title: Architectural Changes of the Biceps Femoris Long Head after Concentric or Eccentric Training.
abstract: OBJECTIVE
  To determine the architectural adaptations of the biceps femoris long head (BFlh) after concentric or eccentric strength training interventions and the time course of adaptation during training and detraining.
  
  
  METHODS
  Participants in this intervention (concentric training group [n = 14], eccentric training group [n = 14], male subjects) completed a 4-wk control period, followed by 6 wk of either concentric- or eccentric-only knee flexor training on an isokinetic dynamometer and finished with 28 d of detraining. Architectural characteristics of BFlh were assessed at rest and during graded isometric contractions using two-dimensional ultrasonography at 28 d prebaseline; baseline; and days 14, 21, and 42 of the intervention and then again after 28 d of detraining.
  
  
  RESULTS
  BFlh fascicle length was significantly longer in the eccentric training group (P < 0.05; d range, 2.65-2.98) and shorter in the concentric training group (P < 0.05; d range, -1.62 to -0.96) after 42 d of training compared with baseline at all isometric contraction intensities. After the 28-d detraining period, BFlh fascicle length was significantly reduced in the eccentric training group at all contraction intensities compared with the end of the intervention (P < 0.05; d range, -1.73 to -1.55). There was no significant change in fascicle length of the concentric training group after the detraining period.
  
  
  CONCLUSIONS
  These results provide evidence that short-term resistance training can lead to architectural alterations in the BFlh. In addition, the eccentric training-induced lengthening of BFlh fascicle length was reversed and returned to baseline values after 28 d of detraining. The contraction mode specific adaptations in this study may have implications for injury prevention and rehabilitation.
authors.affiliation: 1School of Exercise Science, Australian Catholic University, Melbourne, AUSTRALIA; 2School of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, AUSTRALIA; and 3School of Health, Sport and Professional Practice, University of South Wales, Pontypridd, Wales, UNITED KINGDOM.
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Timmins
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Ruddy
authors.forename: Joel
authors.initials: J
authors.lastname: Presland
authors.forename: Nirav
authors.initials: N
authors.lastname: Maniar
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Shield
authors.forename: Morgan D
authors.initials: MD
authors.lastname: Williams
authors.forename: David A
authors.initials: DA
authors.lastname: Opar
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000070633:Hamstring Muscles / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D007537:Isometric Contraction; D007717:Knee; D008297:Male; D053580:Muscle Strength; D055070:Resistance Training; D014463:Ultrasonography; D055815:Young Adult