Muscle recruitment, reflex gain, and perturbation kinematics were quantified before and immediately following a 15-min period of static passive flexion loading of the spine. To impose spinal ligament strain subjects sat on the floor with their trunk in full lumbar flexion and legs extended with a small padded bolster under the knees to reduce hamstring stretch and to tilt the pelvis posteriorly. They relaxed in this flexed posture while observing EMG from the erector spinae displayed on an oscilloscope to assure voluntary de-recruitment of the erector spinae, i.e. flexion-relaxation. Immediately following the flexion-relaxation period neuromechanical measurements of muscle recruitment, reflex gain and perturbation kinematics were repeated.