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Estimation of muscle torque impulses and ability to predict high-risk knee joint mechanics during landing maneuvers

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Jerome Jean Sauret (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Advisor
Randy Schmitz

Abstract: This research first examined the validity of net knee joint moment estimations, calculated as the difference between quadriceps and hamstrings torques estimated using either an isometric or angle and action specific sEMG/Torque ratio calculated during calibration actions, during the impact phase of the initial landing of a drop jump maneuver. Second, this research investigated the extent to which the torque impulses of the medial and lateral aspects of the quadriceps and hamstrings, estimated during the impact phase of the initial landing of a drop jump maneuver using an angle and action specific sEMG/Torque ratio predicted knee joint mechanics associated with ACL injury risk, in the three planes of motion. Forty healthy active females, between the ages of 18 and 25, participated in the study. Participants performed maximal calibration actions on an isokinetic dynamometer (eccentric and isometric quadriceps, concentric and isometric hamstrings) while surface electromyographic (sEMG) data were collected from the vastus lateralis, vastus medialis, bicep femoris and semitendinous. Subsequently, a drop jump maneuver was performed while three dimensional biomechanical data as well as sEMG data from the above mentioned muscles were collected. Based on the calibration actions, individualized isometric as well as angle and action specific (eccentric quadriceps, concentric hamstrings) sEMG/Torque ratios (sEMG amplitude divided by half of the torque produced) were computed for each of the four muscles, from full extension to 90 degrees of knee flexion. Using the knee flexion data during the landing maneuver, the sEMG/Torque ratio was then estimated for the impact phase of the drop jump maneuver. It was then divided by the concurrently acquired sEMG to estimate torques for the four afore mentioned muscles during the impact phase of landing. Muscle torques were resolved into a net joint moment as the difference between the sum of the extensors and flexors, and the impulses were then calculated for each of the muscle torques and for the net joint moments. High risk knee joint mechanics, in the three planes of motion, were observed during the impact phase of the initial landing of the drop jump. A RMANOVA tested differences between the net joint moments estimated based on isometric or angle and action specific measurements and inverse dynamics analysis. Regression models assessed the extent to which the muscle torque impulses, estimated using the angle and action specific sEMG/Torque ratio during the impact phase of the initial landing of a drop jump maneuver, predicted each of the seven variables identified as high risk knee joint mechanics. First, the results revealed that net knee joint moment based on the angle and action specific sEMG/Torque ratio provided a closer estimation of the net knee joint moment calculated using an inverse dynamics analysis than the net knee joint moment based on the isometric sEMG/Torque ratio. Second, muscle torque impulses, estimated using the angle and action specific sEMG/Torque ratio, were significantly predictive of only frontal and transverse moments about the knee. Secondary analyses revealed that when including simple ground contact kinematic variables and impact phase duration into the regression models, muscle torques predictivity of high risk knee joint biomechanics often increased. Hence, it was concluded that the angle and action specific sEMG/Torque ratio provides a better estimation of sagittal joint moments than the traditional isometric approach to sEMG normalization. Future studies should investigate the factors influencing ground contact knee joint kinematics and impact phase duration during the initial landing of a drop jump maneuver.

Additional Information

Publication
Dissertation
Language: English
Date: 2011
Keywords
ACL, Biomechanics, Electromyography, Knee, Muscle, sEMG Torquue
Subjects
Human mechanics
Knee $x Mechanical properties
Anterior cruciate ligament $x Wounds and injuries $x Prevention