HIIT classes are short, sharp bursts of exercises where you’re working out above 85% of your maximum heart rate, and Sean Johnson, regional fitness manager at Orangetheory Fitness, can see why they’re “tempting”.

“A lot of people are pressed for time and seek a ‘quick fix’. To many people, the assumption is ‘no pain, no gain’ and so, therefore, seek out a hard-hitting, pulse-shattering workout to undo the unhealthy habits they may have gotten themselves into,” he says.

“A hard workout can feel very rewarding when you move fast and blast around for a short time.”

Plus, there are benefits to HIIT training, with Johnson saying: “A shorter, more intense workout does have the ability to elicit a longer afterburn compared to a less intense longer workout.”

But is there a chance we’re overdoing it, in a bid to ‘get the most’ out of our workouts? There’s a growing trend for lower-intensity exercise – often using a heart rate monitor so you can track where you’re at – which might provide a whole host of benefits, without making you feel a bit sick.

Signs you might be overdoing it

“Working at a maximal heart rate can sometimes cause people to feel lightheaded, dizzy, faint and nauseous. This isn’t very fun and can also deter people from coming back,” suggests Francesca Sills, exercise physiologist at Pure Sports Medicine.

Johnson agrees: “Working out for too long at an intensity that is too high can put numerous stresses on the body such as fainting, vomiting and even serious cardiovascular and respiratory health issues.”

He doesn’t recommend spending more than a minute in the ‘all out’ section, and other signs you might be overdoing it include “fatiguing earlier than you normally do, dizziness, light-headed, you get injured or have joint and muscle pain regularly”.

Downsides to HIIT?

Sills suggests there aren’t necessarily downsides to HIIT, just “things to be wary of”. She says: “If you’re working very hard for a long time or for longer than you are used to, it’s possible that you’ll finish the session feeling unwell rather than energised.”

Johnson says there is the risk of overtraining with regular HIIT classes. “In the shorter term, working out at an intensity too high can stress your adrenal glands and stimulate the release of cortisol (the stress hormone). In turn, this can have numerous side effects such as increased blood pressure, increased heart rate, encourage fatigue and ultimately hinder recovery.

The benefits of slowing down

Johnson suggests incorporating lower-intensity exercise into your routine can improve your everyday life. “Doing workouts that don’t raise your heart rate to the extremes can help reduce the risk of injury (and risk of falls and trips), reduce fatigue and pain, elevate your mood, improve sleep quality, while still helping to burn calories,” he says.

Sills mentions how ‘zone two’ workouts are a “hot topic” in the fitness world recently – this is a type of low-intensity, sustained exercise where you’re working at around 65-75% of your maximum – for example, going for a gentle jog where you can still hold a conversation.

She says these types of workouts are gaining popularity because of the “large amount of benefit it brings to the health and efficiency of your cardiovascular and metabolic systems”.

Credits: PA; Author: PA;

If you’re used to leaving it all on the floor with an intense workout every time you hit the gym, it can be tricky to know how to slow down. Johnson recommends using the ‘FITT principle’ to adjust your exercise routine:

Frequency: Instead of doing your four workouts next week try doing only three

Intensity: Do your normal four workouts, but take it down a notch in each one.

Time: Instead of doing four x 90 minute workouts next week, maybe try doing four x one-hour workouts.

Type: Switch it up and use different equipment or style of workout.

Johnson adds: “Having slower days will enable you to focus more on the form and technique, which transfers over to the high-intensity days as well.”

Doing HIIT safely

While it’s a good idea to mix up your workouts with different intensities, there are a few things you can do to make sure you don’t overdo it in HIIT. Sills recommends ensuring “you are eating well to fuel your body for performance”, and “get on top of your sleep routine to allow your body to rest and repair”.

And finally, she says: “It’s important to work within your own limits. Often these classes are busy, loud and intense and people can be encouraged to continue to do more weight, more reps, etc. Issues arise when people push too far beyond what they can manage. Instead of working at a 10/10 all the time, drop it back to an eight to nine.”