ECSS Paris 2023: OP-BM22
INTRODUCTION: Random practice, often associated with contextual interference, is known to transiently impair performance during acquisition while enhancing long-term learning [1]. However, its acute effects on neuromuscular fatigue, motor control, and subjective experience remain poorly documented, particularly when compared with intermediate practice structures such as serial organization. This study investigated the immediate effects of constant, serial, and random practice of an isometric force reproduction task on force accuracy, neuromuscular fatigue, and perceptual responses. METHODS: Fifteen physically active men (Age: 24.1 ± 4.3 years) completed three experimental sessions in a randomized crossover design. Each session involved pre-tests, a 15-min practice phase, immediate post-tests, and post-tests after 30 min. Participants performed isometric knee extensions to match different force targets under constant (CON: steady force level), serial (SER: steadily increasing force level), or random (RAN: randomized force levels) practice. Force error during the precision task, maximal voluntary isometric contraction (MViC), surface EMG activity of knee extensors and flexors, Force/EMG ratio, and coactivation were assessed pre, post and post 30min. Subjective responses were evaluated using visual analog scales and the NASA-TLX questionnaire. RESULTS: During practice, force error was higher in RAN than in CON and SER but decreased over time only in RAN. Force accuracy improved from pre- to post-tests in all conditions, with no between-condition differences in retention tests. MViC decreased similarly across conditions (-5,2 ± 8,7%, p=0.002), indicating comparable neuromuscular fatigue. No significant changes were observed in Force/EMG ratio or muscle coactivation. Task enjoyment was significantly higher in RAN compared with CON and SER, while perceived workload did not differ. CONCLUSION: Contrary to some previous studies [2,3], random practice did not improve motor accuracy compared to serial or constant practice after a single session. However, it led to greater enjoyment without inducing additional neuromuscular fatigue. These findings suggest that random practice may enhance motivation or engagement during training, even when immediate motor control benefits are not evident. Future studies should further explore its long-term effects and optimize task difficulty for maximal learning outcomes. REFERENCES: [1] Shea, C. H., & Kohl, R. M. (1990). Specificity and Variability of Practice. Research Quarterly for Exercise and Sport, 61(2), 169–177. [2] Thürer, B., Stockinger, C., Putze, F., Schultz, T., & Stein, T. (2017). Mechanisms within the Parietal Cortex Correlate with the Benefits of Random Practice in Motor Adaptation. Frontiers in Human Neuroscience, 11, 403. [3] Herzog, M., Focke, A., Maurus, P., Thürer, B., & Stein, T. (2022). Random Practice Enhances Retention and Spatial Transfer in Force Field Adaptation. Frontiers in Human Neuroscience, 16, 816197.
Read CV Sylvain DHOTEECSS Paris 2023: OP-BM22
INTRODUCTION: Evidence from a Bayesian meta-analysis1 highlighted potential methodological biases within longstanding psychological research, thus challenging the widely accepted understanding of superior external focus of attention (EF) effects on motor performance. A subsequent systematic review2 revealed limitations in research on EF effects on lower-limb strength in athletes and the quality of associated findings. Addressing these concerns, Pompa et al.’s3 exploratory study showed that focusing on idiosyncratic core action components (ICC) may be more effective than both generally task-relevant EF and internal focus (IF) strategies during explosive isometric back squat performance, whereas no differences were observed for squat jump performance. Uncertainty remains, however, regarding whether focus of attention (FOA) strategies are effective in explosive tasks with short execution times. Therefore, this study examined the effects of three FOA strategies (ICC, EF, and IF) on repeated rebound jump (RRJ) performance in basketball athletes. The repeated nature of the task may provide a longer temporal window for attentional processes to influence execution compared to previous single explosive efforts. METHODS: Twenty-one national-level U19 basketball players (Tier 3.4) performed five consecutive RRJ under each FOA condition on a force plate sampling at 1000 Hz. Variables included total time (TT), total impulse (TIm) and mean force (mF). All variables were analyzed using one-way repeated-measures ANOVA. When significant main effects were observed, Bonferroni-adjusted post-hoc pairwise comparisons were performed. Statistical significance was set at p < .05. RESULTS: Significant main effects common to both averaged and best jump trial were observed for TT (paverage = .020; pbest < .001) and mF (paverage = .028; pbest = .023). Bonferroni-adjusted post hoc comparisons showed that TT decreased for ICC compared to EF (paverage = .015; pbest = .003) but not IF (paverage = .999; pbest = .790). mF increased for ICC compared to EF in the best trial (p = .022) and compared to IF in the averaged trials (p = .036). For the averaged trials, significant main effects were observed for TIm (p = .010). Bonferroni-adjusted post hoc comparisons showed that TIm increased for EF compared to IF (p = .037) but not compared to ICC (p = .412). No statistically significant effects were observed for TIm in the best jump trial. CONCLUSION: These findings suggest that ICC may influence movement execution time without reducing force production. Overall, these results support the potential effectiveness of ICC during repeated explosive efforts, potentially contributing to lower-limb strength development in athletes. References: 1McKay et al., 2024. Psychol Bull, 150(11), 1347–1362. 2Pompa et al., 2024. J Strength Cond Res, 38(2), 419–434. 3Pompa et al., 2025. Int J Sports Physiol Perform, 20(9), 1278–1284. 4McKay et al., 2022. Int J Sports Physiol Perform, 17(2), 317–331.
Read CV Giacomo NazzaroECSS Paris 2023: OP-BM22
INTRODUCTION: Motor surround inhibition (SI) is a neurophysiological mechanism that suppresses the excitability of surrounding muscles during voluntary movement and contributes to skilled motor control [1]. Previous studies indicate that an external focus of attention (EF), compared to an internal one (IF), induces distinct neurophysiological processes [2], including enhanced motor SI [3]. In parallel, augmented feedback (AF) is known to enhance motor performance [4]; however, its effects on underlying neurophysiological mechanisms, such as SI, and its interaction with attentional focus remain unclear. The aim of the present study was to investigate the effects of adopting an IF, EF, AF, or their combination (AF+EF) on motor performance and, most importantly on motor SI in the primary motor cortex (M1). METHODS: Young healthy participants (n = 15, 20-25 y) performed a rate of force development (RFD) task with the right index finger by pressing on a force plate following an auditory cue. Four experimental conditions were tested: IF, EF, AF, and AF+EF. While performing the motor task, single-pulse transcranial magnetic stimulation (TMS) was delivered over the M1, either at rest or just before movement onset. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseous (FDI, prime mover) and the abductor pollicis brevis (APB, surrounding muscle). RESULTS: At the behavioral level, RFD was significantly enhanced (i.e. the steepest slope of the force-time curve) in the AF condition compared to EF and IF, with EF also outperforming IF (all p < 0.02). However, combining AF+EF did not further improve performance. At the neurophysiological level, MEPs recorded from the surrounding muscle (APB) showed the greatest SI in the AF condition, followed by EF and IF, indicating progressively stronger SI across conditions (all p < 0.05). Again, no additional increase in SI was observed in the AF+EF condition. MEP amplitudes at rest in the prime mover (FDI) did not differ across conditions, and no significant differences were found in background electromyographic activity. CONCLUSION: These results confirm that adopting an EF induces stronger motor SI than an IF, in line with previous findings [2, 3]. Most importantly, the present study demonstrates that AF induces immediate changes in neural control strategies, resulting in increased SI and improved motor performance. Overall, this study provides new evidence that performance gains induced by AF are at least partly mediated by enhanced SI within M1. Importantly, these findings identify AF as a novel and potent modulator of motor SI. Although no additional effect was observed when combining AF and EF, it remains unclear whether this reflects a ceiling effect. References 1. Beck et al. (2008). J Neurosci 2. Kuhn & Taube (2025). Exerc Sport Sci Rep 3. Kuhn et al. (2018). Sci Rep 4. Petancevski et al. (2022). Psychol Sport Ex
Read CV Yves-Alain KuhnECSS Paris 2023: OP-BM22