Physical Endurance Tests/Measures McGill has established a performance test to examine the endurance profiles of healthy young men and women for the spine stabilizing musculature. Given the growing support for quantification of endurance, these data of endurance times and their ratios between extensor, flexor, and lateral flexor groups in healthy normal subjects are useful for patient evaluation and for providing clinical training targets. To establish isometric endurance holding times, as well as ratios between torso extensors, flexors, and lateral flexors (stabilizers), for clinical assessment and rehabilitation targets. The tests proved reliable, with reliability coefficients of >.97 for the repeated tests on 5 consecutive days and again 8 weeks later.