An evidence based guide to stretching.

Creasy, John ; Buriak, James

It is common practice in today's society to stretch before performing physical activity. This trend begins to be ingrained into everyone during their young years playing recreational sports, gym classes, high school sports and up through college athletics and elite level athletes. Stretching was always an integral part of practice, but why? It is important to understand both the benefits and the negative effects of stretching before implementing it into daily practice routines. So, what is the difference between stretching and flexibility? This question brings on a lot of confusion in the world of physical fitness and sport. Stretching and flexibility are very different in their definition and application. The American College of Sports Medicine (ACSM) defines flexibility as the range of motion around a joint (ACSM). Stretching is defined as a movement applied by an external and/or internal force to increase joint range of motion (Weerapong, Hume & Kolt, 2004). Stretching is the mechanism used to improve overall flexibility. Stretching is incorporated into almost all fitness routines, but is this actually necessary if we examine it for its primary purposes?

The ACSM recognizes three main methods of stretching commonly used by athletes, coaches, and physical education teachers. These methods are static, ballistic, and proprioceptive neuromuscular facilitation (PNF) stretching. A fourth and relatively new method of stretching that is becoming very popular is dynamic stretching. Static stretching is a slow sustained stretch that is held for approximately 20 seconds (Amako et al., 2003). Ballistic stretching incorporates bouncing movements in which the muscles and tendons are rapidly stretched and relaxed (Garber et al., 2011). PNF stretching is a stretching technique that is usually done with a partner. It consists of a passive stretch, followed by a six second isometric contraction, followed by a 10-30 seconds assisted stretch. (Garber et al., 2011). Dynamic stretching seems to be the new fad in the athletic world but when this method is actually defined, it is recognized that dynamic stretching is a combination of static and ballistic stretching for it is the movement of the body from one body position to another, slowly increasing the length of the stretch with each movement (Garber et al., 2011). The main goals of stretching are to increase range of motion, improve performance, and reduce injuries (McHugh & Cosgrave, 2010; Weerapong, Hume & Kolt, 2004). If stretching does not accomplish any of these goals, pre-exercise stretching is an unneeded aspect of an exercise routine, practice or workout.

A study by Marek et al. in 2005 examined the effects of static and PNF stretching on power output. It was found that when either of these stretching methods was performed there was a decrease in mean power produced (Marek et al., 2005). In a similar study, Bacurau et al. (2009) compared the effects of static stretching exercises and maximal strength to no stretching and maximal strength. This study found that there was a significant decrease in force production after the subj ect participated in a static stretching protocol (Bacurau et al., 2009). From these findings we can conclude that stretching can decrease power output and force production of a muscle and/or muscle group. This would in most cases decrease performance and is not a desired outcome of stretching.

In a large study using military recruits, Pope, Herbert, Kirwan and Graham (2000) studied the effects of pre-exercise stretching specifically on lower limb injury. In stretching of the gastrocnemius muscle, there was no observed reduction in injury rates. This study recognized the idea that the stretch may not have been performed at long enough intervals, however, the conclusion drawn was that there was not a worthwhile reduction in lower limb injury due to pre-exercise stretching (Pope et al., 2000).

Thacker, Gilchrist, Stroup & Kimesy (2003) performed a systematic review of the literature and came to the conclusion that there was no evidence available showing that pre and post stretching exercises prevented injury or reduced muscle soreness. The lack of evidence available had this review neither promoting or rejecting pre and post event stretching (Thacker et al., 2003).

In another systematic review, Small, McNaughton and Matthews (2008) concluded that pre-exercise static stretching is ineffective in reducing injury risk. In the majority of the studies reviewed large risk reductions were not seen in groups that participated in pre-exercise testing, but it was found that there might be small positive effects that are being overlooked. Pre-exercise stretching only showed trends of injury prevention of musculotendinous strains and ligament injuries, which can only suggest a preliminary relationship between stretching and some types of injuries (Small, McNaughton & Matthews, 2008). More research is needed to draw conclusions on these types of injuries in relation to pre-exercise stretching.

The overall conclusion reached by examining these studies is that pre-exercise stretching does not reduce injury risk. Going back to the main goals of stretching being an increased range of motion, improved performance and decreased injury risk (McHugh & Cosgrave, 2010; Weerapong, Hume & Kolt, 2004) this conclusion does not satisfy these goals.

Overall flexibility and injury risk are closely linked according to research. It is important to maintain a normal range of motion. In a study of military recruits, Amako, et al. (2003) observed a decrease in injury after a normal level of flexibility was reached. The extremes of flexibility have also been linked to an increase in injury susceptibility. Low levels of flexibility have been associated with overuse injuries while high levels of flexibility have been found to make individuals at risk for acute injuries (Small, McNaughton & Matthews, 2008). The increase in range of motion associated with stretching and increased flexibility creates body positions that have dangerous loading effects, which could lead to ligaments being stretched too far (Thacker et al., 2003). Stretching increases ones range of motion beyond what is needed for the specific sport; therefore can possibly lead to injury (Small, et al., 2008). Significantly higher risk of injury has been noticed in the most and least flexible participants in studies (Thacker et al., 2003).

It is very difficult to isolate the effects of stretching alone on injury risk making it difficult to say that stretching is the sole preventative measure against injury (McHugh & Cosgrave, 2010). All the research reviewed seems to find that stretching does not prevent injury, yet some small trends always seem to appear saying that it does. It has also been noted that pre-exercise warm-up is very important; this makes it extremely difficult to say what is helping prevent injury (if an aspect is actually helping), the warm-up or the stretching (McHugh & Cosgrave, 2010).

After reviewing the literature available we recommend that athletes, and others performing physical activity, maintain a normal flexibility range throughout a focused program. This flexibility program should consist of static or PNF stretching methods in which the stretch is held for 20 to 30 seconds and repeated three times. All major muscles groups should be stretched at least three times a week. The goal of a program like this is to maintain normal flexibility. Although normal range of motion is difficult to define, The American Academy of Orthopedic Surgeons and other organizations have provided range of motion normative data; however, there is a lot of variance between the charts. Typically normal range of motion is assessed using a bilateral comparison. If, due to injury of the opposite side, it is impractical to compare bilaterally, one would use the range of motion charts as a guide to establish normal range of motion. Range of motion is joint specific and varies from person to person. We also believe that a dynamic warm-up may be the most important factor as a preexercise activity.

There is not much research available that supports the effects of stretching on exercise performance and injury risk, yet it seems that stretching is performed regularly by most athletes. In physical education classes and organized sports teams, practice always starts out with stretching. In some sports (ballet, gymnastics, karate, etc.) there is a greater need for an increase in range of motion. In most individuals and sports, normal (compared bilaterally) range of motion is required. According to Prentice (2011), "It has also been generally accepted that flexibility is essential for improving performance in physical activities. However, a review of the evidence-based information in the literature looking at the relationship between flexibility and improved performance is, at best, conflicting and inconclusive" (p. 176). If an individual is lacking range of motion as compared bilaterally, we would recommend a flexibility program. The evidence suggests that stretching is not proven to be beneficial to performance or help decrease the risk of injury (Bacurau et al., 2009; Pope et al., 2000; Small, et al., 2008). This being the case, why is stretching still such a large part of workout routines and practices?

References

Amako, M., Oda, T., Masuoka, K., Yokoi, H. and Campisi, P. (2003). Effect of static stretching on prevention of injuries for military recruits. Military Medicine, 168, 442-446. PubMed. Web. 4 Nov. 2012.

Bacurau, R., Monteiro G. de A., Ugrinowitsch, C., Tricoli, V., and Cabral L.F. (2009). Acute effect of a ballistic and a static stretching exercise bout on flexibility and maximal strength. Journal of Strength and Conditioning Research, 23(1),304-308. PubMed. Web. 4 Nov. 2012.

Garber, C.E., Blissmer, B., Deschenes, M.R., Franklin, B.A., Lamonte, M.J., Lee, I.M., and Nieman, D.C. (2011). Quantity and quality of exercise for developing and maintaining Cardio-respiratory and musculoskeletal, and neuromotor fitness in apparently health adults: Guidance for prescribing exercise. Medicine and Science in Sports, 43(7), 1334-59.

Marek, S.M., Cramer, J.T., Fincher, A.L., Massey, L.L., Dangelmaier, S.M., Purkayastha, S.,... Culbertson, J.Y. (2005). Acute effects of static and proprioceptive neuromuscular facilitation stretching on muscle strength and power output. Journal of Athletic Training, 40(2), 94-103. PubMed. Web. 4 Nov. 2012.

McHugh, M. P., & Cosgrave, C.H. (2010). To stretch or Not to stretch: The role of stretching in injury prevention and performance. Scandinavian Journal Of Medicine & Science In Sports, 20(2), 169-181. SPORTDiscus with Full Text. Web. 4 Nov. 2012.

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), 271 277. CINAHL. Web. 4 Nov. 2012.

Prentice, W. E. (2012). Rehabilitation techniques for sports medicine and athletic training. New York, NY: McGraw-Hill Companies, Inc.

Small, K., McNaughton, 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. SPORTDiscus with Full Text. Web. 4 Nov. 2012.

Thacker, S.B., Gilchrist, J., Stoup, D.F., & Kimsey, D. (2004). The impact of stretching on sports injury risk: A systematic review of the literature. Medicine & Science in Sports & Exercise, 36(3), 371-378. SPORTDiscus with Full Text. Web. 4 Nov. 2012.

Weerapong, P., Hume, P.A., & Kolt, G.S. (2004). Stretching: Mechanisms and benefits for sport performance and injury prevention. Physical Therapy Reviews, 9(4),189-206. Academic Search Complete. Web. 4 Nov. 2012.

John Creasy, Associate Professor, Health and Human Performance Department, Roanoke College

James Buriak, Associate Professor, Health and Human Performance Department, Roanoke College