In the time it takes to read this sentence, you could do a heart-saving workout. No kidding.

A new study found that exercising in four-second go-hard intervals – repeated five times an hour – quickly prods the body to become stronger and fitter.

Further, these micro-workouts helped to improve fat metabolism – overcoming what’s known as ‘exercise resistance’ – and lower triglyceride levels in the bloodstream.

Exercise resistance is where the body has turned into a physiological blob that derives little to no benefit from moving around.

The flat-out intensity of the four-second sprint apparently jolts the body into overcoming that resistance.

These results were attained by middle-aged and older participants (nearly 70 years old) who would otherwise be killing themselves by sitting around for hours at a time.

Is this some kind of joke?

Researchers and trainers have been banging on about high-intensity interval training (HIIT) for some years.

The argument goes: short, sharp bursts of activity – be it sprinting, spinning on a stationary bike or machine-gun jabbing at a punching bag – delivers better results, especially to physiological performance, than regular longer, steadier exercise.

This has led to a kind of competitive mania where researchers have investigated and advocated increasingly: the five-minute YouTube workout has been pushed aside for the three-minute workout and so on.

Aside from prompting a scatter-shot reaction in the media, these experiments have been seeking to establish the optimum time span that will most efficiently “stress our muscles and other bodily systems enough to jump-start potent physiological changes, but not so much that we groan, give up and decline to try that workout ever again,” as The New York Times handily describes it.

But four seconds?

Professor Ed Coyle, an exercise physiologist at the University of Texas in Austin, was mindful that for older people – especially chronic couch-dwellers – the shortest effective period possible would be a more attractive proposition, and one that their lazy bodies would better cope with.

Professor Ed Coyle has found that four-second bursts of exercise go some way to counteract the consequences of sitting around all day. Photo: University of Texas

And there was some urgency.

After all, sitting for hours at a time is passively putting untold millions of people at risk of bowel disease, heart failure and dementia.

How did the study work?

Professor Coyle initially worked with a small group of fit, muscular athletes – he plonked them on a special stationary bike and measured how long it took them to reach their maximum aerobic effort and power output.

A control group was made to sit for eight hours (with bathroom breaks). A second group sat for eight hours, broken up with five sprints every hour.

Short version: two seconds was all it took for these athletes to hit their maximum effort.

Guessing that older people would take longer, he doubled the interval to four seconds with 39 participants aged 50 to 68.

Over eight weeks, participants trained for 15 minutes three times a week. Each session involved repeated 15 to 30 four-second sprints of power cycling.

After each sprint, they rested for 56 seconds.  In total, over 15 minutes, they accumulated 60 seconds of sprint time.

Two months later, the participants were demonstrably fitter: managing the the workout with just 26 seconds of rest in between the sprints.

They were found to have a 10 per cent lift in muscle mass growth, a significant boost in cardio vascular capacity and cleaner arteries.

What now? But I don’t have a specialised bike

You could use an ordinary exercise bike. Do some star jumps. Buy a skipping rope. Do something, just do it as fast as you can.

Okay, to match the research results you might have to double your workout time. That is, go hard for eight seconds.

The point is to break up your day, and don’t wait for your evening walk in the park or gentle, plod-along session at the gym.

Keep taking those walks, keep hitting the cross trainer. But those four-second bursts will help your body respond better to whatever you do.