Abstract
The effect of bending and rotation of the trunk on the intra-abdominal pressure (IAP) and erector spinae muscle activity when lifting while sitting has been investigated. The analysis of the IAP results shows that the difference between lifting from the middle and lifting from either the left or right is highly significant (P<0·01), whereas the difference between mean values for lifting from the right and left is not significant The iEMG results from the erector spinae of the left of L3 level show that the difference between the mean values of the iEMG when lifting from the right and left is highly significant (P<0·01). The difference between lifting from the right and middle is also significant (P<0·01). Back muscle activity from the erector spinae on the right of L3 level is lower when lifting with trunk rotated to the right and highest when it is rotated to the left as compared to lifting from the middle. Both parameters increased as bending of the trunk increased.