title: Muscle and intensity based hamstring exercise classification in elite female track and field athletes: implications for exercise selection during rehabilitation.
abstract: BACKGROUND
  Hamstring injuries are common in many sports, including track and field. Strains occur in different parts of the hamstring muscle but very little is known about whether common hamstring loading exercises specifically load different hamstring components. The purpose of this study was to investigate muscle activation of different components of the hamstring muscle during common hamstring loading exercises.
  
  
  METHODS
  Twenty elite female track and field athletes were recruited into this study, which had a single-sample, repeated-measures design. Each athlete performed ten hamstring loading exercises, and an electromyogram (EMG) was recorded from the biceps femoris and semitendinosus components of the hamstring. Hamstring EMG during maximal voluntary isometric contraction (MVIC) was used to normalize the mean data across ten repetitions of each exercise. An electrogoniometer synchronized to the EMG was used to determine whether peak EMG activity occurred during muscle-tendon unit lengthening, shortening, or no change in length. Mean EMG values were compared between the two recording sites for each exercise using the Student's t-test.
  
  
  RESULTS
  The lunge, dead lift, and kettle swings were low intensity (<50% MVIC) and all showed higher EMG activity for semitendinosus than for biceps femoris. Bridge was low but approaching medium intensity, and the TRX, hamstring bridge, and hamstring curl were all medium intensity exercises (≥50% or <80% MVIC). The Nordic, fitball, and slide leg exercises were all high intensity exercises. Only the fitball exercise showed higher EMG activity in the biceps femoris compared with the semitendinosus. Only lunge and kettle swings showed peak EMG in the muscle-tendon unit lengthening phase and both these exercises involved faster speed.
  
  
  CONCLUSIONS
  Some exercises selectively activated the lateral and medial distal hamstrings. Low, medium, and high intensity exercises were demonstrated. This information enables the clinician, strength and conditioning coach and physiotherapist to better understand intensity- and muscle-specific activation during hamstring muscle rehabilitation. Therefore, these results may help in designing progressive strengthening and rehabilitation and prevention programs.
authors.affiliation: Department of Physiotherapy, Laboratory of Biomechanics and Ergonomics, Alexander Technological Educational Institute of Thessaloniki, Thessaloniki, Greece ; Department of Mechanical Engineering, Bioengineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Tsaklis
authors.affiliation: National Track and Field Centre, Sports Injury Clinic, Sports Medicine Clinic of SEGAS, Greece ; Thessaloniki Sports Medicine Clinic, Thessaloniki, Greece ; Rheumatology Department, Sports Medicine Clinic, Mile End Hospital, London, UK ; Centre for Sports and Exercise Medicine, Queen Mary, University of London, London, UK.
authors.forename: Nikos
authors.initials: N
authors.lastname: Malliaropoulos
authors.affiliation: Department of Physical Therapy, Zentrum Rehabilitation and Performance Center, Pamplona, Spain.
authors.forename: Jurdan
authors.initials: J
authors.lastname: Mendiguchia
authors.affiliation: Aspetar, Orthopaedic and Sports Medicine Hospital, Doha, Qatar ; Faculty of Physical Education and Sport Science, University of Thessaly, Trikala, Greece ; Hellenic Orthopaedic Manipulative Therapy Diploma, Athens, Greece.
authors.forename: Vasileios
authors.initials: V
authors.lastname: Korakakis
authors.affiliation: K Tsapralis Isokinetic Medical Group, Bologna, Italy.
authors.forename: Kyriakos
authors.initials: K
authors.lastname: Tsapralis
authors.affiliation: Rheumatology Department, Sports Medicine Clinic, Mile End Hospital, London, UK.
authors.forename: Debasish
authors.initials: D
authors.lastname: Pyne
authors.affiliation: Centre for Sports and Exercise Medicine, Queen Mary, University of London, London, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Malliaras
keywords: exercise; hamstring injuries; rehabilitation