Gillian Treasurer, (pictured) a solicitor from Edinburgh, talks about the daunting effort involved in the Men's Health Survival of the Fittest challenge.

"I was a little fat, chubby kid at school; I didn't do any sport. I'm 26 now and a couple of years ago started going to British Military Fitness classes. Before that I hadn't really done any kind of exercise whatsoever. I tried military because I wouldn't have been motivated to do anything else and the classes were literally outside my front door on the Meadows in Edinburgh. It was horrible all the way through the first hour; I thought I was going to die or pass out, but at the end I just got this euphoric feeling.

"Last year, about 50 of us from the military fitness class decided we would enter Men's Health Survival of the Fittest. I guess I wanted to do it because it was a bigger challenge than a 10k – I find running in a straight line for 10 kilometres quite boring. This was the next level.

"For training, the military fitness helps a lot because you're doing circuits and a lot of sit-ups and push-ups and you need that kind of training to be able to climb over things in Survival of the Fittest, which has an obstacle every kilometre. You start at Edinburgh Castle and you run down the Royal Mile and the first thing you encounter is a stack of bales of hay.

"As I started to go round the course, I was thinking: this is horrible. But it's kind of fun as well. One minute you're just running along the street, and the next you're climbing over hay or going through a giant inflatable or running up and down stairs with disco lights. We also had to go down a giant water slide. It was hilarious.

"The race is about 70% men, 30% women and both the men and the women seem to have the same approach. We're all in it together although in the top group quite often the women are better than the men. There are some tough women who take part. One of my friends was the top woman last year and beat about 95% of the men. But we didn't view it as men versus women; we just wanted to get the best time. And everybody is watching out for each other.

"For someone like me who didn't do sport for years and years, I needed something to motivate me and it was the team element that worked, but also having funny things to talk about afterwards. So, although it was tough going round, you think 'I'd like to do that again'. And at the end of it, it felt like a massive achievement. The last obstacle is a 9ft wall and once I got over that, I found myself just smiling; I was really excited. I am also massively healthier since I did Survival of the Fittest and the event has given me a focus.

"Training is going well for this year's event. I do military fitness classes three or four times a week, and I go to the gym. I try to do something every day. It's never more than an hour at a time.

"Part of the reason I'm doing it again is because I want to beat my time from last year, which was 1 hour, 4 minutes. The aim this year is to get under the hour.

"I think Survival of the Fittest is a fitness trend that will continue. In the last couple of years there have been more and more of these events cropping up. Some people say to me: 'That must be really tough' but I don't feel tough. I'm certainly not any less girly. I run these things with a full face of make-up and it's usually intact by the end. Exercise is exercise – it shouldn't make a difference if you're a man or a woman."

Men's Health Survival of the Fittest is in Edinburgh on Sunday, October 21. For information, visit www.mhsurvival.co.uk