Final answer:
The primary energy substrate used during a 400-meter sprint is glycogen, a stored form of glucose in muscles and the liver facilitating anaerobic respiration to meet the intense energy demands of sprinting.
Step-by-step explanation:
During a 400 meter training sprint lasting 60 seconds, glycogen is the primary energy substrate used by a sprinter's muscles.
Glycogen is a complex carbohydrate stored in the liver and muscle tissues and is broken down into glucose for energy during intense, short-duration activities like sprinting. This process is known as anaerobic respiration, which does not require oxygen and supports the high power output in short spurts. Since the 400-meter dash is completed in less than two minutes, aerobic respiration cannot supply energy fast enough; thus, the muscles rely on anaerobic glycolysis, with glycogen providing the glucose needed for this high-intensity exercise.
Throughout training and especially before races, sprinters may engage in 'carbo-loading' to maximize their glycogen stores, ensuring a readily available energy source for explosive activities such as the 100-meter dash. This tactic is helpful because it replenishes the glycogen reserves for subsequent high energy demands that are characteristic of sprinting events.
Glycogen is a complex carbohydrate and is the main form of stored glucose in animals, including humans. It is stored in the liver and muscle tissue and can be quickly broken down into glucose to provide energy for intense, short-term activities like sprinting.
During the sprint, Jerry's muscle cells will use anaerobic respiration to generate energy from the glycogen, as aerobic cellular respiration cannot produce energy quickly enough to meet the demands of the intense activity.