If you're running low on time but still want to get a decent, calorie-burning workout in, interval training is your best option. Research shows that interval training—workouts in which you alternate periods of high-intensity exercise with low-intensity recovery periods—increases fitness and burns more calories over a short period of time than steady-state cardio (doing the same thing for your whole workout time).
So how do you get the most out of interval training, and how long should each push and recovery be? One of the many great things about intervals is that there's no single hard-and-fast rule. Different lengths of work and recovery bring different benefits—and they're all good.
More: Calculate your Caloric Needs.
Start with the following three interval training plans. The good news is each workout has a cross-training option in case you don't want to run that day. Before you start, keep in mind: Interval training is tough, so if you're just starting to work out, spend a few weeks to one month building your stamina with cardio workouts before adding interval training to your routine. Add these interval training plans to your gym routine once a week to burn more calories, build more fitness, and get out of the gym faster.
More: How to Increase the Calorie-Burning Effects of Running
Cardio Blaster
This cardio workout is one of the best workouts you can do to improve fitness. It burns lots of calories in a short time.
How to do it: Start with a 15-minute warm-up, then run, bike or row for three minutes at 90 to 95 percent of your maximum heart rate (should feel like 8.5 to 9 on a scale of 1 to 10). Take three minutes active recovery and repeat 3 to 4 more times. Finish with a 10-minute cooldown.
Bonus benefit: This workout is like weight training for your heart—it strengthens your cardiovascular system, which improves your health.
More: 5-Minute High Intensity Circuit Training for Runners
Speedplay
There's nothing like sprinting to get your legs, glutes and core tight and toned. Sprinting increases your muscle power, which helps you push harder in everything you do. It makes your other workouts feel easier so you can challenge yourself and burn even more calories.
How to do it: Start with a 15-minute warm-up, adding a few 20-second bursts at the end to prepare for the workout. Then run, bike or row for 30 seconds at a nearly all-out effort. Take three minutes active recovery and repeat 5 to 6 more times. Finish with a 10-minute cooldown.
Bonus benefit: Because of its very high intensity, this workout is very short.
More: Get More Out of High-Intensity Training By Doing Less
Cardio-Sprint Pyramid
This workout mixes cardio training with sprint training for a fun workout you'll never forget.
How to do it: Start with a 15-minute warm-up, adding a few 20-second bursts at the end to prepare for the workout. Then run, bike or row for 30 seconds, 1 minute, 2 minutes, 4 minutes, 2 minutes, 1 minute and 30 seconds at a rate of perceived exertion of 8 to 10 (adjusting the effort with the length of the segment). Follow each hard segment with an active recovery interval equaling the same amount of time. Finish with a 10-minute cooldown.
Bonus benefit: This big calorie-burner workout gives you the best of both worlds—high-octane cardio and muscle-sculpting sprinting.
More: How to Get Fit Quickly in Less Than 3 Hours a Week
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