Monday, 25 February 2013

90-seconds of exercise (HIIT)

The WEEK reported (a few weeks ago) an article on the "90-second exercise routine". As with The WEEK it pulls on all the different British newspapers for its stories, I couldn't find the exact story which it had drawn upon or even find, by searching through PubMed, the original study or even the abstract but I did find a similar article from MNT (Medical News Today) (albeit slightly outdated and which may represent ideas which have since been investigated further and maybe even improved on/discarded so please take the dates of these articles into account when reading them)(

The WEEK (Issue 902) (loosely taken from the Daily Mail)
"Scientists from the universities of Bath, Nottingham and Birmingham say that having warmed up for two minutes, people should engage in three, 30-second bursts of really intense exercise with 60-second rest periods in between. Results from an ongoing study involving hundreds of middle-aged people indicates that HIIT (High Intensity Interval Training) is just as effective as long sessions in the gym. The team isn't sure why this should be so, but notes that one advantage of HIIT is that it seems to suppress appetite; by contrast, longer workouts tend to leave people hungry."

However although this form of exercise known as HIIT sounds easily carried out, it has to be done properly for it to be effective. The 30-second bursts of high intensity workout should be something like "running up a flight of stairs or pedalling furiously on an exercise bike" (The WEEK (as above)) at almost maximum intensity.

For example "recent [be aware this report is from the 6th of March 2012] HIT research shows, that doing ten one-minute sprints on a stationary exercise bike with about one minute of rest in between, three times a week, is as good for improving muscle as many hours of less strenuous conventional long-term biking" (

In a study a few years ago (by Gibala around 2010) "participants had to pedal at their maximum possible effort level on a specially adapted lab bike. The thinking then was that 'all out' was an important part of the HIT [High Interval Training (referring to the same style of training as HIIT)] method.

But then, in 2010, Gibala and colleagues published
another study
in The Journal of Physiology, where they showed how a less extreme form of HIT worked just as well for people whose doctors might be a bit worried about them adopting the 'all out' method, for instance those who might be older, less fit and overweight.

In that form of HIT, the workout was still beyond the comfort zone of most people (about 95% of maximal
heart rate), but was only half of what might be regarded as an 'all out' sprint" (

The BBC ran a Horizon episode on HIIT with someone (known as Mosley) doing a HIIT programme for 4 weeks to observe the health effects. His programme ran like this (from
1.    First, you warm up for a couple of minutes with some gentle cycling: then you cycle as fast as you possibly can for 20 seconds.
2.    Cycle gently again for a couple of minutes while you catch your breath, then do another 20 seconds 'flat out'.
3.    Then, for a final time, two minutes gentle cycling to catch your breath, followed the third period of 20 seconds at 'full throttle'.
One of the health effects that the HIIT/HIT had on Mosley was on his insulin sensitivity...
"The researcher (Timmons) had tested Mosley for a number of health indices before he started, and then, after his 4 weeks of HIT, Mosley went back to the lab to be re-tested. A main test was for insulin sensitivity. When they measured Mosley's insulin sensitivity before he started his HIT exercise regime, the result showed he was just inside what would be regarded as healthy tolerance. Timmons told Mosley that research from a number of centers shows that doing 3 minutes HIT a week can improve insulin sensitivity by 24%. And this is exactly the amount by which Mosley's own index improved.

But bigger improvements than this have also been recorded, albeit with a slightly different HIT regime. A 2011 study by Gibala's group at McMaster published in Medicine & Science in Sports & Exercise found a 35% improvement in insulin sensitivity after only two weeks.

Insulin sensitivity is important for keeping blood sugar/glucose stable. It is not clear how HIT affects insulin sensitivity, but Timmons, and some other scientists that Mosley spoke to, suggest it could be because HIT uses many more muscles than conventional aerobic training. HIT engages 80% of the muscles of the body, compared to up to 40% during moderate jogging or cycling. HIT engages not only leg muscles, but also the muscles in the upper body, such as the arms and shoulders.

One of the effects of exercise is to break down glycogen in muscles. Glycogen is a stored form of glucose. The theory is that removing stores of glycogen makes way for fresh glucose to be deposited from the bloodstream. So the more muscle tissue that come under this influence, the more space that is available for new glucose deposits.

However there are some things that HIT will not necessarily do for you. For example, in Mosley's case, it didn't improve his aerobic fitness, the other main health index that Timmons and colleagues tested.

The evidence that ties aerobic fitness to health shows that one of the best predictors of a healthy long life is the body's ability to take in and use oxygen while we are exercising maximally. The more blood the heart pumps around the body, the more oxygen our muscles use and the lower our risk of disease and early death.

This idea stresses the idea that the more you do, does not necessarily mean the more you benefit.

What we are learning is that the link between exercise and health is an individual thing. Methods like HIT are useful, because very quickly, without spending a lot of time and effort, you can find out what works for you, and what doesn't, and fine-tune a program that you can fit more easily into your lifestyle." (


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