HIIT stands for ‘High Intensity Interval Training’ and is basically a training method where bouts of high intensity exercise are followed by a recovery phase and then repeated for several times.

The effectiveness of HIIT has been demonstrated in several research studies. Here are a few of them:

A recent study, done in Canada at McMaster University and often referenced as the Gibala Study after lead researcher Martin Gibala, compared 20 minutes of high intensity interval training, consisting of a 30 second sprint followed by a four minute rest, with 90 to 120 minutes cardio training in the target heart rate zone. The result was amazing. Subjects got the same improvement in oxygen utilization from both programmes. What is more amazing is that the 20 minute programme only requires about two minutes and 30 seconds of actual hard work.

A second study that has become known as the Tabata study again shows the extreme benefits of interval training. Tabata compared moderate intensity endurance training at about 70% of VO2 max to high intensity intervals done at 170% of VO2 max. The workout consisted of seven to eight sets of 20 seconds exercise at an intensity of about 170% of VO2max with a 10 second rest between each bout. Again, the results were nothing short of amazing. The 20/10 protocol improved the VO2 max and the anaerobic capabilities more than the steady state programme.

Further evidence for the superiority of higher intensity work can be found in the September/October 2006 issue of the ACSM Journal. Dr David Swain stated “running burns twice as many calories as walking.” This is great news for those who want to lose body fat. The conclusion: More intensity equals greater energy expenditure per minute.

Interval Training Methods

There are two primary ways to performing interval training. The first is the conventional Work to Rest method. This method uses a set time interval for the work period and a set time interval for the rest period. Ratios are determined, and the athlete or client rests for generally one, two or three times the length of the work interval before repeating the next bout. The big drawback to the Work to Rest method is that since there is no actual measurable feedback to see what is actually happening inside the body, we simply guess the duration of the optimum work and rest periods.

Heart Rate Method

Thanks to the availability of accurate, yet low cost heart rate monitors these days, we no longer have to look at time as a measure of recovery, as we formerly did in the rest to work ratios. We can now measure physiological change. Heart rate and intensity are closely related, and although heart rate is not a direct and flawless measure of either intensity or recovery status, it is far better than simply choosing a time interval to rest. To use the heart rate method, simply choose an appropriate recovery heart rate, like, say, 60% of theoretical max heart rate. After a work interval of a predetermined time or distance is completed, the recovery is simply set by the time it takes to return to the recovery heart rate. An example of a sample workout using the heart rate method for a well-conditioned athlete or client is show below.

• Interval 1 - Work 60 sec rest 45 sec

• Interval 2 - Work 60 sec rest 60 sec

• Interval 3 - Work 60 sec rest 75 sec

• Interval 4 - Work 60 sec rest 90 sec

*In a conventional 2-1, time based programme the rest period would have been too long for the first three intervals, rendering them potentially less effective. The reverse may be true in a de-conditioned athlete or client. De-conditioned athletes need rest periods of up to eight times as long as the work interval. In fact, it is not uncommon to see athletes who need two minutes rest after a 15 second interval. In the heart rate method the rest times gradually get longer. The first interval is 1:0.75 while the last interval is 1:1.5. For beginners, a 1:3 or 1:4 ratio will work better.

Interval Rest Recommendations (Work to Rest Based)

• 15 sec. Beginners at least 45 sec (3-1), more advanced 30 sec (2-1)

• 30 sec. Rest 1:00 to 1:30 (3-1 or 2-1)

• 1:00. Rest 1:00- 2:00 (2-1 or 1-1)

Research continues to mount that interval training may improve fitness better than steady state work. For maximum effect, get a heart rate monitor and go to work.

One word of caution

If you are out of shape or just starting off, you may need three weeks to a month of steady work to get ready to do intervals. Always start off a fitness programme with a quality strength training programme and some steady state cardiovascular work, before progressing to interval training. Also make sure to have medical clearance from your doctor to engage in a high intensity exercise programme.

Richard Geres is an ACE-certified Personal Trainer

www.richardgeres.com