Regular vigorous exercise has a profound impact on the body. It improves circulation, strengthens the heart, lungs and muscles, reduces body fat, builds up bones, improves the efficiency of the bowels, regulates the hormones in the endocrine system, makes the brain more efficient and has a positive effect on the mind and emotions. In addition, active people tend to retain a youthful complexion and good co-ordination and balance. Exercise also reduces the risk of accidental injury and disability in old age.
All in all, the benefits of physical activity are many. Surely these benefits would be enough for anyone to be motivated to take up some form of exercise.
THE EFFECTS OF EXERCISE ON THE BODY
The heart and blood vessels
During aerobic exercise, the heart rate increases from the average resting level of 60-70 beats per minute to as many as 180-200 beats per minute. The heart of a person who takes regular aerobic exercise pumps more blood around the body at rest as well as during exercise. This is because the left ventricle of the heart enlarges, allowing the heart to slow down and work less hard. Aerobic exercise also enlarges the diameter of coronary arteries and improves the oxygen supply to the heart muscle, reducing any strain on the heart and helping it work more efficiently. The heart rate of an aerobically fit person is lower than that of an unfit person, both during exercise and at rest.
Aerobic exercise also increases the number of capillaries in muscles, so that more blood can be distributed to working muscles by the heart. It brings down raised blood pressure and raised cholesterol levels, which are both risk factors for heart disease. Active people reduce their chances of a heart attack by 50 per cent and their chances of a stroke by more than 30 per cent. Exercise also helps to normalize blood sugar and glucose tolerance, reducing the risk of adult-onset diabetes.
Aerobic exercise does not alter the size of the lungs but it does maximize the body’s natural capacity for respiration. It does this by improving the muscles used for breathing and by enhancing respiratory efficiency so that fewer breaths are needed to transport the same volume of air. Slower, deeper breaths are more efficient because they allow more of each breath to reach the portion of the lungs where oxygen and carbon dioxide are exchanged.
Improving the efficiency of the lungs is thought to be one of the ways in which exercise promotes longevity – animals with a slower rate of breathing live much longer than animals with a more rapid rate of breathing. People with asthma are now encouraged to take regular exercise. People who do not use their lung capacity eventually find that, when they do try to start exercising, their lung capacity is reduced.
When muscles are exercised, they adapt to meet the demands that are made on them. This involves an actual physical change in the fibres that make up the muscles – the change occurs during the days between bouts of exercise. When more exercise is taken, muscles become more efficient at performing their workload. This is called the training effect.
So, the benefits of physical activity result in the training effect, which in turn results in an increase in the size of the different muscle fibres used. Aerobic training (whichfor fuel) enhances the capabilities of ‘slow twitch’ fibres – fibres that are efficient in the use of oxygen. Anaerobic training (which burns mostly glycogen for fuel) enhances the capabilities of ‘fast twitch’ fibres – fibres that use muscle glycogen for short, intense contractions.
The size and number of mitochondria (the cell powerhouses that store energy and release it during aerobic exercise) are increased by the training effect. This is why people who take regular exercise have more energy and stamina. Exercise also increases the amount of myoglobin (a compound that carries oxygen to the mitochondria) in muscles and the concentration of enzymes needed to produce adenosine triphosphate (ATP) – the molecule that supplies the energy used in the contraction of muscle fibres.