How Does Muscle Work

How Muscle Works - Dream Body Six PackIf you have no real idea of how muscle works, then you can’t really know if what you’re spending a lot of time and effort doing in the gym is the best way to train, or if it’s having any effect at all.

Before explaining how muscles work it’s useful to know that not all muscle is the same. There are actually three different types – Cardiac, Smooth and Skeletal.

Cardiac muscle, also known as myocardium, is found only in the heart. It needs oxygen to contract, without which it will die almost immediately, and we have no voluntary control over it.

Smooth muscle surrounds the digestive, reproductive and urinary tracts and blood vessels. When it contracts it causes a constriction, which is a decrease in diameter; when it relaxes it allows dilation, an increase in diameter.

Skeletal muscle, which is the muscle that is of interest to anyone who exercises, is mostly under our voluntary control, though there are also involuntary movements such as those involved with posture. It is made up of individual cells surrounded by a sheath known as the endomysium, which are packaged together into what is called fascicles, which are then wrapped in a perimysium. Several perimysium are then finally bundled together into the epimysium. At the end of the muscle, collagen fibres become denser to form a tendon, which connects to bone. They are well supplied with blood vessels to carry nutrients and oxygen, along with the nerve fibres that stimulate the muscle to contract.

How Muscle Works
How Muscle Works - Dream Body Six PackThe individual muscle cells are packed with strands of myofibril, which is in turn composed of filaments of different proteins, two of which are called Actin and Myosin. The myosin filaments resemble a double-headed golf club, which together form a chain which contact and “pull” against the actin filament during muscle contraction. Each row of myosin is surrounded by six rows of actin to form myofibrils and each myofibril is composed of sarcomeres, which is the actin and myosin.

When a nerve stimulates a muscle to contract the myosin heads attach to the actin, pulling it towards the middle of the sarcomere. They then detach and return to their original position before attaching and pulling again. Lifting with greater resistance than they are used to can cause damage, especially to the myosin heads, which compensate and adapt by repairing with more actin and myosin to prevent this happening again.

How Muscle Works - Dream Body Six PackAny muscle work requires a continuous supply of energy in the form of ATP. Every time a myosin head does its job a single ATP molecule is required, which in a muscle that is exercising means billions of them. Calcium is also vital as it helps connect the myosin head to the actin, which comes first from the muscle stores but then from the blood, which will take it from bone if there isn’t enough if your diet.

Because of the way muscle works, different types of contraction have a slightly different effect. For example, a concentric contraction, which is the lifting phase of an exercise, is not nearly as taxing to the muscle as the eccentric, lowering phase of the movement. This is because during an eccentric contraction, the myosin finds it harder to break contact with the actin, so more myosin and actin interaction needs to occur. This utilises more of the muscle and creates greater tension than a concentric contraction of the same load.

Also, when a muscle is at its shortest or longest, less of the actin and myosin is able to interact, which is why the start point and end point of any lift is the hardest. It’s also why people cheat and just work the middle, easier, part of the movement. Instead these should be the two parts of any exercise that you concentrate on the most, giving you greater benefit without having to increase the weight, which just puts more pressure and wear and tear on joints.

So it’s important to not only vary the types of contraction you do, whether it’s concentric, eccentric, isometric or plyometric, but also to be sure that when training, your muscle works in a way that is going to cause the most improvements. Increasing the amount of weight doesn’t necessarily mean more improvements.

As always, any questions or feedback leave a comment below.

2 Replies to “How Does Muscle Work”

  1. You mentioned the start and of of the movement being the hardest.
    With it being the hardest, does this make it the best parts to complete / worst parts to miss?
    Also, I’ve heard different ideas about the bench press that relate to this.
    That either the upper arm should not go bellow horizontal because it puts too much strain on the rotator-cuff, while others say that the bar should touch the chest because it is the longest range of motion and stops you cheating.

    Can you weigh in on the two approaches, and how they work for building up the chest and avoiding injury?

    1. Hi, Bob

      The start of the movement and the end, fully contracted, part of the movement are the 2 most difficult parts of any exercise. For this reason it’s important to concentrate on them and always get a full range of movement. It means your muscles are working harder with less weight, instead of needing more weight which puts pressure on joints, especially in the long term. You can read more about this here: How Range Of Motion Builds Muscle

      As for the bench press, yes touching your chest with the bar can strain the rotator-cuff, but if you’re using a full range of motion and are controlling the weight instead of just letting it drop and bounce off your chest, this is unlikely. Remember, better technique means less weight is required, which reduces injuries and wear and tear to areas like rotator cuff. The only exception I would make to this is if you already have issues with your rotator cuff, in which case strengthen the muscles with specific exercises.

      Read more about this here: How To Do The Bench Press

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