A gym junkie and exercise noob try the workout that's known for being tougher than HIIT.

This story starts with an email inviting me to trial a workout class that promised to be more intense than HIIT. I got sweaty just reading the description.

It’s called Orangetheory Fitness and it involves using a heart rate monitor to ensure you’re pushing yourself at a constant, high level of intensity. And for an extra kick of accountability, your stats are publicly displayed on screens around the room, alongside those of your fellow workout buddies.

Orangetheory was started in 2010 by David Long, Jerome Kern and Ellen Latham from a single studio in Fort Lauderdale, Florida, and eight years into operations the business has already expanded into 1000 locations and 21 countries (including more than a dozen around around Australia). The secret to the company’s success is simple – the program just damn works at kicking your butt.

It’s estimated you burn 500 to 1000 calories during a 60 minute class, but then continue to burn calories for up to 36 hours after the workout. It does this by tapping into your body’s Excess Post-Exercise Oxygen Consumption, which is when your body needs to make up the oxygen deficit caused by intensive exercise.

Your workout intensity is categorised into five zones, measured using the data transmitted from the heart rate monitor they give you. When you hit the top two zones (orange and red) it means you're pushing your body to its optimum calorie-burning and performance-building potential, and for every minute spent in this zone you get one splat point. Generally, it's recommended you get at least 12 splat points per workout.

Every Orangetheory class is different, and you don't know what you're in for until you arrive. But the structure will generally be the same: half the class participants will spend 30 minutes doing a cardio workout (e.g. on a treadmill), while the half do a weights session. Then you swap midway through the class.

And warning: Orangetheory prides itself on being very intensive.

So, intrigued by the concept, I - a little gym-phobic and not into HIIT-type training at all - roped in Mamamia's resident exercise enthusiast and morning editor, Sophie Aubrey to get our sweat on.

Here's how we did.

Our current fitness level.

Jess: While I wouldn't call myself a fitness buff by any means, I try to get in some incidental exercise by walking home from work (about 30 minutes) and maybe doing a gentle hike on the weekends, although in reality, this maybe happens once a month. On a good week, I'll also try and do three to four intensive yoga classes.

For me, I find exercise more of a mental workout over a physical one, and nothing helps my scatter-brain mind quite like trying to breathe through a dolphin pose.

Sophie: I hate admitting this but I exercise pretty regularly. I'll go to the gym about four days each week, and often go for runs or walks when I have time in between. But my workouts aren't exactly high intensity. I mostly do weight-lifting. So, with Orangetheory involving a fair bit of cardio and interval training to get your heart pounding, that's where I think I'll fall into a wee bit of trouble. And that is totally fine, because if I'm going to sign up for classes, I want a real challenge.

Our first impressions of Orangetheory.

Jess: Keeping in mind, I'm normally used to the essential-oil perfumed halls of yoga studios, walking into the orange-feature coloured walls of Orangetheory was a bit of a change. Their Waterloo gym was clean and very nicely air-conditioned (because you're going to get very sweaty) and everybody was super friendly, and not intimidating at all. Although the trainers push you hard so you get the most from your workout, they're also quick to offer modifications and account for any injuries you might have.

However, five minutes into the workout, I realised this was going to be one heck of a workout. Luckily, it went by relatively quickly.

Sophie: My very first impression is there is a truck-load of orange. Which is, well, very on-brand. The staff at the Melbourne CBD gym were incredibly friendly (one lovely woman named Savannah even lent me her sports bra when I realised I'd idiotically forgotten mine) as they explained the structure of the workout and fitted me with a heart rate monitor. Oh, and the changing rooms are very clean and well equipped, complete with hair straighteners and deodorant if you need to glam up after the session.

Walking into the workout room is at first a little intimidating. There is a long line of flashy new treadmills, rowing machines and weights. There are also several TV screens on the walls, most are displaying every participant's heart rate, while others are to show demonstrations for the weight workouts. And the music is well and truly pumping. I've got to say, the set-up is very sleek, which certainly adds to the motivational vibe.

Our verdict on the Orangetheory workout.

Jess: It was so hard. So, so hard. We started the first half of the class running on the treadmill and I managed to hit and stay in the top two zones within the first few minutes of the class. I noticed my much fitter classmates took a bit longer (oops).

Generally my mantra when it comes to group fitness is 'I'm here and that's good enough,' (and I stand by this 'less is better than nothing' approach), but the Orangetheory model makes it very difficult to slack off during your workout. The psychological effect of knowing everybody can tell if you're taking a self-prescribed break - not that anyone cares, or is actually watching - means you continue to push yourself.

Also, although I couldn't give a toss about burning calories, every time I saw that little number increase, I felt a little pang of pride and it pushed me a little more. I found my competitive inner-monologue willing myself to just keep running, and it worked.

Sophie: The short version is that I had the best time. Why? Firstly, I bloody loved the heart rate monitor aspect. I originally thought it would get me competitive with other people in the class, but it actually mostly made me incredibly competitive with myself. I wanted to accrue as many 'splats' as possible. And as I prefer individual workouts, this was perfect. That's not to say there's not a group aspect to Orangetheory. Having a trainer, heaps of people around you and your heart rate beamed on a screen definitely holds you to account. You're not going to want to be seen slacking off. And the other thing that keeps you challenging yourself on an individual level is the treadmills have guides for what speeds and inclines you should aim for according to your fitness level.

The second aspect I loved was getting my sweat on in a way I don't usually. Personally I found the cardio much more challenging than the weights because it's what I do less of. By the end of the treadmill session, I was completely wiped. And it felt good.

Thirdly, holy crap, the hour went by in a flash. That's definitely a perk - you get all the benefits of a big workout without even feeling like you were actually there for 60 minutes! Win.

How Orangetheory compares with our current fitness regime.

Jess: As someone that opts for yoga over hardcore high-intensity workouts, Orangetheory was a dramatic change from what I'm normally used to, however I can hand-on-heart say that I have never worked out as hard as I did during that one hour session. I walked out of that session having burnt 650 calories (and I definitely felt it), but more importantly, with the satisfaction that I truly did push myself, and the numbers backed it up.

For me, I would do this class on a casual basis. And I think it would be great if I was working towards a particular health goal, or wanted to seriously consider upping my fitness.

Sophie: I'm pretty disciplined with my regime, but that doesn't mean I don't get bored. So Orangetheory fits in really nicely for me as a once-a-week addition. It's more high-intensive and offers a brilliant change from the weight-lifting I normally do, challenging my fitness in a way wouldn't do on my own.

Also, every single class is different, so if I'm stuck in a rut doing the same thing in the gym, Orangetheory ensures I'm constantly on my toes and pushing myself further. Overall, I think Orangetheory can just about slot into anybody's exercise regime because it suits all levels of fitness - all you have to do is go as hard as is right for you.

Orange theory offers three payment plans depending on your budget and and training needs. To find out more information or organise a tour with your local studio, visit the Orangetheory Fitness website.

We all live busy lives and exercise is tricky, luckily for us Sam Wood has some office-approved exercise hacks. Genius.