“A 3-hour workout in 15 minutes”

One of my clients describes his workouts with this phrase when introducing me to his friends. Upon hearing this, they usually think he is half-kidding. They look at me as if to ask “is he joking?” and when they realize he is serious, they ask “How is that possible?”

I admit that it isn’t an easy question to answer with just a sentence or two. However, I can give a short explanation of the scientific principles involved that makes sense to them. I add that even though it may seem to be counter-intuitive, and they may intellectually understand, it isn’t until they experience the workout that they will really feel the difference of effective exercise – activity that safely stimulates the desired physiological changes.

The McMaster Studies

On June 6, 2005 CNN reported on a study published in the Journal of Applied Physiology at Canada’s McMaster University. The research group proclaimed that “six minutes of pure, hard exercise once a week could be just as effective as an hour of daily activity.” J Appl Physiol 98: 1985-1990, 2005

Researchers impaneled 16 recreationally-active college students and tested them for endurance capacity. Then the subjects were divided into two groups – 8 students performed 2-3½ minutes of intense exercise 3 times per week for 2 weeks. The other group was by no means inactive during this time, as they were jogging, cycling, or doing aerobics.

At the end of the two weeks, the intense-exercise group nearly doubled their endurance capacity, and increased the activity of the mitochondrial enzyme citrate synthase by 38%, while the other group showed no change.

Still, there were skeptics in fitness circles, and even from some parts of the medical world. Surely, they said, if researchers had used a controlled, specialized “cardio” training program and compared it to the six-minute-per-week group, the traditional “cardio” group would have the advantage, right?

In fact, the McMaster University researchers had returned to the lab and performed another study that contrasted a low-volume sprint-interval training (SIT) with a high-volume endurance training (ET) group, comparing changes in endurance along with molecular and cellular adaptations in skeletal muscle. The Journal of Physiology, 575, 901-911.

Again, the study involved 16 subjects age 20-22 years old, and tested them to see how long it took them to ride 18.6 miles on a stationary bike. They were then divided into 2 groups:

  • Group 1 (the SIT group) did 30 seconds of high intensity work on a stationary bike @ 250% of V02max followed by 4 minutes of rest until 2-3 minutes of exercise was completed.
  • Group 2 (the ET group) did 90 to 120 minutes of exercise @ 60% V02max.

Both groups trained on 3 non-consecutive days/week for 2 weeks for a total of 6 workouts, and the total workout time for the 6 sessions was:

  • Group 1 (SIT): 12 – 18 minutes
  • Group 2 (ET): 9 – 12 hours

After the two weeks of the program had elapsed, both groups repeated the 18.6 mile cycling test. Both groups were found to have improved to the same degree. When the researchers performed muscle biopsies and other tests to determine the subjects’ fitness levels, these tests also showed that both subject groups ability to absorb oxygen improved to the same level.

Despite having spent 8 - 12 hours more time engaged in exercise, the conventional endurance group (ET) received “zero” additional benefit from all of the extra time spent engaged in exercise. In other words, there is no additional advantage in devoting hours per week in the pursuit of health and fitness, yet there is considerable risk in the wear-and-tear on your body, not to mention the lost time.

In terms of overall health, the key findings in these studies indicate that a properly performed workout consisting of 6 to 9 minutes per week produces the same endurance capacity and muscle enzymes (which are essential for preventing type-2 diabetes) as a workout requiring 4½ to 6 hours per week.

So it appears my client is actually understating the effectiveness of our workouts.

In the next article, we’ll discuss the most important factor to consider in designing an exercise program.

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