In the sci-fi classic E.T. The Extra-Terrestrial, a boy, riding a BMX, glides up into the sky with the help of a friendly alien. More than 20 years have passed since the movie's initial release, but BMX activities are once again gathering momentum following the inclusion of men's and women's BMX cycling events in the 2008 Beijing Olympic Games. BMX, which stands for bicycle motocross, started to take root in the 1960s when children in California modified their bikes to imitate their motocross heroes. The trend quickly spread throughout the US before gaining worldwide appeal. The sport's popularity peaked in the 1980s, when nearly every housing estate in Hong Kong had a gang of BMX bikers. For veteran biker Rex Lau, much of the fun of riding a BMX comes from overcoming self-imposed challenges. 'It may take you a few weeks or even a few months to learn a trick. When you can perform it, that will give you plenty of satisfaction,' Lau said. There are two types of BMX activities: freestyle and racing. While BMX racing is about covering an obstacle-laden circuit, there is more variety in freestyle. These range from flatland - the execution of spectacular tricks, such as spinning on one wheel on a flat ground - to vert, a riding style carried out on a U-shaped halfpipe. Some BMX bikers specialise in park or street riding. Park bikers practise in skate parks fitted with ramps and obstacles, while street bikers perform on all kinds of props, even a ledge on the street. 'Some people say street riding is the highest level of park riding,' said Lau. 'All the obstacles in parks are fixed and standardised. But you have to keep finding new obstacles ... to overcome the streets.' Lau suggests that beginners should first master bunny-hopping - a basic trick in which the bike is lifted off the ground to jump over an obstacle. Another fundamental skill involves raising the front wheel and moving the bike forward by thrusting your waist. Of course, it hurts if you fall - but all sports carry a risk and there are ways of minimising them. For example, never hesitate to abandon your bike - no matter how expensive it is - during a fall. It's better to buy a new bike rather than break your leg. Also, don't rush to practise sophisticated tricks. Like all sports, you have to start from the basics before you can perform at a high level. Above all, don't forget to wear a helmet. '[BMX biking] is a healthy cardiopulmonary sport ... and is a very good alternative to staying at home in front of the computer,' Lau said.