title: A biomechanical investigation of a single-limb squat: implications for lower extremity rehabilitation exercise.
abstract: BACKGROUND
  Single-limb squats on a decline angle have been suggested as a rehabilitative intervention to target the knee extensors. Investigators, however, have presented very little empirical research in which they have documented the biomechanics of these exercises or have determined the optimum angle of decline used.
  
  
  OBJECTIVE
  To determine the involvement of the gastrocnemius and rectus femoris muscles and the external ankle and knee joint moments at 60 degrees of knee flexion while performing a single-limb squat at different decline angles.
  
  
  METHODS
  Participants acted as their own controls in a repeated-measures design.
  
  
  METHODS
  We recruited 10 participants who had no pain, injury, or neurologic disorder.
  
  
  METHODS
  Participants performed single-limb squats at different decline angles.
  
  
  METHODS
  Angle-specific knee and ankle moments were calculated at 60 degrees of knee flexion. Angle-specific electromyography (EMG) activity was calculated at 60 degrees of knee flexion. Integrated EMG also was calculated to determine the level of muscle activity over the entire squat.
  
  
  RESULTS
  An increase was seen in the knee moments (P < .05) and integrated EMG in the rectus femoris (P < .001) as the decline angle increased. A decrease was seen in the ankle moments as the decline angle increased (P = .001), but EMG activity in the gastrocnemius increased between 16 degrees and 24 degrees (P = .018).
  
  
  CONCLUSIONS
  As the decline angle increased, the knee extensor moment and EMG activity increased. As the decline angle increased, the ankle plantar-flexor moments decreased; however, an increase in the EMG activity was seen with the 24 degrees decline angle compared with the 16 degrees decline angle. This indicates that decline squats at an angle greater than 16 degrees may not reduce passive calf tension, as was suggested previously, and may provide no mechanical advantage for the knee.
authors.affiliation: University of Central Lancashire, Preston, United Kingdom.
authors.forename: Jim
authors.initials: J
authors.lastname: Richards
authors.forename: Dominic
authors.initials: D
authors.lastname: Thewlis
authors.forename: James
authors.initials: J
authors.lastname: Selfe
authors.forename: Andrew
authors.initials: A
authors.lastname: Cunningham
authors.forename: Colin
authors.initials: C
authors.lastname: Hayes
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000503:physiopathology / Q000534:rehabilitation; D007719:Knee Joint / Q000502:physiology*; D007866:Leg / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology; D010865:Pilot Projects; D052097:Quadriceps Muscle / Q000502:physiology*; D016059:Range of Motion, Articular; D014891:Weight Lifting / Q000502:physiology*