title: Differences in post-exercise T2 relaxation time changes between eccentric and concentric contractions of the elbow flexors.
abstract: OBJECTIVE
  This study compared maximal eccentric (ECC) and concentric (CON) contractions of the elbow flexors for changes in transverse relaxation time (T2) and indirect markers of muscle damage.
  
  
  METHODS
  Twelve young men performed five sets of six maximal isokinetic (30°/s) ECC with one arm followed by CON with the other arm. Magnetic resonance images to assess T2 and cross-sectional area (CSA) of biceps brachii, brachialis, and brachioradialis, and measurements of maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), and muscle soreness were taken before, immediately after, and 1, 3, and 5 days after each exercise.
  
  
  RESULTS
  MVC torque and ROM decreased greater after ECC than CON (p < 0.05), and muscle soreness developed only after ECC. Biceps brachii and brachialis CSA increased immediately after CON, but delayed increases in brachialis CSA were found only after ECC (p < 0.05). T2 of the muscles increased greater after CON (27-34 %) than ECC (16-18 %) immediately post-exercise (p < 0.05), but returned to baseline by 1 day after CON. The biceps brachii and brachialis T2 increased by 9-29 % at 1-5 days after ECC (p < 0.05). The post-ECC T2 changes showed no significant correlations with the changes in MVC torque, muscle soreness, and CSA, but the T2 increase immediately post-ECC was correlated with the peak T2 in 1-5-day post-ECC (r = 0.63, p < 0.05).
  
  
  CONCLUSIONS
  These results suggest that muscle activity during exercise was lower in ECC than CON, and the T2 changes after ECC do not necessarily relate to the changes in other indirect markers of muscle damage.
authors.affiliation: Faculty of Bioscience and Applied Chemistry, Hosei University, 3-7-2, Kajino, Koganei, Tokyo, 184-8584, Japan. ochi@hosei.ac.jp.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Ochi
authors.affiliation: Faculty of Modern and Life, Teikyo Heisei University, 4-21-2, Nakano, Tokyo, 164-8530, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Tsuchiya
authors.affiliation: Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA, 6027, Australia.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nosaka
mesh_terms: D000328:Adult; D004550:Elbow / Q000502:physiology; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D063806:Myalgia / Q000503:physiopathology*; D010807:Physical Endurance / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology*
keywords: Cross-sectional area; Delayed onset muscle soreness; Magnetic resonance imaging; Muscle damage; Muscle function; Transverse relaxation time