title: EMG reaction in muscles about the knee to passive velocity, acceleration, and jerk manipulations.
abstract: Twenty subjects, ten adults and ten children were tested in this study. Each test consisted of applying an ensemble of velocities to the lower limb using a torque motor in such a way that the entire range of motion of the knee was traversed. Eight velocities between 60 degrees/s and 280 degrees/s were reached at 2-3 different acceleration rates and 1-2 different rates of jerk. EMG from three muscles, vastus, rectus, and hamstring were recorded during each move. Regression and correlation coefficients between EMG and kinematic parameters indicated different reactions in both muscle groups and age groups to each of the three kinematic parameters. Adult muscle was dominated by a reaction to the velocity kinematic while children's muscles were dominated by either acceleration or jerk. The extensor muscles of adults seem to be slightly more sensitive to acceleration and jerk than the flexors. In the muscle responses of children the exact opposite pattern is seen. The small sample size in this study does not allow for a meaningful statistical analysis.
authors.affiliation: Alfred I. duPont Hospital for Children, Gait Laboratory, 1600 Rockland Road, Wilmington, DE 19899, USA. fee@gait.aidi.udel.edu
authors.forename: James W
authors.initials: JW
authors.lastname: Fee
authors.forename: Freeman
authors.initials: F
authors.lastname: Miller
authors.forename: Nancy
authors.initials: N
authors.lastname: Lennon
mesh_terms: D000054:Acceleration; D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D016059:Range of Motion, Articular / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology*