The controversies of stretching, why, how, when?
There are many types of stretching, and many ideas on what stretching is, as well as when and how it should be done. In this post, we are going to consider how stretching works and specifically when we should do two types of stretching that are simple and do not need any assistance from a second person: Static and Dynamic stretching.
When we talk about stretching, we usually are talking about stretching structures such as a shoulder, or a hamstring muscle. When we stretch, we are certainly stretching those things and we feel and can measure improvements in range of motion (ROM) and therefore flexibility. But what is it that is actually changing when we stretch? Is it the muscle, the tendon, the joint capsule? Most people think it is one of those things, but in-fact research is showing other things!
A recent experimental study1 found that although stretching increases flexibility, it does not change the structure of the muscles or the tendons. That means the gains in ROM were not due to a longer muscle fiber or muscle fibers with a less oblique angle. So how do we get increased ROM from stretching? The authors of this study conclude, as do some other studies, that stretching may cause a change in firing of pain nerves (nociceptive nerves) so that the person has more tolerance to stretching and can go further. That suggests that someone who is inflexible inherently has more range available with their anatomy but is being held back by their nervous system. Yes, you can tear muscles and change their structure by over-stretching, but to make meaningful and safe gains requires changes in the nervous system. This makes sense, because we also know that pain leads us to get tight, and have reduced flexibility. When you sprain an ankle and experience pain, those same pain nerves are the ones that are tightening up the ankle muscles, causing you to have a more stable ankle to protect yourself!
Types of stretching:
We need to keep this above knowledge in the back of the mind as we consider the two primary types of stretching:
- Static Stretching: This type of stretching involves placing tension/stretch on the muscle and keeping it in a static position for a prolonged period of time. The limb and therefore the force on the muscle stay constant. Holds are often between 30 and 60 seconds. Demonstrated in the humorous picture to the right!
- Dynamic Stretching: This stretching involves a motion that again places tension/stretch on the muscle, but the limb continues to move meaning the force vectors on the muscle change throughout. The video playlist below shows seven exercises that provide some dynamic stretching. This is a sequence I recommend to runners for warm-up.
When should I stretch?
You might be thinking, “Wait a minute, you haven’t discussed the merits of the two stretch types or what research says about them!” That is because the main issues with these types of stretches are related to when they should be used. The key question we will address in this post is whether or not they should be used before or after sport.
A recent systematic review2 considered a similar question and found that the available research suggested that prior to sport, a warmup and “sports specific” stretching was most efficacious in reducing injury risk. From the articles available to this review, they did not determine a best type of stretch, but did note that stretching and warmup activity should be done within 15min of the performance. If you consider the recommendation that the stretches should be sports-specific, it supports my recommendation to patients: warmup stretching should be dynamic. Another study3 showed that if you choose to use static stretches, they should not be longer than 30seconds; longer stretches were shown to reduce muscle power and performance. In my opinion, however, static stretches are best avoided altogether before sports activity, because they do not mimic most sporting situations. Instead, I recommend dynamic stretches before the performance.
What about after performance? I did not find any conclusive evidence giving us guidance in this area. In my experience, there certainly needs to be a warm-down procedure for an athlete and I don’t think that dynamic stretching is in keeping with this. So, after a performance such as running, an appropriate warm-down is walking, followed by gentle static stretches. I usually suggest 30 second stretches to my patients. This may be sensible given a 60-second3 stretch reduces performance. If the muscles are already tired, you don’t want to do a stretch that reduces performance and leads to an injury getting into the car!
One final point I want to consider is that it is unwise to just focus on stretching sessions as there is research4 that suggests that stretching alone can predispose you to low back pain. Stretching certainly should be a part of an athlete’s routine, but it should not be independent. Interestingly the study found the same was true of weight machine sessions. You need to ensure that in preparing and training for your sport that you have general exercise, warm-up, warm-down, and appropriate stretching relative to the sports and the time. We consider these things when we do running assessments, or wellness screens. If you think you would benefit from review of your training techniques consider booking a wellness assessment with us!
4) Sandler RD, Sui X, Church TS, Fritz SL, Beattie PF, Blair SN. Are flexibility and muscle-strengthening activities associated with a higher risk of developing low back pain?. J Sci Med Sport. 2014;17(4):361-5.