So I’m really struggling to write this review of British Military Fitness. Not because I don’t have anything to say about the camaraderie and the encouraging instructors, not because I didn’t enjoy crawling around the park like a bear… but because my arms feel like they’re made of concrete and typing through the DOMs is a struggle!

Whether you’re a complete beginner or the son of Arnie, you’ll get an amazing workout

Don’t let that put you off though. Yes, I may have got a bit carried away with the press ups, but you can totes take it at your own level, and whether you’re a complete beginner or the son of Arnie, you’ll get an amazing workout.

Plus, your first session is absolutely free of charge and this Saturday, 30 May, as part of National Outdoor Fitness Day, there are more than 90 free sessions going down, so get yourself signed up pronto.

So what is British Military Fitness then?

British Military Fitness, BMF for short, offers group exercise sessions in parks and outdoor spaces across the country. With more than 140 venues and 400 classes a week, all led by instructors with military experience (gulp), getting a military-style beasting is insanely popular these days.

Err, military instructors? Am I fit enough for BMF?

Yep, course you are. It’s going to be a challenge whatever your fitness level – apparently one session can burn around 640 calories – but groups are divided into three ability levels: blue for beginners, red for intermediates, and green for advanced so you’re always with those of a similar level. You get to wear a fetching bib in your group colour – bonus.

So what goes down in a British Military Fitness session?

The classes are based on the physical training doled out in the military, but scaled down for us civilians

The classes are based on the physical training doled out in the military, but scaled down for us civilians. Phew, no para boots and 40kg backpacks then.

I plumped for a 9.30am class on Clapham Common, London, where the attendees seemed pretty evenly split between men and women.

Leaving our bags locked up, we jogged over to the park for a warm up. After repeatedly lying down on my front, standing up and high-fiving my partner, jogging and jump squatting, I was most definitely ‘warm’. Warmer than the surface of the Sun, in fact.

At this point, the group was split by bib colour – I’d plumped for beginner as it was my first session. We finally got rid of those pesky red and greens, and I was secretly hoping things would get easier. I was incorrect.

Our group’s instructor Neal Williams, park manager at Clapham Common, told me that each session is tailored to the ability of the group – and that the local demographic in Clapham is fit! “In some other venues this group would be red, nudging green” he laughed. Bollocks. No easy ride then.

Throughout the hour-long session we worked in groups and with partners on a variety of bodyweight exercises. It was tough but never unachievable; there were burpees, planks, shuttle runs, pull ups on park railings, press-ups, crunches, bear crawls…

Squats were done with your partner pressing down on your shoulders; planks were done crawling backwards, like caterpillars

While many of the exercises were tried-and-tested favourites, everything was given a twist so it seemed new and interesting. Squats, for example, were done with your partner pressing down on your shoulders to add resistance; planks were done crawling backwards, like caterpillars; squats were done as part of a snake-like run (hard to explain, you’ll have to try it yourself).

We jogged around the park between sets, and working with others meant you always had someone to chat to. By the end of the hour I was knackered, starving (no breakfast, idiot) and very, very hot, but I’d had wicked fun and I wanted to do it again – just not immediately, I’m not a weirdo.

What are the benefits of BMF?

You’ll get more of a workout than you would on your own in the gym as you’ve got an instructor encouraging you and telling you what works

It’s definitely a full-body workout – every bit of me aches! The bodyweight work is great for strength, there’s plenty of running around for cardio, and being outdoors is great for boosting your mood.

“You’ll get more of a workout than you would on your own in the gym,” says Neal, “as you’ve got an instructor encouraging you and telling you what works. Plus you always push yourself harder in a group.

“I’ve done a couple of the sessions myself recently as I’m going on holiday, it’s the best way to drop a bit of bulk.” Well, if it’s good enough for Neal…

Sounds good. One last thing, will I get screamed at by men in camo?

They have female instructors as well, y’know. This is 2015. And as for shouting, no. Well, not in my group anyway. I reckon shouting probably costs extra.

To find a British Military Fitness session near you and to sign up for a free session visit britmilfit.com