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epimetheus
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From: http://www.pponline.co.uk/encyc/0860.htm
So what about dynamic flexibility?
Dear Editor,
I have read with keen interest the dialogue in the last few issues of PP regarding the issue of stretching and flexibility. Following the insightful comments of Craig Sharp (in issue 134), I feel there is a body of research that is able to provide sports scientists and coaches with an alternative to pre-competition static stretching. Both Prof. Sharp and Nick Grantham have identified some key research that brings into question the long-standing belief that performers MUST statically stretch before they compete.
For many years the sports science community has been advocating the use of static stretching in athletic performance for two major reasons: injury prevention and performance enhancement. Recent research suggests, however, that these ideas may be flawed. Rod Pope ('Skip the warm-up,' New Scientist, 164(2214), p. 23) an army physiotherapist in Australia, recently carried out a wide study to assess the relationship between static stretching and injury prevention. Pope monitored over 1600 recruits over the course of a year in randomised controlled trials. He found no differences in the occurrence of injury between those recruits who statically stretched and those who did not. Following a review of literature, Gleim & McHugh (1997), would also challenge the premise that stretching, or indeed increased flexibility, reduces the risk of injury ('Flexibility and its effects on sports injury and performance,' Sports Medicine, 24(5), pp. 289-299).
Okay, so if pre-exercise static stretching does not promote injury prevention, does it promote enhanced performance? Both Craig Sharp and Nick Grantham have found evidence to suggest that it may in fact decrease performance in both endurance and speed/power events. Rosenbaum & Hennig (1995) found that static stretching resulted in peak force reduction (5%), rate of force production (8%), EMG amplitudes (16%) and increased the time to peak EMG (3%) in their study of Achilles tendon reflex ('The influence of stretching and warm-up exercises on Achilles tendon reflex activity,' Journal of Sports Sciences, vol. 13, pp. 481-490). In addition, Oberg (1993) found that static stretching resulted in a decrease in torque during eccentric contractions ('Evaluation and improvement of strength in competitive athletes,' in Harms-Ringdahl, K., 'Muscle Strength.' Edinburgh: Churchill Livingstone.)
Even in the light of these findings, it is natural to assume that increased flexibility is beneficial to sports performers. However, to fully understand the situation, the nature of that flexibility needs to be considered. Moscov (1993) found that there is no relationship between static flexibility and dynamic flexibility. This suggests that an increased static range of motion may not be translated into functional, sport-specific flexibility, which is largely dynamic in most sporting situations ('Static ROM, leg power & leg strength as predictors of dynamic ROM in female ballet dancers,' Microform Publications, Eugene, Ore: University of Oregon Gleim & McHugh (1997) propose that functional flexibility might be conceptualised as ease of range of motion and 'compliance' (rather than resistance to deformation). The traditional model of flexibility is based on increasing the total range of motion rather than ease of motion within a range ('Flexibility and its effects on sports injury and performance,' Sports Medicine, 24(5), pp. 289-299).
Several authors (Wolpaw et al, 1983, Tsatsouline, 1998) propose that limitations on flexibility, particularly dynamic flexibility, are neurological rather than structural (within the musculo-skeletal structure) ('Adaptive plasticity within the primate spinal stretch reflex: reversal and development,' Brain Research, 278(1-2), pp. 299-304). Pavel Tsatsouline especially advocated that dynamic stretching is the key to increasing functional flexibility. Practitioners have been implementing these ideas for years in the Eastern Bloc ('Beyond stretching: Russian flexibility breakthroughs.' St Paul, Minnesota: Dragon Door Publications). SAQ have been championing the case for dynamic flexibility warm-ups over the past five years in this country and abroad. There are evolving methods of dynamic flexibility development that receive relatively little coverage in professional literature. However, as Prof. Sharp expressed, sports science follows on behind developing practice.
As a sports scientist, and practitioner, I believe that we need to be critical in our approach and question more of the long-standing beliefs that still shape athletic practice. The issue of dynamic flexibility is one of many that needs to be tackled. The efficacy of long-distance running for aerobic development in gamesplayers is another that is worthy of attention. As sports scientists and practitioners, let's be open to the possibility that there may be a 'better way', and strive continually to find more effective ways of training.
Simon Hartley, MSc, Lecturer in Sport & Exercise Science, University of Sunderland
