title: Muscle fascicle behavior during eccentric cycling and its relation to muscle soreness.
abstract: A single bout of eccentric exercise confers a protective effect against muscle damage and soreness in subsequent eccentric exercise bouts, but the mechanisms underpinning this effect are unclear.
  
  
  OBJECTIVE
  This study compared vastus lateralis (VL) muscle-tendon behavior between two eccentric cycling bouts to test the hypothesis that muscle-tendon behavior would be different between bouts and would be associated with the protective effect.
  
  
  METHODS
  Eleven untrained men (27.1 ± 7.0 yr) performed two bouts of eccentric cycling (ECC1 and ECC2) separated by 2 wk for 10 min at 65% of maximal concentric workload (191.9 ± 44.2 W) each. Muscle soreness (by visual analog scale) and maximal voluntary isometric contraction (MVC) torque of the knee extensors were assessed before and 1-2 d after exercise. Using ultrasonography, VL fascicle length and angle changes during cycling were assessed, and tendinous tissue (TT) length changes were estimated. VL EMG amplitude, crank torque, and knee joint angles were measured during cycling.
  
  
  RESULTS
  Soreness was greater (P < 0.0001) after ECC1 than ECC2, although MVC changes were not different between bouts (P = 0.47). No significant differences in peak EMG amplitude (normalized to EMG during MVC), crank peak torque, or knee angles were evident between bouts. However, fascicle elongation was 16% less during ECC2 than ECC1 (P < 0.01), indicating less fascicle strain in ECC2. Maximum TT length occurred at a smaller knee joint angle during ECC2 than ECC1 (P = 0.055).
  
  
  CONCLUSIONS
  These results suggest that a lesser fascicle elongation and earlier TT elongation were associated with reduced muscle soreness after ECC2 than ECC1; thus, changes in muscle-tendon behavior may be an important mechanism underpinning the protective effect.
authors.affiliation: 1School of Exercise and Health Sciences, Centre for Exercise and Sports Science Research, Edith Cowan University, Joondalup, WA, AUSTRALIA; and 2Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, CHILE.
authors.forename: Luis
authors.initials: L
authors.lastname: Peñailillo
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Blazevich
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nosaka
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000000981:diagnostic imaging / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D063806:Myalgia / Q000503:physiopathology* / Q000517:prevention & control*; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging / Q000502:physiology*; D016059:Range of Motion, Articular; D013710:Tendons / Q000000981:diagnostic imaging / Q000502:physiology*; D013997:Time Factors; D019415:Torque; D014463:Ultrasonography; D055815:Young Adult