It may not feel like your winter workout is producing much perspiration, but chances are you’re still sweating—even if it’s evaporating right off of you, says Michael Bergeron, Ph.D., director of the National Youth Sports Health & Safety Institute. And while dehydration is certainly more of a concern in the heat of the summer, it’s still important to replenish the fluids you lose during a workout—and to maintain good hydration habits—year-round.
“If you’re a recreational exerciser, say you’re running 30 or 45 minutes at a time, you don’t need to be carrying around water and drinking constantly,” Bergeron says, “unless you start out severely hydrated, or you’re wearing so many layers and so much wind protection that you’re sweating profusely.”
Having said that, he adds that athletes are often surprised at how much they continue to sweat when they start exercising in the cold. “You can likely get away with working out harder or for a longer period of time, but if you go long enough and hard enough, you’ll start to see those same challenges to your body’s physiology: increased heart rate and increased body temperature.” And symptoms of mild dehydration and electrolyte loss (cramping, extreme thirst, nausea) can still happen if you’re not drinking adequate fluids throughout the day—more than just caffeinated coffee, that is.
Research has shown that people who drink a frozen slushie mixture before running in the heat can tolerate extreme temperatures for longer, actually delaying the rise of their own body temperature. Bergeron suggests trying the opposite in the wintertime: Hydrate before an outdoor run with something warm and comforting, like tea or soup. “If you’re doing this regularly, you won’t have to worry too much about it or be too aggressive with your hydration,” he says. “But if you ignore it completely and get used to not drinking at all, you’ll set a bad precedent and could be in trouble when it starts to warm back up again.”