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Is High Intensity Training for You?

HIT is often done on an exercise bike

The old excuse, “I don’t have time to exercise” just won’t cut it any more. If you haven’t heard about High Intensity Training (HIT), then hold onto your gym shorts and get ready for 1 minute of vigorous exercise and 6 minutes of gentle recovery—per session. And of course, talk to your doctor first.


HIT comes in several forms

The health benefits of high intensity training were recently highlighted on a BBC TV Horizon program, during which Dr. Michael Mosley discussed and demonstrated his experiences with HIT. However, this is not the first time HIT has been in the news, nor is it a new phenomenon.

First, an explanation of HIT is in order. High Intensity Training involves performing an all-out, intense physical effort for a short time followed by a short recovery time. This cycle is repeated several times, and the length of the vigorous exercise and gentle sessions can vary.

In Dr. Mosley’s case, he repeated the cycle three times a week for a total of 3 minutes of intense exercise, using the following formula:

  • After a brief warmup of gentle cycling (several minutes), pedal as fast as you can for 20 seconds
  • Cycle gently for 2 minutes to catch your breath
  • Cycle all-out again for 20 seconds, followed by 2 minutes of gentle cycling.
  • Repeat all-out cycling one more time.

Dr. Mosley remarked that HIT “goes against everything I was taught in medical school, and everything I have ever read since.”

In 2010, Professor Martin Gibala and his team at McMaster University conducted a study of HIT that involved participants doing 8 to 12 one-minute all-out efforts on a standard stationary bike with 75 seconds of rest in between each effort. In this case, the participants spent 20 to 25 minutes per session.

The researchers found that when subjects did this form of HIT three times a week, it worked equally as well in improving muscle as performing many hours of long-term biking less strenuously. Thus in this case, HIT involved 20-25 minutes per session versus Dr. Mosley’s 7 minutes (1 minute intense, 6 minutes recovery).

Obviously, not all HIT is the same, and therefore individuals should find a High Intensity Training program that takes into account factors such as age, current level of fitness, and presence of health problems (including obesity). Choosing a HIT program should be done with the guidance of your physician.

What to expect from HIT
In the BBC program, Mosley was tested by Jamie Timmons, professor of aging biology at Birmingham University, for several health factors both before he started the HIT program and four weeks later. The main indicator was insulin sensitivity.

In Mosley’s case, his insulin sensitivity improved by 24%. Insulin sensitivity is your responsiveness of your tissues to insulin. In people who have optimal insulin sensitivity, glucose from a meal enters their cells and tissues quickly, while those with poor insulin sensitivity have lingering sugar in their bloodstream.

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Abnormally low insulin sensitivity is known as insulin resistance. Lingering insulin resistance is associated with cardiovascular disease, obesity, and diabetes.

In a new study by Gibala and the McMaster team, published in Diabetes, Obesity & Metabolism in January 2012, the researchers evaluated the impact of HIT on blood glucose in 7 adults with type 2 diabetes. The participants performed 10 one-minute all-out cycling (at about 90% maximal heart rate) with 60 seconds of rest in between each burst.

HIT reduced high blood sugar when compared with control (non-exercise day), indicating “the potential for HIT to improve glycemic control” in type 2 diabetes. In a previous study by Gibala, published in 2011, the team reported a 35% improvement in insulin sensitivity after sedentary healthy adults engaged in HIT for only two weeks.

Will HIT improve aerobic fitness? Don’t count on it. Research indicates that although aerobic activity increases the body’s ability to take in and utilize oxygen, just how well aerobic exercise achieves this goal differs among people, and the difference has something to do with genetics.

In a study conducted by Timmons and his team, they found that some people responded well to aerobic exercise (i.e., their VO2 max, or maximal oxygen update, increased) while other individuals did not. This latter group consisted of about 20% of people, who achieved less than a 5% improvement in maximal aerobic capacity.

Of special interest was the discovery that researchers could identify who would not respond by looking at a person’s genome. That is, whether a person will benefit from aerobic exercise is in his or her genes.

In Dr. Mosley’s case, his aerobic capacity will not improve after HIT because according to a genetic test he was given before participating in HIT, his genes will not allow it.

Timmons noted on the BBC Horizon program that participating in HIT may or may not give participants the results they want. Therefore, the benefits anyone can derive from HIT is highly individual.

Is High Intensity Training for you? That’s a question you should discuss with your doctor before you start any HIT program.

BBC Horizon. The Truth about Exercise, broadcast February 28, 2012, 9PM.
Gibala MJ, Little JP. Just HIT it! A time-efficient exercise strategy to improve muscle insulin sensitivity. J Physiol 2010 Sep 15; 588(PT 18): 3341-42
Gillen JB et al. Acute high-intensity interval exercise reduces the postprandial glucose response and prevalence of hyperglycaemia in patients with type 2 diabetes. Diabetes Obesity & Metabolism 2012 Jan 23
Hood MS et al. Low-volume interval training improves muscle oxidative capacity in sedentary adults. Med Sci Sports Exerc 2011 Oct; 43(10): 1849-56
Little JP et al. A practical model of low-volume high-intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. J Physiol 2010 Mar 15; 588(Pt6): 1011-22
Timmons JA et al. Using molecular classification to predict gains in maximal aerobic capacity following endurance exercise training in humans. J Appl Physiology 2010 Jun; 108(6): 1487-96

Image: Courtesy Wikimedia Commons