Sudden load as an aetiologic factor in low back pain

Unexpected loads, which often occur in the working environment, can lead to high forces in the spine and, thus, may be a cause of low back injury. This paper discusses the effect of 'sudden load' and 'release of load' on the erector spinae reaction time and amplitude. Muscle responses were mediated by several factors including fatigue, expectation and rehabilitation in chronic LBP patients. The subjects were fatigued by holding a 20% maximum voluntary contraction for 1 min. The effect of a functional restoration program was tested for its efficacy in reducing reaction time and EMG amplitude in chronic low back patients. Reaction time was longer and EMG amplitude lower in patients compared to their matched controls. EMG reaction time and magnitude decreased in patients after a 2-weeks rehabilitation program, including specific training of co-ordination and posture control. The effect of sudden loads can be exacerbated if a worker is fatigued. Chronic low back pain patients have less ability to protect themselves from sudden loads but they can be trained to improve their response by means of an appropriate rehabilitation program.