reduction being likely to occur with stretches >60 s. Maximal muscular strength, power and speed performances were similarly affected regardless of stretch duration, with similar trends apparent across lower limb muscle groups and contraction modes. There is strong evidence for a dose-response effect where the likelihood and magnitude of significant impairments exists for stretches ≥60 s, regardless of performance task, contraction mode or muscle group. However, the overwhelming evidence is that short-duration static stretch (≤45 s) does not detrimentally affect maximal muscle efforts (especially speed or power performance) and can be performed in a pre-exercise routine without compromising maximal muscle performance. The detrimental effects of static stretch are mainly limited to longer durations (≥60 s) that are not typically used during pre-exercise routines in clinical or athletic populations and, therefore, have limited practical relevance. No research exists describing the effects of <60 s static stretch on eccentric strength; given that muscle-strain injury risk is typically associated with eccentric muscle actions, this needs to be examined in the future.