title: Development of a functional anatomical subtalar pronator and supinator strength training machine.
abstract: BACKGROUND
  The strength training industry has failed in designing a machine for exercising the pronators and supinators, despite their substantial medio-lateral bracing function.
  
  
  OBJECTIVE
  The present study documents the muscle strength generation capabilities of the pronators and supinators within their functional anatomic movement plane, using an innovative strength training machine with an oblique axis.
  
  
  METHODS
  By using two force transducers, the angle-torque relationship of the pronators and supinators of 18 healthy male subjects was identified during maximum voluntary isometric contractions at five anatomical joint angles. Surface EMG was recorded from anterior tibial (TA), peroneus longus (PL) and soleus (SOL) muscles.
  
  
  RESULTS
  The pronator strength curve showed an inverted U-shaped characteristic, whereas the supinator curve descends from pronated to supinated position. Compared to the muscle activities for one-leg heel raise and toe raise, PL (108-131%) and TA (59-83%), respectively, showed highest activity during pronations. The most activated supinator is SOL (67% of a one-leg heel raise).
  
  
  CONCLUSIONS
  Differences in the shape of the pronator and supinator strength curves revealed that two different variable cams have to be implemented for matching the human torque capability. We anticipate our study to be a starting point for preventive machine-based training interventions.
authors.affiliation: Biomechanics Laboratory, Department of Sport and Movement Sciences, University of Duisburg- Essen, Essen, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Hagen
authors.affiliation: Biomechanics Laboratory, Department of Sport and Movement Sciences, University of Duisburg- Essen, Essen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Lemke
authors.affiliation: Biomechanics Laboratory, Department of Sport and Movement Sciences, University of Duisburg- Essen, Essen, Germany.
authors.forename: Heinrich-Peter
authors.initials: HP
authors.lastname: Kutsch
authors.affiliation: Department of Orthopaedic Surgery, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Lahner
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007866:Leg / Q000502:physiology; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011403:Pronation / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*; D013484:Supination / Q000502:physiology*; D019415:Torque
keywords: Machine-based strength training; ankle stability; muscle activity; strength curves; subtalar joint