It's not that my jeans shrank, it's that I've grown bigger (2)

Shanghai is good for many things: dim-sum, Japanese food, all-day brunch. But it is less good for exercise.

While in London I couldn't leave my house without falling over a jogger, here I have to contend with fried dumplings, the bun lady and the pancake stall before I even clear my building, dooming any attempt to run outside to instant failure.

"I need a new sports regime," I think. "But what?"

Exercise in China strikes me as a peaceful, sociable activity. In the parks, old men practice tai chi for hours. Elderly couples dance ballroom-style in front of Carrefour. In the local stadium, businessmen in suits go round in circles in an intriguing kind of sport known as backward walking. Yet despite the seemingly gentle nature of Chinese exercise, almost no one is fat.

"They don't need Lycra and fancy gym memberships to stay fit," I think. "Sports marketing is all one big lie."

Before I know it, I am signing an 18-month contract to join an expensive American gym downtown. It is the longest thing I have ever committed to. The manager, a muscled Shanghainese guy called Benny, tells me I am making an excellent decision. "You won't regret this," Benny says emphatically, his biceps rippling for effect. "Life in Shanghai is hectic. Good to work out."

Two weeks go by. I am just thinking I haven't been to my new gym yet when I get a call from Benny.

"Hi, it's Benny. We haven't seen you here yet," he says, with evident disappointment in his voice. "How about you come down for a workout?"

I decide to try a cycling class. The instructor's name is Strong. As I look around the room, I notice several people checking their iPhones. One is holding a Starbucks cup.

"This is going to be easy," I tell myself.

Strong starts giving instructions in Mandarin. "I get to work out and improve my Chinese at the same time. This was a great decision!" I think as I cycle.

After 10 minutes it feels as though my legs are being hacked apart with a chainsaw and I am struggling to breathe. I look around. None of my classmates appears to be suffering. One is sending a text message.

I notice Strong saying something to me in Chinese, but I am unable to understand through the pain. Exasperated, he comes over and starts shouting at me in English. "Move more your legs!" he barks. "Straight up your back!"

I feel my face growing red. People turn round to look at me in sympathy. "Maybe next time I'll just try tai chi," I mutter to myself.

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