Your first reaction upon seeing a group of classmates or colleagues perched on giant inflatable balls might be to giggle. But it's them that will be having the last laugh when everyone else is suffering from aching backs and poor posture.
If you haven't seen these balls before, they are the kind that you can find in the gym. Swiss Balls, also known as fit balls, are versatile exercise tools developed more than 30 years ago for physical therapists to treat their patients.
It was not until recently that the ball started turning up in fitness centres, offices or even classrooms as more and more people suffer from posture problems caused by sitting on conventional chairs.
According to Stanley Hui Sai-chuen, an associate professor at the Department of Sports Science and Physical Education of the Chinese University of Hong Kong, in order to maintain good posture you have to strike the right balance of contracting your abdominal and lower back muscles.
The problem with sitting on a normal chair with a back support is that you inevitably lean back and relax. Professor Hui says this encourages the relaxation of the abdominal muscles, while the lower back muscles stay tense.
In the long term, this results in an imbalance between the two sets of muscles.
'Long durations of over-contracting the lower back muscles will induce lower back pain. That's why, in order to maintain back health, it is more effective to stretch the back muscles and tone the abdominal muscles,' Professor Hui explained.