Search

Introduction: Research investigating LAS and CAI has essentially focused on local adaptations. Recently, growing evidence is supporting the hypothesis neural plasticity occurs at both the spinal and cortical levels following (repeated) ligamentous ankle injury. These alterations might explain persisting dysfunctions, an increased injury risk, and the increased probability of developing CAI. This systematic review synthesizes the literature on brain plasticity following LAS and CAI. Methods: Studies eligible for this systematic review investigated the brain with direct outcomes measures in patients with LAS or CAI. The following electronic databases were used for the systematic search from their conception to 19/10/2021: Pubmed, Web of Science, Embase, Scopus, PEDro, The Cochrane Central Registry for Controlled Trials (CENTRAL) and SPORTDiscus. Three authors independently screened 1227 articles from 7 databases using a two-staged process to include 16 studies. The quality assessment tool for observationaland cross-sectional studies was used for the risk of bias assessment. The authors extracted and summarised relevant outcomes from each study in table 1. Results: Patients with LAS showed lower superior cerebellar peduncles (white matter microstructure) compared with healthy controls. CAI populations displayed an increased sensitivity of intermediate inhibitory neurons and a decreased sensitivity of excitatory neurons in the corticospinal pathway. They also found more variability in cortical activation in the superior parietal lobe, pre-and postcentral gyrus and the supplementary motor area with lower corticomotor excitability in several lower limb muscles in patients with CAI. Conclusion: Whilst these findings may support the hypothesis of brain plasticity in patients with ligamentous ankle injuries, all studies were retrospective in nature and most used different measurement methods which makes direct comparisons difficult and limits the strength of evidence of this review. Future research should focus on the understanding of the underlying neurophysiological mechanisms. Correspondence e-mail: alexandre.maricot@vub.be

INTRODUCTION: Mental fatigue, a psychobiological state that is induced when engaging in prolonged cognitive activity, affects both cognitive as well as physical performance. However, the significance and magnitude of these effects has recently been questioned. One of the underlying reasons could be the interindividual differences that are present in mental fatigue-effects. However, it’s not known yet whether these interindividual differences are trait or state-related, or which internal and/or external factors mediate these interindividual differences. The aim of this systematic review and meta-regression was to give an overview of interindividual differences in the effects of mental fatigue on physical performance, and possible internal factors influencing this effect. METHODS: Pubmed, Web of Science, SPORTDiscus and PsycINFO were searched for studies detailing the effect of mental fatigue on dynamic maximal whole body endurance performance. Studies needed to feature healthy participants with the inclusion of at least one internal factor in participants’ characteristics, and were required to include at least one manipulation check. The Cochrane crossover risk of bias tool was used to assess risk of bias. The meta-analysis and regression itself were conducted in R. RESULTS: 29 studies were selected for inclusion, with 24 studies eventually added to the overall random-effects meta-analysis (with 34 distinct effects) based on the successful induction of mental fatigue. This meta-analysis showed a small but significant effect of mental fatigue on endurance performance (g = - 0.31, 95% CI [-0.44; -0.17], t = -4.83, p < 0.001). The multiple meta-regression analysis (incorporating 11 effects) showed a significant influence of physical fitness level on mental fatigue-effects (estimate = 0.18, SE = 0.06, t = 2.84, p = 0.0296). However, this effect was only present when incorporated within the model together with sex ratio, mean age and body mass index. CONCLUSION: The present review confirms findings of the overall literature regarding the mediating influence of physical fitness level on the negative effects of mental fatigue on endurance performance. However, this influence is only apparent when different individual factors, such as sex, are taken into account. Moreover, multiple limitations still undermine these conclusions, from the overall underreporting of different participant characteristics to significant publication bias. An overall experimental study incorporating multiple different internal factors is therefore necessary to draw a definitive conclusion on this subject

The overall purpose of this dissertation was to contribute to clinical decision-making and functional performance testing across the sport injury spectrum. The three specific objectives encompassed: (1) establishing return to sport criteria following lateral ankle sprains, (2) mapping the reliability characteristics of the reactive balance test, (3) exploring electrophysiological brain changes induced by various types of fatigue when participants performed the Y-balance test and reactive balance test. The systematic review (Chapter 2) showed that currently no scientifically sound return to sport criteria following lateral ankle sprain injury can be determined. This was because not one original research study was performed on this topic. Therefore, we provided an overview of the relevant retrieved questionnaires, clinical assessment measures, functional and sport-specific performance tests within ankle sprain populations. Based upon this empirical research, return to sport variables were proposed. This chapter also encompasses rationales and considerations for return to sport decision-making following lateral ankle sprain injury. In Chapter 3, the reliability study is the first study to assess test-retest, intra- and inter-rater reliability of the reactive balance test within a recreationally trained population. Excellent intra- and inter-rater reliability for both outcomes (i.e. visuomotor response time and accuracy) were found. However, test-retest reliability showed good reliability for visuomotor response time and moderate reliability for accuracy. These results indicate that the reactive balance test is suited for performing analyses over time at the group level. The third study (Chapter 4) was designed to evaluate the impact of mental fatigue on electrophysiological brain measurements during Y-balance test and reactive balance test performance. Even though mental fatigue was successfully induced, it did not affect Y-balance test performance. However, an increase in prefrontal cortex theta activity was observed when performing the Y-balance test in a mentally fatigued state. Which means mental fatigue was successfully induced, and might suggest a lower availability of attentional resources and poorer decision-making. Regarding reactive balance test performance, only accuracy was compromised due to mental fatigue. No changes in visuomotor reaction time and electrophysiological brain outcome measures were found following the mental fatigue intervention. In Chapter 5, the results showed that acute physical fatigue impairs the accuracy of the reactive balance test, while Y-balance test performance and visuomotor response time of the reactive balance test remained unaffected. Nevertheless, the underlying changes at the peripheral and central physiological level completely differed from the previous study. During the execution of both tests, acute physical fatigue induced alterations in electrophysiological brain outcome measures in line with previous Wingate literature. Higher α power in the prefrontal cortex, motor cortex and posterior parietal cortex as well as higher β power in the prefrontal and posterior parietal cortex were observed during the execution of the Y-balance test in a fatigued state. Following acute physical fatigue, α and β power increments were found in the posterior parietal cortex and the prefrontal cortex during the execution of the reactive balance test, respectively. In summary, the research findings of this dissertation show that: (1) no scientifically sound return to sport criteria following lateral ankle sprain injury are currently available; (2) the reactive balance test has acceptable reliability characteristics and therefore is suited for performing analyses over time at the group level. (3) mental and acute physical fatigue do not impact YBT performance, even when underlying physiological and psychological changes are present; (4) the reactive balance test is capable of detecting fatigue changes at the group level culminating in decreased accuracy. When mentally fatigued, no changes at the electrophysiological brain level were measured. In a physically fatigued state the electrophysiological findings were partially in line with previous Wingate literature.

The overall purpose of this dissertation was to contribute to clinical decision-making and functional performance testing across the sport injury spectrum. The three specific objectives encompassed: (1) establishing return to sport criteria following lateral ankle sprains, (2) mapping the reliability characteristics of the reactive balance test, (3) exploring electrophysiological brain changes induced by various types of fatigue when participants performed the Y-balance test and reactive balance test. The systematic review (Chapter 2) showed that currently no scientifically sound return to sport criteria following lateral ankle sprain injury can be determined. This was because not one original research study was performed on this topic. Therefore, we provided an overview of the relevant retrieved questionnaires, clinical assessment measures, functional and sport-specific performance tests within ankle sprain populations. Based upon this empirical research, return to sport variables were proposed. This chapter also encompasses rationales and considerations for return to sport decision-making following lateral ankle sprain injury. In Chapter 3, the reliability study is the first study to assess test-retest, intra- and inter-rater reliability of the reactive balance test within a recreationally trained population. Excellent intra- and inter-rater reliability for both outcomes (i.e. visuomotor response time and accuracy) were found. However, test-retest reliability showed good reliability for visuomotor response time and moderate reliability for accuracy. These results indicate that the reactive balance test is suited for performing analyses over time at the group level. The third study (Chapter 4) was designed to evaluate the impact of mental fatigue on electrophysiological brain measurements during Y-balance test and reactive balance test performance. Even though mental fatigue was successfully induced, it did not affect Y-balance test performance. However, an increase in prefrontal cortex theta activity was observed when performing the Y-balance test in a mentally fatigued state. Which means mental fatigue was successfully induced, and might suggest a lower availability of attentional resources and poorer decision-making. Regarding reactive balance test performance, only accuracy was compromised due to mental fatigue. No changes in visuomotor reaction time and electrophysiological brain outcome measures were found following the mental fatigue intervention. In Chapter 5, the results showed that acute physical fatigue impairs the accuracy of the reactive balance test, while Y-balance test performance and visuomotor response time of the reactive balance test remained unaffected. Nevertheless, the underlying changes at the peripheral and central physiological level completely differed from the previous study. During the execution of both tests, acute physical fatigue induced alterations in electrophysiological brain outcome measures in line with previous Wingate literature. Higher α power in the prefrontal cortex, motor cortex and posterior parietal cortex as well as higher β power in the prefrontal and posterior parietal cortex were observed during the execution of the Y-balance test in a fatigued state. Following acute physical fatigue, α and β power increments were found in the posterior parietal cortex and the prefrontal cortex during the execution of the reactive balance test, respectively. In summary, the research findings of this dissertation show that: (1) no scientifically sound return to sport criteria following lateral ankle sprain injury are currently available; (2) the reactive balance test has acceptable reliability characteristics and therefore is suited for performing analyses over time at the group level. (3) mental and acute physical fatigue do not impact YBT performance, even when underlying physiological and psychological changes are present; (4) the reactive balance test is capable of detecting fatigue changes at the group level culminating in decreased accuracy. When mentally fatigued, no changes at the electrophysiological brain level were measured. In a physically fatigued state the electrophysiological findings were partially in line with previous Wingate literature.