Effects of stretching on performances involving stretch-shortening cycles.

Along with its role in athletic conditioning, stretching has frequently been incorporated into warm-up routines prior to athletic performance. Many studies have reported detrimental acute effects on strength following stretching. As a result of this athletes have been advised 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 not received very much attention. Therefore the authors conducted this study to review both the acute and chronic effects of stretching on performances involving the stretch-shortening cycle (SSC). They conducted a systematic search for literature (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. Their review included 43 studies, from which disagreeing evidence appeared. Approximately 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 could 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. While negative effects weren’t reported, robust evidence of the overall beneficial effects within current bibliographic databases remains elusive. Feasible  mechanisms for the observed effects from stretching are discussed, as well as possible factors that may have contributed to contradictory findings between studies.

The study concludes that various types of stretching have differential acute effects on SSC performances. The recommended volume of static stretching needed to increase flexibility could induce a negative acute effect on performances involving rapid SSCs, but the effect sizes of these decrements are commonly 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 need considerable range of motion (ROM) and speed in their sport, long-term stretching successfully improves flexibility without negatively affecting performance. They added that acute dynamic stretching might effective in inducing smaller gains in ROM prior to performance without any negative effects being seen as well.