title: The Ingestion of 39 or 64 g·h(-1) of Carbohydrate is Equally Effective at Improving Endurance Exercise Performance in Cyclists.
abstract: In an investigator-blind, randomized 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 more than 6 hr/wk for more than 3y (n = 20) completed four experimental trials. Each trial consisted of a 2-hr constant load ride at 95% of lactate threshold (185 ± 25 W) then a work-matched time trial task (~30 min at 70% of PPO). Three commercially available carbohydrate (CHO) beverages, plus a control (water), were administered during the 2-hr ride providing 0, 20, 39, or 64 g·hr-1 of CHO at a fluid intake rate of 1L·hr(-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 39 g·hr(-1) (34:19.5 ± 03:07.1, p = .006) and 64 g·hr(-1) (34:11.3 ± 03:08.5 p = .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 64 g·hr(-1) trials respectively. The 20 g·hr(-1) (35:17.6 ± 04:16.3) treatment did not reach statistical significance compared with control (p = .126) despite a mean improvement of -3.7% (95% CI -8.8-1.5%). No further differences between CHO trials were reported. No interaction between CHO dose and pacing strategy occurred. 39 and 64 g·hr-1 of CHO were similarly effective at improving endurance cycling performance compared with a 0 g·hr(-1) control in our trained cyclists.
authors.affiliation: Health & Exercise Sciences Research Group, School of Sport, University of Stirling, Scotland, U.K.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Newell
authors.forename: Angus M
authors.initials: AM
authors.lastname: Hunter
authors.forename: Claire
authors.initials: C
authors.lastname: Lawrence
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Tipton
authors.forename: D R
authors.initials: DR
authors.lastname: Galloway S
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold; D054874:Athletic Performance / Q000502:physiology*; D001628:Beverages; D001642:Bicycling / Q000502:physiology*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004435:Eating; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D010807:Physical Endurance / Q000187:drug effects*; D064133:Sports Nutritional Physiological Phenomena
chemical_list: D004040:Dietary Carbohydrates; D019344:Lactic Acid