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A Narrative Literature Review About the Role of Microsaccades in Sports

Alessandro Piras and Milena Raffi

In many daily and sport situations, people have to simultaneously perceive and process multiple objects and scenes in a short amount of time. A wrong decision may lead to a disadvantage for a team or for a single athlete, and during daily life (i.e., driving, surgery), it could have more dangerous consequences. Considering the results of different studies, the ability to distribute visual attention depends on different levels of expertise and environment-related constraints. This article is a narrative review of the current scientific evidence in the field of eye movements in sports, focusing on the role of microsaccades in sporting task situations. Over the past 10 years, microsaccades have become one of the most increasing areas of research in visual and oculomotor studies and even in the area of sport science. Here, we review the latest findings and discuss the relationships between microsaccades and attention, perception, and action in sports.

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Dual-Task Interference Slows Down Proprioception

Linjing Jiang, Satoshi Kasahara, Tomoya Ishida, Yuting Wei, Ami Chiba, Mina Samukawa, and Harukazu Tohyama

It is well-known that multitasking impairs the performance of one or both of the concomitant ongoing tasks. Previous studies have mainly focused on how a secondary task can compromise visual or auditory information processing. However, despite dual tasking being critical to motor performance, the effects of dual-task performance on proprioceptive information processing have not been studied yet. The purpose of the present study was, therefore, to investigate whether sensorimotor task performance would be affected by the dual task and if so, in which phase of the sensorimotor task performance would this negative effect occur. The kinematic variables of passive and active knee movements elicited by the leg drop test were analyzed. Thirteen young adults participated in the study. The dual task consisted of performing serial subtractions. The results showed that the dual task increased both the reaction time to counteract passive knee–joint movements in the leg drop test and the threshold to detect those movements. The dual task did not affect the speed and time during the active knee movement and the absolute angle error between the final and the target knee angles. Furthermore, the results showed that the time to complete the sensorimotor task was prolonged in dual tasking. Our findings suggest that dual tasking reduces motor performance due to slowing down proprioceptive information processing without affecting movement execution.

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Volume 27 (2023): Issue 1 (Jan 2023): Special Z-Issue in Honor of Vladimir M. Zatsiorsky

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Intramuscle Synergies: Their Place in the Neural Control Hierarchy

Mark L. Latash, Shirin Madarshahian, and Joseph M. Ricotta

We accept a definition of synergy introduced by Nikolai Bernstein and develop it for various actions, from those involving the whole body to those involving a single muscle. Furthermore, we use two major theoretical developments in the field of motor control—the idea of hierarchical control with spatial referent coordinates and the uncontrolled manifold hypothesis—to discuss recent studies of synergies within spaces of individual motor units (MUs) recorded within a single muscle. During the accurate finger force production tasks, MUs within hand extrinsic muscles form robust groups, with parallel scaling of the firing frequencies. The loading factors at individual MUs within each of the two main groups link them to the reciprocal and coactivation commands. Furthermore, groups are recruited in a task-specific way with gains that covary to stabilize muscle force. Such force-stabilizing synergies are seen in MUs recorded in the agonist and antagonist muscles but not in the spaces of MUs combined over the two muscles. These observations reflect inherent trade-offs between synergies at different levels of a control hierarchy. MU-based synergies do not show effects of hand dominance, whereas such effects are seen in multifinger synergies. Involuntary, reflex-based, force changes are stabilized by intramuscle synergies but not by multifinger synergies. These observations suggest that multifinger (multimuscle synergies) are based primarily on supraspinal circuitry, whereas intramuscle synergies reflect spinal circuitry. Studies of intra- and multimuscle synergies promise a powerful tool for exploring changes in spinal and supraspinal circuitry across patient populations.

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Effect of Vertical Jump and Sprint Training on Power and Speed Performance Transfer

Rodrigo Ghedini Gheller, Rafael Lima Kons, Juliano Dal Pupo, and Daniele Detanico

The aim of this systematic review was to investigate the effect of specific sprint and vertical jump training interventions on transfer of speed–power parameters. The data search was carried out in three electronic databases (PubMed, SCOPUS, and SPORTDiscus), and 28 articles were selected (13 on vertical jump training and 15 on sprint training). We followed the PRISMA criteria for the construction of this systematic review and used the Physiotherapy Evidence Database (PEDro) scale to assess the quality of all studies. It included studies with a male population (athletes and nonathletes, n = 512) from 18 to 30 years old who performed a vertical jump or sprint training intervention. The effect size was calculated from the values of means and SDs pre- and posttraining intervention. The percentage changes and transfer of training effect were calculated for vertical jump training and sprint training through measures of vertical jump and sprint performance. The results indicated that both training interventions (vertical jump training and sprint training) induced improvements in vertical jump and linear sprint performance as well as transfer of training to speed–power performance. However, vertical jump training produced greater specific and training transfer effects on linear sprint than sprint training (untrained skill). It was concluded that vertical jump training and sprint training were effective in increasing specific actions of vertical jump and linear sprint performance, respectively; however, vertical jump training was shown to be a superior alternative due to the higher transfer rate.

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Effects of Mental Fatigue on Strength Endurance: A Systematic Review and Meta-Analysis

Carlos Alix-Fages, Jozo Grgic, Pablo Jiménez-Martínez, Eneko Baz-Valle, and Carlos Balsalobre-Fernández

The purpose of the present systematic review and meta-analysis was to explore the effects of mental fatigue on upper and lower body strength endurance. Searches for studies were performed in the PubMed/MEDLINE and Web of Science databases. We included studies that compared the effects of a demanding cognitive task (set to induce mental fatigue) with a control condition on strength endurance in dynamic resistance exercise (i.e., expressed as the number of performed repetitions at a given load). The data reported in the included studies were pooled in a random-effects meta-analysis of standardized mean differences. Seven studies were included in the review. We found that mental fatigue significantly reduced the number of performed repetitions for upper body exercises (standardized mean difference: −0.41; 95% confidence interval [−0.70, −0.12]; p = .006; I 2 = 0%). Mental fatigue also significantly reduced the number of performed repetitions in the analysis for lower body exercises (standardized mean difference: −0.39; 95% confidence interval [−0.75, −0.04]; p = .03; I 2 = 0%). Our results showed that performing a demanding cognitive task—which induces mental fatigue—impairs strength endurance performance. Collectively, our findings suggest that exposure to cognitive tasks that may induce mental fatigue should be minimized before strength endurance-based resistance exercise sessions.

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Principal Component Analysis can Be Used to Discriminate Between Elite and Sub-Elite Kicking Performance

Michal Vagner, Daniel J. Cleather, Petr Kubový, Vladimír Hojka, and Petr Stastny

Contemporary descriptions of motor control suggest that variability in movement can be indicative of skilled or unskilled performance. Here we used principal component analysis to study the kicking performance of elite and sub-elite soldiers who were highly familiar with the skill in order to compare the variability in the first and second principal components. The subjects kicked a force plate under a range of loaded conditions, and their movement was recorded using optical motion capture. The first principal component explained >92% of the variability across all kinematic variables when analyzed separately for each condition, and both groups and explained more of the variation in the movement of the elite group. There was more variation in the loading coefficient of the first principal component for the sub-elite group. In contrast, for the second principal component, there was more variation in the loading coefficient for the elite group, and the relative magnitude of the variation was greater than for the first principal component for both groups. These results suggest that the first principal component represented the most fundamental movement pattern, and there was less variation in this mode for the elite group. In addition, more of the variability was explained by the hip than the knee angle entered when both variables were entered into the same PCA, which suggests that the movement is driven by the hip.

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Decay of Short-Term Motor Memory Regarding Force Reproduction

Koichi Hiraoka, Masaya Ishimoto, Mai Kishigami, Ryota Sakaya, Asahi Sumimoto, and Kazuki Yoshikawa

This study investigated the process that contributes to the decay of short-term motor memory regarding force reproduction. Participants performed tonic flexion of the right index finger with the target force feedback (criterion phase) and reproduced this force level without feedback 3, 10, 30, or 60 s after the end of the criterion phase (recall phase). The constant error for force reproduction was significantly greater than zero, indicating that information about the somatosensation and/or motor command in the criterion phase is positively biased. Constant and absolute errors were not influenced by the retention interval, indicating that neither bias nor error represents the decay of short-term motor memory over time. Variable error, defined as SD of bias (force in the recall phase minus that in the criterion phase), increased as the retention interval increased. This indicates that the decay of short-term motor memory is represented by the increase in inconsistency of memory bias among the trials. The correlation coefficient of the force between the criterion and recall phases with 3-s retention interval was greater than that with longer intervals. This is explained by the view that the contribution of the information of the practiced force to the force reproduction process is great within 3 s after the end of the practice, but the additional contribution of the noise information becomes greater after this time, causing lesser relative contribution of the information of the practiced force to the force reproduction process.

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Dominant and Nondominant Leg Kinematics During Kicking in Young Soccer Players: A Cross-Sectional Study

Francesco Frontani, Marco Prenassi, Viviana Paolini, Giovanni Formicola, Sara Marceglia, and Francesca Policastro

The goal of the study is to analyze the kinematics and provide an EMG analysis of the support limb during an instep kick in adolescent players. We set a video camera, two torque transducers on the knee, and EMG sensors. A sample of 16 adolescent soccer players between 10 and 12 years old performed kicks. The kinematics shows a p = .039 on frontal plane (dominant 15.4 ± 1.8, nondominant 18.8 ± 1.7); the EMG analysis shows a p = .04 on muscular activation timing for the vastus medialis. A difference between the legs on the frontal plane emerges. Moreover, a huge difference on sagittal plane between the adolescent pattern and adult pattern exists (15° in adolescent population, 40° in adult population). The result shows a greater activation of the vastus medialis in the nondominant leg; probably, in this immature pattern, the adolescents use this muscle more than necessary.

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Heating the Skin Over the Knee Improves Kinesthesia During Knee Extension

Meghan Lamers, Erika E. Howe, Geoffrey A. Power, and Leah R. Bent

To determine how heating affects dynamic joint position sense at the knee, participants (n = 11; F = 6) were seated in a HUMAC NORM dynamometer. The leg was passively moved through extension and flexion, and participants indicated when the 90° reference position was perceived, both at baseline (28.74 ± 2.43 °C) and heated (38.05 ± 0.16 °C) skin temperatures. Day 2 of testing reduced knee skin feedback with lidocaine. Directional error (actual leg angle–target angle) and absolute error (AE) were calculated. Heating reduced extension AE (baseline AE = 5.46 ± 2.39°, heat AE = 4.10 ± 1.97°), but not flexion. Lidocaine did not significantly affect flexion AE or extension AE. Overall, increased anterior knee-skin temperature improves dynamic joint position sense during passive knee extension, where baseline matching is poorer. Limited application of lidocaine to the anterior thigh, reducing some skin input, did not influence dynamic joint position sense, suggesting cutaneous receptors may play only a secondary role to spindle information during kinesthetic tasks. Importantly, cutaneous input from adjacent thigh regions cannot be ruled out as a contributor.