THE EFFECT OF CARBOHYDRATE LOADING ON 100-KM CYCLE TIME TRIAL PERFORMANCE

Abstract

296 This placebo-controlled study determined whether a 9 g carbohydrate (CHO) per kg BM loading diet (LOAD), compared to a 6 g CHO·kg−1 BM (NORM) diet, enhanced 100-km time-trial (TT) performance which included five 1-km and four 4-km sprints, when CHO availability was maintained by ingesting CHO. Seven trained cyclists (VO2peak 63.9 ± 4.5 ml·kg−1; PPO 411 ± 50 W) performed two trials on their own racing bicycles mounted on a Kingcycle ergometer. Subjects maintained the same training and dietary regimens before both trials. Two hours after a standardised breakfast (2 g CHO·kg−1BM), subjects commenced the TT and were requested to complete the 100-km and all sprints in the fastest possible time. During both trials, subjects ingested a CHO drink providing 1 g CHO·kg−1BM−1. Pre-exercise muscle [glycogen] was significantly higher after LOAD compared to NORM (572 ±107 vs 485 ±128 mmol·kg−1 dw). However, there were no differences in the time to complete the TT (LOAD: 147:30 ±3:48 vs NORM: 149:06 ±4:12 min) or the mean power output (LOAD: 259 ±15 vs NORM: 253 ±15 W) sustained during the rides. Neither were there any differences in post-exercise muscle [glycogen] (LOAD: 96 ±63 vs NORM: 55 ±28 mmol·kg−1 dw). This study shows that CHO-loading does not provide an additional advantage to the performance of a 100-km TT which included bouts of repeated high-intensity cycling when (a) CHO is consumed throughout exercise and (b) subjects are unaware of the CHO content of their diets.