ELITE MARATHONERS SHOULD DRINK AD LIBITUM
Fudge, B. W., & Pitsiladis, Y. P. (2009). Efficacy of prevailing fluid intake recommendations for elite marathon running. ACSM 56th Annual Meeting, Seattle, Washington, Presentation Number 1972.
This study evaluated whether the fluid intake recommendations of drinking ad libitum 0.4-0.8 L/hour are appropriate for elite marathon running. A retrospective video analysis of the drinking behaviors of the winning male and female runners was undertaken during the 2006 and 2007 London Marathons. To supplement the analysis, a mathematical model was used to predict required fluid intake to prevent a >3% body mass loss or body mass gain when body mass, running speed, and ambient conditions were systematically varied (i.e., 45-75 kg Ss running at 2:04 and 2:30 marathon pace in cold (7.3°C) and warm (24.8°C) ambient conditions).
The derived total drinking durations of 56, 38, 43 and 31 seconds of the winning runners equate to fluid intake rates of approximately 1.5, 1.1, 1.1 and 0.9 L/hour, respectively. The mathematical model predicted that ad libitum 0.4-0.8 L/hour is insufficient to prevent >3% body mass loss or body mass gain across all conditions modeled.
Implication. Fluid intake behaviors of elite endurance runners during a major city marathon do not reflect prevailing fluid intake recommendations. An ad libitum fluid intake strategy may be the best hydration strategy for competitive marathon running in temperate conditions as long as body mass loss is kept within acceptable limits, possibly <3%.
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