title: Eccentric exercise-induced muscle damage of pre-adolescent and adolescent boys in comparison to young men.
abstract: OBJECTIVE
  This study compared changes in indirect muscle damage markers after maximal eccentric exercise of the elbow flexors (EF) among pre-adolescent (9-10 years), adolescent (14-15 years) and post-adolescent (20-25 years) men to test the hypothesis that the magnitude of muscle damage would increase with increase in age.
  
  
  METHODS
  Thirteen untrained men of each age group performed two bouts (ECC1, ECC2) of 30 maximal EF eccentric contractions. Several indirect muscle damage markers were measured from the exercised arm before, immediately after, and 1-5 days post-exercise. Changes in maximal voluntary concentric contraction torque of the EF (MVC), range of motion of the elbow joint, upper arm circumference (CIR), muscle passive stiffness, muscle soreness, plasma creatine kinase activity and myoglobin concentration after ECC1 and ECC2 were compared amongst groups by a mixed-design two-way ANOVA.
  
  
  RESULTS
  MVC before exercise was smaller (P < 0.05) for pre-adolescent (8.9 ± 1.9 Nm) than adolescent (25.1 ± 3.9 Nm) and adult (35.3 ± 4.6 Nm), and for adolescent than adult. Changes in all variables after ECC1 were smaller (P < 0.05) for pre-adolescent and adolescent when compared with adult, and all except CIR changes were smaller (P < 0.05) for pre-adolescent than adolescent. After ECC2, changes in all variables were smaller (P < 0.05) than those after ECC1 for all groups, but the magnitude of the changes was different among groups (P < 0.05) in the same way as that after ECC1.
  
  
  CONCLUSIONS
  These results indicate that the magnitude of muscle damage is increased from pre-adolescent, adolescent to post-adolescent men.
authors.affiliation: Department of Physical Education, National Taiwan Normal University, P.O. Box 97-71, Taipei City, Taipei, 11699, Taiwan, tcchen@ntnu.edu.tw.
authors.forename: Trevor C
authors.initials: TC
authors.lastname: Chen
authors.forename: Hsin-Lian
authors.initials: HL
authors.lastname: Chen
authors.forename: Yi-Chuen
authors.initials: YC
authors.lastname: Liu
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nosaka
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D016022:Case-Control Studies; D002648:Child; D006803:Human Development / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000254:growth & development / Q000502:physiology* / Q000503:physiopathology; D063806:Myalgia / Q000503:physiopathology*; D055070:Resistance Training