Stoop or squat: a review of biomechanical studies on lifting technique.

OBJECTIVE To assess the biomechanical evidence in support of advocating the squat lifting technique as an administrative control to prevent low back pain. BACKGROUND Instruction with respect to lifting technique is commonly employed to prevent low back pain. The squat technique is the most widely advised lifting technique. Intervention studies failed to show health effects of this approach and consequently the rationale behind the advised lifting techniques has been questioned. METHODS Biomechanical studies comparing the stoop and squat technique were systematically reviewed. The dependent variables used in these studies and the methods by which these were measured or estimated were ranked for validity as indicators of low back load. RESULTS Spinal compression as indicated by intra-discal pressure and spinal shrinkage appeared not significantly different between both lifting techniques. Net moments and compression forces based on model estimates were found to be equal or somewhat higher in squat than in stoop lifting. Only when the load could be lifted from a position in between the feet did squat lifting cause lower net moments, although the studies reporting this finding had a marginal validity. Shear force and bending moments acting on the spine appeared lower in squat lifting. Net moments and compression forces during lifting reach magnitudes, that can probably cause injury, whereas shear forces and bending moments remained below injury threshold in both techniques. CONCLUSION The biomechanical literature does not provide support for advocating the squat technique as a means of preventing low back pain. RELEVANCE Training in lifting technique is widely used in primary and secondary prevention of low back pain, though health effects have not been proven. The present review assesses the biomechanical evidence supporting the most widely advocated lifting technique.