Association of Manual Weight Lifting Tasks with Low Back Pain: A Pilot Study LC10-LC15
Ergonomics Laboratory, Defence Institute of Physiology and Allied Sciences, Lucknow Road, Timarpur, Delhi-110054, India.
Introduction: Manual Weight Lifting (MWL) and Low Back Pain (LBP) become closely interrelated when lifting tasks are performed without adhering to lifting norms. Maximum trauma during MWL is encountered by lower body joints which absorb force proportional to the weight being lifted. Therefore, quantification of the injury potential of such tasks in terms of kinetic responses would prove beneficial for further designing of MWL tasks with reduced incidences of LBP.
Aim: To quantify the kinetic responses of lifting tasks using real-time data collection technique and to find out whether real-time kinetics data corroborated with 2D prediction kinetics data analysed using simultaneously recorded 2D images of MWL.
Materials and Methods: This cross-sectional pilot study was conducted on eight healthy participants. Hand grip strength, videos for prediction kinetics and real-time kinetics data were recorded with hand grip calliper, Sony handy cam, and Kistler Force Plate, respectively. Prediction kinetics data from still photographs were extracted and analysed using ergonomics evaluation software ErgoMaster. Real-time Kinetics data were analysed with BioWare(R) software. Repeated measure Analysis of Variance (ANOVA) followed by Bonferroni post-hoc test was applied for statistical treatment.
Results: Some of the real-time and predicted kinetics data (mean±SEM) observed while lifting load at one lift per minute through different heights are given here. The Vertical component of Ground Reaction Forces (VGRF) while lifting 10 kg from Knuckle to Shoulder (K-S) height was 126.5±9.4 N which increased to 157.2±9.2 N for Floor to Knuckle (F-K) height and 178.4±7.4 N for Floor to Shoulder (F-S) height. Other conditions remaining same, while lifting 20 kg load the values of VGRF were 188.5±29.2 N, 270.6±16.0 N and 374.5±44.8 N, respectively. Under similar experimental conditions, the responses for Total Compression Force (TCF) while lifting 10 kg were 3095.22±218.5 N, 3892.9±204.1 N, 3886.1±190.40 N, respectively and similar trend was seen for 20 kg load also. Similar trends of significant changes were observed for all real-time and prediction kinetics parameters reported for lifting both 10 kg and 20 kg loads through F-K and F-S heights involving bending postures as compared to lifting at K-S height. This might be due to overload on spine and requirement for higher magnitudes of force absorption by lower body joints while undertaking such tasks.
Conclusion: The study indicates that, according to both real-time and prediction kinetics data, lifting of loads up to 10 kg from knuckle to shoulder height at one lift per minute is with in acceptable limit. The lifting tasks involving excessive bending may result in higher spinal load leading to LBP.