The effect of abdominal muscle fatigue and training on the intra-abdominal pressure developed during lifting

Abstract

The rise in intra-abdominal pressure (IAP) during lifting reduces spinal stress by acting synergistically with the contraction of the extensor muscles of the spine. If the IAP does not rise during lifting it seems likely that there will be a greater risk of low back injury due to greater spinal instability. It is possible that abdominal muscle fatigue may prevent the development of an adequate IAP during lifting, thereby predisposing an individual to a low back injury. Strengthening of the abdominal muscles by training has been advocated as a way of reducing the likelihood of back injury. An experiment was conducted to investigate the effect of abdominal muscle fatigue and training on the intra-abdominal pressure during lifting. First, abdominal muscle fatigue was induced in six healthy young male subjects who performed ‘sit-ups’ repetitively to exhaustion, after which IAP was measured in a sub-maximal lifting test and compared with values obtained before the fatigue-inducing exercise. There was no statistically significant difference in the IAP developed during the test. Secondly, a 2 week period of training was undertaken in which abdominal muscles were strengthened. The IAPs developed in the sub-maximal lifting test remained unchanged when compared with pre-training values. It is concluded that the IAP developed during sub-maximal lifting is not influenced by fatigue or ‘sit-up’ training of the abdominal muscles. If abdominal muscle fatigue increases the risk of back injury and training reduces the risk, then the present study suggests that it is not due to alterations in the IAP developed during lifting.