Kru Darwin, an instructor at the gym White Tiger, wants me to beat him up. "Come on, Megan. Kick me. Make me fall down." I kick at his stomach, but I can't topple him yet. But I want to. And I'm going back until I do.

Muay Thai brings that competitve spirit out of you — I learned that early in my first lesson.

As I walked up the alley that leads to the gym, near King and Spadina, a woman waves. I know it's Sofia Ramirez, even before she introduces herself — she has a tight, taught body and a toughness that comes from Muay Thai training five days a week.

"Are you Megan?" asks Sofia. But she must have known who I was, too; she could probably sense my nervousness.

She takes me through a pair of grey industrial doors and into White Tiger. The gym is bright and cheerful, but it's no uptown health club. Green pads cover the concrete floor, fluorescent lights blaze overhead and full-length mirrors cover the back wall. It smells dank, like sour sweat.

Sofia apologizes for the gym's appearance: It's a new venture, it needs work. Kru, the instructor, has big plans. But already the gym has an authenticity that the polished health clubs on Bay St. can't imitate.

We change in the men's room — there's no women's locker room, yet. Sofia slips on a pair of brightly coloured silk boxing shorts. They're billowy and beautiful. I want some! But, today, my old pair of running pants will have to do.

The class has already started. It's a Friday night and about a dozen people have formed rows, like an army, in front of Kru.

Sofia and I join the front row and face the mirrors. We stretch. I'm getting nervous. Can I last one and a half hours of intense aerobic exercise?

A techno beat blasting from a small boom box on the floor propels me through the first 10 minutes of skipping. I haven't held a skipping rope since grade school. I'm out of practice. Sofia skips effortlessly; she practises her footwork while she nimbly jumps over the rope at high speed.

The group gasps through sets of sit-ups, push-ups and crunches in between bouts of skipping. Kru yells out encouragement. The North American super lightweight champion is lean and his body rippled with muscle.

He watches me struggle to get through 15 full sit-ups. I get a high five and a grin when I finish the last one.

Sofia is blasting through her set of sit-ups: one, two, three ... she pulls her body up to her knees every second. I want to do that.

Then it begins: Kru shows me how to make a fist, Muay Thai-style: fold your thumb to your palm and close your four fingers over top. You don't want to break your hand.

Next I learn the three golden steps of Muay Thai. It's like a slow waltz, but instead of moving in circles, you move forward, then backward.

I wrap my hands with cotton strips and push them into a pair of Sofia's gloves. And then, for the rest of the class, I learn:

How to hold my hands up to protect my face from incoming blows: One hand by my forehead and one hand by my chin.

How to stand so that my opponent will not be able to knock me down: Legs as wide apart as my shoulders, one leg foreward, toe slightly turned out, the other leg back, toe pointing straight.

How to kick and deliver a brutal blow: Bend my right leg, bring it up to my chest, stand on the ball of my left foot, push my right leg out. My moves are awkward and I look gawky compared to Sofia. She moves like a dancer and throws her limbs like heavyweight boxer.

How to bring my knee up into an opponent's head: My two hands reach up and grab my opponent's head (an imaginary head, today) while I bend my right leg, bring it up to my chest. The head and my knee collide.

It's like I'm studying a new language and it's taking all my concentration. Everything seems to happen in slow motion. I'm focusing on each movement, staring at myself in the mirror, willing my body to get stronger.

So, this is Muay Thai: Intricate technique, impeccable balance, a controlled fury focused to conquer your own fears.