Burpies, squats, lunges and leg jumps; high intensity interval training aka HIIT is a rising star in the fitness world.

But the most effective part of the workout is also the very thing many HIIT aficionados are getting wrong, Rachel Vaziralli, the creative manager of group fitness at Equinox told Well and Good.

An effective way to burn fat, the concept of HIIT is to pack as much intense energy as possible into a short amount of time.

So, what is the optimal period that you should be working out for?

Often seen as a hardcore fitness class, many sessions last more than 60 minutes but it turns out that high intensity, high volume workouts could be doing more harm than good.

The whole point of HIIT is to work at maximum capacity in short bursts so if you’re working out for longer than 30 minutes you might not actually be pushing yourself hard enough.

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If the session is too long, there’s no way you can reach true high intensity.

It’s also important to remember that if you attempt to push to an unsustainable level for an extended period of time, you could cause yourself injury.

That being said, a workout that lasts any less than 15 minutes probably means that you haven’t spent enough time at a high exertion level to make much of a difference either.