title: Static pre-load effect on knee extensor isokinetic concentric and eccentric performance.
abstract: The effect of two static pre-load levels on isokinetic concentric (CON) and eccentric (ECC) performance of the knee extensors at 90 degrees.s-1 was evaluated in 35 healthy subjects. The low pre-load level was 50 N, and the high level was 75% of a maximal voluntary isometric contraction, performed at the start angles of 100 degrees (CON) and 30 degrees (ECC) of knee flexion. A two-way ANOVA with two repeated measures (load and angle) and a Newman-Keuls post hoc analysis were performed to compare the interaction of pre-load and angle at every 5 degrees in the ROM. The differences in average torque, peak torque, and peak torque angle between the pre-load levels were also analyzed with repeated-measures t-tests. The high pre-load condition had a significant increase in torque at 99, 95, 90, and 85 degrees concentrically and 31, 35, 40, 45, and 50 degrees eccentrically. In comparing the two pre-load conditions over the whole torque curve, there was a significant difference in average torque values of both CON and ECC, no significant difference in peak torque in either contraction, and a significant shift in peak torque angle with CON contractions only.
authors.affiliation: Department of Physical Therapy, Sargent College of Allied Health Professions, Boston University, MA 02215.
authors.forename: R C
authors.initials: RC
authors.lastname: Jensen
authors.forename: B
authors.initials: B
authors.lastname: Warren
authors.forename: C
authors.initials: C
authors.lastname: Laursen
authors.forename: M C
authors.initials: MC
authors.lastname: Morrissey
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction; D013314:Stress, Mechanical