title: Force enhancement of quadriceps femoris in vivo and its dependence on stretch-induced muscle architectural changes.
abstract: The purpose of this study was to investigate if force enhancement (FE) in vivo is influenced by stretch-induced changes of muscle architecture. Therefore, 18 subjects performed maximum voluntary isometric (100 degree knee flexion angle) and isometric-eccentric-isometric stretch contractions (80 degrees-100 degrees; ω=60 degrees.s(-1)) whereby pennation angle and fascicle length of vastus lateralis was determined using ultrasonography. We found significant (2-way repeated ANOVA; α=0.05) enhanced torque of 5-10% after stretch as well as significant passive FE but no significant differences in muscle architecture between isometric and stretch contractions at final knee angle. Furthermore, EMG recordings during a follow-up study (n=10) did not show significant differences in activation and mean frequency of contraction conditions. These results indicate that FE in vivo is not influenced by muscle architectural changes due to stretch.
authors.affiliation: Department of Biomechanics in Sports, Faculty of Sports Science, Technische Universität München, Munich, Bavaria, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Seiberl
authors.forename: Daniel
authors.initials: D
authors.lastname: Hahn
authors.forename: Florian
authors.initials: F
authors.lastname: Kreuzpointner
authors.forename: Ansgar
authors.initials: A
authors.lastname: Schwirtz
authors.forename: Uwe
authors.initials: U
authors.lastname: Gastmann
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D007866:Leg / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D052580:Muscle Stretching Exercises; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging / Q000502:physiology*; D019415:Torque; D014463:Ultrasonography