Any activity that increases the strength of the body is exercise. One must exercise in limits and capacity.
Limit is set according to the requirement of the body. It should be so much that you feel tired and fatigued and neither it should be so less that it would not make any difference.
Sushrut says that one must exercise with half power. Half power is a situation when there is a deep breath, there is sweat on the forehead and mouth starts to feel dry.
Benefits of exercise
When done in limits exercise makes one active and refreshed. It increases the strength and capability to do physical labour and digestive fire.
Too much exercise may lead to decrease in strength and makes the person feel sleepy. It may also lead to fever or puke.