Exercise is the central ingredient of good health. It tones the muscles, strengthens the bones, makes the heart and lungs work better, and helps prevent constipation. It increases physical reserve and vitality. The increased reserve function helps you deal with crises. Exercise eases depression, aids sleep, and aids in every day activity of daily life.

There are aerobic or endurance exercises, stretching exercises, and strengthening exercises. You need to know the difference between the three types.

Aerobic (endurance) exercise is the key to fitness. This is the most important kind of exercise. The word “aerobic” means that during the exercise period the oxygen (air) you breathe in balances the oxygen you use up. During aerobic exercise, a number of body mechanisms come into play. Your heart speeds up in order to pump larger amounts of blood. You breathe more frequently and more deeply to increase the oxygen transfer from the lungs to the blood. Your body produces more heat and compensates by sweating to keep your temperature normal. You build endurance.

During endurance exercise periods, the cells of the body develop the ability to extract a larger amount of oxygen from the blood to increase function at the cellular level. As you become more fit, these effects persist. The heart becomes larger and stronger and can pump more blood with each stroke. The cells can take up oxygen more readily. As a result, your heart rate when you are resting does not need to be as rapid, allowing more time for the heart to repair itself between beats.

Stretching exercises are designed to keep you loose. Everyone should do some of them, but they don’t have many direct effects on health. As you age, you want to be careful not to overdo these exercises. Toe-touching exercises, for example, should be done gently. Do not bounce. Stretching should be done relatively slowly, to the point of discomfort and just a little bit beyond.

Stretching exercises can be therapeutic in certain situations. If you have a joint that is stiff because of arthritis or injury, if you have just had surgery on a joint, or if you have a disease condition that results in stiffness, then stretching is usually an important part of the therapeutic solution. Remember that there is nothing mysterious about the stretching process. Any body part that you cannot move through its full normal range of motion needs to be repeatedly stretched so that you slowly – often over weeks or months – regain full motion of that part.

For most people, however, stretching exercises are useful mainly as a warm-up for aerobic or endurance exercise activity. Gently stretching before you begin endurance exercise can begin to warm up the muscles, make them looser, and decrease the chances of injury. Stretching afterward can help prevent stiffness.

Strengthening exercises can also be important. These are the “body building” exercises that are often performed just for cosmetic results. They build more bulky muscles. squeezing balls, lifting weights, and doing push-ups or pull-ups are examples of strengthening exercises. These exercises can be very helpful in improving function in a particular body part after surgery (for example, knee surgery), where it is necessary to build up strength.

Strengthening exercises can help build up muscles and decrease fat even in persons in their eighties and nineties. They can help increase bone strength and make the bones more resistant to fracture. Their drawback? They don’t help protect the heart, so if you do strengthening exercises be sure to do your aerobic exercises as well.