If the muscles are not strengthened, the body will sag and may begin to look older than it actually is. Exercise will strengthen the muscles surrounding joints, which will help prevent certain injuries. It may also shorten the recovery time following an injury. A fit person can handle daily routines, such as walking stairs and gardening, with less effort and without muscle soreness. A fit person can also handle stress and emergencies, either mental or physical, better than an unfit person.
Exercise can even slow down the process of aging, improving the quality of life at an older age.
It helps bone growth among young people and maintains strong bones for people over age 30. Aerobic activity does not have to be very intense but long in duration, which is the key to a good exercise. You should be able to carry on a short conversation while doing aerobic exercise. If you can not keep a conversation going you are probably working anaerobically. This means you will get tired faster and get sore muscles after exercising.