When does an athlete fatigue during exercise performance? In short, time to fatigue is closely linked to muscle glycogen depletion.

Gollnick et al. (1974) have demonstrated that when athletes ran at 80% of VO2max, the time to fatigue was directly linked with the stores of carbohydrate in the muscle (glycogen): athletes with greater muscle glycogen last longer! The success of an athlete is likely down to their many years of training which allow them to use fat as a source of energy during exercise. For example, if athlete 1 is competing in any event at 80% VO2max, and all of their energy is derived from carbohydrate, they will fatigue once muscle glycogen runs out. However, if athlete 2 can support 80% VO2max with 40% of energy coming from fats, they will compete for twice as long as athlete 1.

Long steady distance (LSD) training allows athletes to mobilize body fat as a source of energy, as a result they will glycogen spare and go for longer. Stay tuned for our post on carbohydrate loading and how to do it effectively!