Not too many parents would let their eight-year-old child swim 200m in the sea, let alone join a melee of thrashing limbs that is the start of a triathlon's swim leg.

Zheng Geping and his wife Hong Huifang, both MediaCorp artistes, are an exception. So confident are they of their son Calvert's swimming prowess that they have entered him as part of their relay team in the Mini Category of the upcoming Osim Singapore International Triathlon on July 12.

He will do two legs of the triathlon relay - the 200m swim and the 5km bike race - with his father while his mother takes over for the 2km run.

Although he is an avid swimmer - the St Andrew's Junior School pupil is part of the school's swim team and took part in last year's Asean Invitational Midget Meet - he wasn't exactly thrilled when his Dad broached the idea.

Reason: A fear of sharks. Having been reassured that there are none in the waters here, he is now raring to go.

Roger Tian, medical director for the event, says he's happy to see more children taking part in sporting events such as the Osim Triathlon but cautions that the child should enjoy the exercises and not see them as a chore.

'It helps if the family does it together, like what Calvert's family is doing,' he adds.

Tian, 38, is a sports physician at Changi General Hospital's Sports Medicine Centre. He is also an avid endurance runner and took part in the 70.3 Singapore Half-Ironman last year.

He is adamant that these youngsters should get proper strength and conditioning training from qualified professionals. Injuries can crop up otherwise.

He says the triathlon requires strength, but flexibility and core stability are just as important.

'Regardless of how strong one's arms and legs are, if the core is weak, it will be difficult to translate the limb strength into an effective and efficient power output.

'It's like taking a Formula One car chassis and putting a family sedan's engine inside,' he says.

He recommends stretching at least five days a week, preferably when the muscles are warm. This is especially important for children approaching puberty as bone length often increases faster than muscle length, leading to increased tension at points where the bones and tendons meet.

Tian also points out that core stability is crucial in all three disciplines of the triathlon - trunk rotation and propulsion (swimming); bike control and power (cycling); maintaining a stable pelvis (running).

Here, Calvert demonstrates three exercises recommended by Tian.

STANDING ITB STRETCH

What it works: Lower limbs, which are crucial for cycling and running

How to do it: Stand with your legs crossed, right leg in front of the left. Lift your arms over your head and bend to the left. Hold the stretch at a comfortable spot where there is no pain and return to the start position. Repeat on the other side with the left foot in front. Do three stretches on both sides, holding the stretch for 15 to 30 seconds, five days a week.

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SINGLE LEG SQUAT WITH SWISS BALL

What it works: Glutes and quads for runners

How to do it: Stand near a wall, right leg off the ground with the knee holding a ball against the wall. Slowly bend your left leg as much as you can and return to the start position. Repeat on other side with the left knee holding the ball against the wall. Do three sets of 12 to 20 repetitions with each leg, twice a week.

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TRUNK TWIST WITH STICK

What it works: Trunk, shoulders and core muscles for swimmers

How to do it: Stand with a pole held across your shoulders, holding the ends with your hands. Slowly, using just the trunk, twist to the left. Return to the start position and twist to the right. Do three sets of 20 to 50 twists, twice a week.

This article was first published in Urban, The Straits Times on July 4, 2008.