If 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
The 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.
Any 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.