title: In vivo determination of fascicle curvature in contracting human skeletal muscles.
abstract: Fascicle curvature of human medial gastrocnemius muscle (MG) was determined in vivo by ultrasonography during isometric contractions at three (distal, central, and proximal) locations (n = 7) and at three ankle angles (n = 7). The curvature significantly (P < 0.05) increased from rest to maximum voluntary contraction (MVC) (0.4-5.2 m(-1)). In addition, the curvature at MVC became larger in the order dorsiflexed, neutral, plantar flexed (P < 0.05). Thus both contraction levels and muscle length affected the curvature. Intramuscular differences in neither the curvature nor the fascicle length were found. The direction of curving was consistent along the muscle: fascicles were concave in the proximal side. Fascicle length estimated from the pennation angle and muscle thickness, under the assumption that the fascicle was straight, was underestimated by ~6%. In addition, the curvature was significantly correlated to pennation angle and muscle thickness. These findings are particularly important for understanding the mechanical functions of human skeletal muscle in vivo.
authors.affiliation: Institute of Physical Education, Keio University, Kohoku, Yokohama 223-8521, Japan. mura@hc.cc.keio.ac.jp
authors.forename: Tadashi
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Muraoka
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawakami
authors.forename: Akira
authors.initials: A
authors.lastname: Shibayama
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Fukunaga
mesh_terms: D000328:Adult; D000465:Algorithms; D006801:Humans; D007596:Joints / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D015203:Reproducibility of Results; D012146:Rest / Q000502:physiology; D014463:Ultrasonography