Rebecca was previously the chief sub on Healthy Food Guide. When she's not chasing around after her son Teddy or Harper the dog, you can find her blogging on

Too busy to exercise? How about fitting in just 20 min of hard work, two to four times a week? Studies show you’ll see real gains – whatever your age and ability

High intensity interval training sounds hard, right? Well, it is – and that’s the point. But the silver lining is it’s proven to burn fat, improve fitness and muscle tone, and stave off health issues such as type 2 diabetes and heart disease. And, bonus, it’s over in the blink of an eye… almost.

So what is this auspicious workout – and how does it work? Put simply, high intensity interval training (HiiT) is a series of exercises performed with as much energy as you can muster for 20–40 second bursts, broken up with short recovery breaks. ‘It’s basically a means of getting a whole lot of exercise done fast,’ says Instagram sensation and advocate of HiiT Joe Wicks (aka The Body Coach). ‘It’s one of the most effective training methods for burning fat.’

The any-age workout

If you’re reading this thinking HiiT is clearly something for the young and super-fit (so you’ll stick to the occasional bike ride, thanks very much), think again. In fact, this type of workout could deliver even greater benefits for the over-50s – especially middle-aged men.

Exercise physiologist Dr Peter Herbert, himself in his 70s, is a fan. ‘I’m fitter than I’ve ever been,’ he says. Spending hours in the gym was having ever-decreasing results for Peter’s body shape goals, so he decided to re-evaluate his exercise regime. ‘My hunch was that I needed greater amounts of recovery time,’ he says. ‘I began to cut out my long-duration workouts to do one weekly interval session. Within a couple of months, I was performing better and felt stronger.’


Following his own success story, Peter completed numerous studies, proving his theory that higher-intensity, reduced-frequency exercise sessions can deliver health benefits for the older generation. In recent trials involving men who had been sedentary for over 30 years, he found that a routine of six 30-second sprints performed once every five days resulted in an overall drop in the participants’ body fat.

The science

It may seem difficult to comprehend how exercising less can have a greater impact on weight loss than spending hours pounding the treadmill, but there’s a wealth of scientific evidence to support the HiiT-fat reduction link. A review of studies on high-intensity interval exercise concluded it does seem to result in fat loss, especially abdominal fat, although more research with overweight adults is needed.

The calorie burn that results from HiiT far exceeds the duration of the workout. ‘Unlike low-intensity exercise, such as steady jogging, which only burns calories during the actual workout, HiiT burns calories for up to 18 hours afterwards,’ explains Joe. Here’s where it gets a bit technical: this after-burn effect (or excess post-exercise oxygen consumption, to use its formal title) is caused by the body working hard to return to its natural resting state, replacing the oxygen used up by the workout. ‘During this time your metabolic rate is elevated, so you burn more calories and, therefore, more fat,’ he adds.

HiiT it hard

To reap the full benefits of after-burn, you need to push yourself during each exercise, to the point where you can’t do any more. ‘The more intense your workout, the greater your oxygen debt will be,’ says Joe. The aim is to elevate your heart rate to about 90% of its maximum before letting it recover in the rest periods, so keep an eye on your heart rate monitor or fitness tracker to check you’re working hard enough. Or, if you don’t have the gadgets, Joe suggests this simple work-rate gauge: ‘If you can talk, text or tweet during a HiiT session, you aren’t working hard enough!’

Know your limits

While it’s important to work hard, it’s essential to stay within the realms of your own ability. If you’re over 45 and your current exercise regime involves little more than the occasional stroll, Peter recommends you start with a pre-conditioning programme before attempting HiiT. Do eight to 10 minutes of gentle walking or cycling each day, building up to 20 minutes a day over the course of a month. By week five, you’ll be in good enough shape to ramp up your routine a level, to 30-second bursts of power walking or jogging, broken up with 60 seconds of walking at a regular pace. Do this for 20–35 minutes, a few times a week. As you get fitter, make the 30-second bursts sprints, and shorten the walking sets.

It may not seem like much, but it’s enough to create a calorie deficit – as long as you give it your all. ‘Keep it short and sweet and remember to put 100% into the workout,’ says Rob Smyth, head trainer at F45 Training London Bridge.

To make gains, be sure to vary the exercises you do, as well as the length of the intervals. ‘It’s important to keep the body guessing,’ says Rob. ‘At F45 Training, we vary our work:rest ratios from 40:20 seconds, down to a tough 20:10 seconds.’

Give it a go!

‘Perform each exercise for 20 seconds, followed by a 10-second rest,’ says Rob. ‘Once you’ve completed the full sequence once, rest for 1 minute. Repeat three times – and enjoy it.’

1 Squats (watch the how-to video)
2 Push-ups (watch the how-to video)
3 Mountain climbers
4 V sit-ups (watch the how-to video)
5 Hip thrusters (watch the how-to video)
6 Burpees (watch the how-to video)
7 Plank (watch the how-to video)
8 High-knee run
9 Squat jumps
10 Butt-kick run

Video gallery: 23 weight-loss exercises