Comparison of Two Restraint Systems for Pelvic Stabilization during Isometric Lumbar Extension Strength Testing

This study was supported in part by a grant from MedX Inc., Ocala, FL. Among strength testing methods, varying degrees of stabilization are used. The purpose of this study was to compare isometric lumbar extension strength values obtained from two different restraint systems designed to isolate the lumbar extensors through pelvic stabilization. Both restraint systems stabilized the pelvis by preventing movement of the lower extremities during testing with the subject in a seated position. One restraint system (KNEE) applied pressure just below the knees while the lower leg was positioned at 120 degrees of knee flexion. The other (FOOT) applied pressure to the bottom of the feet while the lower leg was positioned at 60 degrees of knee flexion. Fifteen men (age = 37 +/- 10 yr; height = 177.7 +/- 5.3 cm; weight = 61.4 +/- 10.9 kg) and six women (age = 43 +/- 7 yr; height = 170.9 +/- 7.9 cm; weight = 61.4 +/- 10.9 kg) were tested at seven positions through 72 degrees range of motion with each restraint system. Analysis of variance for repeated measures indicated a significant difference (p 0.05) between restraints were noted at 24, 12, or 0 degrees flexion. Thus, the restraint system employed can influence lumbar extension strength values and affect the shape of the isometric lumbar extension strength curve. J Orthop Sports Phys Ther 1992;15(1):37-42.