Author(s): PAWLOWSKI, M., BRACHMAN, A., Institution: ACADEMY OF PHYSICAL EDUCATION IN KATOWICE, Country: POLAND, Abstract-ID: 2612

INTRODUCTION:
Prolonged isometric force production is required in many everyday and sport-specific movements that require stable interaction with external objects. A well-documented phenomenon observed in such tasks is unintentional force drift, defined as a gradual and unintended change in force output following the removal of visual feedback. Even when individuals are instructed to maintain a constant target force, force output typically decreases systematically over time in the absence of feedback information. Previous research has interpreted this effect within the framework of motor control, emphasizing the role of sensory integration and internal representations. However, it remains unclear whether the characteristics of force drift differ between upper and lower extremities and to what extent aging influences the ability to stabilize force when sensory feedback is limited or delayed. The aim of this study was to determine the magnitude and characteristics of unintentional force drift across different effectors and to examine potential age-related differences in the sustained isometric force production task.
METHODS:
Two groups of right-handed adults participated in a single laboratory session. Force signals were recorded using two independent force sensors while participants performed sustained isometric contractions with both the upper and lower extremities at 20% of maximal voluntary contraction. Visual feedback was either continuously available throughout the trial or provided only during the initial 10 seconds, after which it was removed. All procedures were completed within approximately 60 minutes.
RESULTS:
Following the removal of visual feedback, participants exhibited a slow and progressive decline in force output while consistently reporting that they were accurately maintaining the target force. Task stability decreased under no-feedback conditions, confirming the presence of systematic unintentional force drift. Preliminary analyses suggest that the magnitude and temporal characteristics of the drift may differ between upper and lower limbs and appear to be more pronounced in older adults.
CONCLUSION:
These findings enhance our understanding of effector-specific and age-related mechanisms of force stabilization during sustained isometric force production tasks. Identifying differences in force control strategies across the lifespan may contribute to optimizing sport performance and developing targeted interventions in sport training and rehabilitation contexts.