Assessment of lumbar EMG during static and dynamic activity in pain-free normals: implications for muscle scanning protocols.

The purpose of this study was to provide a thorough description of lumbar surface integrated electromyography (EMG) in pain-free normals during a standardized assessment protocol of static isometric and unresisted dynamic tasks. It has been proposed that in pain-free normals, symmetrical tasks that bend the trunk forward or extend the trunk backward produce symmetrical paraspinal EMG activity, and asymmetrical tasks that rotate or laterally bend the trunk produce asymmetrical paraspinal EMG activity. In addition, it has been observed that lumbar EMG assessment during static tasks has been more consistent than tasks involving dynamic activities. Twenty-eight pain-free normals were assessed during symmetrical and asymmetrical tasks in both static and dynamic activities in a counterbalanced manner. The assessment of paraspinal EMG patterns was conducted while subjects were secured in a triaxial dynamometer, which provided standardization of body position and concurrent measurement of torque, range of motion, and velocity. The results provided experimental evidence for the above-stated propositions. An implication derived from this research is that clinicians may be better served utilizing local norms when using EMG for classification purposes.