Various sports activities involve specific demands for energy. For example, sprinting and jumping are high - energy activities, requiring a relatively large production of energy for a short time. Long - distance running and swimming, on the other hand, are mostly low - energy activities per unit of time, requiring energy production for a prolonged time. Other physical activities demand a blend of both high - and low - energy output. These various energy demands can be met by the different processes in which energy can be supplied to the skeletal muscles.
Energy is produced from the breakdown of nutrient foodstuffs?' This energy is used to produce adenosine triphosphate (ATP), which is the ultimate usable form of energy for muscular activity. Adenosine triphosphate is produced in the muscle tissue from blood glucose or glycogen. Glucose is derived from the breakdown of dietary carbohydrates. Glucose not needed immediately is stored as glycogen in the resting muscle and liver. Stored glycogen in the liver can later be converted back to glucose and transferred to the blood to meet the body’s energy needs. Fats and proteins can also be metabolized to generate ATP.
Once much of the muscle and liver glycogen is depleted, the body relies more heavily on fats stored in adipose tissue to meet its energy needs. The longer die duration of an activity, the greater the amount of fat that is used, especially during the later stages of endurance events. During rest and sub maximal exertion, both fat and carbohydrates are used as energy substrate in approximately a 60% to 40% ratio.
Regardless of the nutrient source that produces ATP, it is always available in the cell as an immediate energy source. When all available sources of ATP are depleted, more must be regenerated for muscular contraction to continue.
