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The Low-Down on High Intensity Training

posted May 22, 2015, 3:44 AM by   [ updated Jul 10, 2018, 11:49 AM by Tracy Ducker, MS, RDN ]

Upping your workout intensity is a hot topic these days, with some people saying that a form of high-intensity physical activity known as high-intensity interval training (HIIT) is much better than more moderate aerobic activity like walking, while others say that pushing yourself too hard can be dangerous. So who’s right?

Before we delve into the pros and cons of HIIT, it is important to review what the Physical Activity Guidelines for Americans have to say about exercise intensity. These guidelines recommend that all adults get a minimum of 150 minutes a week of moderate-intensity physical activity or 75 minutes a week of vigorous-intensity physical activity, or an equivalent combination of moderate- and vigorous-intensity physical activity. The talk test is an easy way to check your activity intensity—check out this month’s handout for more information.

The Physical Activity Guidelines don’t recommend one level of intensity over another. However, the guidelines do point out that since 1 minute of vigorous-intensity activity counts as 2 minutes of moderate-intensity physical activity, vigorous-intensity physical activity may be a more efficient way to make sure you’re getting enough exercise.

So what is high-intensity interval training (HIIT)? According to the American College of Sports Medicine (ACSM), it involves alternating periods of very high-intensity activity (80-95% of your maximal heart rate) with periods of lower-intensity recovery activity (40-50% of your maximal heart rate). The intense periods can be anywhere from 5 seconds to 8 minutes, and the recovery periods are often equally as long. The total workout can last anywhere from 20-60 minutes.

Current research suggests that HIIT provides fitness and health benefits that are at least as good as continuous moderate-intensity physical activity. But the research is still conflicting on whether HIIT is better than continuous activity for improving fitness and health, with some studies showing a definite advantage and others showing little difference between the two forms of exercise.

Based on what we know right now, the main advantage of HIIT is that it is more efficient, making it easier for you to fit in enough activity to improve your fitness and health. Many people also find HIIT more enjoyable than traditional exercise, meaning they’re more likely to stick with it.

But is HIIT safe? It depends on your current level of fitness and your health. If you aren’t currently active, the ACSM recommends starting with continuous activity rather than HIIT in order to build a foundation. Additionally, HIIT may be more risky for people with certain health conditions. To learn more about building a fitness foundation, who HIIT is more risky for, and when to consult your doctor before beginning an exercise program, see the ACSM’s brochure on High-Intensity Interval Training.

The bottom line—if you like HIIT, it’s worth incorporating into your workout routine as long as it’s ok with your doctor. It may help you stick to a workout program and fit in more exercise than you would otherwise. However, if you’re happier doing more moderate-intensity exercise like walking, that’s great too! As always, the best workout is the one you'll actually do.