Stretching Katelyn Bennett David Berning Fall 2005

Introduction There are many theories and myths about the importance and effect of stretching. Coaches tend to put a lot of emphasis on stretching prior to and following activity. Lately there has been controversy on the effectiveness of stretching. Don’t forget to stretch!

Questions about Stretching What type of stretching is best? How long should we stretch? Does stretching prevent injury? Does stretching improve performance?

Types of Stretching Static stretching –Holding a stretching exercise in one position without movement –The stretch is taken to the point where resistance is felt but no pain. Dynamic stretching –Stretching movements that use muscle power to move muscle through full ROM. –Examples: neck rolls, arm circles, knee rotations  Proprioceptive Neuromuscular Facilitation (PNF) –Combination of static passive stretching and isometric stretching –Most common PNF stretching technique is the contract-relax method

Static Stretching Improves ROM [Nelson et al] Impairs warm-up effect [Behm et al] –Decreases balance –Slows muscle activation for about an hour [Fowles et al] Decreases peak torque [Power et al] –Possibly due to altered length-tension relationship or a CNS inhibitory Impairs maximal force production [Cramer et al]

Comparison between Stretching Types Static stretching better than PNF [Davis et al] PNF is more effective post-exercise than before exercise [Funk et al] 30 seconds of static stretch is better than dynamic for hamstring flexibility [Bandy et al.] Static stretching slows muscle activation; dynamic stretching is a better choice before competition [Fowles et al] Results are varied and require more research to determine best mode of stretching

Duration Study 5 week study of static hamstring stretching; comparing 30s, 60s, 90s, 120s –30 seconds best; longer didn’t provide more benefit Effect of 15 minutes of contract-relax stretching on ROM on lower extremities [moller et al.] –Significant increase in hip abduction (+17%), knee flexion (+4%), ankle dorsiflexion w/ knee flexed (+18%), and ankle dorsiflexion w/ knee straight (+16%)

Duration of Stretching Holding stretch for 30 seconds is sufficient to increase ROM [Bandy et al, Ford et al] No change in ROM by increasing duration of stretch to seconds [Bandy et al] Stretching once a day is just as effective as stretching three times a day Total of 15 minutes of stretching for all muscle groups recommended [Moller et al]

Effect of Stretching on Performance Static stretching decrease muscle strength endurance [Nelson et al] –Recommended that heavy static stretching be avoided prior to performance requiring maximal muscle strength endurance Neither static nor ballistic stretching had an effect on vertical jump [Unick et al.] Pre-event stretching negatively impacts high power, short term exercise (example: 20 meter sprints) [Nelson et al]

Stretching and Injury Prevention There is not sufficient evidence to endorse or discontinue routine stretching before or after exercise to prevent injury in athletes [Thacker et al] Decreased incidence of muscle-related injury, but doesn’t prevent bone or joint damage (total injury rate is approximately the same) [Amako et al] Stretching may help aid in prevention of stress fractures [Sanderlin et al] Stretching necessary for sports with high intensity SSC’s to stretch the muscle-tendon unit (soccer, football) [Witvrouw et al] Stretching unnecessary for sports containing limited SSC’s (jogging, cycling, swimming) [Herbert te al]

Reasons Stretching does not Prevent Injury No basic science research shows that an increase in muscle compliance is associated with increased ability to absorb energy [Shrier et al] Most injuries occur eccentrically, within normal ROM [Shrier et al] Even mild stretching can cause damage at the cytoskeletal level [Shrier et al] No effect on activities in which excessive muscle length is not an issue [Shrier et al] Stretching increases pain tolerance, which is not good [Shrier et al]

Conclusion Results from several studies contradicted one another. Research is still needed to make definite conclusions about the best type of stretching and effects of stretching on injury and performance. Since there is no clear cut answer, the decision about how or when to stretch is up to you!

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References of Sports Medicine (2002). Pettineo, S J. "Female ACL injury prevention with a functional integration exercise model." Strength and Conditioning journal (2004). Shrier, Ian. "Stretching before exercise: an evidence based approach." British Journal of Sports Medicine (2000). Shrier, Ian. "Stretching before exercise does not reduce the risk of local muscle injury: a critical review of the clinical and basic science literature." Clinical Journal of Sports Medicine (1999). Thacker, S B., and J Gilchrist. "The impact of stretching on sports injury risk: a systematic review of the literature." Medicine and Science in Sports and Exercise (2004). Witvrouw, Erik. "Stretching and Injury Prevention." Sports Medicine (2004)