Definition

Repeated bouts of high intensity exercise with intermittent rest periods. Can vary frequency, intensity and duration of the periods of intense exercise and also duration of rest periods.

Physiological Rational for Interval Training

1. Intermittent exercise allows the body to increase the total volume of high intensity work performed. Work by Professor Astrand in the early 1960's showed a subject was able to cycle at 350 Watts for only 9 minutes continuously. However, in 3 minute intervals the subject performed 3 times greater achieving 30 minutes of effort.

2. Short work periods dramatically reduce physiological stress despite the same total accumulated time and interval intensity.

The reasons for this are probably the fact that the body does not completely deplete its oxygen store within the muscle during the short exercise period. The result is no oxygen deficit and therefore no build up of lactic acid. During the recovery period between intervals the body is able to replenish the oxygen used during the effort in preparation for the next interval.

Therefore, interval training allows a greater volume of stress to be placed on the heart, vasculature and muscles resulting in improved compliance of the body's systems to high intensity exercise.

Here are some tips on interval training workouts from research in Exercise Physiology.

1. Interval training at or above 100% VO2 max does not provide any additional benefit to aerobic capacity.
2. Intervals of 4-8 minutes at intensities of ~85% VO2 max (or 85% max HR) are perfect for increasing cardiovascular power.
3.Longer intervals of 10-20 minutes at 75-85% max HR benefits skeletal muscle adaptations.
4. 20-30 minutes of accumulated interval training is appropriate for  4-8 minute intervals.
5. 40-60 minutes is appropriate for the longer lower intensity intervals.
6. Rest periods of ~2-4 minutes for high intensity intervals.