Stretching prior to performance – what does the evidence say?
Warming up prior to physical performance is believed to facilitate mental and physical readiness, prevent injuries and improve performance. For many years there has been discussion and debate regarding the importance of stretching in a warm up. Static stretching – once strictly adhered to has since been thought to impair performance and have no impact on injury prevention. As such, static stretching has been replaced over the last 15 years with dynamic stretching. But is it wise to cease static stretching altogether?
The body of research behind stretching is contradictory and often confusing. This blog aims to explain the different types of stretching, discuss the evidence and provide a guide for how to apply the evidence to your warm up.
What are the types of stretching?
Static stretching involves lengthening a muscle until you feel a stretch sensation and then holding the muscle in this position for a period of time. Below is a static hamstring stretch.
Dynamic stretching involves moving a limb and muscle from one end of its range to the other in a slow and controlled manner. For example, a dynamic stretch for hamstrings would involve swinging the leg forwards and backwards.
PNF stretching incorporates static stretching and isometric muscle contractions to increase range of motion. For example – during a lying down hamstring stretch, a partners shoulder is used to push against for a few seconds, to contract the hamstring muscle. The muscle is then relaxed and the stretch pushed to their new limit of range of motion. This should be repeated 3-4 times.
Static and dynamic stretches are most commonly used prior to exercise and are the easiest to administer without the assistance of anyone else or with the guidance of a health professional. Therefore we will focus on the benefits and potential dangers of these stretches.
Why do we stretch prior to physical performance?
Summary of evidence:
• Static stretches have not been found to improve performance
• Sustained static stretches (>20 seconds) have been shown to reduce performance
• Dynamic stretches have been shown to slightly improve performance
• PNF, static and dynamic stretches have been shown to slightly improve flexibility
• Static stretches may slightly reduce risk of soft tissue injury
• Static stretches may slightly reduce delayed onset muscle soreness
There are four main benefits to stretching prior to sport or exercise:
A recent 2016 systematic review looked at static and dynamic stretches in terms of athletic performance. (Behm et al. 2016) Static stretches were examined by 125 studies and overall there was a 3.7% average performance reduction. When static stretches were held for longer than 60 seconds, they found an average decrease in performance of 4.6%. Whereas when they were held for less than 60 seconds, the decrease in performance was negligible. Therefore, it is recommended that static stretches are held for durations of 15-20 seconds. Additionally, most studies measured performance 3-5 minutes after stretching but those that waited ten or more minutes before performance found very little or no negative effects on performance. It is difficult to generalise results across different types of athletic performance as the type of performance varied greatly between studies. It was found that dynamic stretching slightly increased performance by 1.3%. Unlike static stretching, the increase in performance further improved when dynamic stretching occurred immediately before exercise.
It has been established that PNF, static and dynamic stretching can improve range of motion over a short duration. (Behm et al. 2016) Most evidence indicates that PNF and static stretches are the most effective. Static stretches have been found to increase range of motion for up to 120 minutes after stretching! In comparison, dynamic stretching has only been tested over a 10 minute period.
It is often thought that stretching prior to exercise can reduce the number of injuries. Twelve studies have analysed static stretching and have found some effectiveness. No studies found that stretching increased injury risk. Static stretching has no overall effect on complex or overuse injuries but there may be a benefit in reducing acute muscle injuries, especially with repetitive contractions such as with sprinting. There is no high level research for dynamic stretching and injury prevention.
Delayed onset muscle soreness (DOMS) is muscle soreness that occurs between 24 and 48 hours after exercise. DOMS usually occurs when someone is new to a particular exercise or has not performed it at a certain intensity previously, especially when the exercise involves eccentric muscle contraction (when a muscle is active while lengthening). A 2011 systematic review included 12 studies that looked at DOMS and stretching. (Herbet et al., 2011) All but one of the studies looked at static stretching. The final study looked at PNF stretching. The results were consistently positive but only very marginally so – stretching before exercise reduced soreness one day after exercise by an average of half a point out of 100 and stretching after exercise by an average of one point out of 100. However, the only large study, which included 2377 participants, found stretching before and after exercise reduced soreness by 4 points out of 100 over the week following exercise – a slightly more positive result, yet it is still not hugely relevant for most people. While there is certainly no harm in stretching before or after exercise in relation to DOMS, it also appears that there is little benefit. Any benefits may be most relevant for athletes who participate in high intensity exercise daily, and therefore need to recover quickly.
What does this mean for static stretches before performance?
Despite the high number of studies, it is still difficult to say. A wide variety of performance outcomes were measured but most tests were lab based and therefore results may not be applicable to the complex demands of most sports. And although the evidence found that static stretching can briefly inhibit the muscles ability to generate power, this generally occurred when the stretch was held for longer than 60 seconds and the stretch occurred immediately before performance, without further dynamic stretching or warm up. Yet, in studies where stretches were held for less than 20 seconds, 10 minutes before performance, it was found that static stretching had no impact on performance. So stretching statically in this manner is not going to impede performance, but this is hardly a reason to spend valuable warm up time stretching.
However, there is some evidence that static stretches prior to exercise may slightly reduce the risk of soft tissue injury in sports that require explosive movements, such as basketball or soccer. There is also evidence that static stretches prior to exercise may slightly improve flexibility or range of movement. The key here is ‘slightly’ – if static stretching is only having a small affect, again, how do we know if our warm up time may be better spent?
Unfortunately, there is no one size fits all answer to this. Humans are complex individuals and sport and performance is usually comprised of many complex, coordinated activities. Therefore, it is important to carefully consider the requirements of your sport when deciding whether to statically stretch. For example, if your sport requires flexibility or large range of movements, such as gymnastics, you may need to statically stretch prior to the event. Based on the evidence, it is advised that you hold stretches for 15-20 seconds, and complete them at least 10 minutes prior to the performance. Based on the evidence, this will not impede performance yet will give you the extra flexibility required for your event. This should be applied to specific muscles groups when appropriate – eg. Hamstring stretching for kicking sports or hurdles.
If you’re having difficulty knowing how to stretch specific muscles or how to prepare for your sport try the app “Get Set – Train Smarter” which was developed through the International Olympic Committee, the Oslo Sports Trauma Research Centre and several international sport federations.
And what about dynamic stretching?
There is some evidence that dynamic stretching can slightly improve performance, more so than static stretching. There is also some evidence that static stretching can improve flexibility, less so than static stretching. But the evidence is limited as to whether dynamic stretching reduces injuries or DOMS.
So why is dynamic stretching so popular? Generally at the start of a warm up the goal is to raise body temperature, heart rate, respiration rate and blood flow. This could be achieved through the common ‘lap around the field’ or it could be achieved through sports-specific dynamic range of motion exercises that are relevant to the sport and may still improve flexibility! In comparison, static stretching is likely to cool the body down and is generally specific muscle but not to the requirements of your sport. So if you can achieve the flexibility requirements for your sport through dynamic stretching, why not avoid static stretches and spend warm up time on high intensity drills specific to your sport.
A 2012 systematic review by Behm & Blazevich concluded:
“Generally, a warm-up to minimize impairments and enhance performance should be composed of a submaximal intensity aerobic activity followed by large amplitude dynamic stretching and then completed with sport-specific dynamic activities. Sports that necessitate a high degree of static flexibility should use short duration static stretches with lower intensity stretches in a trained population to minimize the possibilities of impairments”
I believe this is a sensible conclusion. We cannot generalise that either static or dynamic stretches are more effective prior to performance, but instead must analyse the requirements of the specific sport as well as the individual. As such, follow the recommendations, apply them to your sport but most importantly, listen to your body and do what feels right for you!
Kay, A and Blazevich A. (2012). Effect of acute static stretch on maximal muscle performance: a systematic review. Journal of Medicine & Science in Sports & Exercise, [online] Volume 44(1), p.154-64. Available at: https://www.ncbi.nlm.nih.gov/pubmed/21659901
Behm, D, Blazevich, A, Kay, A and McHugh, M (2015). Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. Journal of Applied Physiology, Nutrition, and Metabolism, [online] Volume 41(1), p.1-11. Available at: http://www.nrcresearchpress.com/doi/full/10.1139/apnm-2015-0235#.WUhiPROGPVo
Herbert, R, de Noronha, M and Kamper, S (2011). Stretching to prevent or reduce muscle soreness after exercise. The Cochrane Database of Systematic Reviews, [online] Volume 7: CD004577. Available at: https://www.ncbi.nlm.nih.gov/pubmed/21735398