For the study, he designed bumograph, a device to measure the shape buttocks make when seated. The device has 96 sensors, which are used to measure the contour of seated buttocks, and it replaces the seat of the chair with high-density foam.
Tuttle found that students' gender affected the seated buttock shape more than other factors like weight, height or posture. While males had a deeper narrower contour, female students had a broader, flatter shape.
"If the seat width and seat height of an armchair were made to fit the average dimensions of a population, the chair would be unusable for most of the population," ABC Online quoted Tuttle, as saying.
"The contours of the front and back portions of the seat influence sitting posture and the whole of the seat contour affects seat comfort," he says.
"The contour of the seat affects the two most important factors influencing the comfort of the chair,' he added. Tuttle says an immediate solution to back and neck pain in students is for school authorities to buy adjustable and comfortable chairs.
"Life expectancy of school chairs is about 10 years. With Australian authorities spending less than A$40 on each chair that equates to less than A$4 a year per student,' he added. "If you spend an extra 10 Australian dollars a year per student you can have probably the world's best school chair,'' he said.
Tuttle also said that teachers should not ask students to "sit up" or "sit still". He added that leaning back in chairs with legs extended should not be considered a 'lazy' attitude. "If you want to change one attitude it's that there is a correct posture," he says, adding that students should be allowed to wiggle in their seats.
The study is published in the latest issue of the journal Ergonomics.