Wonder how a big cushion of air can help in your quest for fitness? Ask Jennifer Aniston, the Friends star who uses fitball workouts to stay trim.

The classes focus on developing strength in shabby muscles. The emphasis is also on push-ups that work the pectoral muscles in the chest. The low risk of injury associated with exercising on an oversized beach ball, plus visible results in weeks, means the idea is catching on fast over here.

Swiss physiotherapists first used inflatable balls with patients recovering from back injuries in 1909. And indeed, draping yourself over the ball so that your torso is rounded and the spine is stretched will make you feel so relaxed that you will want to freeze in this position forever.

The ball is more than just a trendy piece of fitness equipment. The ball's roundness and pliability make the body work hard if only to stabilize itself. Each balancing and strengthening exercise uses weak muscles that often remain untested in other workouts.

The workout begins with arm-circles to loosen up before using the ball for the other stretches. There’s little chance of straining joints as the ball is positioned to support vulnerable areas in each move. This, says Lyuda, who teaches fitball classes at one of the most handsome and comfortable fitness clubs in Moscow, club Na Bolshoi Tatarskoi, makes it the ideal tool for elderly people who fear losing balance and also for pregnant women who usually have to give up abdominal exercises on hard surfaces. In the United States, fitball is used in antenatal classes where many women find they can tone up easily until weeks or even days before giving birth.

Prepare yourself for mirth when you roll onto the ball, face down, and walk forward on your hands, like a dog, until your hips are centered on top. Then, bending your elbows, lower the chest to the floor 15 times. Afterwards you move onto upper-arm flexes, which involve leaning over the ball with the knees lodged firmly behind it, pushing the weights backward and forward.

Next you lie on your back with the ball between bent legs and squeeze inwards to tone the inner thighs. "The extent to which the ball changes shape is a measure of how hard your muscles are working," expert instructor Lyuda explains.

It’s harder work than everyone expects it to be. You roll, balance, push and squeeze the ball using every muscle. But at any moment during the class, you can deflate the ball slightly so that it gives you less resistance. And after a short breather, you’re sitting on the ball again.

Fitness Club Na Bolshoi Tatarskoi

35 Bolshaya Tatarskaya Ul.

Metro: Paveletskaya

Tel: 729-3375