title: Biceps femoris long head architecture: a reliability and retrospective injury study.
abstract: OBJECTIVE
  This study aimed (i) to determine the reliability of two-dimensional ultrasonography for the assessment of biceps femoris long head (BFlh) architectural characteristics and (ii) to determine whether limbs with a history of strain injury in the BFlh display different architecture and eccentric strength compared to uninjured limbs.
  
  
  METHODS
  This case-control study (control [n = 20], injured group [n = 16], males) assessed the BFlh architecture at rest and during graded isometric contractions using two-dimensional ultrasonography. The control group were assessed three times (>24 h apart) to determine reliability. Previously injured individuals were evaluated once.
  
  
  RESULTS
  The assessment of BFlh architecture was highly reliable (intraclass correlations >0.90). Fascicle length (P < 0.001; d range = 0.67-1.34) and fascicle length relative to muscle thickness (P < 0.001; d range = 0.58-0.85) of the previously injured BFlh were significantly less than the contralateral uninjured BFlh at all intensities. Pennation angle of the previously injured BFlh was significantly greater (P < 0.001; d range = 0.62-0.88) than the contralateral uninjured BFlh at all intensities. Eccentric strength in the previously injured limb was significantly lower than that in the contralateral limb (-15.4%; -52.5 N, 95% confidence interval = -76.2 to -28.4; P < 0.001, d = 0.56).
  
  
  CONCLUSIONS
  These data indicate that two-dimensional ultrasonography is reliable for assessing BFlh architecture at rest and during graded isometric contractions. Fascicle length, fascicle length relative to muscle thickness, and pennation angle are significantly different in previously injured BFlh compared to an uninjured contralateral BFlh. Eccentric strength of the previously injured limb is also significantly lower than that of the uninjured contralateral limb. These findings have implications for rehabilitation and injury prevention practices, which should consider altered architectural characteristics.
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; 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: Anthony J
authors.initials: AJ
authors.lastname: Shield
authors.forename: Morgan D
authors.initials: MD
authors.lastname: Williams
authors.forename: Christian
authors.initials: C
authors.lastname: Lorenzen
authors.forename: David A
authors.initials: DA
authors.lastname: Opar
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D006801:Humans; D007537:Isometric Contraction; D007717:Knee / Q000502:physiology; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology; D015203:Reproducibility of Results; D012146:Rest; D012189:Retrospective Studies; D013180:Sprains and Strains / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000503:physiopathology; D014463:Ultrasonography; D055815:Young Adult