The effects of seat height and foot placement on lumbar spine load during sit-to-stand tasks

Abstract

The purpose of this study was to determine the influence of seat height and foot position in the sagittal plane on L5-S1 joint load. Fourteen healthy male adults stood up from a chair with three different seat heights and positions of the feet in the sagittal plane. L5-S1 net joint torque, mechanical work, range of motion and electromyographic activity of the erector spinae muscle were measured. L5-S1 net joint work increased by about 50% from high to low seat position. The mean and peak L5-S1 net joint torques increased about 30% from foot-back to foot-neutral position. These results were reinforced by a greater integrated electromyography signal from the erector spinae from high to low seat position and from foot-back to foot-neutral position. A high chair and placement of the feet behind the knees may be advisable to lessen lumbar load during sit-to-stand movements.

Abstract

Practitioner Summary: This study evaluated the effect of seat height and foot position on L5-S1 joint work and erector spinae activation during sit-to-stand movements. A high seat with the feet positioned further back decreased L5-S1 joint torque and erector spinae activation. These outcomes may help to reduce spine load during sit-to-stand movements.

Keywords::

• L5-S1 joint
• joint work
• electromyography
• biomechanics