Purposes and background of study: We compared the effects of lumbar muscle-strengthening programmes with and without pelvic stabilisation on low back pain (LBP). A dynamometer employing a stabilisation procedure (lumbar extension machine, MedX, Ocala, FL) is effective in improving strength and reducing LBP symptoms (Nelson et al., Orthopedics, 1995, 18,971–981), and researchers have hypothesised that this effectiveness is due to the pelvic stabilisation (Graves et al., Arch Phys Med Rehabil, 1994, 75,210–215). However, effects of the dynamometer with and without pelvic stabilisation on LBP have not been compared, so we examined this issue.

Methods and Results: Fifty-seven chronic LBP patients were randomly assigned to a lumbar extension training with pelvic stabilisation group (STAB; n=20), a lumbar extension without pelvic stabilisation group (NO-STAB; n=17) and a control group (n=20). STAB and NO-STAB participants completed one weekly session of dynamic variable resistance exercise (one set of 8–12 repetitions to fatigue) on the lumbar extension machine (with or without pelvic stabilisation) for 12 weeks. Pre- and post-test measures of self-reported LBP (101-point visual analogue scale; pre-test mean of 25), related disability (Oswestry disability index; pre-test mean of 34) and lumbar strength were taken. After the exercise programme, the STAB group increased significantly in lumbar strength at all joint angles, and decreased significantly in visual analogue and Oswestry scores. However, there were no significant changes in these variables in the NO-STAB and control groups.

Conclusion: Isolated lumbar extension exercise is very effective in reducing LBP in chronic patients. However, when the pelvis is not stabilised, otherwise identical exercises appear ineffective in reducing LBP.