QUANTITATIVE ASSESSMENT OF LUMBAR PARA-SPINAL MUSCULAR ENDURANCE.

Abstract

1224 The purpose of this study was to evaluate the reliability and variability of repeated measurements of dynamic (D) and static (S) lumbar muscle endurance. An isometric lumber extension strength test to establish peak torque was completed by all subjects (N=8). Participants subsequently completed two trials (T1 and T2) of four lumbar muscular endurance tests (each test separated by 24 hours). S holding time, and D repetition tests were performed on a horizontal Roman chair (RC), and a MedX™ (Ocala,FL) lumbar extension dynamometer (MX). The S-MX was performed at 45 ° of lumbar flexion with a load equal to 40% of the subjects peak torque. The S-RC test was completed with the subject prone at 0 ° of lumbar flexion. The D-MX test was performed with a load equal to 40% of the subject's peak torque, and the D-RC was done using the subject's torso mass as resistance. The order of testing was balanced over subjects. Inter-trial reliability was high for all endurance tests (r = 0.94 to 0.96, p ≤ 0.05). Variability (total error) for S-RC and S-MX was 11.6 and 18.3 seconds, respectively. Variability for D-RC was 1.6 repetitions and for D-MX 2.8 repetitions. This level of variability represented 7.1 to 10.5% of the observed mean values. The D-MX test showed a significant difference (p=.03) between T1 (25.8 reps) and T2(27.8 reps), whereas there was no difference (p > 0.05) between trials for the other endurance tests. These data indicate that lumbar muscle endurance can be reliably assessed by both static and dynamic tests. As shown in previous research, a single bout of exercise on a MedX dynamometer may be associated with an increase in performance.