1. Don't Wait for Your Thirst to Tell You When to Drink
Once you start thinking about a nice, cold glass of water, you're probably already 1 to 2 percent dehydrated, says Jessica Matthews, an exercise physiologist for the American Council on Exercise (ACE).
DO use the "lemonade test." When you peek in the toilet immediately after you urinate, you want to see liquid the color of pale lemonade; if it's a vibrant yellow or looks like apple juice, you need more fluids. ACE's general recommendation is to drink 17 to 20 ounces of water (a typical single-size bottle of water, like you'd buy in a convenience store, is 20 ounces) two to three hours before exercise on a typical day--this takes into account the fact that you'll probably hit the loo before heading outside. Then, during your workout, try to drink an additional 7 to 10 ounces of water every 10 to 20 minutes (this is especially important on sweltering days).
One more thing: Remember that you still sweat even when you're swimming, doing water aerobics or surfing, so leave a bottle of water on the shore or at the side of the pool.
2. Don't Protein-Load Before Your Workout
Some research has suggested that too much protein before a sweat session could elevate your basal temperature, making you feel even hotter. You're better off saving the protein bar for after your workout, when it will help you rebuild muscle.
DO cool off your insides with a slushie. Researchers have known for some time that lowering core body temperature before and during exercise can help athletes perform better, says Rebecca Stearns, director of education at the Korey Stringer Institute at the University of Connecticut--and now we have a tasty, science-backed idea of how to do that. A study published in 2010 in the journal Medicine & Science in Sports & Exercise found that when Australian athletes drank a flavored slushie before running on a treadmill in a hot room, they were able to keep up the pace for an average of 10 minutes longer than when they drank cold, flavored water.
One more thing: Don't plan to stop by the 7-Eleven on your way to the track; Stearns points out that the slushies in the study were more like frozen Gatorades than convenience-store Slurpees. The sodium in sports drinks can help the body retain fluid that is lost through sweat, so for the ultimate workout refresher, try combining your favorite sports drink with some crushed ice.
3. Don't Ignore That Sluggish Feeling
It's 80 degrees, the humidity is above 60 percent, and halfway through your jog, you start to feel like you're wading through a swamp. You may think you're just having an off day, but could be a sign of heat exhaustion, when your internal thermostat goes on the fritz and is no longer able to effectively cool the body. Symptoms can vary, says Marjorie J. Albohm, the president of the National Athletic Trainers' Association (NATA), but early ones include muscle weakness, profuse sweating, an accelerated heartbeat, dizziness and clammy skin.
DO give your body time to adjust to summer. NATA guidelines say it can take from 10 to 14 days to acclimatize to warmer weather. When the temperature first starts to climb, take your workouts down a notch: do fewer intervals, or save that long endurance ride for a cooler day. If you start to feel weak during outdoor boot camp, back off and lighten your weights. Trying to push through heat exhaustion can lead to a potentially life-threatening heatstroke, Albohm says. If symptoms persist, head for the shade or an air-conditioned space and replace fluids by drinking water. If after 30 minutes you're still woozy and feeling nauseated, call a doctor.
One more thing: keep in mind that research shows that one experience of heat exhaustion may make you prone to another bout, so keep an eye on the weather forecast.
4. Don't Swim With a Naked Face
Many freestyle swimmers assume that because their heads are usually halfway underwater, they don't need sunscreen on their face. Not true, says Monica Scheel, MD, a board-certified dermatologist in Kona, Hawaii who treats a lot of sun-exposed athletes. The sun's rays bounce off the water and the ground below to penetrate the skin on both sides of your face, she says, making you prone to serious UV damage.
DO apply a sunscreen that won't leave an oily white cloud on the water's surface--but beware of products that say they're "waterproof," because the FDA recently banned manufacturers from making that misleading claim. Instead, look for the labels that offer "water resistance" and SPF 30 broad-spectrum protection. The new regulations, which will go into effect within the next year, require manufacturers to prove that water-resistant sunscreens provide 40 to 80 minutes of protection in the water. Scheel, a swimmer and former Ironman competitor, likes the TiZO mineral-based sunscreen line by Fallene, which has a sun protection factor of 80 minutes in the water. TiZO2 and TiZO3, both SPF 40 and formulated for the face, use the physical blockers titanium, iron and zinc oxide to provide broad-spectrum UVA and UVB protection.
One more thing: TiZO is only sold by physicians (check the Fallene web site for details).
5. Don't Race in Thin Air
At least not during your first few days in the mountains. Even jogging around a high-elevation city like Santa Fe could cause altitude sickness for someone whose main exercise is playing a weekly social game of doubles tennis, says Michael P. Zimring, MD, director of the Center for Wilderness and Travel Medicine at Mercy Medical Center in Baltimore. When you get above 6,000 feet, the body can have a difficult time adjusting to the decrease in oxygen and the change in air pressure, leading to flulike symptoms such as dizziness, shortness of breath, nausea, headaches, extreme fatigue and confusion.
DO take it slow for the first 24 to 48 hours, because it's easier to prevent altitude sickness than to treat it. Most people are able to acclimate within a few days, but when you go for a hike, pace yourself, and head back downhill if you start to feel ill. There's no way to predict who will get altitude sickness or when, exactly, it will hit, but dehydration makes you more vulnerable, so lay off the coffee and caffeinated sports bars and drink plenty of water.
One more thing: Before your trip, Zimring suggests, ask your doctor for a prescription for acetazolamide, which speeds the body's ability to acclimate to the low oxygen levels at high altitude and also treats unpleasant symptoms after they