THE morning after my first F45 session I'm reporting from court.

The sheriff enters, the "All rise" rings out and I wonder what the penalty for contempt is because I honestly don't think I can stand up.

For some of us, lockdown has not been kind to our waistlines and I am well and truly in that number.

So when the chance to take on the F45 challenge is offered I jump at it - things need to change.

Glasgow Times: Catriona Stewart with coach Greg McPherson  Picture: Colin Mearns

Created in Australia, F45 is a global chain of gyms giving intense 45 minute workouts that are class based but have personal trainers on hand.

The challenge involves doing as many classes as you can in 45 days and sticking to a tailored diet regime with support from the others in your challenge team.

It was only 45 days, I thought. That's not long at all, I thought. Until I stopped and counted and realised it was six weeks.

Would I make it to the end?

Before my first class I made the mistake of Googling the F45 Challenge and read all sorts of terrifying things. Do not do this.

Glasgow Times: Munro the dog  Picture: Colin Mearns

I was so nervous beforehand, worried that I would be the fattest, unfittest person there. That people would laugh or stare or that I would collapse halfway through.

Only one of those things happened. Everyone could not have been nicer, more patient or more encouraging.

There are now thousands of F45 studios around the world - with Glasgow the first in Scotland - and each starts the challenge on the same day.

First, though, you debrief with a personal trainer who gives you a body scan. I was well hydrated but there was nothing else positive to say.

I was all fat, little muscle and showing a biological age two years older than my actual age.

If anything was motivation, that was.

In an F45 class the coaches will first explain how to do the exercises. It's a mix of high intensity interval training (HIIT) and circuits carried out over 45 minutes.

Glasgow Times: Catriona Stewart using the battle ropes with coach Greg McPherson  Picture: Colin Mearns

Once you've seen what to do, a station is assigned and you work at your own level for 45 minutes as the coaches come round with tips on form and morale boosts.

Dance is my thing, and weights are not my thing. But I very quickly found I loved the circuits. The classes go by so quickly because you're intensely focused on what you're doing for short bursts then continually moving on to the next thing.

The morning after the first class I could barely get out of bed. Outside the court there was a JCB digger slowly reversing towards me and I wondered if I would manage to outrun it, my legs were so painful.

I watched the digger inching its way closer and thought, "Well, this is it". Somehow I shuffled to safety and one of the F45 coaches convinced me that the best thing to do was to get back to class.

I found the 45 minute sessions addictive and I put real effort and willpower into sorting out my diet. I cut out alcohol too.

For me, the toughest thing was making time for classes. I work long hours for the Glasgow Times, freelance, have a second job and two volunteer roles alongside caring duties for a family member. So time is tight. Classes start at 6.50am and run throughout the day until 6.20pm. I would have found one more evening class ideal, time-wise, but that's just me.

Glasgow Times: Catriona Stewart with coach Greg McPherson  Picture: Colin Mearns

A real boon was the F45 app which features classes you can do at home. Those were a godsend for the weeks I was struggling to make a class - and one week I didn't have time to go to the studio at all.

On the weeks where I managed the three classes I felt amazing.

In the first phase of the diet you cut out eliminating gluten, dairy, red meat, refined sugars and high-fructose fruits and, again, just didn't have time for the meal prepping involved.

So I used a food delivery service and that was a dream - delicious food and no work.

Glasgow Times: Coach Greg McPherson  Picture: Colin Mearns

We had an F45 WhatsApp group that was full of motivation and support - and further challenges. We were competing to see who burned the most calories and I love a challenge so I found my activity level outwith the gym soared too.

I cycled everywhere, upped my yoga sessions and made more effort in my weekly ballet class.

So how did F45 end up in Glasgow? Well, most people try a fitness class, fall in love with it and buy a season pass. Michael Quigley fell in love with F45 and bought the gym.

He and his wife were in Australia on holiday and tried a class.

Michael said he was "very overweight" at the time and looking to make changes. "I wasn't judged," he says, "You were working out beside athletes and people on their first time at the gym and it was a more comfortable place to go than a bog standard gym.

"So I tried it, came back to Scotland and set one up.

Glasgow Times: Michael Quigley, who is the franchisee  Picture: Colin Mearns

"I'm still on my own fitness journey with it, there's been ups and downs, especially with covid."

The gym, on West Campbell Street, was only open for three months when the pandemic hit - a disaster for any new business.

"I had picked this site because we were going to be targetting offices but then they all closed and even now everyone is technically still working from home."

Michael and his team moved everything online quickly and F45 has online classes on its app.

Twice a day coaches ran classes over Zoom for its members.

Eventually gyms were allowed to open but classes weren't able to be back up and running. However, thanks to F45's model, they were able to rearrange classes to allow members back in.

There is no typical F45 client, Michael says. "We have GB athletes and then have 70-year-olds and they're training beside one another.

"Our clientele ranges from 18 to 74."

You can't get away from the fact that F45 is expensive but Michael insists it is worth the cost.

"Most people," he says, "Are members of a budget gym and they go in and they just stay at a level and they'll hit the weights and look in the mirror and just go through the motions but don't gain anything.

"Then they'll pay £40 an hour for a personal trainer, buy a block of 20 but can't afford to go on so they finish it and it's a vicious cycle.

"We're £40 a week for unlimited classes, which is what an hour with a personal trainer costs.

"You get the one-to-one you get with a personal trainer but you also get that fire from being in another class and competing against and getting encouragement from other people."

The encouragement was a big boon for me. There were times during the early days of the challenge where I was close to fainting in the classes but the coaches kept me going.

At the end, I haven't lost any weight but I have built muscle and I feel so much fitter and stronger.

I've definitely caught the F45 bug and plan to keep going. It's an effective investment in better health - and that's always good value.

For anyone who wants to try F45, there is a free event on tonight at West on the Green from 5pm with personal trainer and fitness model Cory George - also the man on the screens in every F45 gym.

To book see:

F45 has an introductory offer of one month of unlimited classes, two body scans, regular check ins with the coaches and access to at-home workouts, meal plans and recipes for £99.