Whenever you start reading things on weight training you come across a bunch of really long and complicated sounding words. One of these is the word hypertrophy. If you want to get bigger, stronger, bulk up and gain weight and muscle, then this is a word you should pay attention to. It’s just another way of saying increase in the size of muscles.
There are two main functions of skeletal muscles. The first is to contract and thereby cause the body to move and the second one is to provide stability for the posture of the body. As mentioned in previous posts, muscles are made up of many smaller units called fibers. It is at this level that hypertrophy occurs. It happens through the increase of muscle mass, as well as the cross-sectional area. This is done through stimulus from the outside. Muscles adapt to work load. Exercise is often used to simulate this work load. Through exercise, stress is applied to the muscle. The muscle then adapts and generates tension. This results in the increase of size and amount of contractile proteins (actin and myosin) which make up the myofibrils in the fibers. So the muscle fibers get bigger. This is hypertrophy.
There are two main types of hypertrophy: sarcoplasmic and myofibrilar. Sometimes a third type, transient, is mentioned as well, however that one is not as important, as it only means the temporary swelling of the muscle (due to fluid accumulation) after exercise.
Sarcoplasmic hypertrophy means an increase in the volume of the sarcoplasm in a muscle cell. Sarcoplasm is the gel-like fluid-like substance that is enclosed within a muscle cell. It contains all kinds of things, with the largest percentage of it being taken up by water. It also contains glycosomes (granules of stored glycogen), as well as myoglobin, which is a protein that binds oxygen. Sarcoplasm accounts for about 25% to 30% of the muscle cell’s size, so if it gets swollen up, the cell increases in size as well. Here the cross-sectional area of the muscle increases, but the actual density of the muscle fibers decreases. So this is mostly non-functional increase in muscle size. This increases the bulk size and look of the muscles. The strength of the muscle does not increase as much.