At first glance it looks like the kind of exercise bike beloved of housewives in the eighties.

But burning up to 80 calories a minute – or a small glass of wine - the ‘Assault Air Bike’ is no ordinary gym contraption.

Combining the arm-pumping action of a cross-country ski machine with the leg-busting power of cycling, it is already a favourite with celebrities including Ellie Goulding, Cameron Diaz, Jessica Biel and Jason Statham all fans.

A rather less likely convert is Theresa May who uses the machine – known as the ‘devil’s tricycle’ – as part of her Crossfit regime.

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The Assault Air Bike is said to be the most effective workout ever because it can burn up to 80 calories a minute

Said to offer the world’s toughest workout, the Assault bike – which first took off in Los Angeles – has now come to the UK with Virgin Active introducing them to selected gyms nationwide, whilst several independent gyms also feature the innocuous-looking torture devices.

Jamie Hellier, personal trainer at Virgin Active Aldersgate, said: ‘The Assault AirBike really is the great equaliser. There’s no other piece of equipment that can equally push a seasoned athlete or newbie gym-goer to the max, doing exactly the same workout.

‘The harder you push, the harder it gets, so there’s no limit to its toughness. Pushing hard on the Assault Bike gives you an incredible quad burn, while really engaging and testing your endurance in your core, arms, back and shoulders as well – and, of course, lungs.

‘They will also tip you a lot further into a calorie deficit than your current training and burn far more per minute than a standard 5km treadmill run - and that's before you take into account the afterburn effect that any high-intensity exercise provides.

Ellie Goulding is said to be a fan of the Assault bike, which she apparently uses at London's trendy Third Space gym

The bikes are now available in the UK at Virgin Active gyms, but Prime Minister Theresa May apparently uses one during private personal training sessions

‘It really is an unbelievably brutal piece of kit.’

The stationary bike does not have a motor and instead has a fan in its front wheel which provides wind resistance. The harder you pedal your feet and pump your arms, the higher the resistance becomes – and the more calories burned.

An American personal trainer, Rob MacDonald, holds the current world record for the airbike, burning an incredible 87 calories in one minute.

To put this into context, rowing burns around 12.5 calories a minute, whilst running and skipping use up to 11 and 9.5 calories per 60 seconds respectively.

The benchmark for a ten minute session is 300 calories – the equivalent of a McDonald’s Egg McMuffin, or two large glasses of Chablis.

Hollywood actresses Miss Diaz and Miss Biel are said to be fans Stateside, British hardman actor, Statham, uses the bike to hone his buff physique.

Miss Goulding, 30, uses the bike during workouts at London’s trendy Third Space gym and the Prime Minister, reluctantly, steps on board during personal training sessions with her coach, Lee Carnaby.