A Christian Guide to Body Stewardship, Diet and Exercise

Chapter 5: Training for Endurance 99 Oxidative system. The oxidative system is the primary source of ATP production during rest and lowintensity activities. Although carbohydrates and fats are the preferred substrates, the oxidative system can also metabolize protein. At rest, roughly 70% of the ATP production comes from fat and 30% from carbohydrates. As exercise intensity increases, however, there is a shift from fats to carbohydrates. In fact, during high-intensity activity virtually all of the ATP produced comes from carbohydrates. During long duration low activity exercise, both fats and carbohydrates are used to produce ATP. The percentage of contribution coming from carbohydrates and fat is based on exercise intensity, duration, and substrate availability. As mentioned previously, all three energy pathways are always active and contributing to some extent to the overall production of ATP. Therefore, it is recommended to train and develop each of the different energy systems individually. Short distance sprints will help to develop the phosphagen system; longer distance sprints will help to develop the glycolytic system; and long duration, low-intensity exercise will help to develop the oxidative system. Figure 5.1. depicts when the different biological energy systems are used as well as the ATP production capacity of each. Table 5.4 provides recommendations for how to train each of the different energy systems. Figure 5.1. The 3 Biological Energy Systems Used During Exercise