/ 15 June 2012

Get fit in five minutes

High-intensity interval training is showing positive results in reducing both glucose and insulin levels.
High-intensity interval training is showing positive results in reducing both glucose and insulin levels.

If you are one of those people who struggle to meet the recommended 150 minutes of exercise a week, you will be pleased to hear that new research suggests you may not have to. Fitness has shifted towards short but intense workouts, a concept known as high-intensity interval training, or HIT.

“HIT simply involves alternating high- and low-intensity efforts,” said Professor Martin Gibala from the department of kinesiology at McMaster University in Canada.

Research has shown a wealth of positive results from the ever-increasing number of studies on HIT in terms of performance and physiological measures, including aerobic capacity, carbohydrate metabolism and insulin sensitivity.

Gibala first examined the effects of short blasts of effort on fitness in 2005. His subjects, who were active people but not athletes, cycled against high resistance on an exercise bike for 30-second bursts. Each effort was interspersed with four-minutes of rest or easy pedalling and repeated four to six times, three days a week. Within two weeks, the subjects had doubled the amount of time they could cycle at a pre-set intensity from 26 to 51 minutes.

But would a less extreme method of exercise, such as leisurely jogging, not offer equal benefits?

Traditional endurance training
“If we assess the effect of six weeks of HIT compared with as much as 20 weeks of traditional endurance training, the percentage gain in aerobic capacity is within the exact same range.” said Professor Jamie Timmons, the chair of ageing biology at the University of Birmingham in the United Kingdom.

Research at Heriot-Watt University in Edinburgh found that, after only two weeks of HIT, sedentary men experienced reductions in both glucose and insulin levels.

“Typically, endurance training in this population would have a limited impact on glucose, only reduce insulin somewhat and usually not until after many weeks of training,” said Timmons.

“HIT training addresses two of the major health benefits of exercise, insulin sensitivity and aerobic capacity, while simultaneously removing the time barrier to exercise.”
With lack of time often cited as a reason for not exercising, it is certainly appealing that you can complete your exercise regime in less time than your post-workout shower.

But Professor Paddy Ekkekakis, from the department of health and human performance at Iowa State University in the United States, said there was no evidence to suggest this meant a greater adherence.

Muscle-mass
“While non-exercisers frequently bring up lack of time as the main reason for not exercising, there is no indication this is true,” he said.

There was also concern that for the totally inactive, HIT training was likely to be too uncomfortable or even dangerous. It was this that prompted Gibala to assess the effects of a modified form of HIT involving 10 one-minute efforts with one-minute recoveries. “We kept total training time low, decreased the intensity of the intervals, but increased their duration and lowered the recovery period,” he said.

“After just six sessions, the changes we observed both in muscle biopsy and exercise performance were comparable to what we had seen after two weeks of all-out training,” said Gibala.

Mind you, three sessions of 30 minutes a week is a far cry from the allure of three minutes a day and sounds a lot like the type of session many keen exercisers already embark on. For someone who is already active, does HIT present a way to improve your performance?

“For those already doing sprint training and weights as part of their regime, HIT will not add that much,” said Timmons. “But if your training is  sub-maximal, then HIT could improve insulin sensitivity and promote muscle-mass gain.”

The promise of more for less for every exerciser, however reluctant, suggests this is unlikely to be another passing fitness fad. – © Guardian News & Media 2012