There seems to be a lot of confusion around stretching and I am often asked the questions, “What are we actually stretching?”, “Are we stretching muscle or fascia?” and “Should we stretch ligaments?”. One important principle we first need to understand is that stretching will be a different experience depending on your degree of mobility. When I say mobility I mean range of motion at your joints. The different living tissues of our movement system have very different characteristics and qualities. For example, mobility is a quality of joints, stability is a quality of connective tissues and flexibility is a quality of muscles. Here I refer to connective tissue proper, i.e. ligaments, joint capsules, tendons and fascia. Some people have a considerable degree of tension in these tissues (commonly referred to as stiffness) ranging to the other extreme where there is so much laxity of the connective tissues that these people would be classified as hypermobile. For more on hypermobility, please refer to my previous blog ‘Hypermobility – A Blessing or a Curse?’.
The role of ligaments, as they connect bones to bones forming our joints, is to provide us with passive stability. So stiffness in our ligaments is not a bad thing. Here stiffness is important for joint congruity and to protect the joint from derangement. This already answers one of our questions: No, we should not stretch our ligaments! Actually ligaments do not stretch easily as they are mainly composed of collagen fibres. Pushed hard enough they are more likely to incur a sprain or with a lot of force can tear. If we have lax ligaments we will be inherently more mobile at our joints and will therefore reach our end range of movement more quickly. And this is where ligaments come into play. Ligaments protect our joints at their end range of motion. For our stiffer counterparts they will be a long way from the possibility of even stretching their ligaments as they will not yet be at the end range of possible movement of their joints.
Fascia is also connective tissue and contains a lot of collagen fibres with some elastin fibres and contractile cells like muscle. Fascia can stretch to some degree, however, fascia’s adaptability to changes in length and shape is more from the lattice-like arrangement of its fibres. This allows fascia to expand both in length and circumference to accommodate the length and shape changes of the muscles it both envelops and invaginates.
Muscles have a higher proportion of elastin fibres. This gives them the ability to shorten and lengthen depending on the type of contraction or stretch placed upon them. If we look at the relationship between fascia and muscles we will see that they are intimately entwined. Fascia surrounds every muscle fibre (called the endomysium), every bundle of muscle fibres or fascicle (perimysium) and every bundle of fascicles (epimysium). Looking at this structure of myofascia it is NOT possible to stretch muscle without stretching fascia at the same time!
So although muscles and fascia undergo the same process when stretched they do respond differently. Muscles will recoil and regain their shape more readily after a stretch due to their higher content of elastin fibres. Because of their good blood supply muscles are also more adaptable to the stress of a stretch. This also applies in terms of healing. Fascia with less elastin requires longer to deform and once lengthened by a prolonged stretch does not readily recoil. For this reason muscles are sometimes described as elastic and fascia as plastic. When over-stretched fascia is more prone to rupture. After healing the neat, expandable, lattice-like structure will be lost or at least impaired and stiffness usually results at the site of healing.
The multitude of layers of endomysium, perimysium and the outer layer of epimysium around each muscle gather together to form what we call a tendon. This is why tendons are so strong! Tendons then knit into another connective tissue sheath that surrounds our bones, the periosteum. When we stretch our muscles and fascia there will always be a corresponding pull on the tendons and this is exactly what they are designed for. Ten-dons are built for ten-sile forces. They are laden with receptors that measure both stretch and contraction to protect them. Like ligaments tendons are highly resistant to stretch.
What Changes a Stretch
What changes the effect of a stretch is not only WHAT is being stretched but HOW we stretch it! There are different types of stretches and these affect the tissues in different ways. You could classify three types of stretch: active, static and passive. An active stretch is when one muscle performs an action and the muscle that performs the opposite action releases in a process known as reciprocal inhibition. Active stretching is effective and as the name suggests some muscles are active. Active stretches are usually held for a limited period of time, simply, because we will eventually tire.
Every single muscle fibre (an estimated ¼ million in one muscle!) acts as a stretch receptor. So when we begin to stretch our muscle fibres communicate with our nervous system to protect us from over-stretching. We experience this as reaching an ‘edge’, sometimes called the ‘apprehension reflex’ or more technically the ‘myotatic stretch reflex’. When we hold a stretch we overcome or reverse the myotatic stretch reflex. This is then called a static stretch. Note that a static stretch can be done combined with an active or a passive stretch.
Again, as the name implies a passive stretch is where there is no muscle action present. Normally, we are relying on body weight or time to intensify a passive stretch. When static or passive stretches are held for long periods the soft tissues undergo a process know as creep, i.e. they lengthen. The permanent lengthening of soft tissue from a prolonged stretch is called hysteresis. This is a very effective form of stretching but requires more time.
When do we stop stretching myofascia and begin to stretch ligaments? This is very difficult, perhaps impossible to feel. One indicator is if you are at the end possible range of motion of a joint per se. This happens in very mobile people doing postures that require extreme ranges of motion. If you are hyper-mobile, including when pregnant, it is counter-indicated to do long-held stretches at the end range of motion of your joints. Even in a shorter active stretch some people ‘hang off their joints’. It then becomes important to build strength to support flexibility and protect the joint. Extreme flexibility is over-rated. It more often causes problems than it gives extra benefit. Joint mobility and soft-tissue flexibility, like all good things give the greatest benefit in moderation.
Always with you on the mat…
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- Motion is lotion for our joints! - April 29, 2017