336 / Backx, van Someren, and Palmer K. Backx and K.A. van Someren are with the School of Life Science at Kingston University, Kingston-upon-Thames, Surrey, KT1 1LQ, UK. G.S. Palmer is with the School of Sport, Performing Arts and Leisure at the University of Wolverhampton, Walsall, WS1 3BD, UK. 336 One Hour Cycling Performance Is Not Affected By Ingested Fluid Volume Karianne Backx, Ken A. van Someren, and Garry S. Palmer This study investigated the effect of differing fluid volumes consumed during exercise, on cycle time-trial (TT) performance conducted under thermoneutral conditions (20 ∞C, 70% RH). Ten minutes after consuming a bolus of 6 ml · kg– 1 body mass (BM) of a 6.4% CHO solution and immediately following a warm- up, 8 male cyclists undertook a 1-h self-paced TT on 4 separate occasions. During a “familiarization” trial, subjects were given three 5-min periods (15– 20 min, 30–35 min, and 45–50 min) to consume fluid ad libitum. Thereafter subjects undertook, in random order, trials consuming high (HF), moderate (MF), or low fluid (LF) volumes, where 300, 150, and 40 ml of fluid were consumed at 15, 30, and 45 min of each trial, respectively, and total CHO intake was maintained at 57.6 g. During exercise, power output and heart rate were monitored continuously, whilst stomach fullness was rated every 10 min. Addi- tionally, BM loss and BM loss corrected for fluid intake was calculated during each trial. At 40, 50, and 60 min differences in ratings of stomach fullness were found between trials (LF vs. HF and MF vs. HF). There were however no differences in performance or physiological variables (heart rate or BM loss) between trials. These results indicate that when a pre-exercise CHO bolus is consumed, there is no effect of subsequent consumption of different fluid vol- umes when trained cyclists undertake a 1-h performance task in a thermoneutral environment. Key Words: body mass loss, sweat loss, hydration, high intensity Introduction Over the past 10 years, many authors (6, 9, 11, 13, 16, 17) have investigated the effects of different fluid and carbohydrate (CHO) ingestion strategies on high- intensity (>80% peak oxygen uptake [VO 2peak ]), moderate duration (~60 min) cy- cling performance. The results of these trials cause considerable confusion to both the sports scientist and the athlete in determining the optimal CHO/fluid replace- ment strategy for performance in a 1-h cycle time trial. International Journal of Sport Nutrition and Exercise Metabolism, 2003, 13, 336-346 © 2003 Human Kinetics Publishers, Inc.