Fluid Loading Improves Cycling Performance
There's carbo-loading, or gobbling carbohydrate before a long race to maximize muscle and liver glycogen stores, and then there's fluid loading, or drinking extra fluid with glycerol to achieve a "hyperhydrated" state before a race to minimize the effects of dehydration on performance. Scientists from the University of Sherbrooke, Canada, recently investigated the effects of hyperhydration on cycling performance in subjects who consumed small amounts of fluid in a temperate environment.
On two occasions, six trained cyclists completed a two-hour ride at 65 percent of VO2max interspersed with five two-minute intervals at 80 percent of VO2max followed by an incremental ride to exhaustion. They began one trial in a normally hydrated state and the other in a hyperhydrated state and consumed fluid at a rate equaling only 33 percent of the rate of sweat loss throughout both rides. On average, the cyclists finished the post-fluid loading ride only half as dehydrated as they finished the other ride. Most significantly, they also achieved a higher peak power level and longer time to exhaustion in the incremental ride to exhaustion at the end of the post-fluid loading trial. There was no difference in core body temperature between the two trials.
The practical implications of this study are not entirely clear. Under what circumstances would cyclists be able to hyperhydrate before an exhaustive ride yet unable to replace more than 33 percent of fluid losses during the ride? It would be interesting to duplicate this study with runners, who cannot comfortably replace more than 60 or 70 percent of flid losses in race lasting approximately the duration of the cycling protocol used in this study. |
