663 Three-Dimensional Kinematics and Trunk Muscle Myoelectric Activity in the Young Lumbar Spine: A Database John P. Peach, MSc, Chrisanto G. Sutarno, MSc, Stuart M. McGill, PhD ABSTRACT. Peach JR Sutarno CG, McGill SM. Three- dimensional kinematics and trunk muscle myoelectric activity in the young lumbar spine: a database. Arch Phys Med Rehabil 1998;79:663-9. Objective: To document the three-dimensional (3D) kinemat- ics of the lumbar spine and the myoelectric activity of trunk muscles throughout the range of motion in selected tasks performed by healthy subjects. Design: A survey of a single population. Setting: A research laboratory in a university setting. Participants: Twenty-four men and women, university-age, with no history of chronic lower back pain volunteered for this study. Interventions: The selected tasks consisted of lateral bend and axial twists to the right and left plus four different flexion-extension tasks that varied a hand-held weight (10kg and 0kg), and flexion-extension velocity (free-paced and 20°/ see). Main Outcome Measure: 3D lumbar spine kinematics and normalized, linear enveloped electromyogram (EMG) of trunk muscles. Results: The motion time histories were illustrated graphi- cally. Consistent spinal kinematics and EMG activation patterns during each task across subjects were seen. Peak displacement values between tasks, using one-way analysis of variance, showed no significant difference. Conclusion: A database of healthy spine kinematics and normalized linear enveloped trunk muscle activation patterns were developed for future comparison of elderly and pathologi- cal subjects. © 1998 by the American Congress of Rehabilitation Medi- cine and the American Academy of Physical Medicine and Rehabilitation A SSESSMENT OF THE low back often involves recording the end range of motion (ROM) in a single plane. Recently, sophisticated systems have been developed that quantify three- dimensional (3D) spine motion throughout complex move- merit. 1-6 These systems have the advantage of documenting pathology that may manifest anywhere in the movement. Some systems have recognized the importance of examining muscle usage during these tasks and have incorporated electromyo- gram (EMG) time-history information. 7-12 Documenting the From the MusculoskeletalResearch Laboratory, University of Vermont, Burlingon, VT (Mr. Peach); and the Occupational Biomechanics and Safety Laboratories, University of Waterloo, Waterloo, Ontario, Canada (Mr. Sutarno, Dr. McGill). Submitted for publication April 18, 1997. Accepted in revised form October 31, 1997. Supported by the Natural Sciences and Engineering Council of Canada. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Professor Stuart M. McGill, Occupational Biomechanics and Safety Laboratories, Faculty of Applied Health Sciences, Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1. © 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/98/7906-446753.00/0 movement and its corresponding muscle activation pattern may provide the clinician with guidance for optimizing treatment. The purpose of this work was to create a database to document the 3D kinematics of the lumbar spine and the myoelectric activity of 14 trunk muscles over a range of selected move- ments. The rationale for using healthy spines was to provide a basis of comparison for other populations, such as patients with low back pain (LBP) and the elderly. Measuring dynamic spinal motion using goniometers, a finger-to-floor gauge, the Schrber test, and inclinometers 13 is common; however, these techniques lack detailed representa- tion of the motion throughout the range and are chiefly used to measure only sagittal mobility. Static radiographs have primar- ily been limited to measurements in the sagittal and frontal planes. Although a 3D system has been developed, it is invasive and is not widely used. 35 Computer axial tomography and magnetic resonance imaging have also been used to assess the static spine, but evidence of a structural abnormality may or may not be associated with pain symptoms. Machines such as the B-200 Isostation 14 provide 3D kinematics but some axes of rotation are fixed, thereby providing erroneous description of spine rotations. Nonetheless this machine has been used to develop a database of normal ROM, strength, and endurance values 14 for clinical use. The Lumbar Motion Monitor 6 does not significantly constrain the movement and provides continuous measurements of dynamic motion. Video analysis systems have also been used 15,16 but they are very costly, time consuming, and have are limited for measuring small changes. The 3Space Isotrak a solves most of these problems. It is an inductive instrument that measures the position and orientation of a sensor in space. 2 It consists of a source module that can be adapted for mounting over the sacrum, and a sensor, which is mounted on the spinous process of T12. 3 The 3Space transmit- ter sets up an electromagnetic field and the receiver senses its position within the field, relative to the transmitter. Therefore, only movement of the spinal segments between the transmitter and receiver are measured. The 3Space signal was collected at a sampling frequency of 20.5Hz. Because the 3Space instrumen- tation has limitations when rotations approach 90 °, a correction algorithm 17 was used to ensure proper coupling of Euler angles (the interested reader is referred to this paper for a description of the rather involved algorithm). 3D spine motion was recorded and normalized relative to a neutral upright standing posture, and synchronized with the EMG signals. It provides continuous sampling of spinal kinematics with six degrees of freedom and imposes only minor incumbrance to the subject. However, in a study that documented the 3D kinematics of the normal lumbar spine using the 3Space Isotrak and radiographs,l the 3Space was noted to slightly overestimate the lumbar rotation. The muscles of the torso create torque to sustain movement and to stabilize the spine. In doing so, they exhibit consistently recognizable activation patterns, and deviations from these patterns may be indicative of pathology. For example, some studies using LBP-patient populations have demonstrated higher EMG amplitudes 18 relative to healthy controls during motion, whereas some other studies have shown no consistent increase Arch Phys Med Rehahil Vol 79, June 1998