title: Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia.
abstract: BACKGROUND
  We compared absolute and normalized values for peak torque (PT), mean power (MP), rate of velocity development, and electromyography (EMG) amplitude during maximal isometric and concentric isokinetic leg extension muscle actions, as well as the %decrease in PT and %increase in MP from 1.05 to 3.14 rad·s(-1) in younger versus older men.
  
  
  METHODS
  Measurements were performed twice for reliability. Isokinetic measurements were normalized to the isometric muscle actions.
  
  
  RESULTS
  Absolute isometric PT, isokinetic PT and MP, and EMG amplitudes at 1.05 and 3.14 rad·s(-1) were greater in the younger men, although normalizing to isometric PT eliminated the age differences. The older men exhibited greater %decrease in PT (37.2% vs. 31.3%) and lower %increase in MP (87.6% vs. 126.4%) regardless of normalization.
  
  
  CONCLUSIONS
  Normalization eliminated absolute differences in isokinetic strength and power, but the relative differences from slow to fast velocities may reflect dynapenia characterized by age-related decreases in fast-twitch fiber function.
authors.affiliation: University of Nebraska-Lincoln, 211 Ruth Leverton Hall, Lincoln, Nebraska, 68583, USA.
authors.forename: Nathaniel D M
authors.initials: ND
authors.lastname: Jenkins
authors.affiliation: University of Nebraska-Lincoln, 211 Ruth Leverton Hall, Lincoln, Nebraska, 68583, USA.
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Housh
authors.affiliation: Oklahoma State University, Stillwater, Oklahoma, USA.
authors.forename: Ty B
authors.initials: TB
authors.lastname: Palmer
authors.affiliation: University of Nebraska-Lincoln, 211 Ruth Leverton Hall, Lincoln, Nebraska, 68583, USA.
authors.forename: Kristen C
authors.initials: KC
authors.lastname: Cochrane
authors.affiliation: University of Kentucky, Lexington, Kentucky, USA.
authors.forename: Haley C
authors.initials: HC
authors.lastname: Bergstrom
authors.affiliation: University of Nebraska-Lincoln, 211 Ruth Leverton Hall, Lincoln, Nebraska, 68583, USA.
authors.forename: Glen O
authors.initials: GO
authors.lastname: Johnson
authors.affiliation: University of Nebraska-Lincoln, 211 Ruth Leverton Hall, Lincoln, Nebraska, 68583, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Schmidt
authors.affiliation: University of Nebraska-Lincoln, 211 Ruth Leverton Hall, Lincoln, Nebraska, 68583, USA.
authors.forename: Joel T
authors.initials: JT
authors.lastname: Cramer
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D004576:Electromyography; D006801:Humans; D007866:Leg / Q000294:innervation; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D055948:Sarcopenia / Q000175:diagnosis* / Q000503:physiopathology*; D019415:Torque; D055815:Young Adult
keywords: EMG; normalization; power-velocity; reliability; sarcopenia; torque-velocity