I’m sure you don’t need me to tell you cardiovascular activities such as running, cycling, and skipping are good for your heart and arteries. And unless you’ve been living under a rock for the last few decades, you’ll know that performing cardio on a regular basis is a great way to boost your calorie expenditure and help get rid of excess body fat.

But do you know which type of cardio training gives the best results for fitness and fat loss? Should you train harder but for a shorter duration, or put in a more moderate effort over a longer duration? Many people believe that endless hours of exercise give the best results, but science shows otherwise.

Repeated studies have shown that shorter bouts of cardio performed at higher intensity (e.g. fast running or cycling) are superior to longer bouts performed at lower intensities (e.g. jogging or slow cycling). Shorter and harder cardio produces better fitness gains, burns more fat, and helps avoid the muscle breakdown that typically occurs during cardio of excessive duration. (Compare the muscular physique of a sprinter with the emaciated physique of a marathon runner).1-3

There are two ways in which you can boost the intensity of your cardio sessions while reducing their duration. You can simply run or ride faster, or you can intersperse brief bursts of very high intensity effort with low intensity activity. The former style of training is known as High Intensity Interval Training (HIIT) and is enjoying a rapid surge in popularity due to its superior effects on fitness outcomes.

Perhaps the most famous HIIT protocol is that devised by Japanese exercise physiologist Izumi Tabata. The Tabata protocol was developed using stationary cycling, and is structured as follows:

1. Perform 4 minutes of stationary cycling at 50% of maximum effort, then;
2. Perform a 20-second sprint at 100% of maximum effort, then;
3. Perform 10 seconds of stationary cycling at 50% of maximum effort, then;
4. Repeat steps 2 and 3 until you have performed a total of 8 x 20-second sprints, then;
5. Cool down with a further 4 minutes of stationary cycling at 50% of maximum effort.

When the Tabata HIIT protocol was compared with low intensity stationary cycling, both improved maximum oxygen consumption but only HIIT improved anaerobic performance. What’s more, HIIT produced these superior results in a much more time efficient manner. The low intensity group trained for 60 minutes 5 times per week, while the HIIT group trained for only 12 minutes 5 times a week!4

When the Tabata protocol was compared with a 30-second sprint/2-minute rest HIIT routine, the former taxed both aerobic and anaerobic capacity significantly more than the latter.5 According to Tabata, “Six to 8 very hard 20 second intervals with 10 second rest periods may be one of the best possible training protocols”.

A word of warning — HIIT is tough stuff! Although it is the most effective and time efficient method for improving fitness, some people will simply be unwilling to regularly train at the intensity level inherent in high-level HIIT protocols. Even Izumi Tabata has pointed out that his protocol was designed with elite level athletes in mind.  Many laypersons will not have the mental fortitude to perform such intense cardio on a regular basis. If that’s the case, it’s best to stick with either steady-state cardio performed at a relatively high intensity or an HIIT routine where the high intensity phases do not approach 100% maximal effort.

If you would like to try “all-out” HIIT but are currently unfit, then I strongly suggest you begin with steady-state cardio and progress to HIIT after you have improved your fitness to a significant degree. Individuals who are currently unfit, over 35 years of age, or have a personal or family history of heart disease should seek clearance from a medical professional before beginning HIIT.

HIIT principles can still be incorporated into your cardio training if you have heart disease so long as the high-intensity phases are performed at a lower level of intensity than that employed by healthy individuals.  Researchers have found that such modified interval training was well tolerated and improved anaerobic fitness to a greater extent than the traditional cardio routine in stable cardiovascular patients.6 

Again, if you have cardiovascular disease, please consult with a medical or fitness professional experienced in prescribing exercise routines for cardiovascular patients. 

In the next issue, we will focus on cardio exercise for burning calories.

References

1. Laursen PB, Jenkins DG. Sports Medicine, 2002; 32 (1): 53-73.
2. Tremblay A, et al. Metabolism, Jul, 1994; 43 (7): 814-818.
3. Tremblay MS, et al. European Journal of Applied Physiology, Aug, 2005; 94 (5-6): 505-513.
4. Tabata I, et al. Medicine and Science in Sports and Exercise, Oct, 1996; 28 (10): 1327-1330.
5. Tabata I, et al. Medicine and Science in Sports and Exercise, Mar, 1997; 29 (3): 390-395.
6. Warburton DE, et al. American Journal of Cardiology, May 1, 2005; 95 (9): 1080-1084.

[Ed. Note: Anthony Colpo is an independent researcher, physical conditioning specialist and author. Learn more about Anthony's latest book, The Fat Loss Bible, by clicking here.]

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