Do different sit-stand workstations influence lumbar kinematics, lumbar muscle activity and musculoskeletal pain in office workers? A secondary analysis of a randomised controlled trial.

Purpose: To investigate the effect of different sit-stand workstations on lumbar spine kinematics, lumbar muscle activity and musculoskeletal pain. Materials and methods: Thirty-two office workers were randomised to one of three sit-stand workstations (Group 1 , ratio of minutes spent sitting to standing each hour at work was 40:20, n=8; Group 2, 30:30, n=6; Group 3, 20:40, n=7) and a control group (usual sitting, n=11). Intervention groups (Group 1, 2 and 3) were collapsed into one group for analysis (n=21). Data on lumbar kinematics and muscle activity were only collected for 25 participants due to equipment availability. Results: Participants in the intervention group had lower overall lumbar spine flexion angles during the workday compared to the control group (mean difference: 10.6°; 95% CI [-18.1, -3.2]; p=0.008; Cohen's d=1.5). There were no between-group differences for the remaining kinematic measures (i.e. mean flexion angle in standing and sitting, mean side flexion angle in standing and sitting, and the percentage of time in upright sitting), muscle activity or the presence of musculoskeletal pain. Conclusions: Sit-stand workstations reduced overall lumbar spine flexion angles over the course of a workday but had no effect on other kinematic measures, lumbar spine muscle activity or musculoskeletal pain. Trial registration: Australian New Zealand Clinical Trials Registry identifier: ACTRN12615001018505..