Want to get fitter, faster? Then the new Insanity classes rolling out across Britain could be for you.

The hardcore American workout practised by Demi Lovato is focussed on high-intensity interval training (HIIT). She famously tweeted: ‘Just did the #Insanity workout. Amazing.. So intense but I loved it!’

Insanity is for those lacking discipline, a 45-minute gym class has launched where you’re put through your paces with the promise of a possible 1,000-calorie burn. To put that into perspective, a spinning class burns just 331 in the same amount of time.

The cardio-based, total-body conditioning programme and is based on ‘max interval training’, supposedly a faster way of burning calories.

Traditional HIIT workouts, which can burn up to 750 calories in 45 minutes, feature short bursts of maximum intensity with longer periods of rest. But Insanity flips that formula upside-down by combining lengthier periods of high intensity exercise with shorter cool downs, and now, developers Beachbody have taken the principles of the successful Insanity home DVD to create the ‘ultimate HIIT class’, available.
Taking place in venues with an instructor, the equipment-free classes involve non-stop strenuous stamina training and claim to improve fitness in 60 days, if practiced weekly.

Insanity classes target the entire body, beginning with an accelerated warm up and moving into three intense blocks of work, each one targeting a different element of fitness. First is plyometrics and endurance – essentially ‘jump training’ where muscles exert maximum force in as short a time as possible. Then the class moves on to strength and balance before the final section on agility and co-ordination. You finish with eight minutes of functional core work and a stretch.

‘Adding high-intensity exercise forces the body to use fast-twitch muscle fibers not normally engaged in cardio exercise,’ explains a spokesperson for Insanity.

‘These fast-twitch fibers continue burning fuel even during lower-intensity exercise. Insanity’s high-intensity activity forces the body to work for longer periods of time at a higher capacity than traditional workouts.
‘People experience faster increases in cardiovascular fitness, and burn carbohydrates and fat more efficiently – as much as 1,000 calories per hour, with the enhanced calorie burn lasting anywhere from three to 24 hours after completion of the workout.’
As a result, the workout, developed by personal trainer Shaun T. in 2009, claims to be the most effective workout programmes around.