WHY HIIT IS A MISS
Don’t let the ubiquity of highintensity training pull a fast (then slow, then fast) one on your health. Intervals could be all pain, no gain
One expert argues that slowing down may be the key to accelerating your fat loss
Increased cardiovascular function, faster fat oxidisation and maintained muscle mass – all realised by spending less time in the gym. It’s no wonder high-intensity interval training (HIIT) continues to make an impact, topping the American College of Sports Medicine’s 2018 survey of worldwide fitness trends.
Squeezing all the exercise you need into your lunch break is an appetising prospect. But, truth be told, HIIT is a terrible tool for fat loss – all exercise is, really. Burning a marginally increased amount of fat is redundant if you’ve not also created a calorie deficit – most effectively achieved by making good nutritional choices – in order to lose more than you consume.
HIIT’S dominance is more to do with the power of marketing and people’s desire for a minimal-effort magic pill. But a one-size-fits-all workout, however slickly packaged by a boutique studio, can only do so much good – and maybe even some harm. There’s no “best” workout: only the most appropriate given your goals and experience, plus your levels of recovery and stress. A less sexy sell, admittedly.
Personally, I never do more than two HIIT sessions per week, because I am not an elite athlete. Unless you are, you probably shouldn’t either, because they’re seriously demanding. In the original study by Professor Izumi Tabata, who lent his name to the trendsetting Tabata protocol, Olympian test subjects were wiped out after performing the eight debilitating rounds of 20 seconds on, 10 seconds off. That’s intensity 1 . The difference between medicine and poison is the dose – or, in this case, the allostatic load (the “wear and tear” on your body). Your brain doesn’t discriminate between physiological and neurological kinds of stress. So if you’re under the cosh at work, hammering yourself with HIIT will only exacerbate the issue 2 – as will HIIT alone if you lack adequate nourishment and recovery. It’s vital to let your body heal from stress – in life and in the gym. Experienced gym-goers are constantly surprised when they return stronger after a rest week 3 . HIIT can be even more harmful for the uninitiated. A FASEB Journal study found that high-intensity exercise halves the function of the mitochondria that provide your cells with energy to keep them alive.
Meanwhile, the American Journal of Medicine documented cases of rhabdomyolysis – a condition caused by muscle fibres breaking down and leaking their contents into the bloodstream, leading to kidney failure – in subjects following their first spin class. Newcomers to HIIT also face higher injury rates, if the sheer unpleasantness doesn’t put them off exercise altogether. Most classes incorporate explosive movements or heavy loads in order to induce fatigue. But cramming 40 people into a dark room with deafening music and one instructor isn’t exactly conducive to good technique. And while you may feel as though you’ve had a great workout as you lie on the floor in a puddle of sweat, you’d likely derive greater benefits from doing something safer at a lower intensity.
What you need to do is move more, period, with higher quality and variety. Intensity should be the last thing you consider. This is the surest route to sustainable health and fitness. First, how well can you squat, crawl or run? Hone your skill and control before you ramp things up, whether that’s through adding load, repetitions, or both. In other words, don’t sprint before you can walk.