Sometimes it seems like HITT is the only type of workout that I hear about. There are excellent reasons for people who are physically able to do HIIT to do so. Namely, it improves cardiorespiratory fitness both during exercise and at rest and you will continue to burn calories long after the workout is over.

However, HIIT was never supposed to be a daily workout because it is supposed to completely and utterly exhaust the body. People who can do the workouts on consecutive days are probably not pushing themselves quite hard enough.

If you don’t give yourself rest in between HIIT workouts, you’re likely to suffer injury, as your muscle tissue won’t have enough time to repair and grow. Overdoing it with HIIT also risks soft tissue injuries to the joints, tendons, or muscles. In the long-term, overdoing it could cause damage to the joint itself. Ideally, you should only do HIIT two or three days a week.

Proper HIIT training purposefully creates strategic overload and fatigue. Recommendations for efficiently working HIIT into your exercise program include:

    • Follow a program that provides incremental progression along with planned rest and decreases in intensity.
    • Take at least one day completely away from training each week.
    • Make sure that high-intensity days are genuinely high, and those low-intensity days are truly low.
    • Every four to six weeks, insert a training week where intensity is significantly decreased.
    • Work in a few exercises each day for the primary purpose of improving movement/mobility.
    • Don’t merely “go as hard as you can” every day. Instead, develop progressive training intensity goals.

The pendulum is beginning to swing away from HIIT as people crave a gentler and more mindful approach to exercise.  Low-Intensity Steady State training (LISS) is once again vying for position at the gym and involves working out at a slower pace for a more extended period; when you do LISS, you work out at an intensity of 4-6 on a 10-point scale (50-60% of your maximum heart rate) for 45-60 minutes.

LISS is undoubtedly less daunting to exercise newbies and is a good fill-in for days that you won’t be doing HIIT training. Proponents also point out that it’s often safer on the joints, increases blood flow, and promotes oxygen delivery within cells. Some research has shown that longer durations of low-intensity activity improve insulin sensitivity and blood lipid levels more than short stints of vigorous exercise, but not all research agrees.

Both HIIT and continuous aerobic exercise programs carry many health benefits, including increased cardiac muscle mass,  fat oxidation, and improved disposal of metabolic wastes. Athletic trainers warn that if you’re looking to build muscle and burn fat, LISS alone might not be enough to reach your goal. Your body will also adapt to LISS over time, so what was once challenging for you will cease to be challenging enough after many repeats of the same workout.

Some research has shown that people who choose LISS over HIIT tend to stick with the routine  longer, which anyone can attest is half of the battle. A 2013 study published in Nutrition, Metabolism, and Cardiovascular Diseases concluded that “prescribing a higher-intensity exercise decreases adherence and results in the completion of less exercise.” Unlike HIIT, you can do LISS for several days in a row if you want (hopefully, you’ll find a routine that you enjoy enough that you’ll start to crave the movement).

In most everything, variety is vital;  when in doubt, shake up your routine.