Burn More Calories in Less Time with HIIT

What if there was a way to burn more calories, lose more fat and improve your cardiovascular fitness level while spending less time doing cardio? If you think this sounds too good to be true, think again. If you want to take your fitness and fat loss to the next level—without spending more time in the gym—it's time to take a look at high-intensity interval training, also known as HIIT.

Notice that I didn’t say HIIT would be easier, just that it would take less of your time. In fact, the HIIT approach to cardio exercise is very physically demanding, and isn’t for everyone. If you have any cardiovascular problems or other health concerns that limit your ability to exercise at very intense levels, or if you're relatively new to aerobic exercise or not already in good shape, you should probably hold off on HIIT—at least for now. If you're not sure whether it's safe for you, check with your medical professional.

What Is High-Intensity Interval Training?

HIIT is a specialized form of training that involves short intervals of maximum intensity exercise separated by longer intervals of low- to moderate-intensity exercise. To reap the benefits, you need to push yourself past the upper end of your aerobic zone and allow your body to replenish your anaerobic energy system during the recovery intervals. HIIT offers several advantages that traditional steady-state exercise can’t provide:
  • HIIT trains and conditions both your anaerobic and aerobic energy systems. You train your anaerobic system with brief, all-out efforts, like when you have to push to make it up a hill or sprint the last few hundred yards of a distance race.
  • HIIT increases the amount of calories you burn during (and after) your exercise session, because it increases the length of time it takes your body to recover.
  • This type of training causes metabolic adaptations that enable you to use more fat as fuel under a variety of conditions. This will improve your athletic endurance as well as your fat-burning potential.
  • HIIT appears to limit the muscle loss that can occur with weight loss, in comparison to traditional steady-state cardio exercise of longer duration.
The key element that makes HIIT different than other forms of interval training is that the high-intensity intervals involve maximum effort, not simply a higher heart rate. There are many different approaches to HIIT, each involving different numbers of high- and low-intensity intervals, different levels of intensity, different lengths of time for each interval and different numbers of training sessions per week. If you want to use HIIT to improve performance for a particular sport or activity, you can tailor your program to those specific needs and demands.<pagebreak>

General HIIT Guidelines

  • HIIT is designed for people whose primary concerns are boosting overall cardiovascular fitness, endurance and fat loss, without losing the muscle mass they already have.
  • Before starting any HIIT program, you should be able to exercise for at least 20 to 30 minutes at 70 to 85 percent of your estimated maximum heart rate, without exhausting yourself or experiencing problems.
  • Familiarize yourself with understanding exercise intensity if you are unable to wear a heart rate monitor.
  • Because HIIT is physically demanding, it’s important to gradually build up your training program so that you don’t overdo it. The sample training schedule below will safely introduce you to HIIT over a period of eight weeks.
  • Always warm up and cool down for at least five minutes before and after each HIIT session.
  • Work as hard as you can during the high-intensity intervals, until a burning sensation in your muscles indicates that you have entered your anaerobic zone. Elite athletes can usually sustain maximum intensity exercise for three to five minutes before they have to slow down and recover, so don’t expect to work longer than that.
  • Full recovery takes about four minutes for everyone, but you can shorten the recovery times if your high-intensity intervals are also shorter and don’t completely exhaust your anaerobic energy system.
  • If you experience any chest pain or breathing difficulties during your HIIT workout, cool down immediately. Don't just stop, as this can cause lightheadedness or faintness.
  • If your heart rate does not drop back down to about 70 percent of your max during recovery intervals, you may need to shorten your work intervals and/or lengthen the recovery spans.
  • HIIT (including the sample program below) is not for beginner exercisers or people with cardiovascular problems or risk factors. If you are in these groups, do NOT attempt HIIT unless your doctor has specifically cleared you for this kind of exercise.

A Sample Progressive HIIT Program

Please adhere to the general HIIT guidelines above for this program. To maximize fat loss, maintain an intensity level of 60 to 70 percent of your maximum heart rate (RPE of five to six on the 10-point scale) during warm-up, cool-down and recovery intervals.
Week  Warm  up  Work Interval (Max Intensity)  Recovery  Interval
(60-70% MHR)
 Repeat Cool
 Workout  Time
 1  5 min.  1 min.  4 min.  2 times  5 min.  20 min.
 2  5 min.  1 min.  4 min.  3 times  5 min.  25 min.
 3  5 min.  1 min.  4 min.  4 times  5 min.  30 min.
 4  5 min.  1.5 min.  4 min.  2 times  5 min.  21 min.
 5  5 min.  1.5 min.  4 min.  3 times  5 min.  26.5 min.
 6  5 min.  1.5 min.  4 min.  4 times  5 min.  32 min.
 7  5 min.  2 min.  5 min.  3 times  5 min.  31 min.
 8  5 min.  2 min.  5 min.  4 times  5 min.  38 min.

After completing this eight-week program, you can continue increasing the number of work intervals per session, the duration of work intervals or both.

If you find that this schedule is too difficult or too easy, make adjustments to the duration and/or number of high-intensity intervals as necessary. For example, if you want to train for very short, frequent bursts of maximum intensity activity, your program could involve sprinting for 20 seconds and jogging or walking for 60 seconds, and repeating that 15 to 20 times per session.

You don’t need to swap all of your aerobic exercise for HIIT to gain the benefits. A good balance might be two sessions of HIIT per week, along with one to two sessions of steady-state aerobic exercise. As usual, moderation is the key to long-term success, so challenge yourself, but don’t drive yourself into the ground. Get ready to see major changes in your body and your fitness level.