High intensity interval training (HIIT) has been having a moment. It’s popping up everywhere, and with good reason.
HIIT is a training technique that alternates short bursts of intense effort with moderate intensity recovery periods of the same duration or longer. These bursts of concentrated effort make HIIT workouts effective at burning fat and improving endurance and overall fitness, but also provide a complete workout in a short amount of time. For many, HIIT routines are the solution to the “no time to workout” dilemma.
According to the American Council on Exercise, most endurance workouts — walking, running, stair climbing, 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.
Maximum heart rate is based on your age. According to the Centers for Disease Control and Prevention (CDC), 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.
Vigorous-intensity physical activity is considered performing at 70 to 85 percent of your maximum heart rate. Most of the literature about HIIT indicates a 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.
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.
Although it’s 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 occurs 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 to improve insulin sensitivity, increase metabolism, and improve 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 long 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.
A criticism of HIIT is people aren’t likely to adhere to the regimen — for a mostly sedentary population, some think it’s too hard.Indeed, many of the routines that can be found online come with a caution that they are not for beginners. If you’re new to exercise, consult with your doctor about an appropriate starting routine, and be sure to 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 than that and you 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.
If you’re thinking about adding HIIT to your fitness routine, start simple. Come up with a basic plan and after you are comfortable you can add to it.
Always start your workout with at least 5 minutes of moderate warm-up activity.
For a strictly cardio HIIT workout, start by 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). If this is too strenuous, cut the times in half. Alternate four times ending 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, 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 too challenging, shorten the interval time. As you improve, add time or weights to each interval.
Remember, there is no “right” way to do HIIT. Experiment with different interval and recovery times and work in different exercises to keep it interesting. Work with different routines to determine what works best for you, then enjoy the benefits of this super-effective workout protocol.
September 18, 2015
Christopher Nystuen, MD, MBA