title: Impact of exercise selection on hamstring muscle activation.
abstract: OBJECTIVE
  To determine which strength training exercises selectively activate the biceps femoris long head (BFLongHead) muscle.
  
  
  METHODS
  We recruited 24 recreationally active men for this two-part observational study.Part 1: We explored the amplitudes and the ratios of lateral (BF) to medial hamstring (MH) normalised electromyography (nEMG) during the concentric and eccentric phases of 10 common strength training exercises. Part 2: We used functional MRI (fMRI) to determine the spatial patterns of hamstring activation during two exercises which (1) most selectively and (2) least selectively activated the BF in part 1.
  
  
  RESULTS
  Eccentrically, the largest BF/MH nEMG ratio occurred in the 45° hip-extension exercise; the lowest was in the Nordic hamstring (Nordic) and bent-knee bridge exercises. Concentrically, the highest BF/MH nEMG ratio occurred during the lunge and 45° hip extension; the lowest was during the leg curl and bent-knee bridge. fMRI revealed a greater BF(LongHead)to semitendinosus activation ratio in the 45° hip extension than the Nordic (p<0.001). The T2 increase after hip extension for BFLongHead, semitendinosus and semimembranosus muscles was greater than that for BFShortHead(p<0.001). During the Nordic, the T2 increase was greater for the semitendinosus than for the other hamstring muscles (p≤0.002).
  
  
  CONCLUSIONS
  We highlight the heterogeneity of hamstring activation patterns in different tasks. Hip-extension exercise selectively activates the long hamstrings, and the Nordic exercise preferentially recruits the semitendinosus. These findings have implications for strategies to prevent hamstring injury as well as potentially for clinicians targeting specific hamstring components for treatment (mechanotherapy).
authors.affiliation: Faculty of Health, School of Exercise and Nutrition Science, Queensland University of Technology, Brisbane, Australia.|Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.|Queensland Academy of Sport, Centre of Excellence for Applied Sport Science Research, Brisbane, Australia.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Bourne
authors.affiliation: Faculty of Life Sciences and Education, School of Health, Sport and Professional Practice, University of South Wales, Wales, UK.
authors.forename: Morgan D
authors.initials: MD
authors.lastname: Williams
authors.affiliation: School of Exercise Sciences, Australian Catholic University, Melbourne, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Opar
authors.affiliation: Centre for Advanced Imaging, University of Queensland, Brisbane, Australia.
authors.forename: Aiman
authors.initials: A
authors.lastname: Al Najjar
authors.affiliation: Faculty of Health, School of Exercise and Nutrition Science, Queensland University of Technology, Brisbane, Australia.|Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
authors.forename: Graham K
authors.initials: GK
authors.lastname: Kerr
authors.affiliation: Faculty of Health, School of Exercise and Nutrition Science, Queensland University of Technology, Brisbane, Australia.|Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Shield
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D000070633:Hamstring Muscles / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction; D008279:Magnetic Resonance Imaging; D008297:Male; D055070:Resistance Training / Q000379:methods*; D013848:Thigh; D055815:Young Adult
keywords: Exercise rehabilitation; Hamstrings; Injury prevention; MRI; Physiotherapy