Neuromuscular (NM) fatigue can be defined as an exercise-induced decrease in skill-based performance and/or capacity that originates within the NM system (i.e. between activation of the primary motor cortex to the performance of the contractile apparatus (Bigland-Ritchie, 1981)) (Boyas & Guével, 2011). NM fatigue is a fundamental component of athlete training and competition, required for both optimal adaptation and performance. However, in the short-term, NM fatigue can decrease performance and increase injury risk, whilst its accumulation can produce long-term deleterious performance and health consequences. Consequently, athlete fatigue monitoring is recommended for precise management of athlete training adaptation and recovery practices. Regular NM function measurement is a key component of athlete fatigue monitoring; still the best means of assessing fatigue-induced effects on NM function is presently unclear. A broader understanding of the most suitable NM testing methods, and associated NM constructs, would therefore be of value to sport practitioners. As elaborated below, this dissertation aimed to first identify the most suitable NM function test, and then develop the testing technique to better determine the NM responses associated with acute fatigue, an accumulation of exercise stress (i.e. accumulated fatigue), and post-exercise recovery. A secondary aim was to provide a greater understanding of the NM responses elicited by fatiguing exercise. First, the suitability of four NM function tests (e.g. countermovement jump (CMJ), squat jump (SJ), drop jump (DJ), 20-m sprint (SPRINT)) for the regular measurement of NM fatigue was examined. Assessment of test repeatability (mean coefficient of variation for various measures of force, velocity, power, impulse and flight time; SPRINT: 1.2%; CMJ: 3.0%; SJ: 3.5%; DJ: 4.8%) and sensitivity to NM fatigue (substantial post-exercise changes observed up to; SPRINT: 0-hr post; SJ: 24-hr post; CMJ & DJ: 72-hr post) revealed the CMJ test to be the most suitable, with it highly repeatable and sensitive to fatigue-induced changes immediately following fatiguing exercise and during post-exercise recovery. Subsequent investigations further explored the use of CMJ testing for NM fatigue detection. Second, CMJ responses to acute NM fatigue and during post-exercise recovery were examined in recreational athletes. As part of this process, two analytic approaches, anticipated to decrease measurement error and improve test sensitivity through the examination of CMJ mechanics, were utilised. Fatiguing exercise resulted in a biphasic recovery profile. Immediate decreases were evident in most CMJ variables (i.e. small-to-moderate changes), followed by mechanical changes indicative of NM fatigue (i.e. small changes in CMJ time- and rate-based variables) at 72-hour. Observation of mechanical changes at 72-hour, supported the use of the two adopted CMJ analytic approaches. Third, the developed methodology was used with elite snowboard-cross athletes to examine fatigue- and training-induced changes in NM function. Compared to concentric CMJ variables (i.e. peak/mean power/force/velocity), mechanical CMJ changes were more marked following both the fatiguing protocol (ES: moderate-to-large vs. small-to-moderate) and the 19-week training block (large-to-extremely large vs. small-to-very large). The more apparent mechanical changes observed in this highly-trained population (vs. the recreational athletes in Chapter 3) indicated that CMJ mechanical analysis may be of particular value in athlete populations. Fourth, the CMJ testing techniques were used to examine NM changes associated with accumulated fatigue (i.e. an accumulation of exercise and/or non-exercise stress) in a highly-trained population. Alongside increased training loads and decreased wellness, substantial changes in CMJ mechanics (e.g. time to peak force, force at zero velocity) and jump outcome (e.g. flight time, peak displacement) were observed, thereby supporting the inclusion of mechanical CMJ assessment for the monitoring of accumulated NM fatigue effects. This series of investigations support the use of CMJ testing for athlete NM fatigue monitoring, and highlight that NM fatigue can manifest as alterations in the mechanical strategies used to accomplish a task. These changes appear evident in response to acute fatigue (Chapters 3 and 4), alongside increases in training load (Chapters 4 and 5) and during post-exercise recovery (Chapter 3). Practitioners should therefore incorporate analyses of CMJ mechanics to provide a more comprehensive assessment of fatigue- and training-induced changes in NM function. / Graduate / gatherco@uvic.ca

No description available.

The aim of this study was to examine and compare the contribution of central neuromuscular fatigue and peripheral neuromuscular fatigue to total neuromuscular fatigue in the hemiplegic leg of people with stroke, with that of a matched control group.Study Design: This experimental study utilised a repeated measures block design.Participants: Fifteen people with chronic stroke who had mild to moderate physical disability and fifteen age, height and weight matched controls were compared.Main outcome measures: Participants physical function was evaluated using the 30s Chair Stand Test, Comfortable Paced Walking Speed and Fast Paced Walking Speed. Neuromuscular function was measured using maximal voluntary isometric contraction force and voluntary activation. Total neuromuscular fatigue, central neuromuscular fatigue and peripheral neuromuscular fatigue was measured during a 90 second sustained maximal voluntary isometric contraction of the quadriceps muscle.Results: The fatigue profile of stroke participants differed from that of control participants. Stroke participants demonstrated less total neuromuscular fatigue (U=41.00, p=.026) and less peripheral neuromuscular fatigue (U=14.00, p=.000) than the control participants. While stroke participants did demonstrate greater central neuromuscular fatigue than control participants, this finding was not statistically significant (U=80.00, p=.817).Conclusions: Statistically significant differences were found in the performance of people with mild to moderate physical disability following stroke on measures of neuromuscular fatigue when compared to age, weight and height matched healthy adults.

The aim of this study was to examine and compare the contribution of central neuromuscular fatigue and peripheral neuromuscular fatigue to total neuromuscular fatigue in the hemiplegic leg of people with stroke, with that of a matched control group.Study Design: This experimental study utilised a repeated measures block design.Participants: Fifteen people with chronic stroke who had mild to moderate physical disability and fifteen age, height and weight matched controls were compared.Main outcome measures: Participants physical function was evaluated using the 30s Chair Stand Test, Comfortable Paced Walking Speed and Fast Paced Walking Speed. Neuromuscular function was measured using maximal voluntary isometric contraction force and voluntary activation. Total neuromuscular fatigue, central neuromuscular fatigue and peripheral neuromuscular fatigue was measured during a 90 second sustained maximal voluntary isometric contraction of the quadriceps muscle.Results: The fatigue profile of stroke participants differed from that of control participants. Stroke participants demonstrated less total neuromuscular fatigue (U=41.00, p=.026) and less peripheral neuromuscular fatigue (U=14.00, p=.000) than the control participants. While stroke participants did demonstrate greater central neuromuscular fatigue than control participants, this finding was not statistically significant (U=80.00, p=.817).Conclusions: Statistically significant differences were found in the performance of people with mild to moderate physical disability following stroke on measures of neuromuscular fatigue when compared to age, weight and height matched healthy adults.

A incapacidade de produzir repetidamente no tempo um determinado nível de força ou potência muscular designa-se por fadiga neuromuscular. A etiologia da fadiga muscular tem atraído o interesse de pesquisadores há mais de um século. Contudo, os seus agentes e locais definitivos permanecem ainda por serem identificados. Este trabalho teve por objetivo avaliar a fadiga neuromuscular por meio da análise de frequência do sinal eletromiográfico dos músculos masseter e temporal anterior de ambos os lados em 3 grupos distintos: sujeitos saudáveis assintomáticos para disfunção temporomandibular (DTM), pacientes acometidos por DTM tratados com placa oclusal resiliente e pacientes acometidos por DTM tratados com placa oclusal rígida. Para isso, participaram da pesquisa 100 sujeitos assintomáticos para DTM e 30 pacientes com DTM subdivididos em 2 grupos: tratados com placa rígida tipo FARC; e tratados com placa resiliente. Todos realizaram exame eletromiográfico antes e após o tratamento com placa oclusal. Os resultados demonstraram que houve diferenças estatisticamente significantes na comparação da taxa de fadiga avaliada antes e após o tratamento com placa oclusal, tanto para o grupo Placa FARC como para o grupo Placa Soft. Houve diminuição da taxa de fadiga após o tratamento com placa para os músculos masseter esquerdo e temporal anterior direito para o grupo Placa Soft; e diminuição da taxa de fadiga após o tratamento para o músculo temporal anterior esquerdo para o grupo Placa FARC. Pode-se concluir que o tratamento com ambos tipos de placa oclusal foi eficiente na redução da taxa de fadiga neuromuscular em pacientes acometidos por DTM. / The repeated failure to produce in time a certain level of strength or muscle power is called neuromuscular fatigue. The etiology of muscle fatigue has attracted the interest of researchers for over a century. However, their agents and local definitive remain yet to be identified. This work aimed to evaluate neuromuscular fatigue by frequency analysis of the electromyographic signal of the masseter and anterior temporal muscles of both sides in three different groups: healthy subjects asymptomatic for temporomandibular disorders (TMD), patients suffering from TMD treated with resilient occlusal splint and patients suffering from TMD treated with rigid occlusal splint. For this, 100 subjects asymptomatic for TMD participated in the survey and 30 patients with TMD subdivided into 2 groups: treated with rigid splint type FARC, and treated with resilient splint. All electromyographic examinations performed before and after treatment with occlusal splint. The results showed that statistically significant differences when comparing the rate of fatigue assessed before and after treatment with occlusal appliance, for both groups. There was a decrease in the rate of fatigue after treatment with occlusal splint to the left masseter and right anterior temporal in the group Soft Splint; and decrease in the rate of fatigue after treatment for left anterior temporal muscle to the group FARC Splint. It can be concluded that treatment with both types of occlusal splint was effective in reducing the rate of neuromuscular fatigue in patients affected by TMD.

Background: A high injury-incidence in the world of youth team sports requires athletes, teams and healthcare to invest big amounts of money and time. There is a need to find implementable time- and cost-effective strategies that can highlight youth athletes at increased risk of sustaining injuries, to inform the physiotherapist’s/coach’s training plan for training load adjustments. Aim: The primary aim of this report is to investigate whether the rebound jump test (RJ) can be used to detect neuromuscular fatigue, to try minimize the risk of sustaining injuries in youth team sports. The secondary aim is to investigate how the reactive strength index (RSI) in the RJ correlate with the drop jump test (DJ), to try establish concurrent validity of the RJ. Method: In total, 46 male youth soccer players (17,1 ± 1,2 years old) were recruited. RJ were performed in a non-fatigued state and in a fatigued state after a hard football session, whilst the DJ was performed in a non-fatigued state only. Results: RSI-RJ was strongly correlated with the RSI-DJ (r=0,83, r²= 0,69, p<0,01) and there was a significant -12 % difference between RSI-fresh and RJ-fatigue in the RJ (p<0,01). Conclusion: RJ is a valid test to measure neuromuscular fatigue and could inform the physiotherapist/coach about each athletes’ readiness to train on a weekly basis.

A incapacidade de produzir repetidamente no tempo um determinado nível de força ou potência muscular designa-se por fadiga neuromuscular. A etiologia da fadiga muscular tem atraído o interesse de pesquisadores há mais de um século. Contudo, os seus agentes e locais definitivos permanecem ainda por serem identificados. Este trabalho teve por objetivo avaliar a fadiga neuromuscular por meio da análise de frequência do sinal eletromiográfico dos músculos masseter e temporal anterior de ambos os lados em 3 grupos distintos: sujeitos saudáveis assintomáticos para disfunção temporomandibular (DTM), pacientes acometidos por DTM tratados com placa oclusal resiliente e pacientes acometidos por DTM tratados com placa oclusal rígida. Para isso, participaram da pesquisa 100 sujeitos assintomáticos para DTM e 30 pacientes com DTM subdivididos em 2 grupos: tratados com placa rígida tipo FARC; e tratados com placa resiliente. Todos realizaram exame eletromiográfico antes e após o tratamento com placa oclusal. Os resultados demonstraram que houve diferenças estatisticamente significantes na comparação da taxa de fadiga avaliada antes e após o tratamento com placa oclusal, tanto para o grupo Placa FARC como para o grupo Placa Soft. Houve diminuição da taxa de fadiga após o tratamento com placa para os músculos masseter esquerdo e temporal anterior direito para o grupo Placa Soft; e diminuição da taxa de fadiga após o tratamento para o músculo temporal anterior esquerdo para o grupo Placa FARC. Pode-se concluir que o tratamento com ambos tipos de placa oclusal foi eficiente na redução da taxa de fadiga neuromuscular em pacientes acometidos por DTM. / The repeated failure to produce in time a certain level of strength or muscle power is called neuromuscular fatigue. The etiology of muscle fatigue has attracted the interest of researchers for over a century. However, their agents and local definitive remain yet to be identified. This work aimed to evaluate neuromuscular fatigue by frequency analysis of the electromyographic signal of the masseter and anterior temporal muscles of both sides in three different groups: healthy subjects asymptomatic for temporomandibular disorders (TMD), patients suffering from TMD treated with resilient occlusal splint and patients suffering from TMD treated with rigid occlusal splint. For this, 100 subjects asymptomatic for TMD participated in the survey and 30 patients with TMD subdivided into 2 groups: treated with rigid splint type FARC, and treated with resilient splint. All electromyographic examinations performed before and after treatment with occlusal splint. The results showed that statistically significant differences when comparing the rate of fatigue assessed before and after treatment with occlusal appliance, for both groups. There was a decrease in the rate of fatigue after treatment with occlusal splint to the left masseter and right anterior temporal in the group Soft Splint; and decrease in the rate of fatigue after treatment for left anterior temporal muscle to the group FARC Splint. It can be concluded that treatment with both types of occlusal splint was effective in reducing the rate of neuromuscular fatigue in patients affected by TMD.

Orientador: Antonio Carlos de Moraes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Fisica / Made available in DSpace on 2018-08-10T17:31:59Z (GMT). No. of bitstreams: 1 Fontes_EduardoBodnariuc_M.pdf: 546789 bytes, checksum: e5cf58e2e5bc2c9f182d7e783137819d (MD5) Previous issue date: 2008 / Resumo: LFNM estabelecido por diferentes períodos de análise do sinal eletromiográfico e comparar os mesmos com a Potência Crítica - PC em indivíduos saudáveis. A amostra foi composta por 17 voluntários saudáveis do sexo masculino (23,4 ± 5,2 anos, 73,6 ± 5,08 kg, 177,8 ± 7,0 cm). Para determinar o LFNM, cada sujeito realizou entre três e quatro cargas constantes no cicloergometro (modelo Corival 400, Quinton Inc, USA) até a exaustão voluntária, com cadência de 60 rpm. Utilizando um eletromiógrafo de 16 canais (MP150, Biopac Systems, Inc., USA), foram coletados sinais EMG do músculo Vasto Lateral. O LFNM foi calculado pelo modelo matemático proposto por (DEVRIES et al., 1982), no qual a taxa de aumento do sinal eletromiográfico atingido durante as cargas constantes é plotado em função das respectivas cargas, sendo o intercepto ¿y¿ do prolongamento desta reta considerado o LFNM. Tal procedimento foi reproduzido para cada um dos tempos de duração de análise, 30 segundos (T30s), um minuto (T1min), dois minutos (T2min) e tempo total (TTotal). PC foi determinada através do modelo hiperbólico. Utilizando a potência de LFNM encontrada por TTotal, foi verificado ainda a capacidade dos voluntários de permanecer em teste retangular de 30 min, sem evidência de fadiga neuromuscular. Foram encontradas diferenças significativas entre os períodos de análise para determinação de LFNM (ANOVA). Utilizando T30s a média alcançada foi 266,7 ± 23,1 W, com T1min ficou em 243,4 ± 16,2 W, para T2min obteve 232,6 ± 18,3 W, e utilizando TTotal a média foi de 217,2 ± 23,1 W, já para PC, foi encontrado valores médios de 177,9 ± 27,3 W. Foram encontradas diferenças estatisticamente significantes entre T30s e todos os outros períodos de análise, T1min, T2min e TTotal (p<0,01). O LFNM determinado com T1min, foi diferente estatisticamente também de TTotal (p<0,01). Todos os períodos de análise utilizados para determinar LFNM superestimaram estatisticamente PC (p<0,01). Foi encontrada correlação significativa apenas para TTotal e PC (R2 = 0,72). Durante o protocolo de carga retangular de 30 minutos, a média da exaustão ocorreu em 661,6 ± 303,9 segundos, apenas um dos voluntários completou os teste de 30 minutos. O nível de significância adotado para todas as análises foi de 5%. A partir dos resultados do presente estudo, é possível concluir que o tempo de análise influencia na determinação de LFNM, superestimando PC e a capacidade de adultos jovens em realizar exercícios de carga constante de 30 minutos em cicloergômetro / Abstract: The purpose of this study was to establish the Neuromuscular Fatigue Threshold - LFNM determinied by different analysis periods of electromyography sign and compare to the Critical Power - CP in healthy young men. 17 healthy men volunteers (23,4 ± 5,2 years, 73,6 ± 5,08 kg, 177,8 ± 7,0 cm) completed three or four constant loads tests on a cycling ergometer to establish LFNM (model Corival 400, Quinton Inc, USA) until exhaustion, and the pedal cadence was 60 rpm. Using an amplifier with 16 channels (MP150, Biopac Systems, Inc., USA), were collected EMG signs from Vastus Lateralis muscle from the dominant side. The LFNM were calculated by the mathematical model proposed by DeVries et al., (1982) where the LFNM was considered the y intercept of the regression line the EMG slopes from contant load tests plotted against its respective load. CP was calculated using the hyperbolic equation model. The LFNM procedure was done by each period of EMG analysis 30 seconds (T30s), one minute (T1min), two minutes (T2min) and total period (TTotal). Using LFNM established by TTotal, were verified the capacity of the volunteers to complete a 30 minutes constant load test, without neuromuscular fatigue. ANOVA found statistical differences between analysis periods. Using T30s, the mean found were 266,7 ± 23,1 W, with T1mn were 243,4 ± 16,2 W, for T2min were 232,6 ± 18,3 W, and with TTotal, the mean were 217,2 ± 23,1 W, however, for CP were found 177,9 ± 27,3 W. Were found statistical differences between T30s and all the others analysis periods, T1min, T2min and Total (p<0,01). The LFNM established by T1min were also different from TTotal (p<0,01). All the analysis periods overestimated PC (p<0,01). Were found significant correlation between only PC and TTotal (R2 = 0,72). During the 30 minutes constant load test completed, the exhaustion mean time were 661,6 ± 303,9 seconds, and only one volunteer completed all the 30 minutes. The significance level adopted for all analysis was 5%. According to the results of this study, it is possible to conclude that the analysis periods influences the determination of LFNM, and it overestimates CP and the capacity of the healthy adults to complete a 30 minutes constant load test in cycling ergometer / Mestrado / Ciencia do Desporto / Mestre em Educação Física

Placebo treatments have long been used to study the psychological effects of expectancy and conditioning on an inert intervention. Interestingly, open-label placebo treatments (i.e., directly telling subjects they are receiving an inactive intervention) have recently shown promise in minimizing pain in clinical patient populations. We utilized a repeated measures design to examine the acute effects of placebo, open-label placebo, and control treatments on muscle strength and voluntary activation (Experiment #1), as well as neuromuscular fatigue (Experiment #2). Twenty-one untrained males (n=11) and females (n=10) visited the laboratory on three occasions to receive each treatment in a randomized, counter-balanced manner. All visits involved a pretest, 15-minute intervention period, and posttest. In Experiment #1, knee extensor maximal voluntary isometric contraction (MVIC) peak torque and percent voluntary activation were evaluated. In Experiment #2, subjects performed 20, six-second MVICs while surface electromyographic signals were detected from the vastus lateralis. Subjective assessments of energy and perceived exertion were also examined. In Experiment #1, no differences among interventions were demonstrated for peak torque or voluntary activation, but a main effect revealed that energy levels increased following each treatment (p = .016, η2 = .257). Experiment #2 demonstrated that placebo and open-label placebo treatments had no influence on neuromuscular fatigue, but there were main effects for declines in absolute (p = .001, η2 = .675) and normalized peak torque (p = .001, η2 = .765), electromyographic mean frequency (p = .001, η2 = .565), neuromuscular efficiency (p = .001, η2 = .585), and energy levels (p = .006, η2 = .317). Collectively, placebo and open-label placebo treatments had minimal influence on strength, voluntary activation, and fatigue resistance in untrained subjects. We speculate that our subject population and study design intricacies that are unique to placebo trials may explain our findings.

Age-related deficits in muscle mass, strength, and function place an increased burden of work on existing skeletal muscle and may lead to early onset of neuromuscular fatigue (NMF) during activities of daily living. Resistance exercise (RE) is the proven method for improving neuromuscular function in healthy older adults. PURPOSE: To investigate the effects of 6 weeks of RE on the NMF threshold as well as strength and functional performance in older adults. METHODS: Twenty-four older adults were randomly assigned to 6 weeks of RE (EXE; n = 12; age 72 ± 6.3 y; BMI 28.4 kg/m2 ) or control (CONT; n = 12; age 70.3 ± 5.6 y; BMI 27.6 kg/m2 ). Body fat percent (BF%), lean mass (LM), and fat mass (FM) were measured using DEXA and participants performed a discontinuous cycle ergometer test, physical working capacity at fatigue threshold (PWCFT), to determine the onset of NMF. Functional performance was assessed by time to complete 5 chair rises (CHAIR) and walk an 8-foot course (WALK). Lower body strength was assessed by predicted 1-RM leg extension (1RM). Two-way Analysis of Variance (ANOVA; time [PRE, POST] x group [EXE and CONT]) and magnitude based inferences were used to compare dependent variables. RESULTS: RE significantly increased 1RM (35%; p = 0.001) and CHAIR (20%; p = 0.047). RE had a likely beneficial effect on WALK (15%) and a possibly beneficial effect on PWCFT (14%). There were no significant changes to LM or FM, however, women in EXE significantly decreased BF% (p = 0.020). CONCLUSION: Results suggest that RE improves measures of strength and functional performance and possibly the onset of NMF in older adults.