Endurance times for low back stabilization exercises: clinical targets for testing and training from a normal database.

OBJECTIVE: To establish isometric endurance holding times, as well as ratios between torso extensors, flexors, and lateral flexors (stabilizers), for clinical assessment and rehabilitation targets.
DESIGN: Simple measurement of endurance times in four tests performed in random order by a healthy cohort. To measure reliability, a subsample also performed the tests again 8 weeks later.
SETTING: University laboratory. PARTICIPANTS: Seventy-five young healthy subjects (31 men, 44 women).
RESULTS: Women had longer endurance times than men for torso extension, but not for torso flexion or for the "side bridge" exercise, which challenges the lateral flexors (stabilizers). Men could sustain the "side bridge" for 65% of their extensor time and 99% of their flexion time, whereas women could sustain the "side bridge" for only 39% of their extensor time and 79% of their flexion time. The tests proved reliable, with reliability coefficients of >.97 for the repeated tests on 5 consecutive days and again 8 weeks later.
CONCLUSION: Healthy young men and women possess different endurance profiles 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.