Isokinetic trunk-strength deficits in people with and without low-back pain: a comparative study with consideration of effort

The purposes of this study were to determine (a) the degree and distribution of isokinetic trunk strength deficits in people with chronic low-back pain (CLBP) and (b) to what degree subject effort during testing affects those deficits. We measured the isokinetic trunk strengths of three subject groups on the Cybex Trunk Extension/Flexion machine. Groups 1 and 2 consisted of 155 men and women with CLBP who were divided into maximal (n = 115) and submaximal (n = 40) groups according to their torque/position curve variability. Group 3 was made up of 32 back-healthy men and women who served as controls. The results demonstrated that men had higher flexion and extension torques than women did for all groups. The control group had higher flexion and extension torques than the maximal-effort CLBP group did. The extensors had a proportionally greater deficit than the flexors did in this LBP group. Comparing the two groups with CLBP, the maximal-effort group had higher flexion and extension torques than the submaximal effort group did, and the extensors showed a greater deficit. Degree of effort during testing does affect the results. Therapists should consider extensor strengthening and reeducation exercises when designing exercise programs to restore normal function in people with chronic CLBP.