Abstract
The reliability of the trunk Biodex unit (Shirley, NY) was assessed in asymptomatic men (n = 30) and women (n = 29) 20 to 35 years of age. Flexion peak torque (FPT) and extension peak torque (EPT) and maximal repetition work (MRW) were evaluated at 60, 120, and 150 deg/sec. Variables were measured on two occasions on each of 3 days. Data were analyzed using analysis of variance with repeated measures (p < 0.01). Reliability was estimated by intraclass correlation coefficients. For men, EPT at 60 deg/sec on day 1 was significantly lower than on days 2 and 3. For women, values on day 1 were significantly lower than on days 2 and 3 for all parameters measured except EPT at 60 deg/sec, FPT at 60 and 150 deg/sec, and FMRW at 60 and 120 deg/sec. The occasion effect was nonsignificant for women. For men, values for FPT at 60 and 120 deg/sec were significantly lower on occasion 2, suggesting a fatigue effect. Reliability coefficients ranged from 0.81 to 0.98 for men and women, with the exception of EMRW at 150 deg/sec for men (R = 0.54) and 60 deg/sec for women (R = 0.57). Reliable Biodex trunk strength values can be obtained using 1 day of testing for men, except for EPT at 60 deg/sec, which requires 1 day of practice. Women require 1 day of practice for most of the parameters tested. It is not necessary to test men or women twice on the same day. Reliable EMRW at 150 deg/sec for men and 60 deg/sec for women was not achieved.