When does the body use carbohydrates, proteins and fat?
The intensity and duration of exercise determines what energy system the body uses to generate energy. Typically, after about 20 seconds of intense exercise, ATP reserves are depleted and the muscles must then look to other sources of fuel. Glycogen, the stored form of glucose, is used first to replenish ATP. If we don’t add fuel to the body during exercise in the form of sports drinks or juices, for example, our body’s glycogen supply will start to diminish after 30 to 60 minutes. At this point fat from adipose tissue and protein from muscles are used to make ATP. As a result, performance, endurance and overall body composition will be compromised, as protein in muscle is broken down to create glucose. Glycogen stores and protein are key to providing enough energy to sustain activity. The body actually gets stronger when it’s resting and recovering from a workout. This is when glycogen stores are being replaced and the muscles are being nourished. In order for the body to perform thes
