The first time I went to a Barry's Bootcamp class I was shocked. Not just physically, but emotionally.
Walking to work after the 7.10am class had finished, I was dazed. By the next morning I ached so much that it was a struggle to sit down or walk up the stairs.
In hindsight, I should have known. This is a workout with thousands of loyal followers around the world, and word on the street is that it can transform your body in next to no time. With promises like that, it clearly isn't going to be a walk in the park.
So for some reason I found myself heading back two days later, this time for an evening class. I was tempted to cancel and spend the time resting my aching limbs on the sofa, but after few words of gentle encouragement from Barry's official Twitter account (like a sad social media addict, I'd been tweeting incessantly about the pain) and I was back.
The second class was arguably harder than the first, after all I did feel like I'd been run over, but the next day that muscle fever had stopped. And I was hooked.
Barry's Bootcamp is unlike any other workout I've ever tried. And, trust me, I've tried a few.
Their signature hour-long workouts involve 25-30 minutes of interval cardiovascular treadmill routines mixed in with 25-30 minutes of strength training.
The classes are known to burn up to 1000 calories and cater to equally to fitness fanatics and complete beginners.
There is only room for 40 people in each class (20 treadmills and 20 floor spots), you sign up for a spot between 1-20 on either treadmill or floor to begin and then swap at regular intervals with the person with the corresponding number.
On my first class, for example, I started on F-13 (floor 13) and then moved to T-13 (treadmill 13), while the person who started on T-13 took my place on the floor.
There are classes every day of the week, throughout the day, and trainers and muscle groups vary. In short, no class is the same, which keeps the seemingly simple concept fresh for regulars.
The trainers are testament to the effectiveness of the workout. If anything's going to get me to work out harder it's a super fit glamazon like Anya Lahiri shouting to run faster.
I've never worked out as hard or sweated as much as I did at Barry's Bootcamp. Within less than a month (going three time per week) I'm fitter than I've ever been. I started off running at the beginner's speed (trainers give different instructions for beginners, intermediate and advanced) but by my forth class I was pushing myself to get to intermediate speed, and I'm lifting heavier weights than I started with.
As a result my body has changed considerably (I have abs for Christ's sake), and I generally feel more confident.
After just one month at Barry's, I just don't think I can go back to a regular gym class.
Another trainer, Olly Truelove summed it up perfectly when he said in my forth class, when we'd just been on a one minute sprint: "Everything in life is easy compared to Barry's."
Barry's Bootcamp is opening a second London branch in east London in spring 2015