A randomized controlled trial evaluating the effects of new task chairs on shoulder and neck pain among sewing machine operators: the Los Angeles garment study.

STUDY DESIGN

This is a 4-month randomized controlled trial to evaluate the effect of chair design on neck/shoulder pain among sewing machine operators.

OBJECTIVE

Determine whether a chair with a curved seat pan leads to improved changes in monthly neck/shoulder pain scores compared with a control intervention.

SUMMARY OF BACKGROUND DATA

Sewing machine operators experience a high prevalence and severity of neck and shoulder pain in comparison to other working populations probably due to the sustained shoulder abduction and neck and upper back flexion required of the task. An adjustable height task chair that supports a forward sitting posture may reduce these posture-related risk factors and reduce neck/shoulder pain.

MATERIALS AND METHODS

A total of 277 sewing machine operators with neck/shoulder pain were assigned to receive 1) miscellaneous items (control group), 2) a chair with a flat seat pan plus miscellaneous items, or 3) a chair with a curved seat pan plus miscellaneous items. Participants completed a monthly questionnaire assessing neck/shoulder pain severity.

RESULTS

Based on estimates of pain score changes from a repeat-measures linear regression, participants who received the flat seat chair experienced a decline in pain of 0.14 (95% confidence interval, 0.07-0.22) points per month compared with those in the control group, while those who received the curved seat experienced a decline of 0.34 (95% confidence interval, 0.28-0.41) points per month compared with those in the control group. These estimates did not change after adjustment for potential covariates.

CONCLUSIONS

These findings demonstrate that an adjustable height task chair with a curved seat pan can reduce neck and shoulder pain severity among sewing machine operators.