As you have heard me elude to many times before, passively stretching muscles is a complete waste of time - if we are talking about improved mobility, injury rehab, increased flexibility and long term extensibility. Passive stretching is just a means of pulling a muscle to a range where it is not trained to go to, feeling extreme discomfort for a few minutes and then feeling good after the stretch because you are not in horrible discomfort anymore. NEVER will this type of stretching improve mobility, flexibility, sports performance or rehabilitate a muscle injury.
This inso post to delve deep into anatomy and physiology but i will touch on the basics. As we all know, muscles are under complete control of the nervous system. Their strength, their range, their force production, their ability to relax and contract are all under complete control by the CNS. If we pull a muscle to its passive end range (stretch) we are not manipulating the nervous system, again, we are just causing passive discomfort. There is no studies, to date, that show a physiological, mechanical increase in long-term muscle length adaptation via a means of physically passively stretching muscle tissue. PERIOD.
If we look into the anatomy of muscle units and what they include, we find something we are all familiar with if we reach to the back of our brains from anatomy lessons, myosin and actin. These myofilaments are the the reason we are able to contract, and consequently relax muscle tissue. We also have a protein called titin that acts as a stabiliser for these components. Im sure you are all aware of the sliding filament theory and the mechanisms of muscle contraction. Again, the ability of the myosin heads and actin attachment sites are controlled by the pre-requisite actions of the nervous system (neurons and action potential). As we enter passive ranges in stretches, there is detachment of these filaments and the muscle is no longer under nervous control, it has become passive. The titin is now the protein working to prevent the overstretch of the tissue. The reason we are unable to produce maximum force after a stretching routine is because the damage caused by the actin and myosin being detached will mean they are still displaced and the ability to produce force is still impaired, causing a reduction in the potential for optimal cross-bridging. This is the reason sports performance will never be enhanced through stretching.
Passive stretching will never cause long term adaptation of skeletal muscle tissue for these reasons. As we pull out of the active range of a muscle and into the passive range, force production is down, neuromuscular innovation is inhibited, and the ability to manipulate the nervous system is not available, consequently meaning any change to physiology via whatever stretching technique you perform is extremely short lived and sometimes detrimental to injury and sporting performance. Think of it like pulling an elastic band. When we pull the elastic band we will see a temporary change in muscle length, soon after the elastic band is put down, the elastic component of the band will slowly reshape itself back to its original form. No type of long term physiological adaptation has taken place. The elastic band doesn't have a nervous system, surprisingly, so that elastic band will always stay the same length.
Why is it detrimental?
We have what we call passive and active ranges. These should be be assessed throughout our movement screening or assessment. The active range is what we have total nervous control over and the passive range is how far we could physically pull a muscle/joint to. If we perform stretching routines close to training sessions, we temporarily increase the window of passive range from active range. This is the range where you see most muscular injury happen as we have no control over it. This, along with the decrease in sporting performance, why would anyone want to carry out stretching routines anywhere near their training sessions? For injury, stretching is never going to be a valid prescription to rehabilitation. Why? Muscle injuries (muscle strains) are a consequence of over-stretching the tissue, into ranges where it is weak or we have no innovative control, the muscle rips, tears and causes drastic strain to the tissue. Guess what the last thing you want to do is? Stretch it, the exact reason it was damaged in the first place. If you are training or playing sport and you experience a mild strain (a feeling of tightness) in a muscle and are told to ‘stretch it out’, you will only cause more damage. The reason that the muscle has strained is not because of poor flexibility. It’s because it’s too mobile, the passive range is far too much compared with the active range you have, or the tissue is simply not strong enough to tolerate the loads, volume or frequency of your training.
A study was done on the achillies tendonosis where 15 patients carried out conventional therapies such as rest, stretching, anti-inflammatories and the comparison group carried out training protocols. All of the training group regained their pre-injury ability and decreased pain. None of the conventional group showed any improvements in ability or pain.
As always, any questions - please ask.
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Luke French. Health Coach