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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.

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.

Purpose: The aim of this brief review was to present an overview of noninvasive markers in trained to professional endurance athletes that can reflect a state of functional overreaching. Methods: A systematic literature search was conducted in the PubMed, Scopus, and PsycINFO databases. After screening 380 articles, 12 research papers were included for the systematic review. Results: Good consensus was found between the different papers in which noninvasive parameters were able to reflect a state of functional overreaching. Changes in power output (PO), heart rate (HR; [sub]maximal and HR recovery), rating of perceived exertion, and scores in the Daily Analysis of Life Demands for Athletes (DALDA) and/or Profile of Mood States (POMS) were shown to be able to reflect functional overreaching, whereas changes in maximal oxygen uptake and HR-variability parameters were not. Conclusion: Functional overreaching within a maximal performance test was characterized by a decrease in peak PO and a lower maximum HR, whereas a lower mean PO and a lower HR were observed during time trials. Changes in parameters during a standardized submaximal test when functionally overreached were characterized by a higher PO at a fixed HR or a lower HR at a fixed intensity, higher rating of perceived exertion, and a faster HR recovery. Although both the DALDA and POMS were able to reflect functional overreaching, the POMS was not able to differentiate this response from acute fatigue, which makes it unsuitable for accurately monitoring functional overreaching.

Verschenen in het kader van het onderzoeksgebied: 'Monitoring and Predicting on Physical Performance in Daily Life and Sports'

Substitution is an essential tool for a coach to influence the match. Factors like the injury of a player, required tactical changes, or underperformance of a player initiates substitutions. This study aims to predict the physical performance of individual players in an early phase of the match to provide additional information to the coach for his decision on substitutions. Tracking data ofindividual players, except for goalkeepers, from 302 elite soccer matches of the Dutch ‘Eredivisie’ 2018–2019 season were used to enable the prediction of the individual physical performance. The players’ physical performance is expressed in the variables distance covered, distance in speed category, and energy expenditure in power category. The individualized normalized variables wereused to build machine learning models that predict whether players will achieve 100%, 95%, or 90% of their average physical performance in a match. The tree-based algorithms Random Forest and Decision Tree were applied to build the models. A simple Naïve Bayes algorithm was used as the baseline model to support the superiority of the tree-based algorithms. The machine learningtechnique Random Forest combined with the variable energy expenditure in the power category was the most precise. The combination of Random Forest and energy expenditure in the power category resulted in precision in predicting performance and underperformance after 15 min in a match, andthe values were 0.91, 0.88, and 0.92 for the thresholds 100%, 95%, and 90%, respectively. To conclude, it is possible to predict the physical performance of individual players in an early phase of the match. These findings offer opportunities to support coaches in making more informed decisions on playersubstitutions in elite soccer.

Functional performance tests are utilized by clinicians and researchers to compile injury risk profiles, monitor rehabilitation progress and to inform a criteria-based and safe return to sport decision-making approach. Functional performance tests are measurements that evaluate an athlete’s current functional ability. Although literature documents a significant association between some functional performance test outcomes and an increased injury risk, these tests should be interpreted in a more complex, athlete centered approach of sports injuries. In a comprehensive athlete centered approach, functional performance tests should also approximate the athletic context. This highlights the need to continuously develop functional performance tests and evaluate different interactions that arise within the athletic context. Interestingly, the current functional performance test approach neglect the relevance of fatigue and adaptability. Adaptability is defined as the athlete’s ability to modify responses under a broad spectrum of conditions. Fatigue is a multidimensional phenomenon and includes both central and peripheral fatigue mechanisms as well as physical and mental fatigue constructs. The goal of the present dissertation is to gain more insight in how fatigue interacts with functional performance tests, injury risk and adaptability. In our first study (chapter two) we provide a systematic literature review to identify the existing body of evidence on the interaction between acute physical fatigue and prospectively determined injury risk factors for lower extremity injuries. The body of evidence is scarce and of low quality, with no evidence that acute fatigue increases the non-contact ACL, ITBFS or generic lower extremity injury risk profiles. Only limited evidence was found for the statement that acute fatigue negatively affects the lateral ankle sprain, patellofemoral pain syndrome or hamstring injury risk profiles. In chapter three, we describe the systematic development and test protocol of the reactive balance test. The reactive balance test is a neurocognitive single-leg balance test that integrates environmental perception, decision making and reaction time. The outcomes are accuracy and visuomotor response time. The reactive balance test is a functional performance test that allows clinicians to score an athlete’s adaptability. Consequently, we performed two randomized cross-over studies to explore the effect of mental fatigue (chapter four) and acute physical fatigue (chapter five) with four functional performance tests, including three traditional functional performance tests, the Y-balance test, the countermovement jump test, the single leg hop test and the neurocognitive reactive balance test. The results presented in chapter four illustrate that mental fatigue does not affect outcomes of the included traditional functional performance tests, but does impair accuracy in the reactive balance test. Following a 90 minute 100% incongruent Stroop task, participants accuracy significantly decreased in the reactive balance test. Mental fatigue can negatively affect adaptability. The results presented in chapter five illustrate that acute physical fatigue can cause divergent fatigue responses in functional performance test outcomes. While the countermovement jump and Y balance test performance remained unaffected, single leg hop distance significantly decreased following a 30 second all-out sprint effort (Modified Wingate procedure). Acute physical fatigue also impairs accuracy in the reactive balance test and can also negatively affect adaptability. This thesis highlights that acute physical fatigue interacts with functional performance tests, but comprises large intra- and interindividual differences. Clinicians should be aware of this interaction and a paradigm shift is needed towards evaluating individual fatigue responses. Moreover, neurocognitive functional performance test can complement the current use of functional performance tests. For future research, more teamwork is needed to merge insights from fatigue and injury prevention experts. Additionally, evaluating individual fatigue responses might expose patterns that are masked in current data monitoring strategies and group-level analyses. Prospective research is needed to explore the added value of neurocognitive functional performance tests.

Functional performance tests are utilized by clinicians and researchers to compile injury risk profiles, monitor rehabilitation progress and to inform a criteria-based and safe return to sport decision-making approach. Functional performance tests are measurements that evaluate an athlete’s current functional ability. Although literature documents a significant association between some functional performance test outcomes and an increased injury risk, these tests should be interpreted in a more complex, athlete centered approach of sports injuries. In a comprehensive athlete centered approach, functional performance tests should also approximate the athletic context. This highlights the need to continuously develop functional performance tests and evaluate different interactions that arise within the athletic context. Interestingly, the current functional performance test approach neglect the relevance of fatigue and adaptability. Adaptability is defined as the athlete’s ability to modify responses under a broad spectrum of conditions. Fatigue is a multidimensional phenomenon and includes both central and peripheral fatigue mechanisms as well as physical and mental fatigue constructs. The goal of the present dissertation is to gain more insight in how fatigue interacts with functional performance tests, injury risk and adaptability. In our first study (chapter two) we provide a systematic literature review to identify the existing body of evidence on the interaction between acute physical fatigue and prospectively determined injury risk factors for lower extremity injuries. The body of evidence is scarce and of low quality, with no evidence that acute fatigue increases the non-contact ACL, ITBFS or generic lower extremity injury risk profiles. Only limited evidence was found for the statement that acute fatigue negatively affects the lateral ankle sprain, patellofemoral pain syndrome or hamstring injury risk profiles. In chapter three, we describe the systematic development and test protocol of the reactive balance test. The reactive balance test is a neurocognitive single-leg balance test that integrates environmental perception, decision making and reaction time. The outcomes are accuracy and visuomotor response time. The reactive balance test is a functional performance test that allows clinicians to score an athlete’s adaptability. Consequently, we performed two randomized cross-over studies to explore the effect of mental fatigue (chapter four) and acute physical fatigue (chapter five) with four functional performance tests, including three traditional functional performance tests, the Y-balance test, the countermovement jump test, the single leg hop test and the neurocognitive reactive balance test. The results presented in chapter four illustrate that mental fatigue does not affect outcomes of the included traditional functional performance tests, but does impair accuracy in the reactive balance test. Following a 90 minute 100% incongruent Stroop task, participants accuracy significantly decreased in the reactive balance test. Mental fatigue can negatively affect adaptability. The results presented in chapter five illustrate that acute physical fatigue can cause divergent fatigue responses in functional performance test outcomes. While the countermovement jump and Y balance test performance remained unaffected, single leg hop distance significantly decreased following a 30 second all-out sprint effort (Modified Wingate procedure). Acute physical fatigue also impairs accuracy in the reactive balance test and can also negatively affect adaptability. This thesis highlights that acute physical fatigue interacts with functional performance tests, but comprises large intra- and interindividual differences. Clinicians should be aware of this interaction and a paradigm shift is needed towards evaluating individual fatigue responses. Moreover, neurocognitive functional performance test can complement the current use of functional performance tests. For future research, more teamwork is needed to merge insights from fatigue and injury prevention experts. Additionally, evaluating individual fatigue responses might expose patterns that are masked in current data monitoring strategies and group-level analyses. Prospective research is needed to explore the added value of neurocognitive functional performance tests.

Functional performance tests are utilized by clinicians and researchers to compile injury risk profiles, monitor rehabilitation progress and to inform a criteria-based and safe return to sport decision-making approach. Functional performance tests are measurements that evaluate an athlete’s current functional ability. Although literature documents a significant association between some functional performance test outcomes and an increased injury risk, these tests should be interpreted in a more complex, athlete centered approach of sports injuries. In a comprehensive athlete centered approach, functional performance tests should also approximate the athletic context. This highlights the need to continuously develop functional performance tests and evaluate different interactions that arise within the athletic context. Interestingly, the current functional performance test approach neglect the relevance of fatigue and adaptability. Adaptability is defined as the athlete’s ability to modify responses under a broad spectrum of conditions. Fatigue is a multidimensional phenomenon and includes both central and peripheral fatigue mechanisms as well as physical and mental fatigue constructs. The goal of the present dissertation is to gain more insight in how fatigue interacts with functional performance tests, injury risk and adaptability. In our first study (chapter two) we provide a systematic literature review to identify the existing body of evidence on the interaction between acute physical fatigue and prospectively determined injury risk factors for lower extremity injuries. The body of evidence is scarce and of low quality, with no evidence that acute fatigue increases the non-contact ACL, ITBFS or generic lower extremity injury risk profiles. Only limited evidence was found for the statement that acute fatigue negatively affects the lateral ankle sprain, patellofemoral pain syndrome or hamstring injury risk profiles. In chapter three, we describe the systematic development and test protocol of the reactive balance test. The reactive balance test is a neurocognitive single-leg balance test that integrates environmental perception, decision making and reaction time. The outcomes are accuracy and visuomotor response time. The reactive balance test is a functional performance test that allows clinicians to score an athlete’s adaptability. Consequently, we performed two randomized cross-over studies to explore the effect of mental fatigue (chapter four) and acute physical fatigue (chapter five) with four functional performance tests, including three traditional functional performance tests, the Y-balance test, the countermovement jump test, the single leg hop test and the neurocognitive reactive balance test. The results presented in chapter four illustrate that mental fatigue does not affect outcomes of the included traditional functional performance tests, but does impair accuracy in the reactive balance test. Following a 90 minute 100% incongruent Stroop task, participants accuracy significantly decreased in the reactive balance test. Mental fatigue can negatively affect adaptability. The results presented in chapter five illustrate that acute physical fatigue can cause divergent fatigue responses in functional performance test outcomes. While the countermovement jump and Y balance test performance remained unaffected, single leg hop distance significantly decreased following a 30 second all-out sprint effort (Modified Wingate procedure). Acute physical fatigue also impairs accuracy in the reactive balance test and can also negatively affect adaptability. This thesis highlights that acute physical fatigue interacts with functional performance tests, but comprises large intra- and interindividual differences. Clinicians should be aware of this interaction and a paradigm shift is needed towards evaluating individual fatigue responses. Moreover, neurocognitive functional performance test can complement the current use of functional performance tests. For future research, more teamwork is needed to merge insights from fatigue and injury prevention experts. Additionally, evaluating individual fatigue responses might expose patterns that are masked in current data monitoring strategies and group-level analyses. Prospective research is needed to explore the added value of neurocognitive functional performance tests.

Functional performance tests are utilized by clinicians and researchers to compile injury risk profiles, monitor rehabilitation progress and to inform a criteria-based and safe return to sport decision-making approach. Functional performance tests are measurements that evaluate an athlete’s current functional ability. Although literature documents a significant association between some functional performance test outcomes and an increased injury risk, these tests should be interpreted in a more complex, athlete centered approach of sports injuries. In a comprehensive athlete centered approach, functional performance tests should also approximate the athletic context. This highlights the need to continuously develop functional performance tests and evaluate different interactions that arise within the athletic context. Interestingly, the current functional performance test approach neglect the relevance of fatigue and adaptability. Adaptability is defined as the athlete’s ability to modify responses under a broad spectrum of conditions. Fatigue is a multidimensional phenomenon and includes both central and peripheral fatigue mechanisms as well as physical and mental fatigue constructs. The goal of the present dissertation is to gain more insight in how fatigue interacts with functional performance tests, injury risk and adaptability. In our first study (chapter two) we provide a systematic literature review to identify the existing body of evidence on the interaction between acute physical fatigue and prospectively determined injury risk factors for lower extremity injuries. The body of evidence is scarce and of low quality, with no evidence that acute fatigue increases the non-contact ACL, ITBFS or generic lower extremity injury risk profiles. Only limited evidence was found for the statement that acute fatigue negatively affects the lateral ankle sprain, patellofemoral pain syndrome or hamstring injury risk profiles. In chapter three, we describe the systematic development and test protocol of the reactive balance test. The reactive balance test is a neurocognitive single-leg balance test that integrates environmental perception, decision making and reaction time. The outcomes are accuracy and visuomotor response time. The reactive balance test is a functional performance test that allows clinicians to score an athlete’s adaptability. Consequently, we performed two randomized cross-over studies to explore the effect of mental fatigue (chapter four) and acute physical fatigue (chapter five) with four functional performance tests, including three traditional functional performance tests, the Y-balance test, the countermovement jump test, the single leg hop test and the neurocognitive reactive balance test. The results presented in chapter four illustrate that mental fatigue does not affect outcomes of the included traditional functional performance tests, but does impair accuracy in the reactive balance test. Following a 90 minute 100% incongruent Stroop task, participants accuracy significantly decreased in the reactive balance test. Mental fatigue can negatively affect adaptability. The results presented in chapter five illustrate that acute physical fatigue can cause divergent fatigue responses in functional performance test outcomes. While the countermovement jump and Y balance test performance remained unaffected, single leg hop distance significantly decreased following a 30 second all-out sprint effort (Modified Wingate procedure). Acute physical fatigue also impairs accuracy in the reactive balance test and can also negatively affect adaptability. This thesis highlights that acute physical fatigue interacts with functional performance tests, but comprises large intra- and interindividual differences. Clinicians should be aware of this interaction and a paradigm shift is needed towards evaluating individual fatigue responses. Moreover, neurocognitive functional performance test can complement the current use of functional performance tests. For future research, more teamwork is needed to merge insights from fatigue and injury prevention experts. Additionally, evaluating individual fatigue responses might expose patterns that are masked in current data monitoring strategies and group-level analyses. Prospective research is needed to explore the added value of neurocognitive functional performance tests.

Submitted by Paulo Cezar Rocha dos Santos (paulocezarr@hotmail.com) on 2021-05-02T21:41:03Z No. of bitstreams: 1 SANTOS_teseUnesp.pdf: 4849681 bytes, checksum: 5fbc5d27d29e565d1326110fa66f3eec (MD5) Rejected by Ana Paula Santulo Custódio de Medeiros null (asantulo@rc.unesp.br), reason: Prezado Paulo, O documento enviado para a coleção Campus Unesp Rio Claro foi recusado pelo(s) seguinte(s) motivo(s): - Página de rosto: falta constar os nomes de todos os orientadores e coorientadores. - Falta o Resumo em português (elementos obrigatório). - Faltam as palavras-chave (elemento obrigatório) - devem ser colocadas após o texto do resumo. - Falta o Abstract (elemento obrigatório). - Faltam as palavras chaves em inglês (elemento obrigatório) - devem ser colocadas após o texto do abstract. - CAPES: A Portaria nº 206, de 04/09/2018 Dispõe sobre obrigatoriedade de citação da CAPES nos agradecimentos da seguinte forma: Art. 3º Deverão ser usadas as seguintes expressões, no idioma do trabalho (Não alterar, acrescentar ou excluir qualquer informação. 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Deixar apenas uma, constando cabeçalho, título, autor, "tese apresentada...", nomes de todos os orientadores e coorientadores, cidade, estado e ano. - Agradecimento CAPES: como o trabalho está em inglês, é melhor colocar o agradecimento da CAPES em inglês também conforme orientação: - CAPES: A Portaria nº 206, de 04/09/2018 Dispõe sobre obrigatoriedade de citação da CAPES nos agradecimentos da seguinte forma: Art. 3º Deverão ser usadas as seguintes expressões, no idioma do trabalho (Não alterar, acrescentar ou excluir qualquer informação. A frase deve ser colocada idêntica ao que consta na Portaria): "O presente trabalho foi realizado com apoio da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Código de Financiamento 001" - CAPES (para texto em inglês ou idioma estrangeiro): "This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001". 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No. of bitstreams: 1 santos_pcr_dr_rcla_par.pdf: 943279 bytes, checksum: 2085c08229f28220aafd628347d6ca72 (MD5) Previous issue date: 2020-10-07 Outra Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Gezond ouder worden gaat samen met functionele achteruitgang, waaronder die van het lopen, balans en het vermogen om deze aan te passen aan allerei interne en externe verstoringen. Vermoeidheid kan beschouwd worden als een interne verstoring welke resulteert in een afname van fysieke en /of mentale prestaties en een afname in de motivatie om fysieke taken uit te voren. Een belangrijke vraag is, of en hoe leeftijd het vermogen beindvloed om het lopen aan te passen aan spier en mentale vermoeidheid en op wat voor wijze dit effect heeft op dagelijkse activiteiten. Hoofdstuk 2 presenteert een systematisch literatuuronderzoek waarbij studies zijn geanalyseerd die de effecten van experimenteel veroorzaakte spier- en mentale vermoeidheid op het lopen van ouderen onderzochten. Uit het review komt naar voren dat spatiële en temporele kenmerken van het lopen en de en de variabiliteit van de rompversnellingen beinvloed worden door spiervermoeidheid. Daarentegen heeft aanhoudende mentale activiteit alleen invloed op de stapvariabiliteit van het lopen als er tegelijkertijd een cognitieve taak wordt uitgevoerd, zgn. dubbeltaken. Ondanks dat het review heeft aangetoond dat spier- en mentale vermoeidheid de loopprestaties veranderen, blijven de mechanismen die ten grondlag liggen aan de gerapporteerde loopveranderingen onduidelijk. Om meer inzicht te krijgen op welke wijze leeftijd en vermoeidheid het lopen beïnvloeden, hebben we een experiment ontworpen om spiervermoeidheid en mentale vermoeidheid te veroorzaken, en de effecten ervan op het lopen op een loopband te onderzoeken bij 12 ouderen en 12 jongvolwassenen. Spiervermoeidheid werd veroorzaakt door de deelnemers herhaaldelijk een zit-staan taak te laten uitvoeren (repetitive sit-to-stand, rSTS) en mentale vermoeidheid werd veroorzaakt door de deelnemers 30 minuten lang veeleisende mentale taken op een computer te laten uitvoeren. In hoofdstuk 3 laten we zien dat zowel bij ouderen als jongvolwassenen, de rSTS taak en mentale taken, schrede variabelen en de dynamica van het lopen nauwelijks beïnvloedden. Wat betreft de mentale vermoeidheid, kan het zijn dat, aanpassingen in het looppatroon alleen optreden wanneer tegelijkertijd complexere, dubbeltaken worden uitgevoerd. Daarnaast kan het zijn dat leeftijdsspecifieke aanpassingen in de neuromusculaire controle, als gevolg van vermoeidheid, mogelijk de effecten van vermoeidheid hebben gecompenseerd om de loopprestaties te behouden. Bovendien waren de 7 Samenvatting effecten van rSTS taak mogelijk te algemeen om veranderingen in de belangrijkste elementen van het lopen teweeg te brengen. In hoofdstuk 4 onderzochten we de effecten van leeftijd en rSTS taak op spieractivatie tijdens specifieke fases van STS-taak (fasen opstaan en zitten). We vonden dat ouderen in vergelijking met jongevolwassenen opmerkelijk minder STS-herhalingen uitvoerden. Door minder STS-herhalingen uit te voeren, bleven vermoeidheidseffecten op spieractivatie, kracht en de uitvoering van de taak vrijwillige kracht en motoriek tot een minimum beperkt bij oudere volwassenen. Daarom werden minimale veranderingen gevonde loopvariabelen. In hoofdstuk 5 hebben we onderzocht of er een leeftijdsspecifieke aanpassing was in de gemeenschappelijke neurale aansturing van spieren om de spiervermoeidheid tijdens het lopen te compenseren. We vonden dat rSTS een leeftijdsspecifieke compensatiestrategie veroorzaakte in de neurale aansturing van spieren met als doel de loopprestaties te behouden. Hoofdstuk 6 vat de belangrijkste bevindingen samen. De resultaten worden besproken vanuit het perspectief dat: 1) de effecten van leeftijd en vermoeidheid waarschijnlijk meer optreden tijdens looptaken die lijken op het lopen in het dagelijks leven, loopsituaties met cognitieve en motorische dubbeltaken. 2) een vermoeidheid inducerend model dat looptaken omvat en/ of gericht is op specifieke aspecten van het lopen (zoals, vermoeidheid veroorzaakt door lange afstanden te lopen op vlakke en / of hellende oppervlakken, of protocollen voor het ) wellicht duidelijker verschillend tussen jong en oud laten zien in het aanpassingsvermogen van het looppatroon. Echter, al zijn de algemene effecten klein, rSTS taak geeft leeftijdsspecifieke veranderingen in de neurale aansturing van synergetische enkelspieren, wat kan worden geïnterpreteerd als een compensatie voor vermoeidheid die gezonde oudere volwassenen ontwikkelen. O envelhecimento é um processo degenerativo que resulta em declínios funcionais, como aqueles observados na performance do andar, no controle postural e na habilidade de adaptação destas tarefas para com perturbações internas e externas. Perturbações internas surgem devido à uma redução na disponibilidade dos recursos biológicos, podendo ser atribuídas como consequência da fadiga. Uma questão intrigante é quando e como o envelhecimento afeta a capacidade de adaptação à perturbação criada pela fadiga para minimizar a perda da funcionalidade. Portanto, esta tese teve como objetivo examinar os efeitos do envelhecimento e da fadiga induzida experimentalmente no andar. No capítulo 2, nós revisamos sistematicamente estudos que examinaram o efeito da fadiga muscular e mental no andar de idosos. Nós identificamos que, embora as fadigas muscular e mental alterem o desempenho do andar, os mecanismos que explicam o porquê das alterações no andar ocorrem não estão claros. Em conclusão, fadiga muscular afeta parâmetros espaço-temporais do andar e a variabilidade da aceleração do tronco. Em contrapartida, fadiga mental parece afetar a variabilidade do andar somente em condições de tarefa dupla. Buscando entender os mecanismos que explicam como a fadiga afeta o andar, nós induzimos as fadigas muscular e mental experimentalmente e verificamos seus efeitos no andar na esteira de 12 adultos e 12 idosos. A fadiga muscular foi induzida pela repetitiva tarefa do sentar e levantar (rSTS). A fadiga mental foi induzida por tarefas de demanda mental por 30 minutos. No capítulo 3, nos verificamos que o envelhecimento, a rSTS e a tarefa de demanda mental afetaram minimamente as variáveis da passada e a dinamicidade do andar na esteira de idosos e adultos saudáveis. Nós interpretamos que a fadiga mental parece induzir efeitos somente na condição de tarefa dupla; modulações neuromusculares especificas para cada grupo podem ter compensado os efeitos da fadiga para a manutenção do desempenho do padrão do andar induzido pela esteira; e que os efeitos da rSTS talvez não foram específicos o suficiente para induzir mudanças em elementos chaves do andar. No capítulo 4, nós examinamos os efeitos do envelhecimento e da rSTS na ativação muscular durante as fases de levantar e sentar da cadeira, e no nível de força. Nós indicamos que por realizar um substancial menor número de repetições, idosos tiveram minimizados os efeitos da fadiga muscular na atividade do músculo e na produção de força máxima. Isto provavelmente explica as mínimas alterações observadas nas variáveis do passada e na dinamicidade do andar vistas no capítulo 3. No capítulo 5, nós testamos se existiam modulações específicas do envelhecimento no controle neuromuscular para compensar os efeitos da fadiga no andar em esteira. Nós indicamos que apesar de idosos tentarem minimizar os efeitos da fadiga muscular por diminuir o desempenho na rSTS, esta elicitou estratégias específicas da idade no comando neural para os músculos para manter a performance do andar em esteira. O capítulo 6 resume as principais descobertas desta tese. Discutimos os dados na perspectiva de que 1) os efeitos da idade e da fadiga podem ser mais evidentes durante as tarefas do andar quando este é avaliado próximo às condições de vida real, ou em situações de tarefa-dupla em comparação com a caminhada na esteira; 2) talvez, um modelo de indução à fadiga que envolvesse tarefas de andar e/ou que focasse em aspectos específicos da locomoção (como o andar por longa distância em superfícies planas e/ou inclinadas, e subir e descer escadas), pudesse ser mais eficaz para examinar o efeito do envelhecimento nas adaptações do andar. No entanto, mesmo com efeitos limitados, a rSTS provoca alterações específicas da idade no ‘drive’ neural para músculos sinergistas do tornozelo, que podem ser interpretadas como compensação à fadiga para que idosos mantenham o desempenho do andar. Natural aging is a degenerative process accompanied by decline, among others, in motor function, including gait and postural control, and the ability to make adjustments in these tasks when challenged by external and internal perturbations. Fatigability is a form of internal perturbation, resulting in reductions of objective measures of physical and/or mental performance and motivation over a discrete period. An intriguing question is whether and how age affects the ability to adapt gait to the state created by muscle and mental fatigability, in order to minimize a loss of daily function. Therefore, this thesis aimed to examine the effects of age and experimentally induced fatigability on human gait. In Chapter 2, we systematically reviewed studies that examined the effects of experimentally induced mental and muscle fatigability on older adults’ gait. We observed that muscle performance fatigability affects spatial and temporal features of gait and inter-stride trunk acceleration variability. In contrast, sustained mental activity tends only to affect step variability during dual-tasking. Although muscle and mental fatigability alter older adults’ gait performance, the mechanisms that explain why walking changes occur are unclear. Seeking to understand the mechanisms that explain how age and fatigability would affect gait, we experimentally induced muscle and mental fatigability and examined these fatigue effects on treadmill walking in 12 older and 12 younger adults. Muscle fatigability was induced by participants repeatedly performing the sit-to-stand task (rSTS). Mental fatigability was induced by participants performing demanding mental tasks for 30 minutes. In chapter 3, we verified that the rSTS and demanding mental tasks minimally affected the stride variables and the dynamics of walking on the treadmill in the two age groups. Regarding the mental fatigability, we interpreted that demanding mental tasks indicate to induce adaptation on gait only in dual-task conditions. We also speculated that age-specific modulations on neuromuscular control due to fatigability might have compensated for the effects of fatigue to maintain the gait performance. In addition, the effects of rSTS were perhaps not specific enough to induce changes in key elements of gait. In chapter 4, we examined the effects of age and exhaustive rSTS on muscle activation during ascent and descent phases of the STS task. We found that by performing remarkably fewer STS trials, older adults had minimized fatigability effects on muscle activation, voluntary force, and motor function, producing minimal changes in stride outcomes and gait dynamics after rSTS, as seen in Chapter 3. In chapter 5, we examined if there was an age-specific modulation in the common neural drive to muscles to compensate for muscle fatigability and spare gait function. We found that rSTS produced an age-specific compensatory strategy in the neural control of muscles to maintain the gait performance. Chapter 6 summarizes the main findings. We discussed the data from the perspective that: 1) the effects of age and fatigability may be more evident during real-life, overground walking situations involving cognitive and motor dual-tasking compared to walking on a treadmill and 2) perhaps, a fatigue-induction model that involved walking tasks and/or focused on specific aspects of the task (such as fatigue induced by long distances walking over level and/or inclined surfaces, or stairs ascent protocols) could be more effective in examining the effect of aging on gait adaptability. However, even with limited effects, rSTS produced age-specific changes in the neural drive for synergistic ankle muscles, which can be interpreted as compensation for fatigue that healthy older adults develop to maintain walking performance. CAPES: 001

Purpose: To study the association between fatigue and participation and QoL after acquired brain injury (ABI) in adolescents and young adults (AYAs). Materials & Methods: Cross-sectional study with AYAs aged 14-25 years, diagnosed with ABI. The PedsQL (TM) Multidimensional Fatigue Scale, Child & Adolescent Scale of Participation, and PedsQL (TM) 4.0 Generic Core Scales were administered. Results: Sixty-four AYAs participated in the study, 47 with traumatic brain injury (TBI). Median age at admission was 17.6 yrs, 0.8 yrs since injury. High levels of fatigue (median 44.4 (IQR 34.7, 59.7)), limited participation (median 82.5 (IQR 68.8, 92.3)), and diminished QoL (median 63.0 (IQR 47.8, 78.3)) were reported. More fatigue was significantly associated with more participation restrictions (beta 0.64, 95%CI 0.44, 0.85) and diminished QoL (beta 0.87, 95%CI 0.72, 1.02). Conclusions: AYAs with ABI reported high levels of fatigue, limited participation and diminished quality of life with a significant association between fatigue and both participation and QoL. Targeting fatigue in rehabilitation treatment could potentially improve participation and QoL.

Er is een relatie tussen vermoeidheid van piloten en (bijna) ongevallen in de luchtvaart. Dit heeft vooral te maken met vliegroosters van de bemanning en vooral van piloten, waardoor men veel uren maakt, met veel onregelmatigheid te maken heeft, tijdzones passeert, en onvoldoende mogelijkheden heeft om te slapen. Hierdoor is er niet alleen sprake van acute effecten van vermoeidheid, maar ook van opbouw van chronische vermoeidheid. Op de korte termijn zijn zowel de gevolgen van acute als van chronische vermoeidheid een gevaar voor de vliegveiligheid. Met name chronische vermoeidheid kan ook ernstige gezondheidsschade opleveren. Maatregelen om de acute gevolgen van vermoeidheid tegen te gaan zijn effectief op de korte termijn, maar zijn onvoldoende om de chronische vermoeidheid tegen te gaan. Hiervoor moet structureel rekening gehouden worden met het gezond plannen van roosters, zodat daadwerkelijk herstel optreedt.

Er is een relatie tussen vermoeidheid van piloten en (bijna) ongevallen in de luchtvaart. Dit heeft vooral te maken met vliegroosters van de bemanning en vooral van piloten, waardoor men veel uren maakt, met veel onregelmatigheid te maken heeft, tijdzones passeert, en onvoldoende mogelijkheden heeft om te slapen. Hierdoor is er niet alleen sprake van acute effecten van vermoeidheid, maar ook van opbouw van chronische vermoeidheid. Op de korte termijn zijn zowel de gevolgen van acute als van chronische vermoeidheid een gevaar voor de vliegveiligheid. Met name chronische vermoeidheid kan ook ernstige gezondheidsschade opleveren. Maatregelen om de acute gevolgen van vermoeidheid tegen te gaan zijn effectief op de korte termijn, maar zijn onvoldoende om de chronische vermoeidheid tegen te gaan. Hiervoor moet structureel rekening gehouden worden met het gezond plannen van roosters, zodat daadwerkelijk herstel optreedt.

MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2016 Mechanical screening is an important process which is used in a wide range of industries. This study focused on screens in the agricultural industry used for cleaning and classifying of grain. Mathematical models were developed and also implemented in computer programs used for design analysis of a vibration screen. This was regarded as necessary to investigate effective screening of maize in order to remove unwanted larger and smaller particles, and also to provide acceptable service life from a fatigue point of view. A three degree of freedom mathematical model was developed and used for prediction of static and dynamic displacements, static and dynamic forces, and also system natural frequencies. Another mathematical model was formulated and implemented in a computer program and used for fatigue analysis. All the input parameters required for the computer programs were characterised. Different mathematical models were also developed for characterisation of the screen rubber mount vertical and also horizontal stiffness and damping coefficients. Different measured data obtained from different test set-ups were used as input data for these programs respectively. Mount static stiffness coefficients were also experimentally determined. The required amplitude and frequency for a certain layer of maize was also characterised with electrodynamic Shaker tests, and two different feasible sieve apertures identified. Three different design goals for an optimisation approach were identified. Firstly, the criteria for vibration isolation an objective function based on the transmission of dynamic forces to the fixed foundation was formulated. Secondly, two different constraints that also influenced vibration isolation were also formulated. These constraints were regarded as necessary to ensure enough movement for effective sieving, but also to limit the horizontal and vertical mount displacements during transient conditions. Three-dimensional graphical representations and contour plots were constructed in a Matlab environment, and used to determine vertical and horizontal mount stiffness coefficients chosen as design variables, for an optimum design according to the criteria formulated. A Finite Element Analysis (FEA) approach was followed to investigate possible structural resonance of the elastic screen, and also to evaluate the structure’s vertical stiffness coefficient at the point of investigation. An FEA approach was also used to determine static and dynamic material stresses used for fatigue analysis to investigate the screen structure service life. The optimised design parameters were used to build and then test the vibration screen. Effective sieving was evaluated to remove the larger and smaller unwanted particles such as weed seeds, sand, small broken maize kernels, stalks, and maize plant stems as typically present, from harvested maize. Sufficient maize mass flow rates were also evaluated for different screen angles, and with two different sieves simultaneously used. The underlying three degree of freedom mathematical model for the vibration screen was experimentally validated. The predicted responses, dynamic forces, and also the system natural frequencies were compared to the corresponding measured values respectively. This was done for several operational conditions (transient and steady state), at an empty and fully loaded screen respectively. Transient conditions include start-up and shut-down of the screen. The grain vibration screen was designed to mainly sieve maize, but other grain such as sunflower, soybean, canola, groundnuts, wheat, barley, oats and sorghum could also be sieved. Masters

Chemotherapie gaat vaak gepaard met verminderde fysieke fitheid en spierkracht, en een toename in vermoeidheid. Steeds meer onderzoeken suggereren dat lichamelijke beweging tijdens chemotherapie kan bijdragen aan het verminderen of voorkomen van deze problemen. Het is echter onduidelijk welke vorm en intensiteit van bewegen het beste is; een gestructureerd, begeleid programma of juist een programma dat thuis kan worden uitgevoerd. In dit artikel wordt de achtergrond en de opzet van een multicentrum, gerandomiseerde studie beschreven, die als doel heeft deze vragen te beantwoorden.

Background Research suggests that cancer rehabilitation reduces fatigue in survivors of cancer. To date, it is unclear what type of rehabilitation is most beneficial. Objective This randomized controlled trial compared the effect on cancer-related fatigue of physical training combined with cognitive behavioral therapy with physical training alone and with no intervention. Design In this multicenter randomized controlled trial, 147 survivors of cancer were randomly assigned to a group that received physical training combined with cognitive-behavioral therapy (PT+CBT group, n=76) or to a group that received physical training alone (PT group, n=71). In addition, a nonintervention control group (WLC group) consisting of 62 survivors of cancer who were on the waiting lists of rehabilitation centers elsewhere was included. Setting The study was conducted at 4 rehabilitation centers in the Netherlands. Patients All patients were survivors of cancer. Intervention Physical training consisting of 2 hours of individual training and group sports took place twice weekly, and cognitive-behavioral therapy took place once weekly for 2 hours. Measurements Fatigue was assessed with the Multidimensional Fatigue Inventory before and immediately after intervention (12 weeks after enrollment). The WLC group completed questionnaires at the same time points. Results Baseline fatigue did not differ significantly among the 3 groups. Over time, levels of fatigue significantly decreased in all domains in all groups, except in mental fatigue in the WLC group. Analyses of variance of postintervention fatigue showed statistically significant group effects on general fatigue, on physical and mental fatigue, and on reduced activation but not on reduced motivation. Compared with the WLC group, the PT group reported significantly greater decline in 4 domains of fatigue, whereas the PT+CBT group reported significantly greater decline in physical fatigue only. No significant differences in decline in fatigue were found between the PT+CBT and PT groups. Conclusions Physical training combined with cognitive-behavioral therapy and physical training alone had significant and beneficial effects on fatigue compared with no intervention. Physical training was equally effective as or more effective than physical training combined with cognitive-behavioral therapy in reducing cancer-related fatigue, suggesting that cognitive-behavioral therapy did not have additional beneficial effects beyond the benefits of physical training.

Knee injuries commonly occur in later stages of competition indicating that fatigue may influence dynamic knee stability. Force sense (FS) is a submodality of proprioception influenced by muscle mechanoreceptors, and, if negatively affected by fatigue, may results in less effective neuromuscular control. OBJECTIVES: To determine the effects of peripheral fatigue on FS of the quadriceps and hamstrings. DESIGN: Quasi-experimental study design. PARTICIPANTS: Twenty healthy and physically active females and males (age: 23.4±2.7 years, mass: 69.5±10.9kg, height: 169.7±9.4cm) participated. INTERVENTIONS: Fatigue was induced during a protocol with two sets of 40 repetitions, and the last set truncated at 90 repetitions or stopped if torque production dropped below 25% of peak torque. MAIN OUTCOME MEASURES: FS of the hamstrings and quadriceps was tested on separate days before and after three sets of isokinetic knee flexion and extension to fatigue by examining the ability to produce a target isometric torque (15% MVIC) with and without visual feedback (FS Error). Electromyographic data of the tested musculature were collected in order to calculate and determine median frequency shift. T-tests and Wilcoxon Signed Rank tests were conducted to examine pre-fatigue and post-fatigue FS Error for flexion and extension. RESULTS: Despite verification of fatigue via torque production decrement and shift in median frequency, no significant differences were observed in FS Error for either knee flexion (pre=0.54±2.28 N·m; post=0.47±1.62 N·m) or extension (pre=-0.28±2.69 N·m; post=-0.21±1.78 N·m) pre-fatigue compared to the post-fatigue condition. CONCLUSIONS: Although previous research has demonstrated that peripheral fatigue negatively affects TTDPM, it did not affect FS as measured in this study. The peripheral fatigue protocol may have a greater effect on the mechanoreceptors responsible for TTDPM than those responsible for FS. Further investigation into the effects of fatigue across various modes of proprioception is warranted.

Knee injuries commonly occur in later stages of competition indicating that fatigue may influence dynamic knee stability. Force sense (FS) is a submodality of proprioception influenced by muscle mechanoreceptors, and, if negatively affected by fatigue, may results in less effective neuromuscular control. OBJECTIVES: To determine the effects of peripheral fatigue on FS of the quadriceps and hamstrings. DESIGN: Quasi-experimental study design. PARTICIPANTS: Twenty healthy and physically active females and males (age: 23.4±2.7 years, mass: 69.5±10.9kg, height: 169.7±9.4cm) participated. INTERVENTIONS: Fatigue was induced during a protocol with two sets of 40 repetitions, and the last set truncated at 90 repetitions or stopped if torque production dropped below 25% of peak torque. MAIN OUTCOME MEASURES: FS of the hamstrings and quadriceps was tested on separate days before and after three sets of isokinetic knee flexion and extension to fatigue by examining the ability to produce a target isometric torque (15% MVIC) with and without visual feedback (FS Error). Electromyographic data of the tested musculature were collected in order to calculate and determine median frequency shift. T-tests and Wilcoxon Signed Rank tests were conducted to examine pre-fatigue and post-fatigue FS Error for flexion and extension. RESULTS: Despite verification of fatigue via torque production decrement and shift in median frequency, no significant differences were observed in FS Error for either knee flexion (pre=0.54±2.28 N·m; post=0.47±1.62 N·m) or extension (pre=-0.28±2.69 N·m; post=-0.21±1.78 N·m) pre-fatigue compared to the post-fatigue condition. CONCLUSIONS: Although previous research has demonstrated that peripheral fatigue negatively affects TTDPM, it did not affect FS as measured in this study. The peripheral fatigue protocol may have a greater effect on the mechanoreceptors responsible for TTDPM than those responsible for FS. Further investigation into the effects of fatigue across various modes of proprioception is warranted.

Background. The aims of the study were to examine the effects of a multidimensional rehabilitation program on cancer-related fatigue, to examine concurrent predictors of fatigue, and to investigate whether change in fatigue over time was associated with change in predictors. Methods. Sample: 72 cancer survivors with different diagnoses. Setting: rehabilitation center. Intervention: 15-week rehabilitation program. Measures: Fatigue (Multidimensional Fatigue Inventory), demographic and disease/treatment-related variables, body composition (bioelectrical impedance), exercise capacity (symptom-limited bicycle ergometry), muscle force (handheld dynamometry), physical and psychological symptom distress (Rotterdam Symptom Check List), experienced physical and psychological functioning (RAND-36), and self-efficacy (General-Self-Efficacy Scale, Dutch version). Measurements were performed before (T0) and after rehabilitation (T1). Results. At T1 (n = 56), significant improvements in fatigue were found, with effect sizes varying from −0.35 to −0.78. At T0, the different dimensions of fatigue were predicted by different physical and psychological variables. Explained variance of change in fatigue varied from 42%–58% and was associated with pre-existing fatigue and with change in physical functioning, role functioning due to physical problems, psychological functioning, and physical symptoms distress. Conclusions. Within this selected group of patients we found that (a) rehabilitation is effective in reducing fatigue, (b) both physical and psychological parameters predicted different dimensions of fatigue at baseline, and (c) change in fatigue was mainly associated with change in physical parameters.

The effects of short-term oral creatine supplementation (20 g a day for 6 days) on muscle activation, fatigue and recovery of the m. quadriceps femoris and on maximum performance sprint cycling were investigated during electrical stimulation. Twenty-three well-trained rowers participated in this double blind, placebo-controlled study. Forty repetitive electrically stimulated concentric contractions were imposed at a constant angular velocity of 180°/s (from 90°-140° knee angle). To determine recovery, torque was measured at various intervals after the last contraction. In addition, two maximum 30 second sprints were performed on a cycle ergometer (4 minutes rest). Body mass (mean ± SEM) increased significantly from 85.7± 2.7 to 87.3 ± 2.9 kg in the creatine group (placebo group: 82.6 ± 3.0 to 82.7 ± 2.9 kg). Creatine supplementation had no effect on maximal voluntary isometric torque or on electrically-elicited torque production, fatigability or the recovery rate. Furthermore, there were no significant effects on peak power, time to peak power and work to peak power, or on total work during the two sprints. It was concluded that short-term oral creatine supplementation does not enhance muscle performance or maximum output during sprint cycling.

Background Burn injuries have a major impact on the patient’s physical and psychological functioning. The consequences can, especially in pediatric burns, persist long after the injury. A decrease in physical fitness seems logical as people survive burn injuries after an often extensive period of decreased activity and an increased demand of proteins leading to catabolism, especially of muscle mass. However, knowledge on the possibly affected levels of physical fitness in children and adolescents after burn injury is limited and pertains only to children with major burns. The current multidimensional study aims to determine the level of physical fitness, the level of physical activity, health-related quality of life and perceived fatigue in children after a burn injury. Furthermore, interrelations between those levels will be explored, as well as associations with burn characteristics. Methods/design Children and adolescents in the age range of 6 up to and including 18 years are invited to participate in this cross-sectional descriptive study if they have been admitted to one of the three Dutch burn centers between 6 months and 5 years ago with a burn injury involving at least 10% of the total body surface area and/or were hospitalized ≥ 6 weeks. Physical fitness assessments will take place in a mobile exercise lab. Quantitative measures of cardiorespiratory endurance, muscular strength, body composition and flexibility will be obtained. Outcomes will be compared with Dutch reference values. Physical activity, health-related quality of life and fatigue will be assessed using accelerometry and age-specific questionnaires. Discussion The findings of the current study will contribute to a better understanding of the long-term consequences of burn injury in children and adolescents after burns. The results can guide rehabilitation to facilitate a timely and optimal physical recovery. Trial registration The study is registered in the National Academic Research and Collaborations Information System of the Netherlands (OND1348800).

Chemotherapie gaat vaak gepaard met verminderde fysieke fitheid en spierkracht, en een toename in vermoeidheid. Steeds meer onderzoeken suggereren dat lichamelijke beweging tijdens chemotherapie kan bijdragen aan het verminderen of voorkomen van deze problemen. Het is echter onduidelijk welke vorm en intensiteit van bewegen het beste is; een gestructureerd, begeleid programma of juist een programma dat thuis kan worden uitgevoerd. In dit artikel wordt de achtergrond en de opzet van een multicentrum, gerandomiseerde studie beschreven, die als doel heeft deze vragen te beantwoorden.

De term vermoeidheid of fatigue heeft de laatste jaren veel aandacht gekregen in de zeescheepvaart. Redenen hiervoor zijn recente studies die aangaven dat vermoeidheid een serieus onderwerp is en oorzaak is van ernstige ongelukken als strandingen, aanvaringen en "near misses". Maar is er inmiddels genoeg gedaan om dit te ondervangen?

The aim of this study was to investigate the effect of using a notebook stand on the physical load when working with a notebook in a home environment. Sixteen subjects evaluated working with a notebook by performing three different tasks using two notebook stands and without using a notebook stand. Body posture, productivity, perceived fatigue and comfort / discomfort and personal preference were measured. The authors found that subjects have significantly less neck flexion when using a notebook stand compared to using only a notebook. They also rated significantly less subjective fatigue in the neck when using a notebook stand. From this study, it can be concluded that the neck posture is objectively more neutral and subjectively less fatiguing. www.humanfactors.nl

Op aandringen van de arbodienst voerde Corus in 2006 een nieuw ploegenrooster in dat minder schadelijk zou zijn voor het personeel. Recent onderzoek laat zien dat dit ook zo uitpakt. Dat geldt voor aspecten als ziekteverzuim, vermoeidheid, werkdruk en dergelijke. Maar wat de heilzame werking van het nieuwe rooster precies bewerkstelligt, weet niemand nog.