Swinging for the slopes this weekend? Besides your board and goggles, make sure to grab a sports drink.

“Don’t be fooled into thinking that you don’t sweat in the cold,” says Michele Macedonio, MS, RD, CSSD. Even in the winter, hydrating is absolutely crucial, because you generate heat, and therefore sweat, when you engage in physical activity. You also lose fluids through the humidification of air in your lungs.

So why’s all this important? Because when you sweat, you also lose electrolytes—minerals like sodium and potassium that help your body control the fluid exchange within and outside of cells. They play a crucial role in helping muscles function, and an electrolyte imbalance in your body can leave you feeling one or more of these side effects:

• Extreme thirst
• Fatigue
• Irritability
• Nausea
• Mental confusion or lack of mental sharpness
• Headache
• Dizziness
• Muscle cramping
• Red, flushed face

Avoid keeling over by maintaining a proper fluid balance. Macedonio recommends consuming a sports drink instead of water if you lose a significant amount of sweat. Look for a drink that has 14g of carbs and at least 70mg of sodium per eight-ounce serving. The sodium facilitates rehydration.

Michele Macedonio, MS, RD, LD, CSSD, is the owner of Nutrition Strategies, a nutrition consulting company based in Cincinnati, Ohio. In addition to active membership in the American Dietetic Association and SCAN, she’s the sports dietitian for Ignition APG and the Cincinnati Bengals and Kings.