Any exercise in addition to your normal level of activity will benefit your health in a very short time. And the more exercise you do, within reason, the greater the benefits. If you lead a very inactive life, a simple daily twenty-minute walk will quickly make you fitter and more energetic, sharpen your mind and senses, and give you that extra zest for life.

You should aim to fit in at least three brisk twenty-minute walks each week - in the park, around the block or even in your own living room. Also perhaps add some other sporting activities to improve your strength and suppleness.

As per Wikipedia

Physical exercise is the performance of some activity in order to develop or maintain physical fitness and overall health. It is often directed toward also honing athletic ability or skill. Frequent and regular physical exercise is an important component in the prevention of some of the diseases of affluence such as cancer, heart disease, cardiovascular disease, Type 2 diabetes and obesity.

Exercises are generally grouped into three types depending on the overall effect they have on the human body:

Flexibility exercises such as stretching improve the range of motion of muscles and joints.

Aerobic exercises such as walking and running focus on increasing cardiovascular endurance.

Anaerobic exercises such as weight training, functional training or sprinting increase short-term muscle strength.

Physical exercise is considered important for maintaining physical fitness including healthy weight; building and maintaining healthy bones, muscles, and joints; promoting physiological well-being; reducing surgical risks; and strengthening the immune system.

Proper nutrition is at least as important to health as exercise. When exercising it becomes even more important to have good diet to ensure the body has the correct ratio of macronutrients whilst providing ample micronutrients, this is to aid the body with the recovery process following strenuous exercise.

Proper rest and recovery is also as important to health as exercise, otherwise the body exists in a permanently injured state and will not improve or adapt adequately to the exercise.

The above two factors can be compromised by psychological compulsions (eating disorders such as exercise bulimia, anorexia, and other bulimias), misinformation, a lack of organization, or a lack of motivation. These all lead to a decreased state of health.

Delayed Onset Muscle Soreness can occur after any kind of exercise, particularly if the body is in an unconditioned state relative to that exercise.