The detrimental impact of concurrent grasp execution on anticipatory grasp planning is sex-dependent.

Fast and efficient planning of manual actions is essential for everyday activities. In this study, we investigated an object-grasping judgment task assessing participants' ability to anticipate an appropriate grasp that ensures an optimal final hand posture (end-state comfort effect). While the detrimental effects of concurrent cognitive tasks on action planning are well documented, the impact of concurrent motor tasks remains unclear, particularly when it shares common action representations with grasp planning. Additionally, despite substantial evidence for sex differences in cognitive and motor skills, their impact on anticipatory grasp planning has received limited attention. To fill these gaps, we compared right-handed male (n = 32) and female (n = 32) participants under either a static condition, in which the hands were immobile, or a dynamic condition, in which participants performed rhythmic grasping with the right hand while simultaneously performing the right-hand object-grasping judgment task. Results revealed that object-grasping judgment was impaired in the dynamic condition compared to the static condition, as reflected by reduced accuracy and increased response times. While the decrease in accuracy was similar in males and females, a sex differential effect was observed in RTs. Notably, while female RTs increased under the dynamic condition, this increase was not observed in males. Taken together, these results indicate that concurrent grasp execution is associated with poorer performance in object-grasping judgments. This effect may reflect competition between anticipatory grasp planning and ongoing grasp execution for overlapping action representations, although more general dual-task costs, attentional demands, or response-related interference cannot be excluded.