Are You Doing Too Much HIIT? |

Are You Doing Too Much HIIT?

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HIIT – or high intensity interval training – has long been hailed as the best way to get fit. Promising impressive results in a short amount of time, it’s no wonder HIIT is the hero of the fitness world. But despite its body-boosting credentials, could you have too much of a good thing? We found out…

What exactly defines a HIIT workout?

It’s a super-quick workout in which you should elevate your heart rate for a brief period, followed by resting for a given amount of time. For example, 30 seconds of sprinting could be followed by 60 seconds of rest, repeated ten times. This exertion/rest combo can be translated to anything from a Barry’s class to a spin session, or just running outside. The key lies in giving it your all during the working phase and taking the time to let your heart rate come down before going again.

What are the benefits?

HIIT is synonymous with fat burning. Research shows that interval training can repair the metabolism by reducing inflammation and forcing the body to improve its ability to use and burn energy; meaning you’ll burn fat at a faster rate, and continue to torch calories long after your workout is done (a phenomenon known as EPOC, or excess post-exercise oxygen consumption). Plus, when HIIT is done correctly and paired with a solid nutrition plan, fitness experts say you can blast belly fat, increase the size and strength of your fast-twitch muscle fibres (the ones used for sprinting) and improve heart health. And that’s all without slogging on the treadmill for an hour.

How often should you be doing it?

This is where it gets interesting. HIIT advocates Joe Wicks (aka Lean in 15) and Kayla Itsines champion HIIT in their cult programmes, saying it can be done up to five times per week. While both stress the importance of rest days, it’s clear their fitness sessions are very much HIIT-driven, leaving little flexibility for other types of workouts, such as endurance training (e.g. a long run) or strength training. At the same time, if you’re doing a HIIT session properly, it’s unlikely you’ll be able to do it five times a week, unless you’re a professional athlete. As Founder of Twenty Two Training Dalton Wong explains, “True HIIT should make you feel like your gas tank is completely empty. If you’re doing a 30-second sprint during a HIIT interval, you shouldn’t be able to get to 31 without wanting to collapse.”

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What’s the downside of doing HIIT every day?

Unless you’re doing every HIIT session with a PT, chances are the likes of high-impact burpees and squat jumps carried out at breakneck speed won’t be technically accurate, which can lead to injury. Nutritionist Jessica Sepel is also quick to speak out against HIIT, saying that over-exercising can sabotage hormone levels, which in turn can take their toll on our weight. “Studies have shown that intense exercise can increase cortisol levels – high cortisol does not allow fat to be burned and it also impacts thyroid function. Although we need some cortisol to function well, it’s important to keep it well-balanced. Our bodies weren’t designed to be pushed to extremes so be wary of HIIT workouts and instead exercise moderately (think yoga, Pilates or brisk walking) for 30 minutes a day, no more, five times a week,” she says. 

What are the signs you’re overdoing the HIIT?

If you’re constantly tired and dread working out, this is the first sign that you’re over-training and could benefit from more rest days and a more varied workout plan. In this state, your body begins to tolerate the stress hormones cortisol and adrenaline that normally get you going during exercise; when you’re constantly in this state, your heart works harder than normal, even when it shouldn’t have to – like when you’re sleeping. As a result, you feel inexplicably drained and your motivation plummets. This also explains why having trouble sleeping and a higher than normal resting heart rate are common symptoms of over-training.

So there is such a thing as too much HIIT?

In short, yes. Aim for two to three HIIT sessions per week, making an effort to build in 24 hours of rest and recovery between workouts. While HIIT’s fat-burning, toning credentials shouldn’t be ignored, try to take a varied approach to your fitness regime – including a couple of cardio-based sessions will help you build strength and power when it comes to your HIIT, meaning you’ll work harder and more efficiently. At the same time, if you notice continuous improvement in your ability to complete and recover from your workouts, don’t be afraid to take it up a notch. Listen to your body and reap the benefits.


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