3 main components of exercise are resistance training, aerobic, stretching and flexibility.

Resistant training: helps strengths the muscle and burn more calories as you exercise. Increased weight on the muscles helps growth of small proteins inside each muscle cell to create more force. Resistant training usually consists of using weights and doing it for 2-3 times per week. Resistant training could increase bone mineral and prevent osteoporosis.
Aerobic activity: helps give oxygen to our muscles and we need to use our larger muscles in order to make our heart and lungs work better. Aerobic activity could help reduce a lot of mayor diseases pertaining to the heart. A person should do aerobic exercise at least three hours a week to help straighten the heart.
Stretching and Flexibility: Stretching may increase flexibility and improve the range of motion of your joints. Stretching is to lengthen the connective tissue that surrounds the muscle fibers.

Some signs that a person is exercising too much are if you start to notice that your recovery takes longer than a couple of days, performance is not at it used to be and you are physically over stressed.

Warming your body before every workout could prevent exercise injuries, another way to prevent injuries is to stretch before and after every workout. Staying hydrated and well nourished could also help prevent exercise related injuries.

Some ways the body responds to exercise or physical activity is by using your muscles and starts demanding the rest of your body to start working. The heart starts to beat faster during exercise so that it could pump more blood to the muscles. Muscles require energy and they used the chemical called (ATP) for energy source and it starts the process of burning energy that we consume.
Some benefits of regularly exercise is that it helps control weight management, boost energy, helps fight a lot of diseases, improves mood, helps with sex life and to sleep better all to help you maintain a healthy life style.
Some basic steps to take for a basic fitness program is to start by committing yourself to a better healthy living, surround yourself with positive role motivated individuals, you might want to start in a gym with a personal trainer. Finding yourself with something that you are confortable doing, start by doing small changes instead of something drastic.
The best way to determine exertion