1. Craig C.Freudenrich, Ph.D. 2003 How Stuff Works HOW EXERCISE WORKS an introduction to Energy Systems

2. Craig C.Freudenrich, Ph.D. What Happens? W hen you exercise or compete in sports, several things happen to your body. Breathing – heavier, faster Heart – faster Muscles – hurt, fatigue Sweat/Perspire All normal responses from a ‘weekend warrior’ to an elite athlete.

3. Craig C.Freudenrich, Ph.D. Your Body’s Response to Exercise Any type of exercise uses your muscles As you use them, they begin to make demands on the rest of the body. When exercising, your muscles act like ‘electric motors’ Your muscles take in a source of energy and use it to generate force. Your muscles are biochemical motors – that is they use a chemical called ATP for their energy source. ATP is the fuel currency of the body. It MUST be available for muscles to contract and produce force. During the process of ‘burning’ ATP, your muscles need three things:

4. Craig C.Freudenrich, Ph.D. Three things your muscles need to burn ATP 1. OXYGEN – because chemical reactions require ATP and Oxygen is consumed to produce ATP 2. ELIMINATE WASTES – they need to eliminate metabolic wastes (CO2, Lactic acid) that the chemical reactions generate 3. They need to get rid of HEAT – just like a working motor, a working muscle generates heat that it needs to remove.

5. Craig C.Freudenrich, Ph.D. What if your body can’t meet these three requirement? In order to continue exercising, your muscles must continually make ATP To do so, your body must supply sufficient oxygen, eliminate wastes and heat The more strenuous the exercise, the greater the demands of the working muscle. If these demands are not met., then exercise will cease – that is you become exhausted and you won’t be able to keep going. Obviously, some people do this much better than others, hence the difference between the average person and a world class athlete.