Impact of acute weight loss and/or thermal stress on rowing ergometer performance

The impact of acute weight loss on rowing performance was assessed when generous nutrient intake was provided in 2 h of recovery after making weight. Competitive rowers (N = 17) completed four ergometer trials, each separated by 48 h. Two trials were performed after a 4% body mass loss in the previous 24 h (WT) and two were performed after no weight restrictions, that is, unrestricted (UNR). In addition, two trials (1 x WT, 1 x UNR) were in a thermoneutral environment (NEUTRAL, mean 21.1 +/- SD 0.7 degrees C, 29.0 +/- 4.5% RH) and two were in the heat (HOT 32.4, +/- 0.4 degrees C, 60.4 +/- 2.7% RH). Trials were performed in a counterbalanced fashion according to a Latin square design. Aggressive nutritional recovery strategies (WT 2.3 g x kg(-1) carbohydrate, 34 mg x kg(-1) Na, 28.4 mL x kg(-1) fluid; UNR ad libitum) were employed in the 2 h after weigh-in. Both WT (mean 2.1, 95% CI 0.7-3.4 s; P = 0.003) and HOT (4.1, 2.7 - 5.4 s; P < 0.001) compromised 2000-m time-trial performance. Whereas WT resulted in hypohydration, the associated reduction in plasma volume explained only part of the performance compromise observed (0.2 s for every 1% decrement) Moreover, WT did not influence core temperature or indices of cardiovascular function. Acute weight loss compromised performance, despite generous nutrient intake in recovery, although the effect was small. Performance decrements were further exacerbated when exercise was performed in the heat.