All About HIIT and RPM

High-intensity interval training (HIIT) involves alternating short, intense work periods with recovery periods during a single cardio session. HIIT takes less time than traditional cardio, yet has been shown to trigger a longer “afterburn” of calories, raising your metabolism, breaking through plateaus, and helping you lose fat. HIIT has also been shown to be very effective at increasing cardiovascular fitness.

You can do HIIT on a cardio machine or as sprints. (A few ideas here.)

Know that when done correctly, HIIT requires more recovery time than strength training or steady-state cardio. Therefore, I don’t recommend doing HIIT more than 2x/week, depending on what other activities you do (if you don’t do anything else, you could probably get away with 3x/week). Remember: With fitness, you can’t just keep adding on without a cost (i.e., injuries or recovery issues).

Measuring Aerobic Intensity

The Rate of Perceived Exertion (RPE) scale is easy and simple for estimating how hard to work during aerobic exercise. (Heart rate monitors don’t have a great reputation for being accurate.) As I said, HIIT work periods require an all-out level of intensity to reap the metabolic benefits. Your work periods may be only 10-30 seconds long, while your recovery periods may be 30 to 120 seconds long. Over time you can work up to shorter recovery periods and longer work periods.

Rate of Perceived Exertion (RPE)

RPE measures exercise intensity on a scale of 1-10. Most people should exercise less than 8-9 for sustained bouts of cardio. For HIIT, your work periods should be around around 8-10 on the RPE scale and recovery should be anywhere from 5-7.

RPE table

Determining Work and Recovery Periods

Work Periods

Work as hard as you can (“all out”) for a short burst or sprint (around 85% of your max heart rate, or 8-10 RPE). During work periods, you can increase/decrease the intensity on your machine by adjusting the resistance level, incline, or both. Just be sure you can easily make adjustments quickly.

Recovery Periods

Slow down, lower the intensity, and let your heart rate come down to 65-70% of your heart rate max, or 4-5 RPE. This may take quite awhile if you’re just starting out. Be patient – your cardiovascular health will improve quickly if you stick with it.

Aim for a 1:1 ratio of work to recovery. So, for example, 30 seconds of sprints with 30 seconds of recovery.

What if you’re having trouble recovering between work phases?
You can always start with longer recovery periods and work up! If it takes longer than a 1:1 ratio for your heart rate come down, lower the intensity of the work period or recover 30-60 seconds longer until you can work up to doing more. Your endurance will increase over time.

See this for HIIT Ideas!

This article originally appeared on

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