High-Intensity Interval Training (HIIT) has become an integral part of how many people train over recent years.

The approach – short bursts of high-effort exertion > brief rest period > repeat – has been adopted by millions of time-poor people looking to blitz away the fat.

But is there a risk of over-doing it?

Put simply, HIIT does come with risks, and millions of people are over-doing it – risking fatigue, blow-out and even serious injury.

To be clear, I’m not saying don’t do HIIT. On the contrary. It can be super-effective. CrossFit, The BodyCoach and Shaun T have used HIIT to help 100,000s people worldwide feel better about themselves. 

HIIT does this by burning calories during and post-workout by inducing ‘after-burn’ or excessive post-exercise oxygen consumption (EPOC), which can raise metabolism above resting levels for >10hrs – thought to be to do with the body replenishing itself getting back to pre-exercise levels.

So what’s the problem?

The clue is in the name! By definition, HIIT is High Intensity.

  • Problem 1: However fit you are your body needs rest post-workout to come back stronger – Insufficient recovery time (at least 24hrs for a HIIT session) means no gains!
  • Problem 2: However tight your technique when the session kicks-off, insufficient recovery time between sessions or sets can lead to poor technique and risk injury

My point? HIIT can be a force for good – with sufficient rest and done at the right intensity for YOU.

The boundary between hard training and over-training can be unclear. But if you’re feeling fatigued, injury prone or aren’t performing to your best in training then… listen to your body and dial down the training regime! Whether that means doing less HIIT or ensuring at least 1 full rest day per week just think about it…

… and the next time you’re tempted to hit 2 HIITs in 2 days, think of 26-time Tour de France stage winner Mark Cavendish’s words:

“It takes balls to rest and do nothing” – The hard work is easy, but it takes courage to rest. In an era when everyone thinks that more and harder is better few are brave enough to step back, to tell friends, “I’m taking it easy today.” I can hear the jibes from here. But one of my maxims is, “when in doubt, rest” and I admonish with it frequently.”

Work + Rest = Training

Don’t Do The Work If You Don’t have the Guts To Rest