BEIJING, July 31 -- Lu Yiran walks out of the Pilates classroom with a group of girls and the 45-minute class has worn her out. She passes the weights area, but doesn't feel capable of doing her usual three successions of dumbbell lifts. She then tries to run on the treadmill and after a mere 5 minutes, stops breathlessly.

A model shows how to use a fitness machine at an international bodybuilding fair held in Beijing last Friday.Insert: Members of a gym follow their trainer in a workout session on May 3, 2006. The gym was packed during the week-long May Day holiday. (Xinhua Photo) Photo Gallery>>>

    "I have never felt that exercise can be so painful," says the 29-year-old.

    "I was physically strong 10 years ago. I ran 3 kilometers every day and did 60 sit-ups in a row." As a member of the Mountain Climbing Team of Peking University, she once easily went through the intensified training.

    Like many other white-collars, Lu sits for most of the time at work, and gave up physical exercise years ago. About a month ago she became obsessed with the extra fat on her waist and thighs, so she purchased an one-year membership at a gym near her apartment. But she can't guarantee a regular workout even on weekends.

    "Sometimes I work overtime on Saturday. So on Sunday, I would rather sleep, go shopping and meet friends than workout," she says.

    "It takes you hours to prepare, to exercise and to take a shower. When I'm back home, I'm too exhausted to go out and have fun. That is also why many people like me avoid the gym."

    She wonders whether she can regain good curves before her enthusiasm for fitness burns out.

    Her concerns are echoed by a large female population in the fitness centers, who, as the summer rolls on, plunge whole-heartedly into body building.

    "During this time of the year, we usually see an increase of women members," says Chen Baobing, who works at a fitness center in Beijing. "Through training programs, they hope to fit perfectly into their short, tight clothes."