High Intensity Interval Training
High intensity interval training (HIIT) is a very effective, time efficient workout for improving cardio function and fat loss. High intensity exercise is proving to be a better choice for fat loss than traditional long duration aerobic exercise.
HIIT is short bursts of intense exercise (work intervals) followed by longer periods of recovery (rest intervals). Work intervals (or sprints) may be as short as 10 seconds or as long as 4 minutes. With short sprints, intensity can be very high, while longer intervals make very high intensity unsustainable. In general, short sprints require longer recovery; longer sprints require less. I prefer to measure intensity with the Rate of Perceived Exertion Scale:
Rate of Perceived Exertion (RPE) is used to rate your effort while exercising. On a scale of zero to ten, 0 is no physical exertion and 10 is too intense to sustain. These ratings can be applied to how your working muscles feel, your breathing, or an overall feeling of effort throughout your body. Shorter sprints are usually done between 6-9 on the RPE scale; longer sprints around a 5 RPE. Recovery from each sprint should be low intensity, about a 1-2 RPE.
Interval training can be done on just about any type of equipment (bike, stair climber, rowing machine, etc.) or outside on a grass field or running track. It’s best to gradually incorporate it into your exercise program, starting with once per week and adding one or two other sessions as you become more fit.
When you need greater challenge, increase the overall intensity of an HIIT workout by working slightly harder during each sprint (up to a 9 RPE), increasing the time of each sprint, or decreasing recovery time. Just like other types of cardio training, always do a warm-up and cool down.
Caution! Before attempting high intensity interval training, consult your physician to ensure it is safe for you to engage in high intensity exercise. If you are new to exercise or have been inactive for a period of time, take two to six weeks to condition yourself with steady state exercise prior to engaging in high intensity intervals.