If you cover one mile by walking or by jogging, you spend same amount of energy in both cases. Because in both cases you are moving the same weight the same distance. The speed does not matter. Of course, if you jog rather than walk for 30 minutes, you'll cover more distance and consequently burn more calories.

The best exercise should be moderate, enjoyable and refreshing and not too strenuous and unpleasant. 

Walking is one of the best exercises.

Vigorous stretching exercises DO NOT keep the muscles flexible. Stretching exercises should be done slowly and deliberately allowing the muscles to relax. When doing stretching exercises like bending or twisting at the waist and touching toes, it is advisable to move slowly and when the first sign of tension occurs, hold that position for several seconds, then relax. Repeat the exercise for several times.

The minimum amount of time one should spend exercising in a day is 20 minutes.

Brisk walking has tremendous benefits. It also affects the human capillary systems. There are approximately 60,000 miles of blood vessels in the body. These are mostly minutes vessels responsible for the irrigation of the flesh. When the muscle is at rest only few capillaries would open and perhaps 50 times as many will open while the muscle is being exercised. A regular daily striding will not only open up more capillaries but would also help in the formation of new vessels to nourish the muscles. Exercise not only stimulates development of blood vessels in the skeletal muscles tissue, it also does the same with the heart. Thus a fit person is better prepared to survive the occlusion of a vessel. It has been shown that exercise even helps in the formation of new vessels even after an occlusion has occurs. 

Striding has beneficial effect on the mind. It is said to clear the mind and improve thought process. A brisk long walk in the evening has some tranquillizing effects. They say regular brisk walking benefits anxiety and depression.