10 Things Trainers Wish You Knew About Your Workout

9. A Death Grip on the Cardio Machine Strains Your Body and Burns Fewer Calories

When you hold the treadmill or stair-climber handles so tightly that your knuckles turn white (because you can’t keep up with the speed, perhaps), your body is forced into an uncomfortable position, which can put strain on your muscles. And “because your legs don’t have to work as hard when you lean on the machine, the number of calories you burn plummets,” says Deborah McConnell Plitt, a trainer for the Life Fitness Academy, in Myrtle Beach, South Carolina.

Action plan: Maintain proper form. On the treadmill, you should be able to stand tall and pump your arms. On the stair-climber, keep your body centered over the pedals, with your head up and shoulders relaxed. It’s OK to hold the handrails lightly, as long as your posture is correct.

10. The Fat-Burning Zone Isn’t Really a Fat-Burning Zone

If you’ve ever played around with the controls on a cardio machine, you may have experienced the “fat burning” program, in which you exercise at a low, steady intensity. The idea is that low intensity is better for weight loss than more vigorous effort, because you can sustain it longer. But studies show that even in a shorter workout, boosting your intensity can burn as many, if not more, calories than long, steady-state cardio. And “when it comes to losing or maintaining weight, it’s the total number of calories that counts,” says Halevy. Plus, by working harder, you can get out of the gym faster.

Action plan: Slow, steady workouts are a good place to begin if you’re just starting a cardio routine. But as you get more fit, bump up the intensity. Try interval training once or twice a week on nonconsecutive days: Work at a high intensity for a short spurt (say, 30 seconds), lower the intensity to recover (for 90 seconds), and repeat for 20 to 30 minutes.