But according to Ng, this bad posture - coupled with overuse of computers, handheld game devices and smartphones - is putting children and teenagers at risk of aches and pains later in life.

'They may not feel any pain now because they are young and have a lot of joint space, and their muscles are very flexible. But carry on like this and they are risking a lot of problems when they are older,' she says.

Ng, who chairs the public relations committee of the Hong Kong Chiropractors' Association (HKCA), says more people in their 20s and 30s are suffering back and neck problems more often associated with much older people.

The view among her colleagues is that in many cases bad posture shown while using computers, handheld games and smartphones for long periods is to blame. They have even begun using the term 'iPhone syndrome' to describe a range of symptoms they are seeing increasingly in the young.

'Back problems are getting worse. We are seeing more cases of kids with round shoulders and slouching backs,' says Ng.

'You may think it is only bad posture, but bad posture can cause problems for children still in their growing stages. When a child slouches, they will tire much more easily because their muscles are not in a balanced state.

'When they become adults, they will be more prone to degenerative conditions than would a person with normal, healthy posture.

'We are also treating more people in their 20s for nagging shoulder pain. Before, it was mostly in late 30, 40s and up; now they're coming in their 20s. It is not good.'

Ng says that if left unchecked, bad posture in children can lead to overuse of muscles and tendons in the neck, shoulder, wrist, and in the thumbs. In the long term, it could cause degenerative conditions and arthritis in adulthood.

It may also lead to the development of bone spurs, extra growths of bones in the joints in the neck, which can impinge and damage the nerves leading down the arms and hands.

'Lifestyles have changed,' Ng says. 'The way children study has changed. In the past, they read books and did a lot of writing by hand. Now they research on the internet and type rather than write.

'There are kids now who are being given smartphones by their parents, so that by the time they reach their 30s, they will have been using them for 20 years already. I have even heard of kids developing iPhone syndrome when they are 15 and 16.'

However, Ng says the blame doesn't lie with just laptops, mobile phones and games; long-term incorrect use of a desktop computer could also cause problems for children, especially when screens and keyboards are badly positioned and chairs aren't at the right height and lack adequate back support.

There is also the much publicised issue of school bags, with many children carrying bags laden with textbooks and far too heavy, to the extent of potentially damaging their spines and necks and risking scoliosis - curvature of the spine.

'Some schools now have lockers to try to resolve this problem,' Ng says. 'But in Hong Kong, we have found the locker doesn't help much, because children have a lot of homework and still have to bring the books home.

'Some schools started using online study resources. But that again is controversial, as it takes us back to the issue of computer use.'

Ergonomics expert Professor Chetwyn Chan Che-hin carried out a survey last year on computer and laptop use among children and adults for the Occupational Safety and Health Council.

In the survey, he found that around one in 10 schoolchildren said they spent more than six hours a day at their computers - either desktops or laptops.

'On average, around 60 per cent said they used an adjustable chair, but only 17.9 per cent say they had satisfactory sitting posture while using a computer,' says Chan, a professor of rehabilitation sciences at Polytechnic University and the spokesman for the Hong Kong Ergonomics Society.

When it came to discomfort caused by computer use, about 12 per cent of schoolchildren said they suffered eye strain and shoulder and neck pain, and 5.6 per cent said they had lower back discomfort.

'Around 43 per cent say the discomfort is the result of long hours using the computer, and 35 per cent say it's because of improper sitting posture,' says Chan.

The jury still out, however, on which is the worse offender - the laptop or the desktop.

Ng advocates using a desktop because of the control teachers and parents can take in ensuring, the chair, screen and key pads are positioned at the best height.

But Chan says the laptop is evolving fast and now offers better screens and inputting options such as touch screens and voice recognition, which help children avoid holding the same posture for long periods.

But both agree that, given the trend in computer use, parents and schools must take the initiative in educating children on using them sensibly and about posture.

Chan doubts that enough is being done and points to the results of his survey, in which 95 per cent of the schoolchildren interviewed said they had not been trained on how to use a computer.

'Information on how to use computers properly should be made accessible to these users,' he says. 'It should be taught in schools. If they are using these devices every day, schools should be including how to use them in the curriculum.'

Ng regularly visits schools to conduct workshops on posture, computer use and backpacks and even footwear.

'You can't keep telling kids to sit up all the time,' she says. 'You need to teach them to do it subconsciously. Prevention is better than cure, and that is why education in ergonomics is so important.'

Teach your children good posture

Sit comfortably: ergonomics are important. The chair should have a back support and be positioned so knees are at a 90-degree angle when seated. The desk should be elbow height when sitting upright.

Eyes right: the screen should be positioned so your child's eyes are horizontal to the middle of the monitor so he or she does not have to flex his or her neck unnaturally to use the screen. Use arm and wrist pads to help keep wrists in relaxed position while typing and using a mouse. Good lighting is also important.

Take regular breaks: 'The maximum time you should use these devices should be an hour,' says Dr Sophia Ng, of the Hong Kong Chiropractors' Association (HKCA).

'The most important thing is not to do it too long. If you maintain bad posture all day, you will develop problems.'

Stretch it out: encourage your child to stretch and exercise during breaks. The HKCA promotes a three-minute exercise routine devised by spinal experts which can prevent muscle fatigue and strain. 'These exercises do not need any equipment. You can do them any time,' says Ng. 'All you need is a little space. They only take a few minutes so kids won't become impatient.'

Get the big picture: when buying a laptop, avoid small screens and keyboards, says Professor Chetwyn Chan of the Hong Kong Ergonomics Society.

Choose a medium to large screen for a wide viewing angle. Go for one that is not too heavy and has a good battery life so your child doesn't have to carry the charger.

Off your lap: despite its name, a laptop is not meant for laps. 'Sitting with it on your lap is one of the worst postures you can adopt,' says Ng.

Carry it well: make sure your child has a good backpack to carry books and the laptop, and encourage them to carry it correctly over both shoulders. Look for a model with a waistband, padded shoulder straps and some padded back protection.

Lose weight: encourage children to use lockers at school and not to carry all their books around. If they don't have lockers, talk to the school about providing them.