Effects of carbohydrate availability on cycling endurance at the maximal lactate steady state

The impacts of carbohydrate (CHO) availability on time to task failure (TTF) and physiological responses to exercise at the maximal lactate steady state (MLSS) have not been studied. Ten participants (3 females, 7 males) completed this double-blinded, placebo-controlled study that involved a ramp incremental test, MLSS determination, and four TTF trials at MLSS, all performed on a cycle ergometer. With the use of a combination of nutritional (CHO, 7 g/kg, and placebo, PLA, 0 g/kg drinks) and exercise interventions [no exercise (REST) and glycogen-reducing exercise (EX)], the four conditions were expected to differ in preexercise CHO availability (RESTCHO > RESTPLA > EXCHO > EXPLA). TTF at MLSS was not improved by CHO loading, as RESTCHO (57.1 [16.6] min) and RESTPLA (57.1 [15.6] min) were not different (P = 1.00); however, TTF was similar to 50% shorter in EX conditions compared with REST conditions on average (P < 0.05), with EXCHO (39.1 [9.2] min) similar to 90% longer than EXPLA (20.6 [6.9] min; P < 0.001). There were effects of condition for all perceptual and cardiometabolic variables when compared at isotime (P < 0.05) and task failure (TF; P < 0.05), except for ventilation, perceptual responses, and neuromuscular function measures, which were not different at TF (P > 0.05). Blood lactate concentration was stable in all conditions for participants who completed 30 min of exercise. These findings indicate that TTF at MLSS is not enhanced by preexercise CHO supplementation, but recent intense exercise decreases TTF at MLSS even with CHO supplementation. Extreme fluctuations in diet and strenuous exercise that reduce CHO availability should be avoided before MLSS determination.