Muscular Stretching: The evidence behind what it DOES and DOES NOT achieve
Stretching as long been a staple of exercise in training and rehabilitation plans. Throughout history, there have been many conflicting views on when and how to stretch and about what therapeutic effect this actually achieves (Weldon et al, 2003). To clear up this confusion, the following information outlines what stretching is, and summarises the evidence around what stretch does and does not achieve.
What are the Different Types of Stretching?
There are a variety of different types of stretching that are used in common practice in an attempt to improve flexibility and movement capacity. The most common of these modalities used in sports and gyms programs are static and dynamic.
Static Stretching
Static is the most common stretching technique and is executed by extending the targeted muscle group to its maximal point and holding it for 30 seconds or more. In most of the evidence behind this kind of stretch it is recommended that the stretch is completed 4 times with 30second holds. This kind of stretch has long been used before and after sporting games in the hope of preventing injuries and aiding the cool down process (Thacker et al., 2004).
Dynamic Stretching:
Unlike static stretching, dynamic stretching requires the use of continuous movement patterns that mimic the exercise or sport to be performed. An example of dynamic stretching would be a sprinter doing long, exaggerated strides or walking lunges to prepare for a race. Unlike static stretching, dynamic stretching increases full body circulation, heart rate, and respiratory rate by using active muscle contraction and motor control as part of improving tissue extensibility (McMillan et al., 2006).
What the evidence shows stretching DOES do
Stretching does improve ROM and flexibility both in the short term and long term (Yuktasir, & Kaya, 2007).
This has important implications for function and injury risk. Improving how well the joints can move enables a wider range of activities without limitation. It also has the effect of reducing injury risk if the individual does not have the requisite flexibility to perform the required movements of the activity. If this is the case static stretching can be used to achieve greater range of movement, however should not form part of a warm up.
Both static and dynamic stretching do prevent loss of range of motion (how much a joint can move) or restore after injury (Yuktasir, & Kaya, 2007).
Adding further to the point above, both dynamic and static stretching can play an important part of injury recovery. Normal joint movement is important for all of the activities we do throughout the day. Injuries can lead to a loss of joint movement as a part of the healing process. It is therefore important to prevent this loss of movement in the first place and stretching of the effected joint is a really go way to do this, especially if your normal daily activities are affected.
Dynamic stretching warm ups do decrease the rate of sports related injuries (McMillan et al., 2006).
This could due to a variety of variables such as improved neural control (how our bodies control our muscles), increased tissue extensibility (how far our muscles can lengthen), increased blood flow, and an increase in tissue temperature. Regardless of the mechanism, dynamic stretching has an important role to play in injury prevention.
Static stretching does provide a fast and easy treatment for acute muscle cramps (Miller & Burne, 2014)
Fatigue-induced muscle cramping is a common affliction most active adults will have experienced at some point. These uncomfortable and involuntary muscle contractions are reliably eased with a stretch of the effected muscle.
Stretching can help to relieve both chronic and acute pain (Chen et al., 2014); (Franca et al., 2012).
Stretching has an important role to play in the management of pain. Whilst the mechanism of how is largely unknow, stretching may help to ease pain simply because it feels good. This feel-good response has an analgesic (pain relieving). Furthermore, stretch exercises have been shown to improve future tolerance to stretch in people with chronic musculoskeletal pain which may lead to an overall decrease in pain experienced on movement (Law et al., 2009)
What the evidence shows stretching DOES NOT do
Static stretching before exercise/activity/sporting games DOES NOT change injury risk
Multiple large systematic reviews (a high level of scientific evidence) have shown that performing static stretching before exercise neither increased or decreases the risk of injury during exercise (Tacker et al., 2004) (Weldon et al., 2003).
There have been two streams of thought when it comes to static stretching before exercise. One suggests that stretching before exercise is an essential part of a warm up, that decreases risk of injury through improved extensibility of muscle fibres. The other, directly opposes this theory, and postulates that static stretching before exercise actually increases injury risk. There has been a wealth of research into both the possible benefits and risks associated with this. The research has shown that static stretching does not provide any benefit when performed pre-exercise and it does not decrease the injury risk. It has also shown that aggressive static stretching can cause a small decrease strength and power output (2-4%) (Costa et al., 2013). This loss in strength is small and likely only lasts from a couple of minutes to an hour at maximum. It is therefore unlikely to increase injury risk and if there is an increase it is a very small one, especially among amateur athletes (Mchugh & Cosgrave, 2010). Therefore, it is not recommended to include static stretching in warm up programs, however if you fell a strong personal benefit physically or psychologically, if done in combination with other warm up strategies it is very unlikely to be harmful.
Static stretching before exercise DOES NOT change performance (MacMillan et al., 2006)
In a similar way the impact of stretching on injury risk is small, the effect on performance is small too. As stated above, static stretching is very unlikely to either improve or reduce performance.
Stretching does not prevent soreness/DOMs post exercise (Jamtved et al., 2010)
Although it has long been regarded as a good prevention method for the delayed muscle soreness you may get after an increase in a certain exercise or load, static stretching will not provide any level of prevention for DOM’s.
So, Should I Stretch?
Simply put, if you like stretching and it feels good, then yes, stretching can be beneficial; just take care to minimise static stretching right before sporting games or high intensity exercise. If static stretching is a big part of your current warm up, substituting those for dynamic stretching exercises may provide greater benefit.
By Sophie Chapman, Physiotherapy student at Exercise Thought
References
Chen, H.-M., Wang, H.-H., Chen, C.-H., & Hu, H.-M. (2014). Effectiveness of a Stretching Exercise Program on Low Back Pain and Exercise Self-Efficacy Among Nurses in Taiwan: A Randomized Clinical Trial. Pain Management Nursing, 15(1), 283–291. https://doi.org/10.1016/j.pmn.2012.10.003
Costa, P. B., Ryan, E. D., Herda, T. J., Walter, A. A., DeFreitas, J. M., Stout, J. R., & Cramer, J. T. (2013). Acute effects of static stretching on peak torque and the hamstrings-to-quadriceps conventional and functional ratios. Scandinavian Journal of Medicine & Science in Sports, 23(1), 38–45. https://doi.org/10.1111/j.1600-0838.2011.01348.x
Jamtvedt, G., Herbert, R. D., Flottorp, S., Odgaard-Jensen, J., Håvelsrud, K., Barratt, A., Mathieu, E., Burls, A., & Oxman, A. D. (2010). A pragmatic randomised trial of stretching before and after physical activity to prevent injury and soreness. British Journal of Sports Medicine, 44(14), 1002–1009. https://doi.org/10.1136/bjsm.2009.062232
Law, R. Y. W., Harvey, L. A., Nicholas, M. K., Tonkin, L., De Sousa, M., & Finniss, D. G. (2009). Stretch Exercises Increase Tolerance to Stretch in Patients With Chronic Musculoskeletal Pain: A Randomized Controlled Trial. Physical Therapy, 89(10), 1016–1026. https://doi.org/10.2522/ptj.20090056
McMillian, D. J., Moore, J. H., Hatler, B. S., & Taylor, D. C. (2006). Dynamic vs. static-stretching warm up: the effect on power and agility performance. Journal of Strength and Conditioning Research, 20(3), 492–499. https://doi.org/10.1519/18205.1
Miller, K. C., & Burne, J. A. (2014). Golgi tendon organ reflex inhibition following manually applied acute static stretching. Journal of Sports Sciences, 32(15), 1491–1497. https://doi.org/10.1080/02640414.2014.899708
Mchugh, P., Cosgrave, H. (2010). To stretch or not to stretch: the role of stretching in injury prevention and performance. Scand J Med Sci Sports. 20(2):169-81.
Thacker, B., Gilchrist, J., Stroup, F., & C, Kimsey. (2004). The impact of stretching on sports injury risk: A systematic review of the literature. Medicine and Science in Sports and Exercise, 36(3), 371–378. https://doi.org/10.1249/01.MSS.0000117134.83018.F7
Weldon, S..., & Hill, R. (2003). The efficacy of stretching for prevention of exercise-related injury: a systematic review of the literature. Manual Therapy, 8(3), 141–150. https://doi.org/10.1016/S1356-689X(03)00010-9
Yuktasir, B., & Kaya, F. (2007). Investigation into the long-term effects of static and PNF stretching exercises on range of motion and jump performance. Journal of Bodywork and Movement Therapies, 13(1), 11–21. https://doi.org/10.1016/j.jbmt.2007.10.001.