The following correction was printed in the Guardian's Corrections and clarifications column, Monday June 13 2005
The article below on high-intensity training stated that research carried out at McMaster University in Canada and published in the Journal of Applied Physiology had shown that three types of training regime had produced the same results. One of the regimes involved a two-minute cycling session. Martin Gibala, the researcher responsible for the study, has asked us to point out that our article was based on data from a later, similar study and not the one published in the journal.
As a rule, papers that are published in the Journal of Applied Physiology don't generate much interest outside of the publication's small community of specialist contributors and subscribers. The latest edition, however, has made an unprecedented splash, with cries of "Please let it be so!" from reluctant exercisers fed up with spending long hours working out for little apparent reward.
The cause of the fuss is a study conducted at McMaster University in Canada by Professor Martin Gibala, who compared the effects of different workout regimes on 23 individuals. Group one cycled for two hours each time, at a moderate, manageable pace. The second group did 10 minutes of cycling per session, including some reasonably intensive 60-second bursts. Group three pedalled like billy-o for four 30-second periods, each interspersed with a four-minute rest. Two hours, 10 minutes and two minutes, then, were the durations of the sessions.
At the start of the three-week study, everyone did an 18.6-mile cycle time trial, and they did the same at the end, to measure and compare progress. The results, music to the ears of so many gym-goers heartily fed up with plodding away interminably, were all exactly the same. Despite those wildly differing times spent in the saddle, everyone had improved to the same degree, and the rate at which their muscles absorbed oxygen, also known as VO 2 Max, and a good gauge of cardiovascular fitness, had also improved by the same amount. Gibala concluded: "Short bouts of very intense exercise improved muscle health and performance comparable to several weeks of endurance training."
Get fit in two minutes per day: it sounds like the answer to the increasingly obese and time-limited western world's prayers, the kind of system that even the Homer Simpsons can adhere to. Rather than follow the Department of Health's three to five sessions per week of 20-30 minutes of gentle aerobic exercise, six minutes of full-pelt intensity is all that's required.
High intensity interval training (HIIT), as the regime is known, has actually been around for several decades, and there are sports science studies aplenty extolling its virtues. The breakthrough paper, by Tremblay and Bouchard, was published in 1995, and came up with similar conclusions to Gibala. Over a six-week period, the "sprint" cycle group lost more than three times as much body fat as the slow, aerobic group, despite only expending about half as many calories during the actual exercise. The aerobic group did its same-speed sessions for up to 45 minutes up to five times per week, while the interval crowd spent a piffling 30 minutes in total (including warm up and down and recovery spells) three times per week doing their thing. The fat loss would appear to have come from the post-exercise elevated metabolic rate that followed the intervals. A 1996 University of Alabama study found this higher rate of metabolism resulted in the burning of an extra 160 calories 24 hours after an HIIT session.
Bodybuilders are big HIIT fans. Steve Blades, a Peterborough-based personal trainer, specialises in devising workouts for bodybuilders, and he's also an advocate of HIIT. "Doing steady state cardio, the easy pace stuff, means that when you finish, you almost stop burning calories," he says. "With HIIT, you go into a state of Epoc [excessive post-exercise oxygen consumption], which means you burn more calories afterwards. The shortness of the actual sessions means you're not using up muscle as fuel, so it's ideal for retaining muscle and losing fat. I recommend people do it on the bike, the stepper, the rowing machine or cross trainer. I think it's good for intermediate and advanced trainers. Lower levels of fitness aren't able to reach those peaks: they can't cane it to the same degree."
That's the big proviso. Rather than getting fit via HIIT, it's imperative that you're in pretty good nick in the first place. Those cyclists in Gibala's study weren't couch potatoes; they were all "reasonably fit and active".
"We need to be careful that we're not advocating this approach for the majority of the population," says John Brewer, director of the Lucozade Sports Science Academy. "I don't disagree with the study, but to suggest that this is all you should do is misleading. Good-quality interval training has been carried out for years, and this is a version of that; it elevates your heart rate, and the impacts and forces that go through the ligaments and tendons can lead to strength increases.
I think the fat-burning angle is slightly misleading; you're not going to be burning much more than 15 calories per minute during a hard session, and if it only lasts a few minutes then that's not a huge total of calories burned, before or after. Intensity is important, but so is duration. You have to have a reasonable level of fitness to start with, though; you have to have trained regularly for some time before incorporating these sorts of sessions into your programme. For the majority of the population, three to five sessions of 20-30 minutes per week still holds true."
Brian Mackenzie, a senior coach with UK Athletics, concurs. "As a component of your exercise schedule, once you've got a good aerobic base, then it's good. If you're doing any sport, it's likely that running is going to be involved, and if you do your intervals as running sprints, they'll develop that elastic strength that you need, the ability to rush for the ball, or to the net in tennis or badminton, or whatever. Being an ambler doesn't help anyone when they're competing. People who are quite fit should also consider it if they are constrained by time. Without a good fitness base, though, it shouldn't be done. It's like going up to someone in the street and getting them to run 100m flat out. They will tear every muscle in their body."
Athletes trained by Mackenzie do benefit from the occasional HIIT session. "The stresses put upon the body cause an adaptation including capillarisation [artery and vein improvement], strengthening of the heart muscles, improved oxygen uptake and improved buffers to lactates. All this leads to improved performance, in particular within the cardiovascular system."
Arnold Schwarzenegger once said, "I come to the weights room to make progress, not friends", and that is the kind of mindset that is required by those doing HIIT sessions. It is far removed from the community-based world of exercise classes, and in a parallel universe to yoga.
"One of the things I love about the classes that I do," says Hot Yoga practitioner Deborah McIntyre, from Brighton, "is that feeling of everyone being in there together for an hour and a half, drawing on a kind of common energy that we create. The idea of going to gym, head down, rushing through a routine and then getting out as quick as you can is so unappealing. It sounds like torture!"
Paul Larkins, editor of Running Fitness magazine, competed for Great Britain as a middle-distance runner in the late 1980s, having been on a sports scholarship at Oklahoma State University. "When I arrived there, intense interval training was the order of the day, and it definitely worked. It gave rise to some very successful runners. It appeared to give better results quicker than doing slow, steady distance work. The trouble was, the burn-out factor was so high. A guy in my year ran 800m in 1 minute, 46 seconds, very fast for his age, but he retired as soon as he left college. The thought that every time you trained, you had to do all those flat-out sessions was just too much. I much prefer the sport-for-all approach, where you enjoy what you do, you almost look forward to it, and you're able to carry on doing it for ever."
