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    As quickly as exercise scientists work to banish them, new fitness misconceptions rear their ugly heads. Meanwhile, other untried and untrue myths just won’t go away. Here, we round up a few of the most common fitness falsehoods, and ask researchers and other experts to help correct the record.
    —Cindy Kuzma

  • Photo: prochasson frederic/Shutterstock

    You Can't Trust Your Thirst

    Truth: Evolution did us a solid on this one. Thirst serves as a pretty accurate guide to your body’s hydration needs, says Eric Goulet, Ph.D., who studies the issue at the Université de Sherbrooke in Quebec. This means you can skip complicated formulas based on body weight and sweat measurements.

    “Believe it or not, there are no studies out there so far that show completely replacing sweat losses during exercise helps performance more than drinking according to the dictates of thirst,” he says. “And remember, the best endurance athletes in the world are often those who terminate an exercise the most dehydrated.” Of course, sometimes practical concerns reign supreme—as you head into a stretch of path that extends 45 minutes without a water stop, you might want to sip even if you don’t feel parched at the moment.

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    Low Intensity Exercise Burns More Fat

    Truth: This belief persists in part because of the charts printed on cardio machines. But in fact, this fabled fat-burning wonderland originated with fuzzy math. “While it is true that you burn a higher percentage of fat calories at lower intensities, you burn a greater number of total fat calories and total calories overall at higher intensities,” Holland says.

    And when it comes to shedding pounds, you want to increase your total calorie expenditure, not just the percentage that comes from fat. For maximum burn—plus additional health and performance benefits, from lower cholesterol to better nerve-muscle coordination—include high-intensity intervals in your cardio routine. After a warm-up, work in 10- to 60-second periods at near-maximum effort. Follow each with an easier rest period one to four times that length.

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    Antioxidant Supplements Boost Performance

    Fact: Diets rich in antioxidants—think brightly colored fruits and veggies—help your health and your performance. But mega-doses don’t necessarily multiply the effects and may even block the benefits of your workout, according to a recent research review in the journal Sports Medicine.

    Here’s the scoop, according to study author Tina Tinkara Peternelj, a Ph.D. candidate at the University of Queensland in Australia: When you exercise, your body uses more oxygen and produces more byproducts, including reactive oxygen species. In large amounts, these compounds damage your cells. But you actually need some reactive oxygen for your body to adapt to the challenges of your workout, and taking supplements may interfere with your body’s natural response. Your best bet: Load your cart with produce, and check with your doctor or a nutritionist to assess your antioxidant status before adding supplements.

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    Popping Pain Relievers Is Safe

    Fact: Sure, you can buy them without a prescription. But non-steroidal anti-inflammatories or NSAIDs—including ibuprofen and naproxen—come with a laundry list of side effects, including many exacerbated by exercise. They may leave you prone to ulcers and gastrointestinal bleeding, increase your core temperature so you run the risk of overheating, and alter your kidney function and increase your risk of hyponatremia (dangerously low electrolyte levels). Like high-dose antioxidants, they may also negate your workout altogether.

    “Several studies are demonstrating that NSAIDs may reduce the body’s natural ability to adapt and get stronger, faster, and bigger from exercise,” says John Martinez, M.D., a primary care sports medicine doctor in San Diego and a member of the medical staff with USA Triathlon. He currently recommends avoiding NSAIDs or aspiring for 24 hours before a workout.

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    Resting Means You're Weak

    Fact: This myth builds on another fundamental misunderstanding: that your workout itself makes you stronger. “When we exercise, we are in effect tearing apart our muscle fibers and breaking down our immune and cardiovascular systems,” Holland says. “It is during our times of rest that our bodies are allowed to repair and rebuild; these adaptative periods are when we get stronger and faster.” Training hard without recovery leads to so-called overtraining syndrome and its friends poor performance, illness, and burnout. For endurance athletes and others training hard, Holland advocates at least one rest day per week.

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    Skip Carbs After Exercise

    Truth: After a hard session—be it running or strength-training—you do need 15 to 25 grams of protein within an hour to repair and build new muscle. But just like superheroes need a sidekick, protein doesn’t act alone. “We advise our athletes that you actually need carbs there too—physiologically, carbs helps to get your cells open and ready to accept the protein. Symbiotically, they work together very well,” says Jennifer Gibson, M.Sc., R.D., a nutritionist for the U.S. Olympic Committee. Pair your protein source with a half-gram to a gram of carbs per 2.2 pounds of body weight—think Greek yogurt with fruit or an omelet with veggies.

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    You Don't Need to Strength Train

    Truth: Hitting the weight room could actually help your running, cycling, or triathlon performance, research indicates. Most recently, an Italian study published in the Journal of Strength and Conditioning Research showed runners who lifted heavy weights for 12 weeks while marathon training improved their running economy, a measure of efficient oxygen use that allows you to run harder for longer.

    Another reason to pump iron: Injury prevention. “Most people have one or more weak links in their kinetic chain; strength training helps balance these weak links, whether they are muscle imbalances or weaknesses, help making the athlete ‘bullet-proof,’” says Tom Holland, M.S., an exercise physiologist and author of The Marathon Method and Beat the Gym. Endurance athletes can reap huge rewards from one to three 15- to 30-minute strength-training sessions per week, he says.

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    Exercise Cancels Out the Dangers of Your Desk Job

    Fact: What you do outside the gym or off the trail matters, too. Study after study has linked time spent on your rear end to diabetes, heart disease, and early death. Scientists suspect that the longer the large muscles of your legs and trunk stay immobile, the more harmful blood fats and sugar can build up in your bloodstream.

    “It’s an incredibly frightening scientific finding that no amount of exercise seems to offset time spent sitting,” Holland says. “We therefore need to find as many ways as possible to add movement, even small amounts, into our daily life.” If your boss won’t spring for a treadmill or bike desk, at least get up for a minute or two every half hour during your workday. And hop up from the couch at least twice during each episode of Orange Is the New Black.

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    Exercise Always Makes You Hungry

    Fact: Some people do report increased hunger after long-lasting, low-intensity efforts (leading some runners to actually gain weight training for a marathon). But higher-intensity exercise often has the opposite effect, Gibson says. As blood flows to your hard-working muscles, it bypasses your gut, and the adrenaline released to power your efforts essentially shuts down your digestive processes.

    Regardless of your hunger level, eating soon after your workout not only speeds the recovery process, it also can prevent you from feeling deeply ravenous and overeating later on, Gibson says. You can also avoid overcompensating by keeping a realistic tally of the calories you burned, recognizing that as you gain experience as an athlete, your perform more efficiently and hence burns less fuel.

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    Stretch Before Exercising

    Fact: Your fifth-grade PE coach was wrong—touching your toes before warming up actually decreases your performance and doesn’t do a thing to prevent injury. Instead, perform a dynamic warm-up, with full-body moves that closely match what you’ll be doing in your workout (think skipping, butt-kicks, and lateral shuffles). “One of the goals of this warm-up is to increase blood flow to the working muscles, increase core temperature, and increase muscle enzyme activity,” Holland says. Save static stretches for after your workout, when warm muscles more easily lengthen.

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