A. The experimental setup for evoking short-latency stretch reflexes from the lumbar paraspinal muscles. B. The tip of the electromechanical tapping apparatus was gradually pressed into the tissue to a pre-load of 30-Newtons was reached at which time the device delivered a rapid mechanical tap to the muscle with a net force of 90-Newtons. C. Representative examples of a short-latency stretch reflex recorded from the lumbar paraspinal muscles in response to a mechanical tap. SA= Stimulus artifact.