ECSS Paris 2023: CP-BM16
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.
Read CV AWF Katowice Michał PawłowskiECSS Paris 2023: CP-BM16
INTRODUCTION: Motor skill acquisition represents a fundamental lifelong capacity. However, it is well established that this process varies across individuals. Indeed, there is considerable variation in the speed of acquisition, the quality of performance, the resilience, and the generalization of learning across individuals [1]. Multiple studies have shown that customized training to individual’s performance promotes longer retention and stronger transfer [2]. Learning triggers brain reorganization to allow long term retention [3]. It is supposed that this restructuration is mediate by Beta-band activity, dominated by bursts (high amplitude transient activity) within the motor cortex, is closely linked to movement-related processing. Yet its transient burst dynamics during long-term learning remain poorly understood [4]. By combining electroencephalography (EEG), burst-resolved metrics, and a longitudinal design, this study aimed to clarify how beta activity reorganizes in M1 with practice to support motor skill learning under adaptative training. METHODS: The study included 32 participants (16 f; age = 21 ± 2.46 years). The protocol lasted 13 sessions over 8 weeks, and EEGs were realized in session 2, 3, 9 to assess change in brain activity linked to practice. Participants completed a visuomotor training task and were either in an adaptive difficulty (AG) or non-adaptive training group (NAG). To increase EEG analysis precision, EEG-MRI co-registration and a neuronavigation system were used. A source level analysis was done to restrict beta bursts detection to M1. Session-related changes in transient beta activity were examined in individualized primary motor cortex (M1) regions during motor training. Source signals were filtered around peak beta frequency and bursts were detected using an optimized, data-driven threshold. Burst probability, post-movement timing variability, and amplitude were quantified across task phases. RESULTS: Both training conditions led to motor skill learning. AG showed significantly greater gains during training but a significant decline in retention performance. These changes reflected underlying burst dynamics: post movement bursts became more temporally confined and consistent, with increased probability and reduced timing variability across sessions for both groups. However, only the AG showed a session-related increase of amplitude. CONCLUSION: These results demonstrate that beta burst features reorganize with practice, providing a temporally precise neural readout of training progression and revealing how different learning conditions can shape cortical dynamics over time. AG burst amplitude increases can be due to more synchronized synaptic input in M1 and might be refinement of internal models.
Read CV Diarra KaneECSS Paris 2023: CP-BM16