Muscular system – part II
We’ve seen that a (skeletal) muscle has 3 possibilities:
1- To contract – this is the only “active” possibility, there is a generation of force that will lead to some result
2- To relax – this is a releasing of the contracting force, anyway being an act of release we could say it’s active as well even if the action is the “un-doing” of a previous contracting action
3- To be stretched – it’s normally a passive situation, it happens when the attachments of the muscle are pulled apart so that the muscle lengthens -> probably it’s in the “antagonist modality” or maybe we’re intentionally practicing some stretching technique (or should i say yoga??!)
Each of the 3 possibilities will lead to one of this 3 states:
1- State of contraction: it happens when you’re doing an active muscular effort… but the muscle can remain in (partial) contraction when you “forget” to release it after the effort (muscular tension, stress and so on… we’ll talk much more on this!). A certain amount of muscle contraction is always happening, that’s the muscular tone, for example it keeps you ready for action or it keeps you in your actual position through the postural muscles
2- State of relaxation: the switch is on the “off” position and the muscle is resting… this very idealistic though! We’ve seen that the contraction level of the muscle depends by how many sarcomeres are contracting in that moment… let’s say that more sarcomeres are relaxed the more the muscle is relaxed. In deep sleep or deep meditation we reach our highest levels of muscular relaxation!
3- State of stretch: this is a pleasant state with many benefits! How do you feel stretching your arms and legs when you wake up? Or when you are tired and sleepy? Do you get that refreshing sensation? Yes man, your muscles LOVE to be stretched, all your body LOVES to be stretched!!! We’ll talk much more on this (hehhe it’s a yoga blog, remember?)… for the moment consider this… your muscles can contract and can relax… but they can’t stretch by themselves, it’s a passive movement that requires action somewhere else, yoga at a physical level is mostly about stretching your muscles, instead of continuously contracting them as you do at the gym or running or in most of modern days physical activities!
Talking about contraction we can distinguish 3 types of contraction:
1- Isotonic contraction: the contraction shortens the muscle and movement happens… when you bend your arm at the elbow joint the biceps are performing an isotonic contraction
2- Isometric contraction: the muscle is contracting but there is no shortening of its fibers… because you’re not allowing it or the weight you are trying to lift is higher than the force applied (if possible to apply more force maybe the isometric contraction will become isotonic) or the object you’re trying to move is unmovable… try to push a wall away, that’s an isometric contraction
3- Eccentric contraction (aka eccentric lengthening): the muscle is lengthening while actively contracting. The result will be a smoothing or a slowing down of the movement, you will have more control on it. Imagine to be standing with an heavy weight in your hand and the bent elbow… if you allow your arm to straighten without opposing any force the movement will be a quick jerk (gravity will quickly pull down the weight!) that can injury the joint or the tissues. If you release the arm in a slow and controlled way it will be because of the eccentric contraction of your biceps