You know you’re supposed to drink water when you work out. After all, not being properly hydrated can put you at risk for dehydration, cramping and lack of energy as well as other serious health issues like heat stroke, especially during the hotter months.
Not drinking enough water can also affect your athletic performance, particularly if you have a hardcore cardio workout lined up. “Entering into an activity with a mere 2–3% level of under-hydration has been shown in research to reduce strength by at least 2%, power by approximately 3% and high-intensity endurance by around 10%,” says Jennifer Novak a strength and conditioning coach and founder of PEAK Symmetry Performance Strategies.
Here’s everything you need to know about staying hydrated for different types of workouts in all seasons.
Drinking water before you get your heart pumping is crucial. “You should aim to be fully hydrated within an hour of starting your workout, because the act of drinking water only starts the hydration process,” explains Mike Israetel, PhD, co-founder and chief sport scientist of Renaissance Periodization and a U.S. Olympic Sports Nutrition Consultant.
“It takes some time for water to reach all of the parts and compartments of your body that need hydration,” Israetel says. The best way to tell if you’re hydrated before a workout, he says, is to check the color and quantity of your urine. “If you’re peeing clear-yellow voluminously several times in the hours before training, you’re probably good to go.”
As for how much you need to drink to achieve this, it depends on various factors like size and muscle mass, so you may have to experiment a bit to figure out what works best for you. “You can also have around 8–12 ounces of fluid 20 minutes or so before activity if you feel the need to top off,” Israetel says.
Once your workout has started, it’s a good idea to continue drinking a little bit of water throughout. “During activity, you should aim to drink 5 ounces of fluid every 20 minutes or so, unless you’re really just too full and can’t handle that much fluid,” Israetel says. “If you’re training super hard and it’s super hot, it might be more than this, and easier training in colder conditions might be less.” The more you sweat, the more hydration your body is losing, so if you’re dripping wet during your workout, you may want to increase the amount you’re drinking.
“The big issue with intra-workout hydration is that by the time you feel thirsty, you’re already dehydrated enough to have slightly lower performance,” Israetel notes. “You’re not in danger or anything, but your training won’t be optimal.” So if performance is a concern, do your best to keep your water breaks regular before you actually feel thirsty. “Nothing crazy, but just steady and slow intake so you can keep performing at your best.” If you’re mainly working out to burn calories, trusting your own thirst as a cue is a good strategy, too.
The only time you might not want to drink during a workout is immediately before a super high-intensity exercise, like a set of 50 burpees. “In vulnerable people, this could create nausea or reflux but discomfort at minimum,” Novak says. So time your water breaks strategically and don’t gulp huge amounts right before an extremely intense set.
This might sound weird, but if you’re concerned about hydration, it’s a good idea to weigh yourself before and after your workout. That way, you know exactly how much water you lost. “Athletes typically weigh in before and after practice and hydrate accordingly,” Novak says. “Post-exercise, the recommendation is at least 16 ounces of fluid for every pound lost during activity,” she adds. “Men may require more than women due to body size and muscle mass differences.”
You don’t have to step on the scale every time you work out, but if you know you lose 1 pound of water weight during a spin class, you know for the future that you need to drink about 16 ounces of water after every class.
Since sweat is a major determining factor in fluid loss, it’s natural to wonder about the differences between hydrating for an indoor workout versus an outdoor one. Ultimately, it comes down to temperature. “A studio class is likely temperature-controlled to an extent (unless it’s hot yoga), while a long endurance run outside is not,” Novak points out.
“The hotter it is, the more you sweat,” Israetel says. “The more you sweat, the more diligent you have to be about fluid replacement. It’s that simple. So when you’re drinking fluids and you’re sweating a ton in hot, outdoor training, try to push to the top end and even above the recommended intra-workout hydration numbers (5 ounces every 20 minutes.)”
And contrary to popular belief, cold weather exercise still creates fluid loss, Novak says. “Seeing one’s breath in the cold is actually water vapor leaving your body and being cooled by the outside temperature. Additionally, sweat may not be as apparent due to clothing layers.” Because of this, it’s a good idea to follow similar intra-workout hydration patterns for outdoor workouts, even in colder temperatures.
Short answer: Yes. Don’t go way over the recommended guidelines, particularly if you’re doing a very long endurance workout such as a three hour run or cycle.
Long answer: “There’s a condition known as hyponatremia caused by very low sodium levels in the blood,” Novak explains. “This can happen when large amounts of sodium are lost due to sweating or in combination with drinking large amounts of plain water at the same time.” In other words, when your body loses a ton of sodium through sweat and you drink large amounts of water, your blood becomes too diluted. “The symptoms include nausea and/or vomiting, confusion, lethargy, irritability and/or muscle cramps.”
To avoid this, you’ll want to grab a sports drink or tablet with electrolytes (more on that next), to replenish sodium levels. If you’re not an endurance exerciser logging workouts that last 90 minutes or more, you probably don’t need to worry about this.
There are many, many sport hydration drink options out there, from pre-mixed ones to powders to tablets. The bottom line on whether you need one comes down to how long and how intensely you’re working out. “If you’re training for an hour or less and not sweating bullets, water is just fine pre- and during training,” Israetel says. After training, water with food can provide the electrolytes you need.
“For training longer than an hour or where you get really sweaty, an intra-drink of electrolytes is a very good idea,” Israetel says. “A calorie-free electrolyte tab or squirt bottle can go a long way. Brand doesn’t matter much, just stay away from added sugars (unless you need those too … but you probably don’t unless you’re a competitive athlete). It’s also important to make sure the electrolyte concentration is high by following the fluid amount mixing recommendations on the product. “If it tastes a bit weird, it’s probably the right concentration!”
Lastly, these should be consumed at the same rate as water during a workout, so around 5 ounces every 20 minutes.