title: Bilateral Strength Deficit Is Not Neural in Origin; Rather Due to Dynamometer Mechanical Configuration.
abstract: During maximal contractions, the sum of forces exerted by homonymous muscles unilaterally is typically higher than the sum of forces exerted by the same muscles bilaterally. However, the underlying mechanism(s) of this phenomenon, which is known as the bilateral strength deficit, remain equivocal. One potential factor that has received minimal attention is the contribution of body adjustments to bilateral and unilateral force production. The purpose of this study was to evaluate the plantar-flexors in an innovative dynamometer that permitted the influence of torque from body adjustments to be adapted. Participants were identically positioned between two setup configurations where torques generated from body adjustments were included within the net ankle torque (locked-unit) or independent of the ankle (open-unit). Twenty healthy adult males performed unilateral and bilateral maximal voluntary isometric plantar-flexion contractions using the dynamometer in the open and locked-unit mechanical configurations. While there was a significant bilateral strength deficit in the locked-unit (p = 0.01), it was not evident in the open-unit (p = 0.07). In the locked-unit, unilateral torque was greater than in the open-unit (p<0.001) and this was due to an additional torque from the body since the electromyographic activity of the agonist muscles did not differ between the two setups (p>0.05). This study revealed that the mechanical configuration of the dynamometer and then the body adjustments caused the observation of a bilateral strength deficit.
authors.affiliation: Laboratoire d'Automatique, de Mécanique et d'Informatique industrielles et Humaines (LAMIH)-UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis (UVHC), Valenciennes, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Simoneau-Buessinger
authors.affiliation: Laboratoire d'Automatique, de Mécanique et d'Informatique industrielles et Humaines (LAMIH)-UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis (UVHC), Valenciennes, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Leteneur
authors.affiliation: Laboratoire d'Automatique, de Mécanique et d'Informatique industrielles et Humaines (LAMIH)-UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis (UVHC), Valenciennes, France.
authors.forename: Anis
authors.initials: A
authors.lastname: Toumi
authors.affiliation: Laboratoire de l'Effort et du Mouvement, Haute Ecole Provinciale de Hainaut (HEPH)-Condorcet, Tournai, Belgium.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Dessurne
authors.affiliation: Laboratoire d'Automatique, de Mécanique et d'Informatique industrielles et Humaines (LAMIH)-UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis (UVHC), Valenciennes, France.
authors.forename: François
authors.initials: F
authors.lastname: Gabrielli
authors.affiliation: Laboratoire d'Automatique, de Mécanique et d'Informatique industrielles et Humaines (LAMIH)-UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis (UVHC), Valenciennes, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Barbier
authors.affiliation: School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, Canada.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Jakobi
mesh_terms: D000328:Adult; D000842:Ankle / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque; D055815:Young Adult