Would it shock you to learn that you can't really slim your belly with crunches? If so, you’ve been had by hearsay, a common belief with no science behind it. For your consideration, we offer five more adages about exercise that, on closer inspection, actually have no merit.
No pain, no gain.
Exercise shouldn’t hurt. Period. If a trainer uses that cliché to motivate you, find someone else for your fitness advice. Pain is your cue to stop, says chiropractor Joshua Kollmann. “The body is equipped with a sophisticated nervous system that alerts us to potential damage,” he says.
Muscle soreness is different and is to be expected after a good workout. It’s part of the muscle-strengthening process, in which you stress your muscles just enough to cause microtears that your body quickly repairs. This soreness normally happens 24 to 48 hours after exercise. Reduce it with ice, elevation, or compression, and take ibuprofen only if necessary.
You can slim your belly with crunches.
Doing sit-ups to burn belly fat seems logical but is physiologically impossible. That’s because exercising a particular part of your body burns kilojoules all over, not just in the area you’re targeting. In a Chilean study, participants performed 1 set of approximately 1,000 leg presses 3 times a week using only their nondominant leg. The assumption might be that the exercised leg would become leaner than the other. On the contrary: Although researchers measured an average reduction of 5% in overall fat mass among the participants, almost none of that fat loss came from the exercised leg.
To see results, you need to do an hour-long workout.
Quality matters more than quantity. Research shows that a short bout of vigorous exercise can deliver the same benefits as a much longer workout done at a moderate pace. In a recent study, adults who bicycled at high intensity for 10 minutes 3 times a week for 12 weeks had the same uptick in fitness and cardiovascular health as those who did 50 minutes of moderately paced cycling. To hit that superefficient zone, exercise at about 80% of your maximum heart rate, says fitness expert and trainer Kira Stokes. (Determine your maximum rate by subtracting your age from 220.)
Doing long, slow stretches before exercise can help prevent injury.
This type of warm-up—known as static stretching—may actually make workouts less effective, according to research in the Scandinavian Journal of Medicine & Science in Sports. “Stretching before exercise is important, but it has to be the right kind of stretching—dynamic stretching,” says Kollmann.
A dynamic stretch involves movement, so you warm up the muscle while you’re stretching it—by doing, for example, a lunge with a torso rotation. The key is mimicking a movement that will be part of your normal workout but doing it at a lower intensity, says personal trainer Sarah Kusch.
Strength training is better than cardio if you’re trying to lose weight.
Cardiovascular exercise burns more kilojoules per minute than strength training does, so it’s the clear choice when the goal is fat burning and weight loss.
In 2012, Duke University researchers ran a study comparing the two types of exercise. They placed 119 overweight people into one of three groups: cardio, strength training, or cardio combined with strength training. After 8 months, those who did cardio reduced their waist circumference and lost weight (and an average of 1.5kg of that was fat). The strength-training group added muscle but lost no fat. The group that did both lost fat, weight, and inches, but their workouts were longer than the other groups’.
“Resistance training is great for improving strength and increasing lean body mass,” says study coauthor Cris Slentz. “But if you’re overweight and want to lose belly fat, cardio exercise is the better choice, most likely because it burns more kilojoules.”
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