Why Intense Workouts Are Killing Your Progress

Go big or go home? Why Shape says you may want to scale back your intense workouts.

High Intensity Interval Training (HIIT) keeps skyrocketing in popularity. But with everyone from your bootcamp coach to your spin instructor telling you to HIIT it, and the results you see convincing you to keep at it, could you end up pushing yourself too hard? Definitely, says Shannon Fable, director of exercise programming at Anytime Fitness. "People are always searching for the silver bullet, and anything that promises twice the results in half the time is going to win the race," says Fable.

HIIT intervals can last anywhere from six seconds to four minutes, with rest periods of varying lengths between them. The catch is that to truly be working at the HIIT level, you need to be reaching greater than or equal to 90 percent of your maximal aerobic capacity at each interval, according to researchers. To measure your intensity in class, pay attention to your breathing, says Fable. If you're at the right intensity, you won't able to talk during intervals and should need to take the break that's coming.

Sound like the intensity you typically reach? If so, you only need about 20 percent of all your workouts to be HIIT, says Fable. To lessen your risk of injury, experts say you should cap your HIIT workouts at three per week. Going overboard can lay the foundation for plateaus or keep you sidelined with pain or other issues, adds Fable. Incorporating HIIT into your routine can have many benefits, but don't forget to round out your routine with steady-state cardio and less intense exercise, so you score the best results while avoiding the injury list. (See 8 Benefits of High-Intensity Interval Training.)