"Tablet users may be at high risk to develop neck discomfort based on current behaviours and tablet designs," it warned.

A team led by environmental health researcher Jack Dennerlein of the Harvard School of Public Health asked seven men and eight women who were experienced tablet users to carry out tasks on an iPad2 and a Motorola Xoom.

Using a motion-analysis system, the team filmed the 15 volunteers as they worked on the tablet in four common configurations.

In the first position the tablet was not placed in its proprietary case but held on the lap in one hand while the other was used to touch the screen.

In the second the tablet was placed on the lap, but stayed in its case. The user worked with both hands on the screen.