Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

When Antagonist Muscles at the Ankle Interfere with Maximal Voluntary Contraction under Isometric and Anisometric Conditions

Version 1 : Received: 2 December 2021 / Approved: 6 December 2021 / Online: 6 December 2021 (19:29:42 CET)

How to cite: Billot, M.; Duclay, J.; Rigoard, P.; David, R.; Martin, A. When Antagonist Muscles at the Ankle Interfere with Maximal Voluntary Contraction under Isometric and Anisometric Conditions. Preprints 2021, 2021120095 (doi: 10.20944/preprints202112.0095.v1). Billot, M.; Duclay, J.; Rigoard, P.; David, R.; Martin, A. When Antagonist Muscles at the Ankle Interfere with Maximal Voluntary Contraction under Isometric and Anisometric Conditions. Preprints 2021, 2021120095 (doi: 10.20944/preprints202112.0095.v1).

Abstract

Purpose: While resultant maximal voluntary contraction (MVC) is commonly used to assess muscular performance, the simultaneous activation of antagonist muscles could dramatically underestimate the strength of the agonist muscles. While quantification of antagonist torque has been performed in plantar- (PF) and dorsi-flexion (DF) joint in isometric conditions, it has yet to be determined in anisometric (concentric and eccentric) conditions. Methods: The experiment was performed in 9 participants through 2 sessions (reliability). The MVCs in DF and PF were measured in isometric, concentric and eccentric conditions (10°.s-1). 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, where participants were asked to maintain a level of EMG activity, corresponding to antagonist EMG activity and related to the muscle contraction type, according to a visual EMG bio-feedback displayed on a screen. Results: 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 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. The difference between DF eccentric and concentric MVC was attenuated when considered agonist torque (12%) rather than resultant torque (45%). Conclusion: Estimation of the antagonist torque in isometric or anisometric condition brings new insights to assessment of muscular performance and could result in costly misinterpretation in strength training and/or rehabilitation programs.

Keywords

coactivation; agonist; strength; muscular performance; dynamic contraction; eccentric; concentric.

Subject

MEDICINE & PHARMACOLOGY, Sport Sciences & Therapy

Comments (1)

Comment 1
Received: 13 December 2021
Commenter: Daniel Hahn
The commenter has declared there is no conflict of interests.
Comment: Unfortunately, in their manuscript, the authors completely miss the problem of crosstalk when trying to assess co-contraction from EMG measures. Recently, it has been shown by EMG and ultrasound measures that antagonostic co-contraction is negligible during isometric plantar flexion and dorsiflexion despite the presence of antagonist electromyographic activity (Raiteri et al. 2015; https://doi.org/10.1152/japplphysiol.00825.2014). Accorindgly, the authors' data is potentially misleading and their conclusion does not hold true.

On another note, in the discussion, the authors state that in situ studies have reported slight increases or no change in eccentric compared with isometric MVC only. However, this is at least incomplete as similar to in vitro studies, eccentric forces / torques of up to 1.5-1.8 times that of maximal voluntary isometric contractions have been reported (Hahn 2018; https://doi.org/10.1016/j.jshs.2018.05.003).
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