With warmer weather finally here and for most runners/triathletes our racing season is kicking into high gear. This warmer weather will increase the chance of losing that PR due to improper dehydration. Following is a couple of brief paragraphs relating to the performance loss due to hydration written by Asker Jeukendrupp and Micheal Gleeson. So as we head out door for our longest runs/rides and races, think about what and when you going to replace your fluids to ensure you are going to performance at your PR capabilities.
Fatigue toward the end of a prolonged sporting event may result as much from dehydration as from fuel substrate depletion. Exercise performance is impaired when an individual is dehydrated by as little as 2% of body weight. Losses in excess of 5% of body weight can decrease the capacity for work by about 30% (Armstrong et al. 1985; Craig and Cummings 1966; Maughan 1991; Sawka and Pandolf 1990).
Even in cool laboratory conditions, maximal aerobic power ( .VO2max) decreases by about 5% when persons experience fluid losses equivalent to 3% of body mass or more, as is shown in figure 8.6 (Pinchan et al. 1988). In hot conditions, similar water deficits can cause a larger decrease in .VO2max. The endurance capacity during incremental exercise is decreased by marginal dehydration (fluid loss of 1% to 2% of body weight), even if water deficits do not actually result in a decrease in .VO2max. Endurance capacity is impaired much more in hot environments than in cool conditions, which implies that impaired thermoregulation is an important causal factor in the reduced exercise performance associated with a body-water deficit. Dehydration also impairs endurance exercise performance. Fluid loss equivalent to 2% of body mass induced by a diuretic drug (furosemide) caused running performance at 1,500, 5,000, and 10,000 m distances to be impaired (Armstrong et al. 1985). Running performance was impaired more at the longer distances (by approximately 5% at 5,000 and 10,000 m) compared with the shortest distance (approximately 3% at 1,500 m).
The main reasons dehydration has an adverse effect on exercise performance can be summarized as follows:
• Reduction in blood volume
• Decreased skin blood flow
• Decreased sweat rate
• Decreased heat dissipation
• Increased core temperature
• Increased rate of muscle glycogen
Here is the link to read the full study. http://www.humankinetics.com/excerpts/excerpts/dehydration-and-its-effects-on-performanceuse
See you on the roads