Question

BACKGROUND INFORMATION

Vinnie is a professional road cyclist participating in the 2020 Giro d’Italia, a three-week race nearly 3,600 km in distance with some stages exceeding altitudes of 2,700 m above sea level (i.e., Stelvio Pass, Italy). As the newly hired head of the high-performance team, it is your responsibility to manage his preparation for the event. You must demonstrate to your team a fundamental understanding of physiology, the chronic adaptations expected from his training, and methods that could be implemented to improve the likelihood of success.

QUESTION

Given that the average distance of each leg is 170.5 km in distance, and sometimes undulating in elevation, you understand that fatigue is inevitable. The energy depletion model of fatigue focuses around the concept that depleted substrates are just one source of fatigue, particularly observed in muscle glycogen and phosphocreatine stores.

A. As an aerobic event, why do you expect depletion in glycogen and phosphocreatine?

B. Why, specifically, is it crucial to replenish muscle glycogen stores prior to the next leg?

Answer 1

A. The event of cycling is an aerobic event. But as the event starts for the first 2-7 seconds phosphocreatinine serves as fuel for energy. The phosphocreatinine anaerobically provides phosphate group to adenosine diphosphate in the presence of creatinine phosphate to produce ATP.
After the first few seconds body switches its fuel from phosphocreatinine to glycogen.
The glycogen is converted to glucose which acts as a substrate for kreb's cycle to produce energy.
Utilization of phosphocreatinine and glycogen as fuels during the first few minutes results in their depletion.
B. As we know that glycogen levels deplete during prolonged exercise sessions. It is important to replenish the glycogen stores before the next leg because glycogen acts as the main substrate for glucose utilized in energy synthesis. Also decreased glycogen decreases the blood glucose levels which may cause volitional exhaustion and damage brain cells. So it is necessary to replenish the depleted glycogen.