Effects of Stretching on Performances Involving Stretch-Shortening Cycles.

Effects of Stretching on Performances Involving Stretch-Shortening Cycles.

In addition to its role in athletic conditioning, stretching has often been integrated in warm-up routines before athletic performance. Many studies have reported detrimental acute effects on strength after stretching. Due to this, athletes have been recommended to discontinue stretching as part of warm-ups. In contrast, studies indicate that chronic stretching performed as a separate bout from training or competition may enhance performance. However, the influence of stretching on complex performances has gotten relatively little attention. The authors’ undertook this study in order to review both the acute and chronic effects of stretching on performances involving the stretch-shortening cycle (SSC). A systematic search for literature was undertaken (January 2006-December 2012) in which only randomized controlled trials (RCTs) or studies with repeated measures designs were included. The Physiotherapy Evidence Database (PEDro) rating scale was used for quality assessment of the evidence. The review was made up of 43 studies, from which conflicting evidence emerged. About half of the studies assessing the acute effect of static stretching reported a detrimental effect on performance, while the remainder found no effect. In contrast, dynamic stretching showed no negative effects and improved performance in half of the trials. The effect size associated with static and dynamic stretching interventions was commonly low to moderate, indicating that the effect on performance might be limited in practice. Factors were identified that might have contributed to the conflicting results reported across studies, such as type of SSC performance and carrying out dynamic activity between the stretching bout and performance. Few studies since 2006 have addressed the chronic effect of stretching on functional and sports performance. Although negative effects were not reported, robust evidence of the overall beneficial effects within current bibliographic databases remains elusive. Probable mechanisms for the observed effects from stretching are discussed, as well as possible factors that may have added to contradictory findings between studies. Considerable heterogeneity in study design and methods makes comparison between studies challenging. No regression analysis of the contribution of different predictors to variation between trials had previously been performed. Hence, predictors had to be selected on the basis of a qualitative analysis of the predictors that seemed most influential, as well as being identified in previous narrative reviews.

The review found that different types of stretching have differential acute effects on SSC performances. The recommended volume of static stretching required to increase flexibility might induce a negative acute effect on performances involving rapid SSCs, but the effect sizes of these decrements are frequently low, indicating that the acute effect on performance might be limited in practice. No negative acute effects of dynamic stretching were reported. For athletes that demand great range of motion (ROM) and speed in their sport, long-term stretching successfully enhances flexibility without adversely affecting performance. Acute dynamic stretching may also be effective in inducing smaller gains in ROM prior to performance without any negative effects being observed.

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