High Intensity Aerobic Interval Training

In my posting of November 18, 2009, I mentioned some strong advantages to interval training. The type of interval training discussed involved cycling for 10 seconds at all-out intensity followed by 20 seconds of easy pedaling, repeating this 10 times. This 5-minute workout produced aerobic improvements similar to those of running steadily for 20-25 minutes and, in addition, produced improvements in max power output and in resistance to fatigue from repeated work bouts.

A different type of interval training is discussed in an article by Schoenfeld and Dawes in the Strength and Conditioning Journal (vol. 31, no. 6, December 2009). The High Intensity Aerobic Interval Training (HIIT) described involves work intervals of about 1 minute each, interspersed with recovery intervals (1 minute long for trained athletes and up to 4 minutes long for the less fit. The following program for the highly fit is included with the article.

Time (min)            Perceived Difficulty
                   (1-10 where 1= very easy, 10 = very difficult)
     3                              3 (warm-up)
     4                              5
     1                              7
     3                              5
     1                              8
     1                              5
     1                              9
     1                              5
     1                              9
     1                              5
     1                              9
     1                              5 
     1                              9
     2                              5
     1                              8
     3                              5
     1                              7
     3                              3 (cool-down)

The authors cite research evidence for the advantages of this type of training over steady-rate endurance training. They include greater improvements in maximal rate at which oxygen can be used to produce energy, blood-vessel wall health, blood pressure, insulin action, and reduction of body fat deposited under the skin.

CAUTION: No-one should engage in an exercise program without first determining whether a doctor's clearance is needed first. See our Exercise Risk Questionnaire. Even if you are cleared for general exercise, you may not be ready yet for interval training, which should only be undertaken by people who are already well-conditioned. It is an intense form of exercise that puts considerable strain on the heart, lungs, muscles, and bones. Running intervals can easily cause muscle pulls or other musculoskeletal injuries, so very thorough pre-interval warm-ups are necessary. Cycling and rowing intervals involve less impact and peak force on the musculoskeletal system than running and are thus less likely to produce injury. However, any interval training must be approached with caution. Overtraining can occur with excessive high-intensity training. Symptoms include fatigue, decline in performance, unexpected weight loss, poor sleep, fast pulse, and lack of motivation. The key points are to start with a well-conditioned individual, warm up very thoroughly, and start at a moderate level of difficulty, increasing the intensity of intervals over a period of several weeks.