Affiliations: [a] Biomechanics Laboratory, Department of Sport and Movement Sciences, University of Duisburg- Essen, Essen, Germany | [b] Department of Orthopaedic Surgery, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany
Correspondence:
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Corresponding author: Marco Hagen, Biomechanics Laboratory, Institute of Sport and Movement Sciences, University of Duisburg-Essen, Gladbecker Str. 182, 45141 Essen, Germany. Tel.: +49 201 183 7386; Fax: +49 201 183 7309; E-mail:marco.hagen@uni-due.de
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.
