The Ingestion of 39 or 64 g·hr-1 of Carbohydrate is Equally Effective at Improving Endurance Exercise Performance in Cyclists

Abstract

In an investigator-blind, randomised cross-over design, male cyclists (mean±SD) age 34.0 (± 10.2) years, body mass 74.6 (±7.9) kg, stature 178.3 (±8.0) cm, peak power output (PPO) 393 (±36) W, and VO2max 62 (±9) ml·kg-1·min-1 training for >6h/wk for >3y (n=20) completed four experimental trials. Each trial consisted of a 2h constant load ride at 95% of lactate threshold (185 ± 25W) then a work-matched time trial task (~30min at 70% of PPO). Three commercially available carbohydrate (CHO) beverages, plus a control (water), were administered during the 2h ride providing 0, 20, 39 or 64g·h-1 of CHO at a fluid intake rate of 1L·h-1. Performance was assessed by time to complete the time trial task, mean power output sustained, and pacing strategy used. Mean task completion time (min:sec ± SD) for 39g·h-1 (34:19.5 ± 03:07.1, p=0.006) and 64g·h-1 (34:11.3 ± 03:08.5 p=0.004) of CHO were significantly faster than control (37:01.9 ± 05:35.0). The mean percentage improvement from control was -6.1% (95% CI: -11.3 to -1.0) and -6.5% (95% CI: -11.7 to -1.4) in the 39 and 64g·h-1 trials respectively. The 20g·h-1 (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared to control (p = 0.126) despite a mean improvement of -3.7% (95% CI -8.8 to 1.5%). No further differences between CHO trials were reported. No interaction between CHO dose and pacing strategy occurred. 39 and 64g·h-1 of CHO were similarly effective at improving endurance cycling performance compared to a 0g·h-1 control in our trained cyclists.