The Science behind Stretching
At some point in our lives, we have all engaged in some form of stretching to reduce stiffness and pain or increase flexibility and range of movement. However, much of the current information regarding the benefits of stretching appear to be conflicting, with research both supporting and rejecting the suggested benefits....so who do you believe?
Stretching is when the muscle fibers and tendons are put into a position of lengthening where the proposed benefits include an increased joint range of motion, decreased muscle tightness, increased muscle length, decreased pain and improved circulation.
Conventionally, stretching has been commonly promoted for injury prevention and performance enhancing for sport. However, some authors have suggested stretching does not necessarily prevent injury in health individuals. Additionally, current research suggests that stretching does not seem to reduce the effects of delayed onset muscle soreness (DOMS).
So why stretch?
It could be argued that stretching doesn’t actually make your muscles permanently longer, however it may be that the nervous system is being trained to tolerate a greater degree of muscle extension without firing off pain signals. Therefore your ability to move better improves, which could lead to what’s described as an increase in flexibility.
The nervous system is the main conductor determining how much pain the body can handle at a given point. If a muscle and tendon don’t feel safe at a given length, your nerves are telling you “hey you better stop otherwise you’re going to cause some damage”.
There is no question that practices like Pilates and Yoga have the potential to transform your ability to move better and become more flexible, which can be seen through personal experiences or from what other’s tell you. So it appears research cannot fully explain what happens during a stretch and whether the perceived benefits felt are physical or simply psychological. Having said that, it doesn’t mean you should stop stretching as everybody responds differently to any form of exercise.
Being able to touch your toes is often seen as a reflection of how fit you are. However the ability to touch your toes is determined by more than just hamstring flexibility. It comes down to a combination of hip, lumbar and thoracic spine mobility as well as flexibility in the muscles of the back, glutes and hamstrings.
However even if we worked on all those elements, some physical factors will still hold you back from touching your toes. Factors such as genetics, arm to leg length ratio, work positions and injuries. So, while touching your toes is a great measure of flexibility and mobility, it’s not a necessity.
Being flexible and mobile to complete daily tasks is more functional and if we wanted to reach our toes, we can simply move our spine, hips, knees and ankles with less strain. Even an exercise such a dead-lift doesn’t require the ability to touch your toes, but it does require an adequate amount of mobility and flexibility in various parts of the body to a certain extent.
Stretching should be pain free…most of the time. You should never enforce irregular range of motion on your body, it should be accommodated by your body without too much excess force. Some people are genetically born with the natural ability to stretch their body to abnormal limits, while most people have to work at preserving their normal range of motion due to a loss of flexibility from a lack of mobility or age.
There are three different types of stretching that can be performed. Static, dynamic and proprioceptive neuromuscular facilitation (PNF) stretching.
Static stretching involves moving the muscle or joint into a lengthened position and holding that position for an extended period of time. In the past this type of stretching was used to prepare the muscle for exercise, however, current research has consistently demonstrated a reduction in muscular power immediately after static stretching. As a result, this type of stretching is reserved for post training recovery and on non-training days. The only exception for pre-training static stretching would be for rehab purposes recommended by a health practitioner.
Dynamic stretching is when soft tissues and joints are taken through their range of motion during movement. This type of action is more specific to preparation for exercise and sports in particular. Dynamic stretching has been shown to significantly increase tendon elasticity and flexibility This type of stretching technique is not recommended during the rehabilitation process and care should be taken not to ‘bounce a muscle that is recovering from injury. However, it has been promoted for end-stage rehabilitation for tendon injuries. Care should be taken when performing this type of stretch as it involves eccentric contractions, which may result in soreness or injury if performed too forcefully.
PNF stretching involves the combination of excessively stretching the target muscle and contracting the opposite muscle. This type of stretching method is particularly aggressive but can result in rapid increases in flexibility. PNF stretching should not be performed more than 1-2 times a week and should be cycled in and out of a training periodisation, as it can cause some muscle damage.
People who participate in regular exercise are at some point susceptible to injury if they lack flexibility to meet the demand of their exercise regime or even their daily tasks. In such cases, regaining or maintaining flexibility of soft tissues and joints, is an essential component of the rehabilitation process. Inflammation, pain and stiffness can limit joint range of motion and the normal extensibility of the muscle can be compromised following an injury. Adequate soft tissue extensibility after an injury is essential to encourage pain free range of motion.
As previously mentioned, there is not enough evidence that proves any specific method of stretching to be a clear winner for the proposed benefits of stretching. In saying that, it doesn’t mean you should stop stretching. In my opinion the purpose of stretching is to aid your body to be functionally capable to complete tasks with ease. If it works for your body and you feel benefits, do it, otherwise reconsider the timing and form or stretching you are performing.
Brukner, P., & Khan, Karim. (2017). Brukner & Khan's clinical sports medicine: Volume 1 : Injuries (5th ed.).
Behm, D., Blazevich, A., Kay, A. and 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), pp.1-11.
Blazevich, A., Gill, N., Kvorning, T., Kay, A., Goh, A., Hilton, B., Drinkwater, E. & Behm, D. (2018). No Effect of Muscle Stretching within a Full, Dynamic Warm-up on Athletic Performance. Medicine & Science in Sports & Exercise, 50(6), pp.1258-1266.
Weppler, C. and Magnusson, S. (2010). Increasing Muscle Extensibility: A Matter of Increasing Length or Modifying Sensation?. Physical Therapy, 90(3), pp.438-449.
Hotta, K., Behnke, B., Arjmandi, B., Ghosh, P., Chen, B., Brooks, R., Maraj, J., Elam, M., Maher, P., Kurien, D., Churchill, A., Sepulveda, J., Kabolowsky, M., Christou, D. and Muller-Delp, J. (2018). Daily muscle stretching enhances blood flow, endothelial function, capillarity, vascular volume and connectivity in aged skeletal muscle. The Journal of Physiology, 596(10), pp.1903-1917.
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