Among various strength testing methods, different degrees of stabilization are used. The purpose of this study was compare isometric lumbar extension values obtained from two machines with different lower extremity restraint systems, KNEE and FOOT, 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. KNEE applied pressure just below the knees with the lower leg positioned at 120° of knee flexion, while FOOT applied pressure to the bottom of the feet while the lower leg was positioned at 60° of knee flexion.
The study included 15 men and 6 women; they were all asymptomatic for back pain and had no orthopedic problems or other medical conditions that would affect lumbar extension exercise. Each individual was tested at seven positions through 72° range of motion with both restraint systems, the tests were conducted on different days and separated by a minimum of 72 hours, but no more than one week. Analysis of variance for repeated measures indicated a significant difference between restraint systems and a significant restrain system by joint angle interaction. Subjects generated 9.4% to 10.9% more torque at 72, 60, 48, and 36 of lumbar flexion with the KNEE restraint system compared to the FOOT restraint system. The study concluded that the restraint system employed can influence lumbar extension strength values and the shape of the isometric lumbar extension strength curve.
Keywords: Restrain systems, knee, foot, lumbar extension, isometric, pelvic stabilization
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