Lung capacity began to decline slowly at the age of 20, and by the age of 40, some people were panting. Part of the reason is that the muscles that control breathing and chest become stiff, which makes it more difficult for the lungs to operate. It also means that some air will remain in the lungs after exhaling-leading to breathlessness. At the age of 30, men inhale an average of 2 pints (about 946 ml) of air per breath, but by the age of 70, this figure has dropped to 1 pint (about 473 ml).

Muscles have been growing and failing; Grow again and then fail. Young people keep a good balance in this process. But after the age of 30, the speed of muscle failure is greater than the growth rate. After the age of 40, people's muscles began to decrease at a rate of 0.5% to 2% per year. Regular exercise helps to prevent muscle aging.

With the aging of our bodies, the efficiency of the heart to deliver blood to the whole body begins to decline. This is because blood vessels gradually lose their elasticity, and arteries may become hard or blocked. These changes are caused by the accumulation of coronary artery fat-excessive intake of saturated fat. After that, the blood delivered to the heart decreases, causing angina pectoris. Men over 45 and women over 55 are more likely to suffer from heart disease. A new study by a British pharmaceutical company found that the average age of the British heart is five years older than their actual age, which may be related to their obesity and lack of exercise.