title: The relationship between passive stiffness and muscle power output: influence of muscle cross-sectional area normalization.
abstract: BACKGROUND
  We examined the relationship between passive stiffness of posterior hip and thigh muscles and muscle power output before and after normalization of passive stiffness to muscle cross-sectional area (CSA).
  
  
  METHODS
  Pearson correlation coefficients (r) were used to assess the relationships between the normalized and non-normalized slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve and peak power output (Pmax).
  
  
  RESULTS
  A significant positive relationship was observed between the non-normalized slope of phase 1 and Pmax (r = 0.723; P ≤ 0.001); however, no correlations were observed between the normalized slope of phase 1 and Pmax (r = 0.244; P = 0.299) nor between Pmax and the normalized and non-normalized slopes of phase 2 (r = -0.159-0.418; P = 0.067-0.504).
  
  
  CONCLUSIONS
  The findings suggest that muscle size, rather than stiffness, accounted for a significant portion of the variance in muscle power output.
authors.affiliation: Department of Health and Human Performance, Oklahoma State University, Stillwater, Oklahoma, USA.
authors.forename: Ty B
authors.initials: TB
authors.lastname: Palmer
authors.forename: Nathaniel D M
authors.initials: ND
authors.lastname: Jenkins
authors.forename: Brennan J
authors.initials: BJ
authors.lastname: Thompson
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Smith
authors.forename: Joel T
authors.initials: JT
authors.lastname: Cramer
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006615:Hip; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D009129:Muscle Tonus / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D013848:Thigh; D055815:Young Adult
keywords: musculotendinous unit; normalization; passive stiffness; power; vertical jump performance