ECSS Paris 2023: CP-BM11
INTRODUCTION: Healthy individuals perform motor sequencing tasks more effectively with their right hand. However, aging and task complexity appear to influence this behaviour through various, sometimes conflicting, neurological mechanisms. The primary objective of the study is to investigate how hemispheric lateralization of neural activity changes with aging and task complexity. METHODS: Fifteen younger (age = 22.8 ± 2.5 years, 7 females) and fifteen older (age = 59.5 ± 4.0 years, 6 females) participants performed finger key presses on a numeric keypad with each hand across four levels of sequence complexity, in a randomized order. Accuracy, reaction time (RT), motor execution time (MT), and subjective workload, as measured by NASA-TLX, were evaluated. RESULTS: Statistical analysis revealed that older participants were less accurate than younger participants only on the most complex task (p < 0.001, d = 5.31). In addition, older participants reacted significantly more slowly than younger participants only on the most complex tasks (level 4: p < 0.001, d = -1.57), and their MT was slower at level 3 (p = 0.001, d = -4.13) and level 4 (p < 0.001, d = -8.56). Lastly, the subjective workload associated with RT and MT was observed only among older participants at levels 2 and 4, suggesting that most participants’ subjective ratings of task difficulty did not align with the intentionally designed sequence complexity. CONCLUSION: Our findings indicate consistent right-hand superiority in motor sequencing, supporting the theory of left-hemisphere specialization across age groups and task difficulty. However, this lateralization does not reduce age-related declines, which are disproportionately evident during high-complexity tasks. The strong association between subjective workload and performance, observed only in older adults, suggests that aging necessitates a shift toward more cognitively demanding, conscious monitoring strategies to maintain motor output. Our ongoing study aims to determine the underlying neuronal mechanisms of these age- and complexity-dependent processes.
Read CV Kinga EnyediECSS Paris 2023: CP-BM11
INTRODUCTION: Leg attacks are fundamental offensive techniques in wrestling, characterized by high-speed, aperiodic movement. Traditional analyses rely on subjective phase segmentation and isolated kinematics, failing to capture temporal structure and inter-limb coordination underlying skilled performance. From an ecological dynamics perspective, skilled movement emerges through functional coupling of body segments into synergies [1]. However, objective methods to quantify phase structure and coordination in combat sports remain limited [2]. This study aimed to: (1) establish data-driven phase segmentation using Hidden Markov Models (HMM) [3]; (2) extract coordination patterns using Non-negative Matrix Factorization (NMF) [4] ; and (3) compare differences between elite and sub-elite wrestlers. METHODS: Forty-six female freestyle wrestlers (24 elite, 22 sub-elite) were paired within skill levels and performed single-leg and double-leg takedowns (5 trials each) under partner-present cooperative contexts. Full-body kinematics were captured using inertial motion capture (Xsens Link, 240 Hz). A 5-state Gaussian HMM was fitted for each task using 14 kinematic features [5]. Within each state, NMF (k = 8) extracted coordination patterns from segment angular velocities [4]. Activation time-series were parameterized by onset, duration, amplitude, and CV. Group comparisons used Welch’s t-tests. RESULTS: HMM segmented both tasks into five phases: Preparation-Dive-Grab-Lift-Control. Elite wrestlers showed higher CoM height during Grab (0.57 ± 0.05 vs 0.53 ± 0.04 m, p<0.001) , greater L5S1 flexion (12.8 ± 3.2 vs 8.1 ± 2.9deg, p<0.001), and stronger head rotation toward attack side (-9.4 ± 4.1 vs -0.3 ± 5.2deg, p<0.001). NMF revealed proximal-to-distal coordination with components for propulsion, trunk control, and grasping. Elite wrestlers showed: (1) higher activation amplitude (20-90% greater, p<0.001); (2) earlier onset timing (35-50% reduction); (3) longer Grab duration (0.92 ± 0.08 vs 0.82 ± 0.1, p<0.001); and (4) a “stable core-flexible periphery” CV pattern. CONCLUSION: The HMM-NMF framework provides an objective approach to characterize temporal structure and coordination in non-periodic combat techniques. Elite wrestlers exhibit distinctive motor signatures: earlier anticipatory head orientation, greater activation amplitude, compressed sequences, and differentiated stability-flexibility organization. These findings extend coordination research to partner-present cooperative contexts [2] and offer indicators for talent identification.
Read CV Naidan XuECSS Paris 2023: CP-BM11
INTRODUCTION: Movement complexity in climbing is often quantified using global trajectory entropy, but global measures cannot distinguish whether learning reduces complexity uniformly or redistributes it into specific transitions. Moving-window entropy profiling was utilised along with Dynamic Time Warping (DTW) to test whether practice reduces local complexity and whether whole-attempt movement patterns converge despite differences in execution time. METHODS: An experienced male climber (height: 1.80m, wingspan 1.90m) completed five attempts on two bouldering problems (easy and hard). Hip trajectories were analysed in frontal (XY), transverse (XZ), and sagittal (YZ) planes, where the Z axis corresponded to the wall-normal (depth) direction. In each plane, local entropy was calculated in sliding windows to illustrate how movement complexity changed over time within each attempt. To compare attempts while allowing for different speeds, DTW was applied to (i) 2D hip trajectories in each plane, and (ii) the time-series of windowed entropy in each plane. DTW produced pairwise similarity scores and an alignment path, with further analysis on the shift in distribution of complexity and concentration of complexity within the trajectory to draw conclusions. RESULTS: In the easy route, entropy DTW distances were generally smaller and showed earlier consistency, especially in YZ (Attempt pair 2–5 = 0.025, 63.7% decrease from Attempt pair 1-5). Entropy patterns for the hard route became more consistent across later attempts in the XY (Attempt 4-5 = 0.045, 59.1% decrease) and YZ (Attempt 4-5 = 0.042, 57.1% decrease) planes, but XZ remained less stable (Attempt 4-5 = 0.077, 2.29% decrease), suggesting ongoing re-organisation of transverse-plane control. Trajectory DTW distances showed a stark difference, with high initial distances for the easy route (Attempt 1-5 = 1.93) that dropped from the second attempt onwards (Attempt 2-5 = 0.21, 89.1% decrease), while the hard route saw closer consistency (Attempt 1-5 to Attempt 4-5 = 0.39 to 0.18, 53.9% decrease). For entropy concentration, only the XZ plane (hard route) decreased consistently across attempts (Gini: 0.35 to 0.26), indicating smoothing of movement complexity distribution. CONCLUSION: Local entropy and DTW describe different aspects of learning in climbing. Entropy profiles show how complexity is distributed over time within each attempt, while DTW shows how similar attempts are without speed differences and amount of time-warping needed. Across practice, the climber showed clearer stabilisation in some planes (XY and YZ), while the hard route showed continued changes in out-of-plane behaviour (XZ). Trajectory DTW on the easy route also highlighted how rapid reorganisations cause a step-drop in DTW distance. Overall, this combined approach can potentially identify which parts of a movement become stable with practice, offering a practical way to pinpoint how and where reorganisation occurs during complex whole-body skill learning.
Read CV Chen LimECSS Paris 2023: CP-BM11