Final answer:
Body weight and composition, and exercise intensity, are the two primary factors affecting the energy systems used in sports. These elements influence whether anaerobic or aerobic metabolism is used for ATP production, as well as an athlete's overall energy needs.
Step-by-step explanation:
The two factors that have the greatest impact on which energy systems are used in sport are body weight and composition and the intensity of physical activity. Factors like increased energy intake and protein consumption can help alter an athlete's body composition to potentially benefit performance in sports such as football and weightlifting. However, this must be balanced carefully as an optimal body composition varies across different sports and individual needs.
The intensity of the exercise greatly influences whether anaerobic or aerobic metabolism is primarily used for ATP production. For example, low-intensity activities rely more on aerobic metabolism, while high-intensity activities require a combination of both metabolisms. Furthermore, the energy needs of an athlete are shaped by their energy expenditure which is dependent on the intensity, duration, and frequency of the exercise, as well as the athlete's gender, age, and weight.