MADONNA does it, Jennifer Aniston swears by it and Andrew Murray considers it an integral part of his training.

So, when I was invited to take part in the only hot yoga session taking place in Hertfordshire right now, I snapped up the opportunity to discover what it was that had converted so many celebrities and athletes to the practice.

Exercising for 90 minutes in a heated room might not appeal to everyone but the reasoning behind it is enlightening.

The idea is that the series of stretching postures and breathing exercises in a heated environment allows your body to stretch and compress more deeply and this minimises the risk of injury or strain.

The warmth also gets you sweating and this has a de-toxifying effect.

I run 20-35 miles a week and although I’ve never picked up a long-term injury, I often get stiff and no amount of pre or post-run stretching can alleviate it.

Friends and other runners have recommended yoga and pilates to me, but despite a 15 minute DVD session that left me squinting at the TV screen whilst trying to align my chakras, I’ve never taken them up on it.

I arrive at the hot yoga session on Wednesday night at John Lawes School in Harpenden. The class runs from 8.10pm to 9.40pm and I’m advised to hydrate beforehand and avoid a heavy meal two to three hours prior to arriving.

The atmosphere when I arrive is electrifying: there’s a genuine excitement about getting started but first I fill in the vital health-check forms.

I’m also informed by the very warm and welcoming Nina Sebastiane, the founder of Hot Yoga and Bikram qualified yoga instructor, about how best to handle the heat in the room with the appropriate breathing techniques.

The session starts slowly, with our bodies becoming accustomed to the heat. We are encouraged to be our own practitioners and do what we feel we can do.

My concerns that I’d spend the entire session in the cat posture – the only yoga move I know – quickly dissipate. I get sweaty – very sweaty – and feel my body welcoming the stretches.

Nina’s soft voice and words of encouragement act as a guide, but she hands over the session to you: you choose how much to put into each posture and she teaches you how to get the best from it. It’s empowering and impressive to feel that you’re both part of a group, connected in your shared movements, but also that you’re working on your own.

The heat embraces your body and gives you the strength to push it that little bit more than you would be able to in a colder room. I worry a little about my delicate Achilles tendon as we move into the stretching, but find that there’s not even a niggle.

The session isn’t just about physical health but the mental wellbeing of participants – and as the session comes to a close I feel as though I’m floating, my concerns of the week having melted away. As we lie there, focusing on the breath, Nina tells us to “feel it, recognise it and let it go” – I find that’s exactly what is happening and I can’t believe how totally at peace I feel.

The sleep I had that night was indescribable – a lovely deep sleep that left me feeling totally energised. My body felt as though it had done intense exercise, but I didn’t feel pummelled or unable to function – I felt strong.

After the class I caught up with Nina, whose enthusiasm for yoga is infectious. She’s been a devotee of hot yoga sessions for many years. When she lived and worked in London she would often attend sessions at a local studio, using the activity to balance out her hectic lifestyle as she worked in broadcasting, presenting TV and radio shows. She credits yoga with enabling her to have children after initial tests to check her compatibility for IVF revealed she wasn’t suitable.

She said: “I was devastated and threw myself into yoga and became determined that I’d make myself fertile. A few months after my intense yoga sessions, my follicle-stimulating hormone levels had improved and the clinic was able to clear me for IVF treatment, which led to the birth of my daughter Olivia, who is now seven.”

Nina moved to Hertfordshire with her family, which now includes her second daughter, Anastasia, but soon grew frustrated that there were no hot yoga sessions to attend.

“Then one day it occurred to me that if I wanted to do hot yoga so badly, I should start running my own sessions.” That led her to enroll in a three-month course in California where she trained with Bikram Choudhury himself, the yoga guru who brought Bikram yoga into the public consciousness.

“It was a very intense three months – a boot camp designed to make or break you – but it taught me an incredible amount.”

To learn more about hot yoga visit www.hotyogaherts.co.uk or call Nina on 07956 360 166.