title: Effectiveness of hamstring knee rehabilitation exercise performed in training machine vs. elastic resistance: electromyography evaluation study.
abstract: OBJECTIVE
  The aim of this study was to evaluate muscle activity during hamstring rehabilitation exercises performed in training machine compared with elastic resistance.
  
  
  METHODS
  Six women and 13 men aged 28-67 yrs participated in a crossover study. Electromyographic (EMG) activity was recorded in the biceps femoris and the semitendinosus during the concentric and the eccentric phase of hamstring curls performed with TheraBand elastic tubing and Technogym training machines and normalized to maximal voluntary isometric contraction-EMG (normalized EMG). Knee joint angle was measured using electronic inclinometers.
  
  
  RESULTS
  Training machines and elastic resistance showed similar high levels of muscle activity (biceps femoris and semitendinosus peak normalized EMG >80%). EMG during the concentric phase was higher than during the eccentric phase regardless of exercise and muscle. However, compared with machine exercise, slightly lower (P < 0.05) normalized EMG values were observed using elastic resistance at 30- to 50-degree knee joint angle for the semitendinosus and the biceps femoris during the concentric and the eccentric phase, respectively. Perceived loading (Borg CR10) was significantly higher (P < 0.001) during hamstring curl performed with elastic resistance (7.58 ± 0.08) compared with hamstring curl performed in a machine (5.92 ± 0.03).
  
  
  CONCLUSIONS
  Hamstring rehabilitation exercise performed with elastic resistance induces similar peak hamstring muscle activity but slightly lower EMG values at more extended knee angles and with higher perceived loading as hamstring curls using training machines.
authors.affiliation: From the National Research Centre for the Working Environment, Copenhagen, Denmark (MDJ, ES, CHA, LLA); Department of Psychology, Lund University, Lund, Sweden (RP); Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark (MDJ, ES); and Arthroscopic Centre Amager and Gait Analysis Laboratory, Copenhagen University Hospital, Hvidovre, Denmark (MKZ).
authors.forename: Markus Due
authors.initials: MD
authors.lastname: Jakobsen
authors.forename: Emil
authors.initials: E
authors.lastname: Sundstrup
authors.forename: Christoffer H
authors.initials: CH
authors.lastname: Andersen
authors.forename: Roger
authors.initials: R
authors.lastname: Persson
authors.forename: Mette K
authors.initials: MK
authors.lastname: Zebis
authors.forename: Lars L
authors.initials: LL
authors.lastname: Andersen
mesh_terms: D000328:Adult; D000368:Aged; D018592:Cross-Over Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007718:Knee Injuries / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D055070:Resistance Training / Q000295:instrumentation / Q000379:methods*