How much HIIT should we be doing? Fitness trainers explain why you shouldn’t be interval training every day.
Over lockdown, many of us adapted to the world of bodyweight training by doing HIIT, or high intensity interval training. Now that gyms are closed, you might be keen to continue doing cardio circuits in your training routine – but is that a good idea?
“In order for HIIT workouts to be beneficial they should be done in short bursts of very hard work. It should be around 85% of your max heart rate, or if you were to rank the feeling out of 10, it would be around a nine, as though you could not possibly work harder,” says trainer Alice Miller.
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How often should you do HIIT?
“I think you should be doing about 20-30 minutes of HIIT a week, total. You can divide that up and perhaps do it over two sessions. Even then, it will depend on what your health state is, if you’ve been signed off to do it, if you have any heart conditions or any joint issues that would be exasperated by random bursts of HIIT.
A lot of people like the feeling of getting super sweaty and ‘beasting’ it in their workouts, so they turn to HIIT. But we shouldn’t be pushing our bodies to that extreme on a regular basis. Mix up your 30 minutes of HIIT with a few strength training sessions and maybe some steady state cardio, and you’re doing enough.”
“Right now, as we’re at home, people think they need to be doing HIIT all the time. But, in fact, doing HIIT workouts every day could actually be detrimental to your health, your progress and your fitness journey. The most important things to think about are your goals and your current fitness level. If you want to get stronger, HIIT isn’t beneficial to you. If you’re brand new to fitness, ease yourself in so your body isn’t broken after the first week. I’d do max 30 minutes a week for the first few months. If you are already fit, you could maybe push it to an hour, but I wouldn’t do anything more than that unless you are advanced.”
Why shouldn’t you do HIIT every day?
“When your body is undergoing high intensity exercise, cortisol is released as a byproduct because your body is under incredible amounts of stress. In the right amounts, this release is great and has health benefits, such as boosting the immune system, speeding up your metabolism, enhancing your strength, improving your body’s cardiovascular system and endurance. But too much cortisol can lead to mood disturbance, fatigue and joint pain. You need adequate recovery, and daily HIIT won’t allow that.”
“In a HIIT workout, we work extremely hard. We want our exercise to make us stronger, boost immunity, help us move better. But if we put our body through such intense work every day we’re going to end up with the opposite result. You’ll probably suffer joint pain or get injuries and your sleep might be thrown out, basically you end up running yourself into the ground. It’s especially true for the high levels of cortisol that are released during HIIT workouts – too much of that is so stressful on the body.
It’s also important to remember that adding more volume doesn’t necessarily mean you’ll get more results. You need time to recover between sessions and if you’re always doing HIIT your body will never slow down.”
Is HIIT bad for you?
“No – HIIT is not bad. It has its place in moderation. The overuse of HIIT is what is bad. It’s great when you don’t need equipment, it gets you sweaty, it releases endorphins. But we need to balance it with things like lifting weights, which is a low impact workout that increases bone density and protects against muscle atrophy. Strength training is still a stress on the body, but it’s nowhere near the same stress compared to HIIT.
“No, it’s not bad at all. It’s actually great: it elevates your heart rate, gets your metabolism going, increases your body’s ability to manage oxygen flow and increases fitness. But doing it every day would be bad for the body.”
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Chloe Gray is the senior writer for stylist.co.uk's fitness brand Strong Women. When she's not writing or lifting weights, she's most likely found practicing handstands, sipping a gin and tonic or eating peanut butter straight out of the jar (not all at the same time).