As we’ve noted, a muscle which is used grows and a muscle which isn’t used begins to waste away. This is not the whole story however, for a muscle reacts not only to the amount it’s used but to the range of it’s movement.
A common example of this in modern life involves the hamstring muscles, a group of muscles which run from the back of the knee, up the back of the leg and joins with the hips. When the knee is straight the hamstring muscles are stretched. To use the knee you contract these hamstring muscles which pull on the knee joint and so bend the knee.
With a modern sedentary life, people tend to sit down much more than we did when we evolved striding around on the seat-free pains of Africa, meaning that the knee is bent to about 90 degrees for hours at a time. The hamstring muscles get used to being contracted, and begin to lose some of their full length. The muscles end up short and tightened so that when you do stand up, the muscle pulls down on the hip-bones tilting them back and making the spine curve back which is nice for well paid osteopaths and hunchback fans but not so much for those who aren’t keen on back pain.
As people get older, they tend to become less and less flexible. They aren’t able to bend the joints as far as they used to, to straighten them as much as they used to, to have to full range of movement that they had when younger. It feels as though this is a function of the joints themselves, that the joints are more creaky, perhaps ceasing up and in need of oil. In fact, while this is true of arthritis, the reason for this lack of range of movement is more often connected to the muscles which pull that joint. Because they’re rarely extended to the full capacity, they become tight and short like the hamstring we just described, being unable then to stretch far enough for the joint to have it’s full range of movement.
The mechanism under which your muscles learn to constrain their movement is still debated. Some think that the muscles themselves, being constantly regenerated by the damage-repair process mentioned last week, build new fibres to fit the shape that they’re used for. I.E. that the length of the muscles themselves physically changes. On the other hand some think that the stretch reflex is tuned. The Stretch reflex is a short neuron loop built practically into the muscle. When the nerve is stretched it sends a signal to the muscle to contract, thus constraining the muscle by a simple feedback mechanism. Normal learning precesses and conditioning can effect these neurons, so that a muscle which is rarely stretched has a more active stretch-reflex. Rather than the muscle physically shrinking in length, the stretch-reflex becomes over-active restricting the muscle’s full movement. Probably both of these effects and more are actually involved to some extent.
Either way the old maxim still applies: use it or lose it. If you want the full range of flexibility and motion available to your body then you must use the full range of motion and flexibility available to you, indeed, you must be constantly pushing the limits, increasing that flexibility and motion.
The good news is that muscle memory is quite short-term, and if you get into the habit of extending your range of movement by deliberately extending your muscles to the full extent you can gradually rebuild the full range of moment your body allows. You’ll even learn to enjoy this process, to take pleasure from stretching your muscles within their tolerances. To enjoy pushing the boundaries and keeping your muscles capable of their full abilities. You’ll learn to love building new muscle tissue, making your muscles larger and more flexible, with an extended range.
The excercises we’ll introduce next week mostly involve stretching some muscles, attempting to ensure you keep your full range of movement, building the kinaesthetic senses and at the same time conditioning the stretch reflex to allow muscles to reach further, and to build strength and flexibility.
To use our example of the ham string muscles, if they begin to tighten and shrink thanks to being sat down for too long, conscious and deliberate stretching of the ham-string muscles can reverse these effects. A ham-string stretch will indeed be introduced next week.
Micro-damage to the muscle fibers is a natural part of movement, the mechanism under which muscle change occurs. However too much muscle damage causes scarring, creating new scar tissue rather than muscle tissue. Scar tissue can’t stretch and contract like muscle tissue can and weakens the muscle. Furthermore, stretch damage to the tendons is not a natural part of movement and the repair mechanisms for tendon damage in fact reduce their length, possibly permanently. Stretching is good, over-stretching is very bad. If it starts to actually hurt, stop. The feeling of a stretching muscle is quite pleasant when you get used to it. But if you experience actual pain, that’s not a result of useful micro-damage but muscle ripping and scarring, over-strained tendons. If you damage a tendon you will regret it and won’t gain extra range of movement or muscle growth.