Purpose: ‘Durability’ refers to resilience to the effect of prolonged exercise on physiological profiling variables, such as power output at the moderate-to-heavy intensity transition. The effect of carbohydrate ingestion on durability of the moderate-to-heavy intensity transition has not been studied. Therefore, the purpose of this investigation was to determine the effect of carbohydrate ingestion during prolonged exercise on durability of the moderate-to-heavy intensity transition and severe-intensity performance.

Methods: Twelve well-trained cyclists and triathletes (10 males, 2 females; V̇O2peak, 59 ± 5 mL kg-1 min-1; training volume, 14 ± 5 h week-1) underwent a characterisation trial and three experimental trials. Participants performed an incremental test and 5-min time-trial (TT) without prior exercise (PRE), and after 150-min of moderate-intensity cycling, with (POSTCHO) and without (POSTCON) carbohydrate ingestion.

Results: Power output at the moderate-to-heavy intensity transition was lower in POSTCHO (225 ± 36 W, ∆ -7 ± 3 W, ∆ -3 ± 2%, P = 0.0265) and POSTCON (216 ± 35 W, ∆ -13 ± 9 W, ∆ -6 ± 4%, P = 0.0011) than PRE (229 ± 37 W), and lower in POSTCON than POSTCHO (∆ -7 ± 9 W, ∆ -3 ± 4%, P = 0.0186). The prolonged exercise-induced reduction in metabolic power was greater in POSTCON than POSTCHO (P = 0.0101). Mean power output in the 5-min TT was lower in POSTCHO (351 ± 53 W, ∆ -15 ± 12 W, ∆ -4 ± 3%, P = 0.0251) and POSTCON (328 ± 63 W, ∆ -35 ± 38 W, ∆ -10 ± 10%, P = 0.0272) than PRE (363 ± 55 W), but POSTCHO and POSTCON were not significantly different (∆ 25 ± 37 W, ∆ 9 ± 13%, P = 0.1859).

Conclusion: These data suggest that durability of the moderate-to-heavy intensity transition is improved with carbohydrate ingestion. Athletes are therefore able to maintain higher power outputs in relation to their intensity domain transitions during prolonged exercise when ingesting carbohydrate. Additional research is necessary to further understand the underlying mechanisms.