Bilateral handgrip deficit is modulated by testing sessions in strength-trained subjects

Background: Although the bilateral deficit (BLD) is a well-documented neuromuscular phenomenon, most studies rely on single-session assessments or strength training interventions, limiting insights into motor learning and task familiarization effects. Objectives: This study aimed to examine the presence of BLD during handgrip contractions across multiple sessions and to assess differences in maximal strength between the dominant and non-dominant hand in unilateral and bilateral conditions, as well as potential sex-related differences. Methods: Thirty-seven resistance-trained participants (19 males, 18 females) performed unilateral and bilateral maximal isometric voluntary contractions (MIVCs) during a handgrip on two separate days. Results: BLD was present in the first session but absent in the second. Sex and handedness dominance did not affect this deficit, but the specific practice of the assessed task did. Conclusions: Our findings indicate that simply performing the grip BLD test significantly modulates bilateral force production. Our findings suggest the need to practice the task being assessed to objectively measure this deficit. This could be relevant from a methodological perspective in the study of this phenomenon.