The impact of a change in work posture on work-related musculoskeletal disorders among sewing-machine operators, managed within a physiotherapy and ergonomics programme

Abstract

When implementing a managed healthcare intervention among a working population, evidence-based healthcare is critical. In the current study, the change of work posture of sewing-machine operators from seated to stand-up (the intervention) was managed within a physiotherapy and ergonomics programme (programme) in Johnson Controls Automotive S.A. (Pty) Ltd (company) without local evidence to guide the postural transition. The management of the intervention, implemented over a period of 4.5 years, presented the opportunity for a retrospective longitudinal study. The study determined the impact of the change in work posture on the incidence of work-related musculoskeletal disorders (WRMSDs) from June 2004 to January 2009 (period). The role of the physiotherapist in the programme was to deliver manual therapy to all sewing-machine operators with WRMSDs, and to provide a clinical - ergonomics service, as a member of a multidisciplinary team, to the company. The population of sewing-machine operators (n=123) was described in terms of personal factors (e.g. age, medical history, musculoskeletal history, and body mass index (BMI)), ergonomic risk factors (e.g. work posture, force and duration) and overall incidence of WRMSDs. The associations of risk factors (personal and ergonomic) with WRMSDs, and work posture with WRMSDs among sewing-machine operators were statistically determined. The majority of the population (97.6%) was female, with mean age 42.3± 8 years. At baseline, 17.9% were hypertensive, 3.3% had arthritis, 6.5% were diabetic, and the mean BMI was 29.7 kg/m² (22% of BMIs was normal). The largest proportion of the sewing-machine operators were sewing cloth and leather (79.7%) (compared to sewing cloth and vinyl), and the remainder performed forceful precision stitching (20.3%), including headrest covers, airbags and top stitching on the final product. Job rotation took place between forceful precision stitching and straight stitching (for 36.6% of the sewing-machine operators).p> The intervention was implemented within the study period. At baseline 100% of sewing machine operators were sewing in the seated work posture. Early in the study, 17.9% of them changed their work posture from seated to stand-up, 30.1% changed to the stand-up work posture in January 2007, and 34.9% a year later. The last 17.1% remained seated till the last year of the study period. From July 2008, 100% of the sewing-machine operators were sewing in the stand-up work posture. The results indicated two strong associations of risk factors and a change in work posture with WRMSDs. Obesity (specifically morbid obesity) was a personal risk factor for upper limb disorders and working in the stand-up work posture was protective for spinal disorders, compared to working in the seated work posture. Furthermore, the results indicated a high incidence of disorders (specifically of the spinal area and upper limb) during the first three months of the programme, as well as an increased incidence of lower leg disorders for the first and consecutive month of the change in work posture from seated to standing up. Lower limb disorders were specifically associated with obesity. The increase of lower limb disorders during the postural adaptation phase was temporary, and was addressed within the programme with proper shoe wear, silicone innersoles, supportive stockings and exercises. The combination proved to be effective in preventing and/or managing lower limb disorders. The outcome of the current study provided evidence on the incidence of WRMSDs, and associations between risk factors and work posture, and WRMSDs among sewing machine operators managed within the programme.