Reliability of lumbar isometric torque in patients with chronic low back pain.

In this study, the test-retest reliability of lumbar isometric strength testing in patients with chronic low back pain (CLBP) was assessed. Isometric torque measurements were obtained from 89 patients with CLBP at seven different angles of lumbar flexion. Because previous studies have demonstrated significant strength differences between male and female subjects, separate data analyses were performed for each gender. Results indicated moderate to high reliability for patients with CLBP when tested at individually determined angles of flexion within their idiosyncratic range of motion (ROM) (female subjects: r = .59-.96, P less than .05, SEE = 12.0-24.2 N.m; male subjects: r = .71-.93, P less than .05, SEE = 25.1-62.1 N.m). For comparison with previously published data on asymptomatic controls, an additional set of analyses was conducted for subjects with full lumbar ROM. Similar reliability was demonstrated for this subsample (female subjects: r = .57-.93, P less than .05, SEE = 12.4-27.9 N.m; male subjects: r = .63-.93, P less than .05, SEE = 34.2-44.2 N.m). The authors concluded that isometric lumbar extension torque could be reliably measured in patients with CLBP at multiple positions within the full ROM, although reliability decreased at the most extended positions. The demonstrated reliability will allow researchers to assess treatment effects and group differences without undue concern for artifact attributable to measurement error.