Antagonist muscle torque at the ankle interfere with maximal voluntary contraction under isometric and anisometric...

While resultant maximal voluntary contraction (MVC) is commonly used to assess muscular performance, the simultaneous activation of antagonist muscles may dramatically underestimate the strength of the agonist muscles. Although quantification of antagonist torque has been performed in isometric conditions, it has yet to be determined in anisometric conditions. The aim of the study was to compare the mechanical impact of antagonist torque between eccentric, isometric and concentric contractions in PF and DF MVCs. The MVCs in dorsiflexion (DF) and plantar-flexion (PF) were measured in isometric, concentric and eccentric conditions (10° s^-1) in nine healthy men (26.1 ± 2.7 years; 1.78 ± 0.05 m; 73.4 ± 6.5 kg) through two sessions. Electromyographic (EMG) activities from the soleus, gastrocnemius medialis and lateralis, and tibialis anterior muscles were simultaneously recorded. The EMG biofeedback method was used to quantify antagonist torque. Resultant torque significantly underestimated agonist torque in DF MVC (30-65%) and to a lesser extent in PF MVC (3%). Triceps surae antagonist torque was significantly modified with muscle contraction type, showing higher antagonist torque in isometric (29 Nm) than in eccentric (23 Nm, p < 0.001) and concentric (14 Nm, p < 0.001) conditions and resulting in modification of the DF MVC torque-velocity shape. Estimation of the antagonist torque in isometric or anisometric conditions provides new relevant insights to improve neuromuscular performance assessment and to better design strength training and rehabilitation programs related to the torque applied by agonist and antagonist muscles.