title: Dynamics of viscoelastic creep during repeated stretches.
abstract: The present study examined the viscoelastic creep responses in vivo during repeated constant-torque stretches in human skeletal muscle. Twelve healthy participants completed four consecutive 30-s constant-torque passive stretches of the right plantar flexor muscles. Position and surface electromyographic (EMG) amplitude values were quantified at every 5-s period and the percent change in position was quantified for each 5-s epoch relative to the total increase in ankle joint position for each stretch. In addition, the absolute changes in position were plotted on a logarithmic time scale and fit with a linear regression line to examine both the rate of increase (slope) and the overall increase in position over the entire stretch (y-intercept). The percent change and slope were similar (P>0.05) over all four stretches, with the majority of increases in position occurring within the initial 15-20 s of each stretch (84%). Absolute ankle joint position and the y-intercept increased (P<0.05) following both the first and second stretch but plateaued (P>0.05) after the third stretch. In addition, EMG amplitude values did not change (P>0.05) during or between each 30-s stretch. These data indicate that the amount and rate of viscoelastic creep were similar during practical durations of constant-torque stretching despite no change in ankle joint position following three 30-s stretches.
authors.affiliation: Applied Musculoskeletal and Human Physiology Laboratory, Department of Health and Human Performance, Oklahoma State University, Stillwater, Oklahoma, USA. eric.ryan@okstate.edu
authors.forename: E D
authors.initials: ED
authors.lastname: Ryan
authors.forename: T J
authors.initials: TJ
authors.lastname: Herda
authors.forename: P B
authors.initials: PB
authors.lastname: Costa
authors.forename: A A
authors.initials: AA
authors.lastname: Walter
authors.forename: J T
authors.initials: JT
authors.lastname: Cramer
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D004576:Electromyography; D005528:Foot / Q000502:physiology*; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D052580:Muscle Stretching Exercises; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D019415:Torque