In recent years, physical exercise has attracted more and more attention. Regular physical exercise can not only allow people to keep healthy but also do good to the muscles. Composed of muscular tissue, muscles play an important role in bodily functions. Muscles can be divided into three types: skeletal muscle, smooth muscle and cardiac muscle. Smooth muscle and cardiac muscle are involuntary and will not contract according to the will of human beings. Skeletal muscles are voluntary and account for about 40% of total body weight. Muscles are essential to maintain normal physiological functions because they can produce movement, maintain posture, stabilize joints and generate ...view middle of the document...
Mitochondria are the main places where oxidation reactions occur and ATP is generated. In endurance exercise such as long-distance running, the amount of mitochondria in the fast-twitch muscle fibers and slow-twitch muscle fibers increases. An increase in the mitochondria can provide more energy for muscle activities. Experiments show that physical exercise can enlarge the membrane area and increase the amount of membrane protein and membrane phospholipids of mitochondria. A research involves fourteen young males shows that the more the training time is, the more the mitochondria are. After about 28 weeks of training, the amount and volume of the participants is similar to that of top athletes.
Improvement of cardiovascular and respiratory systems and the capillary network
The cardiovascular and respiratory systems can provide nutrients and oxygen for the muscles and remove the waste it generates. When the body is getting physical exercise, muscles need more nutrients and oxygen to produce energy. In this way, the circulation of blood increases and overall metabolism becomes more efficient. Protein and muscle glycogen in cardiac muscle cells increase; cardiac muscle fibers and the heart wall become thicker; the amount of blood capillary increases. Therefore, the force of cardiac muscle contractions increases. Physical exercise can also increase the volume of the heart, which can improve the functions of the cardiovascular system. For example, the weight of common people’s heart is about 250-300 grams while the weight of the athletes’ heart is about 500 grams. In addition, physical exercise can extend the capillary network, which allows more blood to provide the muscles with nutrients and oxygen.
An increase in the size and bulk of muscles
As is discussed above, physical exercise can accelerate the blood circulation and muscle cells can absorb more nutrients and become thicker. The volume of muscle cells enlarges while the number of muscle cells remains the same. As the volume of muscles becomes larger, the muscles become stronger. A popular theory that can explain why muscle cells become thicker is called super-compensation. Within a specific range, the faster the substance is consumed, the faster the...