THE SCIENCE OF SWEATBy James Mirtle, Globe and Mail Update February 5, 2008 Professor Lawrence Spriet a University of Guelph researcher has over the past three years examined the science of sweat. His latest study, based on work with the Canadian junior team, discovered that elite hockey players lose more fluid during practices than most other athletes. Spriet said one-third of hockey players tested did not adequately replace lost fluid during practice and, as a result, lost more than 1 per cent of their body mass. At the extreme end of the scale, Spriet said, players lost as much as 2 per cent of their weight in two hours of activity. "Typically what you find is that, when they're not drinking, they don't feel as well," he said. "Their heart rates are higher and their core temperatures are higher. So, physiologically, their body is struggling to handle the situation. Spriet has worked with the Canadian juniors since 2005, tested the Toronto Raptors during their NBA training camp, helped the NHL's New York Rangers improve hydration techniques and, most recently, worked with the Guelph Storm of the Ontario Hockey League during games. The work by Spriet and PhD student Matt Palmer with the Canadian world juniors was recently accepted into the journal Applied Physiology, Nutrition and Metabolism. The testing essentially involved weighing players and measuring their water bottles before and after practice, and using a complex formula to determine fluid and salt loss because of sweat. According to the study, the average player at the Canadian world junior camp sweated about 1.8 litres an hour and replaced about one litre of that with water or sports drinks. Goaltenders were the heaviest sweaters, averaging nearly three litres an hour, which was almost double the amount forwards and defencemen lose. Previous studies have found sweat rates of 1.6 litres an hour for soccer players, 1.8 for runners and 2.1 for football players, although Spriet noted that body size was not taken into account, making direct comparisons difficult. Elite hockey players are heavy sweaters in general, Spriet said, because of three factors: a high-intensity workout, considerable protective equipment and warm arenas (between 14 and 17.7 during games). Spriet, who since 2005 has been the advisory board chairman with Canada's Gatorade Sports Science Institute, also said hockey players have a culture that makes them more likely to use water instead of sports drinks to hydrate on the bench during practices and games. The study's conclusion states "elite ice hockey players have very high sweat rates and despite numerous opportunities to drink, replace only 60 per cent of the sweat losses." The study also suggests players would benefit from individually tailored hydration profiles, given the wide variation among athletes when it comes to sweating during workouts. "Basically, the bottom line as a scientist is that if you work with humans, you see a lot of variability," Spriet said. "If you work with genetically bred mice or rats, you see very little variability. I prefer to work with humans because it's more fun, but you know, it's amazing how variable things can be between people." Earlier studies of activities such as basketball, cycling and soccer have shown that losing more than 2 per cent of one's body mass affects "absolute power production," and Spriet's work with the Storm this season is designed to measure how a hockey player's performance is affected by being in a state of "hypohydration" or dehydration. He expects the results will surprise some people. "I always say to the hockey players, 'You would never go on the ice with skates that aren't sharpened properly or your stick the way you like it, so why would you go on the ice in a dehydrated situation?' It's just one more thing in their arsenal." HYDRATION What kind of drink is the most effective at preventing and relieving sports dehydration? Here is one product that I use that has the clinical tests to back it up. Research has concluded a dilute electrolyte and glucose solution is absorbed more quickly and completely than water alone. Combined with the correct ratio of potassium and sodium ions the absorption can be sped up even more. Many common sport drinks on the market today do not offer these benefits, and they are not iso-tonic (not able to be absorbed quickly-- instead needing water from your body to be processed). So, if you interested in learning more on the science of hydration, go to http://www.vitalyte.com for full product details.
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