The Benefits of High Intensity Interval Training (HIIT)

High intensity interval training can result in shorter workouts, yet it may be more effective in burning fat. Here's what you can do to fire up your workout.

High intensity interval training (HIIT) has grown in popularity over the years, and with good reason.

HIIT is a training technique that alternates short bursts of intense effort with moderate intensity recovery periods. These bursts of concentrated effort make HIIT workouts effective at burning fat and improving endurance and overall fitness. It also provides a complete workout in a short amount of time. For many, HIIT routines are the solution to the “no-time-to-workout” dilemma.

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What does “high intensity” mean?

According to the American Council on Exercise, most endurance workouts — walking, running, stair climbing, and rowing — are done at moderate intensity, or an exertion level of 5 to 6 on a scale of 1 to 10. High-intensity intervals are done at an exertion level of 7 or higher. Your degree of effort is determined by your heart rate.

Calculating your heart rate

Maximum heart rate is based on your age. According to the Centers for Disease Control and Prevention, you can estimate your maximum heart rate by subtracting your age from 220. For example, the maximum heart rate for someone who’s 50 would be 170 beats per minute (220 - 50 = 170).

Moderate-intensity physical activity is generally performed at 50 to 70 percent of your maximum heart rate, or between 85 and 119 beats per minute (bpm) for someone who’s 50.

• At a 50 percent level of activity: 170 x 0.50 = 85 bpm
• At a 70 percent level of activity: 170 x 0.70 = 119 bpm

Vigorous-intensity physical activity is considered performing at 70 to 85 percent of your maximum heart rate. Most of the research about HIIT indicates an optimum target heart rate of 80 to 95 percent of your maximum during the interval, and 40 to 50 percent during the recovery period. The actual effort it takes to get to those levels will vary depending on your conditioning.

Checking your heart rate

After you’ve determined your target heart rate for your activity, you’ll need to pause briefly to check your pulse during your workout. Place your fingers (not your thumb) on your wrist in line with your thumb to find your pulse. Starting with “0,” count your pulse for 15 seconds and multiply by 4 to calculate your bpm. (Or, count for 30 seconds and multiply by 2.)

You can also use the talk test. During moderate-intensity exercise you should be able to talk, but not sing. At a vigorous level, you won’t be able to say more than a few words without pausing for breath.

Why is high intensity interval training so popular?

Although often associated with cardiovascular exercise — walking, running, cycling, stair climbing — HIIT can incorporate a wide variety of activities, including bodyweight exercises, kettlebells, and free weights. Many group exercise classes incorporate elements of HIIT, as does Tabata training, CrossFit, OrangeTheory Fitness, and other popular workout programs.

You can modify HIIT to any fitness level and, because of its versatility, it’s easy to mix up your workout and prevent the boredom that can occur when doing the same routine repeatedly. This makes it more likely that you’ll stick with your exercise program.

HIIT accelerates health and fitness gains. Although more research is needed to fully understand the physiological mechanisms at work, studies have shown HIIT can improve insulin sensitivity, increase metabolism, and reduce risk factors for cardiovascular disease and type 2 diabetes. 

HIIT is also effective at burning calories and building muscle. The aerobic and anaerobic components of most HIIT routines cause you to burn more calories faster, and you may continue to burn calories for as many as 24 hours after the workout.

You can find many articles and apps on the internet to download onto your phone or other device to time your intervals or provide complete HIIT workouts.

It’s not for everyone

A criticism of HIIT is that many sedentary people aren’t likely to adhere to the regimen. Some people think it’s too hard. Many of the routines found online come with a caution that they are not for beginners.

If you’re new to exercise, talk with your doctor about an appropriate starting routine. Make sure you discuss any underlying health conditions you may have.

Don’t do a HIIT routine more than two to three times per week, and make sure to allow ample time (at least two days) between workouts for complete recovery. More HIIT workouts than that increase your risk of injury. It also isn’t recommended as your only form of exercise. Mixing up your workout routine is important to achieve continued improvements in strength and fitness.

What you can do

If you’re thinking about adding HIIT to your fitness routine, start simple. Come up with a basic plan. You can add more to your routine once you are comfortable.

Always start your workout with at least 5 minutes of moderate warm-up activity.

For a strictly cardio HIIT workout, start with brisk walking. Then alternate 1 minute of all-out running (80 to 95 percent effort) with two minutes of recovery (50 to 70 percent effort). Recovery exercises include walking, yoga, or swimming.

If the workout is too strenuous, cut the times in half. Alternate four times and end with a 5-minute cool down. As your conditioning improves, increase the time and the number of intervals.

For a strength-based HIIT circuit, start with four or five exercises such as squats, push-ups, planks, crunches, burpees (push-ups followed by leaps in the air), mountain climbers, jumping rope, box jumps, or high jumps.

Perform as many reps of one exercise as you can for 30 seconds. Rest for 10 seconds. Then perform the next exercise for 30 seconds, followed by a 10 second rest. Progress through each exercise, then rest for 45 to 60 seconds.

Begin again, completing the entire routine four to six times. If it’s too challenging, shorten the interval time. As you improve, add time or weights to each interval.

There is no “right” way to do HIIT. Experiment with different interval and recovery times, working in different exercises to keep it interesting. Try different routines to determine what works best for you, then enjoy the benefits of this super-effective workout protocol.

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