title: Influence of age on isometric, isotonic, and isokinetic force production characteristics in men.
abstract: OBJECTIVE
  Most previous studies have focused on the effects of age on muscle performance of a single type of contraction, usually isometric, and usually on only a single muscle group. Instead,we investigated the influence of age on isometric, isotonic, and isokinetic muscle performance in men aged 20-83 years and determined relationships between regional lean body mass and muscle performance.
  
  
  METHODS
  Seventy-five volunteers were placed into designated 10-year age groups: 20-29 (n=13), 30-39 (n=14), 40-49 (n=15), 50-59 (n=10), 60-69 (n=14), and 70+ years (n=9). Muscle performance was characterized by a number of parameters, including strength, time, and rate for maximal voluntary contractions using all 3 contraction types and 4 muscle groups (elbow extensors, elbow flexors, knee extensors, and knee flexors). Measures of lean body mass were obtained by dual energy x-ray absorptiometry.
  
  
  RESULTS
  There were significant age group differences in maximal force (P < or = 0.05) for each type of muscle contraction, and in maximal rates of isometric force production (P < or = 0.05), with declines beginning around 60 years of age. Differences in muscle performance between age groups remained when body composition differences were controlled statistically.
  
  
  CONCLUSIONS
  Chronological age affected performance of both upper and lower extremity muscles, independent of muscle mass, and regardless of contraction type; however, isometric performance was the least affected.
authors.affiliation: Neuromuscular Research Laboratory, Department of Health and Exercise Science, University of Oklahoma, Norman Campus,Norman, OK 73019, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Runnels
authors.forename: Debra A
authors.initials: DA
authors.lastname: Bemben
authors.forename: Mark A
authors.initials: MA
authors.lastname: Anderson
authors.forename: Michael G
authors.initials: MG
authors.lastname: Bemben
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007551:Isotonic Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*