Carbohydrate ingestion during prolonged exercise blunts the reduction in power output at the moderate-to-heavy intensity transition.

Purpose: 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 trained cyclists and triathletes (10 males, 2 females; $\dot{V}{\text{O}}_2$ peak, 59 ± 5 mL kg^-1 min^-1; training volume, 14 ± 5 h week^-1) performed an incremental test and 5-min time trial (TT) without prior exercise (PRE), and after 150 min of moderate-intensity cycling, with (POST_CHO) and without (POST_CON) carbohydrate ingestion.

Results: Power output at the first ventilatory threshold (VT₁) was lower in POST_CHO (225 ± 36 W, ∆ -3 ± 2%, P = 0.027, n = 11) and POST_CON (216 ± 35 W, ∆ -6 ± 4%, P = 0.001, n = 12) than PRE (229 ± 37 W, n = 12), and lower in POST_CON than POST_CHO (∆ -7 ± 9 W, ∆ -3 ± 4%, P = 0.019). Mean power output in the 5-min TT was lower in POST_CHO (351 ± 53 W, ∆ -4 ± 3%, P = 0.025) and POST_CON (328 ± 63 W, ∆ -10 ± 10%, P = 0.027) than PRE (363 ± 55 W), but POST_CHO and POST_CON were not significantly different (∆ 25 ± 37 W, ∆ 9 ± 13%, P = 0.186). Blood glucose concentration was maintained in POST_CHO, and was significantly lower at the 120 and 150-min timepoint in POST_CON (P < 0.05).

Conclusion: These data suggest that durability of the moderate-to-heavy-intensity transition is improved with carbohydrate ingestion. This has implications for training programming and load monitoring.