The effectiveness of pre-activity stretching on injury rates in sport

The downside to activity in sport is the risk of injury. Injuries can be expensive, difficult to manage and can result in both short-term and long-term consequences to a person’s health. For example long-term knee injuries may prevent a person from exercising and therefore may contribute to long-term obesity and cardiovascular disease.

Injury prevention therefore is an important topic and with the ever increasing amount of literature this is now easier to study. This paper looked at 16 different systematic reviews and six other reviews or clinical trials.

Types of stretching. The various types of stretching described in the literature were static stretching, dynamic stretching, proprioceptive neuromuscular facilitation (PNF) stretching and ballistic stretching.

Physiological effects of stretching. There are two main effects stretching of structural level on soft tissue. Firstly of what is termed viscoelastic effects. Put simply this means that if some force is applied to the tissue it has the capacity to elongate and the forces removed it will gradually return to its original length (elastic behaviour). With higher forces and repeated application of lower forces this elongation can become permanent (viscous behaviour) and with biological soft tissues this often results in injury. The other effect stretching is a neural effect. It would appear that we stretch biological soft tissues in particular muscles the neural output to the muscle reduces meaning that there is less resistance to stretch (6).

Variables. A discussion of stretching needs to take into account the

-          time stretched

-          the frequency and

-          Intensity of the stretch

We examined the effect of pre-activity stretching on:

-          Strength

-          Performance

-          muscle soreness

-          range of motion and flexibility

-          injury risk

 

Strength and performance. The literature seems fairly conclusive that an acute bout of static stretching will cause both a loss of strength immediately after stretching and a loss of performance. Loss of performance seems to be less than a loss of strength and could probably be reduced if the stretch is accompanied by a warmup (6). Dynamic stretching may actually improve performance (14).

Muscle soreness. The studies examined are conclusive that stretching before activity and after activity does not reduce muscle soreness.

Range of motion and flexibility (1, 2). Static, dynamic and PNF stretching and short-term effects of less than one hour range of motion (1, 6, 8). Dynamic stretching improves dynamic flexibility more than static stretching (1).

On injury rates and risks. This is a topic of stretching becomes somewhat controversial.

-          There seems to be no adverse effects of stretching (5).

-          It seems fairly conclusive that stretching has no effect on overuse injuries (2,3,4,5,6), and no effect on ligament injuries risk (1,2,3,4,5,6).

-          There several studies showing that stretching has no effect on overall injury rates and risks (2, 3, 4, 5, 6). However many of these studies had very short stretching protocols and it was therefore no surprise that they had no effect on muscle injuries?

-          Also several of the studies looked at overall injury risk or rate (2, 3, 4, 5), and these would have included contusions, fractures and other injuries which could have caused any positive effects from stretching to be lost or missed. In fact when the rate of muscle injuries is looked at from this data, we find a reduction in muscle tears with stretching (6).

-          Also when longer stretching protocols were put into place, several studies have concluded that muscle strains can be reduced by stretching (1, 6, 7).

Conclusion and comments.

-          If you are in a sport that requires a certain amount flexibility to perform and activity, for example kicking in martial arts, and you do not have this, then you should stretch regularly to obtain the necessary flexibility. This may be necessary pre-competition in these sports.

-          Pre-competition static stretching is to be avoided for most sports. It offers no advantages over dynamic stretching, and may impair performance.

-          Dynamic stretching may improve performance.

-          Dynamic stretching offers advantages over the other forms of stretching as well. PNF stretching requires a partner, and may impair performance. Ballistic stretching may be unsafe.

-          It is not known if pre-activity dynamic stretching will have an effect on injury risk. Studies which show no effect have generally very short stretching protocols.

References

1.       Behm, D., Blazevich, A., Kay, A., & McHugh, M. (2016). Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. Applied Physiology, Nutrition, And Metabolism, 41(1), 1-11. doi: 10.1139/apnm-2015-0235

2.       Gill, A. (2018). Stretching the truth: a review of literature on the effects of static and dynamic stretching protocols on strength and power performance. Journal Of Australian Strength And Conditioning, 24(7).

3.       Herbert, R. (2002). Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review. BMJ, 325(7362), 468-468. doi: 10.1136/bmj.325.7362.468

4.       Lauersen, J., Bertelsen, D., & Andersen, L. (2013). The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. British Journal Of Sports Medicine, 48(11), 871-877. doi: 10.1136/bjsports-2013-092538

5.       Leppänen, M., Aaltonen, S., Parkkari, J., Heinonen, A., & Kujala, U. (2014). INTERVENTIONS TO PREVENT SPORTS RELATED INJURIES: A SYSTEMATIC REVIEW AND META-ANALYSIS OF RANDOMISED CONTROLLED TRIALS. British Journal Of Sports Medicine, 48(7), 626.1-626. doi: 10.1136/bjsports-2014-093494.179

6.       Lewis, J. (2014). A Systematic Literature Review of the Relationship Between Stretching and Athletic Injury Prevention. Orthopaedic Nursing, 33(6), 312-320. doi: 10.1097/nor.0000000000000097

7.       McHugh, M., & Cosgrave, C. (2009). To stretch or not to stretch: the role of stretching in injury prevention and performance. Scandinavian Journal Of Medicine & Science In Sports. doi: 10.1111/j.1600-0838.2009.01058.x

8.       Parkkari, J., Kujala, U., & Kannus, P. (2001). Is it Possible to Prevent Sports Injuries?. Sports Medicine, 31(14), 985-995. doi: 10.2165/00007256-200131140-00003

9.       POPE, R., HERBERT, R., KIRWAN, J., & GRAHAM, B. (2000). A randomized trial of preexercise stretching for prevention of lower-limb injury. Medicine & Science In Sports & Exercise, 32(2), 271. doi: 10.1097/00005768-200002000-00004

10.   Rogan, S., Wüst, D., Schwitter, T., & Schmidtbleicher, D. (2012). Static Stretching of the Hamstring Muscle for Injury Prevention in Football Codes: a Systematic Review. Asian Journal Of Sports Medicine, 4(1). doi: 10.5812/asjsm.34519

11.   Small, K., Mc Naughton, L., & Matthews, M. (2008). A Systematic Review into the Efficacy of Static Stretching as Part of a Warm-Up for the Prevention of Exercise-Related Injury. Research In Sports Medicine, 16(3), 213-231. doi: 10.1080/15438620802310784

12.   THACKER, S., GILCHRIST, J., STROUP, D., & KIMSEY, C. (2004). The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature. Medicine & Science In Sports & Exercise, 36(3), 371-378. doi: 10.1249/01.mss.0000117134.83018.f7

13.   Van Mechelen, W., Hlobil, H., Kemper, H., Voorn, W., & de Jongh, H. (1993). Prevention of running injuries by warm-up, cool-down, and stretching exercises. The American Journal Of Sports Medicine, 21(5), 711-719. doi: 10.1177/036354659302100513

14.   Worrell, T., & Perrin, D. (1992). Hamstring Muscle Injury: The Influence of Strength, Flexibility, Warm-Up, and Fatigue. Journal Of Orthopaedic & Sports Physical Therapy, 16(1), 12-18. doi: 10.2519/jospt.1992.16.1.12