Michael Mosley
Can you really get fit by exercising for two minutes a week?
The great thing about making science documentaries is that you constantly discover things that surprise you. I first came across High Intensity Interval Training (HIIT) more than five years ago while making a documentary for Horizon. At the time, I learned that just three minutes a week of intense cycling could greatly improve aerobic fitness and blood sugar control.
I kept in touch with the scientists, and was delighted to get another chance to try out HIIT. This time it was for a recent BBC documentary, The Truth About
Getting Fit, and the novelty was that the HIIT protocol was now even shorter.
Dr Neils Vollaard at Stirling University has research showing that just two minutes of intense exercise a week (two bursts of 20 seconds, three times a week) would be enough to give the unfit a significant boost.
His studies have been done in labs, but we wanted to see if you could get the same results in an office. So we installed an exercise bike in a London office and asked six workers to do five weeks of Vollaard’s HIIT regime.
Before they started, Vollaard assessed their aerobic fitness by measuring their VO2 max in the lab. Get an estimate of yours here: bit.ly/aerobic_fitness
VO2 max is a great predictor of how well you’re ageing and your life expectancy. The attraction of HIIT is it can produce the same sort of improvements in VO2 max that you’d get from longer sessions of less vigorous activity. “To achieve the same results we get with HIIT, you’d have to run at a decent pace for 45 minutes, three times a week,” Vollaard told me.
Why? Well, Vollaard says that when you do a short, high-intensity sprint your body breaks down glycogen, a form of sugar stored in your muscles. This sets off a cascade of other reactions, including the release of signalling molecules. You then have a breather before your next short sprint, when these signalling molecules are activated. This in turn helps stimulate the growth of other muscle, like heart muscle.
That’s the theory. But how well would it work in practice? Five weeks after our first set of tests, we returned to see how our office workers had got on. Everyone improved, and the group as a whole saw an improvement in fitness levels of 11 per cent. If they kept it up, this would mean a reduction of around 20 per cent in the risk of developing heart disease.
HIIT isn’t for everyone. If you’re unfit then you should start slowly, doing just one 10-second sprint per session for the first week or so. If you are on medication, are injured or have concerns about your heart, then you should consult your GP.
For Vollaard’s regime, you will need an exercise bike where you can easily vary the resistance. Start by getting on the bike and doing a short warmup of gentle cycling. After a minute or so begin pedalling fast, then crank up the resistance – it should be high enough so that after 15 seconds your thighs begin to feel it and the speed at which you are pedalling slows because your muscles are beginning to fatigue. After your first burst of fast sprinting, drop the resistance and do three minutes of gentle pedalling. Then do the 20-second sprint again. It is important that each 20-second workout involves maximum effort. Finish with a couple of minutes of gentle cycling before stepping off the bike.
No access to a bike? You can run up stairs for 20 seconds or put in short, flat-out sprints when jogging.