- Low back extensor moment (strength) appears to be greater in more flexed lifting postures and this may be driven by an optimized length tension relationship in the spinal erector musculature.
BACKGROUND & OBJECTIVE
Low back pain (LBP) is the leading cause of disability in the world (1), and lifting is one of the known risk factors for LBP in manual workers (2). Due to these two factors, clinicians and manual handling advisors commonly recommend lifting with a “straight” or extended rather than a flexed lumbar spine. However, this practice has been recently questioned due to a lack of in vivo research demonstrating a clear relationship between a flexed lumbar spine when lifting and low back pain or injury.
Furthermore, manual handling interventions advising people to minimize lumbar flexion when lifting have failed to reduce LBP. To date, the influence of lumbar posture on trunk muscle recruitment, strength and efficiency during high intensity lifting has not been fully explored. Therefore, the purpose of this study was to investigate this relationship.
Combined with the lack of in vivo evidence that lifting with a flexed back is associated with low back pain and injury, the current advice to ‘lift with a straight back’ should be further questioned.
An experimental, repeated measures study design was undertaken to investigate the effects of three lumbar postures (fully flexed, mid-range and maximal extension) during maximal voluntary isometric force exertions in a symmetrical lifting posture. The muscle activity of three paravertebral muscles