What can we learn from static stretching research?

by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

A single research study is not enough.

The effect static stretching may have on flexibility, performance enhancement, and injury prevention is a complex issue that cannot be sufficiently tackled with a single research study. Static stretching affects multiple body systems and tissues, and a variety of static stretching techniques and protocols are utilized by wellness professionals. It is not responsible to sensationalize a single study, or utilize the results from a single study to promote a product or change the safe practices of wellness professionals. The research review and meta-analysis by Thacker et al, and review by Anderson are great examples of publications that consider the full body of research available (at least all research that was available to the researcher at the time) to challenge previous assumptions about stretching1-2. Both publications reinforce the idea that general flexibility programs may not have an effect on injury or sports performance; however, this differs from the specific flexibility programs used by some health and wellness professionals. Although, this is an important step in refining our practice, neither review attempted to propose a single set of guidelines for stretching. The current body of research is substantial, but leaves many questions unanswered making it hard to define a single set of parameters.

It is important that as wellness professionals we remain skeptical and curious, and view each new study as an important piece of the puzzle that is best practice.

You cannot expect specificity from a general program.

Although it is beyond the scope of this article to discuss the intricacies of motor behavior; a muscle may act as an agonist, synergist, neutralizer, or stabilizer; each role placing unique stress on a muscle. The “role” a muscle plays in a motor program influences its propensity to become tight, elongated, weak, or overactive. Reinforcing this idea, studies have noted that elite athletes have specific limitations in range of motion3,4. It is likely that stretching some muscles will increase performance and reduce the risk of injury, and stretching other muscles will lead to a decrease in performance and increase the risk of injury. In essence, the specificity of exercise selection that is expected when developing cardiovascular and/or resistance training programs must be applied to flexibility programs as well. If we are to expect a specific increase in flexibility, performance, or a reduction in the risk of injury; the muscles stretched, the technique utilized, and the protocol followed must be specific to the relative flexibility of the individual and athletic endeavor.

Specificity requires assessment.

There are approximately 640 muscles in the human body, but most research studies aimed at static stretching examine hamstring flexibility. That is, stretching the hamstrings without consideration for relative hamstring length or the role the hamstrings play in common movement patterns. What happened to assessment? How do we know whether the hamstrings need to be stretched? Of all the muscles on the human body why the hamstrings? Assessment is the logical first step for wellness professionals, but is lacking in the majority of research. That is not to say that research fails to measure or track changes in flexibility, only that most research does not utilize these measures to determine a need for stretching, or hypothesize the outcome based on pretreatment muscle length. Without considering relative muscle length it is not possible to hypothesize or correlate the effect a stretch protocol may have on improving length tension relationship, force couplings, neuromuscular efficiency, or joint arthrokinematics, all of which may have a profound impact on performance and the risk of injury. It is also likely that changes in ROM will vary greatly between someone who exhibits limitations and someone who exhibits flexibility at or beyond normal; the results may be similar to the differences in gains between novice and experienced weight lifters. In a preliminary study and presentation by Serrano et al. comparing sit and reach hamstring stretches, it was noted that those individuals who possessed excellent flexibility before the intervention gained nothing from the flexibility program5.

The lack of assessment has left many questions unanswered about how to stretch, much less, what effect static stretching may have on performance, and the risk of injury. Interestingly, in the one study I could locate that selected individuals from a sample who exhibited clinical tightness before commencing a hamstring stretching program, performance in a single leg hop test improved; this contradicts many research studies on flexibility and performance6.

The details count.

Even if great research and appropriate assessment lead to the creation of a flawless program, poor technique or a mistaken protocol can render the best intentions ineffective. Just as form is important to resistance training exercise, and the calculations of heart rate zones leads to better cardiovascular programs, stretching technique is as important to effective stretching programs. For example, the length of time a person holds a static stretch is a major confounder of research results on static stretching, as research holding a static stretch for less than 30 seconds has been inconclusive. In a study by Pope et al, 1538 army recruits participated in a randomized trial to determine whether a general stretching program would have an effect on the number of injuries during 12 weeks of training7. Unfortunately, this study used a 20 seconds per stretch protocol; confounding the results that supported the recent notion that stretching does not significantly reduce the risk of injury. Can we infer that a general flexibility program does not reduce the risk of injury, or is it that holding a stretch for 20 seconds has no effect on the risk of injury? In research, every study tells us something, in the case of Pope et al. a “maybe” is a stepping stone that leads to further research and adds to our body of knowledge.

Unfortunately, wellness professionals may not reap a benefit from a protocol that is “possibly” efficacious. For example, if an individual’s performance has been compromised by a limitation in ROM, that individual may expect results from a flexibility program. If a particular stretching protocol was ineffective than the failure to meet expectations may have an effect on the business of wellness professional and the performance of the individual. Often the cause of such a failure is a small oversight in practice, not only decreasing the benefit of a stretch, but rendering it ineffective. It is up to the wellness professional to use the current body of research to refine their practice, utilize evidence from their education and practice, and mind every detail of technique to ensure best practice.

Conclusion:

Evidence-, or research-based practice is an important step for the growth of health and wellness field, and may be essential to the inclusion of many wellness professions into an exclusive allied health network. The research that supports our practice is growing, but simply having research is not as important as its use. The realization of this growth is dependent on the interpretation of research to ensure better results for those under our care.

• Be careful to weigh each study as a piece of the overall picture.
• Do not expect specificity from a general program.
• Practice assessment techniques to create specific programming.
• Be exacting in the execution of exercise techniques to ensure the expected result.

Bibliography

(in order of appearance in the article)

1. Thacker B, Gilchrist J, Stroup F, Kimsey Jr., D. The impact of stretching on sports injury risk. Med Sci Sports Exerc. 2004;36(3):371-378
2. Anderson J. Stretching before and after exercise: effect on muscle soreness and injury risk. J Athl Train. 2005;40(3):218-220
3. Craib M, Mitchell V, Fields K, Cooper T, Hopewell R, Morgan D. The association between flexibility and running economy in sub-elite male distance runners. Med Sci Sports Exerc. 1996;28(6):737-743
4. Sell T, Tsai Y, Smoliga J, Myers J, Lephart S. Strength, flexibility, and balance characteristics of highly proficient golfers. J Strength Cond Res. 2007; 21(4):1166-1171
5. Serrano, Ronnie; Russo, Anne Marie; Marino Joseph; Lamonte, Alyson; Wygand, John; Otto Robert M. A Comparison of the Traditional Vs The Unilateral Back Saver Sit and Reach Hamstring Stretch: 490 Board #81 2:00 PM - 3:30 PM. Medicine and Science in Sports and Exercise: 2005;37(5) S92
6. Ross M. Effect of a 15-day pragmatic hamstring stretching program on hamstring flexibility and single hop for distance test performance. Res Sports Med. 2007;15:271-281
7. Pope R, Herbert D, Kirwan J, Graham B. A randomized trial of preexercise stretching for prevention of lower limb injury. Med Sci Sports Exerc. 2000;32(2):271-277

© 2011 Brent Brookbush

Questions, comments, and criticisms are welcomed and

encouraged –