Fatigue is defined as an exercise-induced decrease in maximal voluntary force produced by a muscle. Fatigue may arise from central and/or peripheral mechanisms. Supraspinal fatigue (a component of central fatigue) is defined as a suboptimal output from the motor cortex and measured using transcranial magnetic stimulation (TMS). Reductions in O2 supply (hypoxia) exacerbate fatigue and as the severity of hypoxia increases, central mechanisms of fatigue are thought to contribute more to exercise intolerance. In study 1, the feasibility of TMS to measure cortical voluntary activation and supraspinal fatigue of human knee-extensors was determined. TMS produced reliable measurements of cortical voluntary activation within- and between-days, and enabled the assessment of supraspinal fatigue. In study 2, the mechanisms of fatigue during single-limb exercise in normoxia (arterial O2 saturation [SaO2] ~98%), and mild to severe hypoxia (SaO2 93-80%) were determined. Hypoxia did not alter neuromuscular function or cortical voluntary activation of the knee-extensors at rest, despite large reductions in cerebral oxygenation. Maximal force declined by ~30% after single-limb exercise in all conditions, despite reduced exercise time in severe-hypoxia compared to normoxia (15.9 ± 5.4 vs. 24.7 ± 5.5 min; p < 0.05). Peripheral mechanisms of fatigue contributed more to the reduction in force generating capacity of the knee-extensors following single-limb exercise in normoxia and mild- to moderate-hypoxia, whereas supraspinal fatigue played a greater role in severe-hypoxia. In study 3, the effect of constant-load cycling exercise to the limit of tolerance in hypoxia (SaO2 ~80%) and normoxia was investigated. Time to the limit of tolerance was significantly shorter in hypoxia compared to normoxia (3.6 ± 1.3 vs. 8.1 ± 2.9 min; p < 0.001). The reductions in maximal voluntary force and knee-extensor twitch force at task-failure were not different in hypoxia compared to normoxia. However, the level of supraspinal fatigue was exacerbated in hypoxia, and occurred in parallel with reductions in cerebral oxygenation and O2 delivery. Supraspinal fatigue contributes to the decrease in whole-body exercise tolerance in hypoxia, presumably as a consequence of inadequate O2 delivery to the brain.

O objetivo do presente estudo foi analisar os efeitos da execução prévia de exercício físico e cognitivo sobre os componentes central e periférico da fadiga neuromuscular durante um teste contrarrelógio de 4 km de ciclismo. Para tanto, oito ciclistas treinados (n = 8) participaram de três diferentes estudos. No estudo 1, os atletas realizaram o teste contrarrelógio após assistir documentário (CON) ou após tarefa cognitiva (TC). No estudo 2, o teste de 4 km de ciclismo foi realizado após 100 drop jumps (DJ), 48 horas após 100 drop jumps (48h-DJ) e sem a realização prévia de exercício (CON). No estudo 3, o teste contrarrelógio foi realizado após fadiga prévia de membros superiores (FB) e inferiores (FP) e sem fadiga prévia (CON). Em todos os estudos, parâmetros de fadiga central e periférica foram avaliados por meio da técnica de estimulação elétrica no nervo femoral em repouso, pré e pós 4km de ciclismo. Estudo 1: O desempenho foi similar (P> 0,05) entre CON (376 ± 26,9 s) e TC (376,3 ± 26 s). Do mesmo modo, não encontramos diferenças significativas (P> 0,05) para parâmetros de fadiga central e periférica entre CON e TC. Estudo 2. O desempenho foi significativamente (P< 0,05) prejudicado em DJ (-2,3%) e houve uma tendência em 48h-DJ (-1,8%). A redução no desempenho em 48h-DJ foi devido à menor potência na parte inicial da prova (P< 0,05). Em DJ a piora no desempenho foi em decorrência de menor potência (P< 0,05) na parte inicial e final da prova. Houve uma exacerbada (P< 0,05) fadiga periférica após o contrarrelógio em DJ (1Hzpot= -44,7%) comparado com CON (1Hzpot= -20,1%). Além disso, significante fadiga de baixa frequência foi observada em DJ comparado com CON. Por outro lado, parâmetros de fadiga central e periférica apresentaram valores similares entre CON e 48h-DJ (P> 0,05). No entanto, foi encontrado aumento significativo (P< 0,05) na dor muscular tardia em 48hDJ comparado com CON e DJ. Estudo 3: O desempenho foi reduzido em FP (-2,3%) e FB (-1,5%) quando comparado com CON. O menor desempenho nas condições FP e FB foi acompanhado por redução na potência (P< 0,05) na parte inicial (condição FP) e na parte final (condições FP e FB) a prova. Ao final dos 4 km de ciclismo, os participantes apresentaram menor (P< 0,05) fadiga periférica em FB (1Hzpot= -11,9%) comparado com CON (1Hzpot= -20,1%). Em FP, houve maior fadiga periférica em comparação a condição CON e FB. Em conclusão, os resultados destes estudos sugerem que apenas a execução prévia de exercício envolvendo a musculatura utilizada no ciclismo promove alterações nos componentes periféricos da fadiga neuromuscular após 4 km de ciclismo / The aim of this study was to analyze the effects of previous execution of physical exercise and cognitive on the central and peripheral components of the neuromuscular fatigue during a 4 km cycling time trial. Eight trained cyclists (n = 8) participated of three different studies. In study 1, the athletes performed the 4 km cycling time trial test after watching a documentary (CON) or after a cognitive task (CT). In study 2, the 4-km cycling test was performed after 100 drop jumps (DJ), 48 hours after 100 drop jumps (48h-DJ) and without previous exercise (CON). In study 3, the time trial was performed after pre-fatigue of the upper (FU) and lower (FL) body and without prefatigue (CON). In all studies, central and peripheral fatigue parameters were evaluated via electrical stimulation in femoral nerve at rest, before and after 4km cycling. Study 1: Performance was similar (P> 0.05) between CON (376 ± 26.9 s) and TC (376.3 ± 26 s). Likewise, we found no significant differences (P> 0.05) for parameters of central and peripheral fatigue between CON and CT. Study 2: Performance was significantly (P< 0.05) impaired in DJ (-2.3%) and there was a trend in 48h-DJ (-1.8%). This reduction in performance in 48h-DJ was due to a lower power at first part of the time trial (P< 0.05). In DJ condition, loss in performance was due to lower power (P< 0.05) at the start and end phases of the test. There was exacerbated (P <0.05) peripheral fatigue after the time trial in DJ (1Hzpot = -44.7%) compared to CON (1Hzpot = 20.1%). Furthermore, a significant low frequency fatigue was observed in DJ compared to CON. On the other hand, central and peripheral fatigue parameters showed similar values between CON and 48h-DJ (P> 0.05). However, a significant increase in delayed onset muscle soreness was found in 48h-DJ than CON and DJ. Study 3: Performance was reduced in FU (-2.3%) and FL (-1.5%) compared to CON. The lowest performance was accompanied by a reduction in power (P< 0.05) in the initial (FL) and final (FL and FU phases of the time trial. After 4 km cycling, participants had a lower (P< 0.05) peripheral fatigue in FU (1Hzpot = -11.9%) compared with CON (1Hzpot = -20.1%). In FL, there was a greater peripheral fatigue compared to CON and FB condition. In conclusion, the results of these studies suggest that only the previous execution of exercise involving the muscles used in cycling causes changes in the peripheral components of the neuromuscular fatigue after 4 km of cycling

A presente dissertação procurou determinar as fases do pacing strategy em \"U\" e analisar o desenvolvimento da fadiga neuromuscular e o perfil metabolômico em um teste contrarrelógio de 4 km no ciclismo (4 km CT). No estudo 1, foi proposto dois modelos (visual e matemático) para determinar as três fases do pacing strategy em \"U\" durante um 4 km CT. Foram recrutados 15 ciclistas para realizar dois testes 4 km CT em dias separados. Para o modelo visual, quatro avaliadores experientes analisaram o pacing strategy duas vezes, sete dias de diferença. O modelo matemático foi composto pela média da potência durante a fase 2 (1 até 3 km) mais dois desvios padrões, identificando o ponto de mudança (PM) da fase 2 entre fase 1 (PM1) e 3 (PM2). O PM1 ocorreu em 419 ± 186 e 415 ± 178 m e PM2 ocorreu em 3646 ± 228 e 3809 ± 213 m para o modelo visual e matemático. Não houve diferença entre os modelos para ambos PM (p > 0,05). A reprodutibilidade intra avaliadores no modelo visual para PM1 e PM2 foi ICC >= 0,87 e >= 0,96 (p < 0,05), e entre avaliadores foi ICC >= 0,89 (p < 0,05). Gráficos de Bland-Altman mostraram boa concordância entre modelos, maioria da diferença ficou abaixo de 5%. O estudo 1 sugere que ambos modelos são reprodutíveis e produzem valores similares para determinar as fases do pacing strategy em \"U\". No estudo 2, 11 ciclistas visitaram o laboratório em seis ocasiões, sendo familiarizados três vezes com 4 km CT e técnica de estimulação elétrica no nervo femoral. Nas últimas três visitas, o mesmo pacing strategy da familiarização foi reproduzido, porém foram interrompidos ao final da fase 1 (F1FINAL), fase 2 (F2FINAL) e fase 3 (F3FINAL), randomizado. Antes e logo após o exercício, os ciclistas realizaram a técnica de estimulação elétrica e amostras sanguíneas foram coletadas para determinar o perfil metabolômico. A F1 teve duração de 68 ± 14 s (83,1% acima do ponto de compensação respiratória (PCR), em relação ao tempo total da F1), a F2 durou 287 ± 17 s (24,9% acima do PCR, tempo total da F2) e F3 durou 33 ± 7 s (74,5% acima do PCR, tempo total da F3). Houve apenas efeito principal de tempo para maioria das variáveis neuromusculares (p < 0,05) e não houve efeito principal de condição (p > 0,05). Apenas 5 metabólitos tiveram diferença estatística. Valores menores de 2-oxoisocarporate e dimatilamina para F1FINAL comparado com F2FINAL (p < 0,05). Valores menores de succinato para F1FINAL comparado com F3FINAL (p < 0,05). Asparagina e lactato apresentaram valores menores para F1FINAL em comparação à F2FINAL e F3FINAL (p < 0,05). Esses achados sugerem que, ao longo de um teste 4 km CT, o nível de fadiga neuromuscular é estabelecido logo no início e mantido até o final da tarefa. Não obstante, o perfil metabolômico parece estar associado com metabólitos da via oxidativa e outros marcadores relevantes para o SNC controlar a intensidade do exercício / The present dissertation aimed to determine the distinct phases of \"U\" pacing strategy and the development of neuromuscular fatigue and metabolomic profile during a 4 km cycling time trial (4 km TT). The study 1 developed two models (visual and mathematical) to determine the three different phases of \"U\" pacing strategy during a 4 km TT. Fifteen cyclists were recruited to perform two 4 km TT at different days. For the visual model, four experienced evaluators analysed the pacing twice, seven days apart. The mathematical model was composed by the mean of power output during phase 2 (1 until 3 km) plus two standard deviation, which was the criteria to distinguish the change point (CP) of phase 2 among phase 1 (CP1) and 3 (CP2). CP1 occurred at 419 ± 186 and 415 ± 178 m and CP2 occurred at 3646 ± 228 and 3809 ± 213 m for the visual and mathematical models. There was no difference between models for both CP (p > 0.05). The intra-evaluator reliability of visual model for CP1 and CP2 were ICC >= 0.87 and >= 0.96 (p < 0.05), and the betweenevaluator was ICC >= 0.89 (p < 0.05). The Bland-Altman plots showed great agreement between models, with most values lower than 5% of difference. In conclusion, both models were reliable and produced similar values to distinguish the phases during \"U\" pacing strategy. At study 2, 11 cyclists visited the lab on six occasions, where they were familiarized three times with the 4 km TT and the femoral nerve stimulation technique. On the last three visits, the same pacing strategy from the familiarization was performed, but the cyclists were interrupted at the end of phase 1 (P1END), end of phase 2 (P2END) and end of phase 3 (P3END), randomized. Before and immediately after the exercise, the cyclists performed the stimulation technique and blood samples were collected to determine the metabolimic profile. The P1 had duration of 68 ± 14 s (83.1% above the respiratory compensation point (RCP), in relation with total time of P1), P2 lasted 287 ± 17 s (24.9% above RCP, from total time at P2) and P3 lasted 33 ± 7 s (74.5% above RCP, from total time at P3). Most of neuromuscular variables showed main effect of time (p < 0.05) but no main effect of condition (p > 0.05). Only five metabolites were statistically different among conditions. 2- oxoisocarporate and dimethylamine were lower for P1END compared with P2END. Succinate was lower for P1END compared with P3END. Asparagine and lactate were lower for P1END compared with P2 END and P3END. Those findings suggest that during a 4 km TT, the level of neuromuscular fatigue is established at P1END and maintained until the end of the exercise task. Moreover, the metabolimic profile might be associated with oxidative metabolites and other relevant markers for central nervous system, which may act as feedback to control the exercise intensity

Real world exposures to physiologically and/or psychologically stressful environments are often multifactorial. For example, high-altitude typically combines exposure to hypobaric hypoxia, solar radiation and cold ambient temperatures, while sea level thermal stress is often combined with supplementary or transient stressors such as rain, solar radiation and wind. In such complex environments, the effect of one stressor on performance may be subject to change, simply due to the presence of another independent stressor. Such differential influences can occur in three basic forms; additive, antagonistic and synergistic, each term defining a fundamental concept of inter-parameter interactions. As well as the natural occurrence of stressors in combination, understanding interactions is fundamental to experimentally modelling how multiple physiological strains integrate in their influence on or regulation of - exercise intensity. In this thesis the current literature on neuromuscular fatigue and the influence of thermal and hypoxic stress is reviewed (Chapter 1). This is followed by an outline of the methodological developments used in the subsequent experiments (Chapter 2). In the first experimental study (Chapter 3) a novel approach was adopted to investigate the combined effect of muscle cooling and hypoxia on neuromuscular fatigue in humans. The results showed that the neuromuscular system s maximal force generating capacity declined by 8.1 and 13.9% during independent cold and hypoxic stress compared to control. Force generation decreased by 21.4% during combined hypoxic-cold compared to control, closely matching the additive value of hypoxia and cold individually (22%). This was also reflected in the measurement of mechanical fatigue (electromechanical ratio), demonstrating an additive response during combined hypoxic-cold. From this study, it was concluded that when moderate hypoxia and cold environmental temperatures are combined during low intensity exercise, the level of fatigue increases additively with no interaction between these stressors. Before conducting a more complex investigation on combined stressors, a better understanding of the role of muscle temperature on central fatigue - i.e. voluntary muscle activation via the afferent signalling pathways was sought. The focus of Chapter 4 was to quantify the relationship between muscle temperature and voluntary muscle activation (central fatigue) across a wide range of temperatures. The primary finding was that different muscle temperatures can induce significant changes in voluntary activation (0.5% reduction per-degree-centigrade increase in muscle temperature) when neural drive is sustained for a prolonged effort (e.g. 120-s); however this effect is not exhibited during efforts that are brief in duration (e.g. 3-s). To further explore this finding, Chapter 5 investigated the effect of metaboreceptive feedback at two different muscle temperatures, using post-exercise muscle ischemia, on voluntary activation of a remote muscle group. The results showed that at the same perceived mental effort, peripheral limb discomfort was significantly higher with increasing muscle temperature (2% increase per-degree-centigrade increase). However any influence of increased muscle temperature on leg muscle metaboreceptive feedback did not appear to inhibit voluntary muscle activation - i.e. central control - of a remote muscle group, as represented by an equal force output and voluntary activation in the thermoneutral, contralateral leg. In Chapter 6, the psycho-sensory effects of changes in muscle temperature on central fatigue during dynamic exercise were investigated. During sustained dynamic exercise, fatigue development appeared to occur at a faster rate in hot muscle (4% increase per-degree-centigrade increase) leading to a nullification of the beneficial effects of increased muscle temperature on peak power output after a period of ~60-s maximal exercise. In support of previous studies using isometric exercise (Chapter 4 and 6), participants reported significantly higher muscular pain and discomfort in hot muscle compared to cooler muscle during dynamic exercise (2 and 1% increase per-degree-centigrade increase respectively), however this did not result in a lower power output. From Chapters 4, 5 and 6 it was concluded that in addition to faster rates of metabolite accumulation due to cardiovascular strain, it is possible that a direct sensitisation of the metaboreceptive group III and IV muscle afferents occurs in warmer muscle. This likely contributes to the reduction in voluntary muscle activation during exercise in the heat, while it may attenuate central fatigue in the cold. It was also interpreted that muscle afferents may have a similar signalling role to cutaneous sensory afferents; the latter of which are recognised for their role in providing thermal feedback to the cognitive-behavioural centres of the brain and aiding exercise regulation under thermal stress. The impact of body core and active muscle temperature on voluntary muscle activation represented a similar ratio (5 to 1 respectively) to the temperature manipulated (single leg) to non-temperature manipulated mass (rest of body) in Chapters 4, 5 and 6. This indicates that voluntary muscle activation may also be regulated based on a central meta-representation of total body heat content i.e. the summed firing rates of all activated thermoreceptors in the brain, skin, muscle, viscera and spine. Building on the initial findings of Chapter 3, Chapter 7 investigated the causative factors behind the expression of different interaction types during exposure to multi-stressor environments. This was achieved by studying the interaction between thermal stress and hypoxia on the rate of peripheral and central fatigue development during a high intensity bout of knee extension exercise to exhaustion. The results showed that during combined exposure to moderate hypoxia and mild cold, the reductions in time to exhaustion were additive of the relative effects of hypoxia and cold independently. This differs from the findings in Chapter 3, in which fatigue was additive of the absolute effects of cold and hypoxia. In contrast, combining moderate hypoxia with severe heat stress resulted in a significant antagonistic interaction on both the absolute and relative reductions in time to exhaustion i.e. the combined effect being significantly less than the sum of the individual effects. Based on the results in Chapter 7, a quantitative paradigm for understanding of systematic integration of multifactorial stressors was proposed. This is, that the interaction type between stressors is influenced by the impact magnitude of the individual stressors effect on exercise capacity, whereby the greater the stressors impact, the greater the probability that one stressor will be cancelled out by the other. This is the first study to experimentally model the overarching principles characterising the presence of simultaneous physiological strains, suggesting multifactorial integration be subject to the worst strain takes precedence when the individual strains are severe.

O objetivo do presente estudo foi analisar os efeitos da execução prévia de exercício físico e cognitivo sobre os componentes central e periférico da fadiga neuromuscular durante um teste contrarrelógio de 4 km de ciclismo. Para tanto, oito ciclistas treinados (n = 8) participaram de três diferentes estudos. No estudo 1, os atletas realizaram o teste contrarrelógio após assistir documentário (CON) ou após tarefa cognitiva (TC). No estudo 2, o teste de 4 km de ciclismo foi realizado após 100 drop jumps (DJ), 48 horas após 100 drop jumps (48h-DJ) e sem a realização prévia de exercício (CON). No estudo 3, o teste contrarrelógio foi realizado após fadiga prévia de membros superiores (FB) e inferiores (FP) e sem fadiga prévia (CON). Em todos os estudos, parâmetros de fadiga central e periférica foram avaliados por meio da técnica de estimulação elétrica no nervo femoral em repouso, pré e pós 4km de ciclismo. Estudo 1: O desempenho foi similar (P> 0,05) entre CON (376 ± 26,9 s) e TC (376,3 ± 26 s). Do mesmo modo, não encontramos diferenças significativas (P> 0,05) para parâmetros de fadiga central e periférica entre CON e TC. Estudo 2. O desempenho foi significativamente (P< 0,05) prejudicado em DJ (-2,3%) e houve uma tendência em 48h-DJ (-1,8%). A redução no desempenho em 48h-DJ foi devido à menor potência na parte inicial da prova (P< 0,05). Em DJ a piora no desempenho foi em decorrência de menor potência (P< 0,05) na parte inicial e final da prova. Houve uma exacerbada (P< 0,05) fadiga periférica após o contrarrelógio em DJ (1Hzpot= -44,7%) comparado com CON (1Hzpot= -20,1%). Além disso, significante fadiga de baixa frequência foi observada em DJ comparado com CON. Por outro lado, parâmetros de fadiga central e periférica apresentaram valores similares entre CON e 48h-DJ (P> 0,05). No entanto, foi encontrado aumento significativo (P< 0,05) na dor muscular tardia em 48hDJ comparado com CON e DJ. Estudo 3: O desempenho foi reduzido em FP (-2,3%) e FB (-1,5%) quando comparado com CON. O menor desempenho nas condições FP e FB foi acompanhado por redução na potência (P< 0,05) na parte inicial (condição FP) e na parte final (condições FP e FB) a prova. Ao final dos 4 km de ciclismo, os participantes apresentaram menor (P< 0,05) fadiga periférica em FB (1Hzpot= -11,9%) comparado com CON (1Hzpot= -20,1%). Em FP, houve maior fadiga periférica em comparação a condição CON e FB. Em conclusão, os resultados destes estudos sugerem que apenas a execução prévia de exercício envolvendo a musculatura utilizada no ciclismo promove alterações nos componentes periféricos da fadiga neuromuscular após 4 km de ciclismo / The aim of this study was to analyze the effects of previous execution of physical exercise and cognitive on the central and peripheral components of the neuromuscular fatigue during a 4 km cycling time trial. Eight trained cyclists (n = 8) participated of three different studies. In study 1, the athletes performed the 4 km cycling time trial test after watching a documentary (CON) or after a cognitive task (CT). In study 2, the 4-km cycling test was performed after 100 drop jumps (DJ), 48 hours after 100 drop jumps (48h-DJ) and without previous exercise (CON). In study 3, the time trial was performed after pre-fatigue of the upper (FU) and lower (FL) body and without prefatigue (CON). In all studies, central and peripheral fatigue parameters were evaluated via electrical stimulation in femoral nerve at rest, before and after 4km cycling. Study 1: Performance was similar (P> 0.05) between CON (376 ± 26.9 s) and TC (376.3 ± 26 s). Likewise, we found no significant differences (P> 0.05) for parameters of central and peripheral fatigue between CON and CT. Study 2: Performance was significantly (P< 0.05) impaired in DJ (-2.3%) and there was a trend in 48h-DJ (-1.8%). This reduction in performance in 48h-DJ was due to a lower power at first part of the time trial (P< 0.05). In DJ condition, loss in performance was due to lower power (P< 0.05) at the start and end phases of the test. There was exacerbated (P <0.05) peripheral fatigue after the time trial in DJ (1Hzpot = -44.7%) compared to CON (1Hzpot = 20.1%). Furthermore, a significant low frequency fatigue was observed in DJ compared to CON. On the other hand, central and peripheral fatigue parameters showed similar values between CON and 48h-DJ (P> 0.05). However, a significant increase in delayed onset muscle soreness was found in 48h-DJ than CON and DJ. Study 3: Performance was reduced in FU (-2.3%) and FL (-1.5%) compared to CON. The lowest performance was accompanied by a reduction in power (P< 0.05) in the initial (FL) and final (FL and FU phases of the time trial. After 4 km cycling, participants had a lower (P< 0.05) peripheral fatigue in FU (1Hzpot = -11.9%) compared with CON (1Hzpot = -20.1%). In FL, there was a greater peripheral fatigue compared to CON and FB condition. In conclusion, the results of these studies suggest that only the previous execution of exercise involving the muscles used in cycling causes changes in the peripheral components of the neuromuscular fatigue after 4 km of cycling

<p>Primena biomarkera ćelijske energetike, uključujući indikatore metabolizma kreatina u krvi, je relativno novijeg datuma, gde se ovi indikatori koriste kao mogući pokazatelji stanja organizma pri maksimalno intenzivnim fizičkim aktivnostima. Cilj istraživanja je obuhvatao utvrđivanje efekata pojedinačnih epizoda aerobnog i anaerobnog vežbanja maksimalnog intenziteta na biomarkere perifernog zamora i ćelijske bioenergetike kod mladih mu&scaron;karaca i žena. Istraživanje je dizajnirano tako da obuhvati populaciju fizički aktivnih mu&scaron;karaca i žena, kao i populaciju aktivnih sportista. U prvom eksperimentalnom tretmanu fizički aktivni ispitanici mu&scaron;kog (n =12) i ženskog pola (n = 11) podvrgnuti su test protokolima aerobnog i anaerobnog opterećenja maksimalnog intenzivnog i kratkog trajanja. Tokom aerobnog test protokola ispitanici su trčali do maksimalnog voljnog otkaza na tredmil traci sa progresivnim povećanjem opterećenja. Pri anaerobnom test protokolu ispitanici su izvr&scaron;ili testiranje snažne izdržljivosti gornjih ekstremiteta do otkaza potiskom sa ravne klupe, uz opterećenje od 25% od njihove telesne težine. Drugi eksperimentalni tretman je sačinjen iz pre-eksperimentalnog testiranja kardiorespiratorne forme i eksperimentalne protokol sesije trčanja do maksimalnog voljnog otkaza na pokretnoj traci, pri konstantnoj individualnoj brzina trčanja na anaerobnom pragu. U ovom eksperimentalnom tretmanu bila je uključena populacija aktivnih sportista&nbsp;&nbsp;&nbsp;&nbsp; (n = 10). Pre, tokom i nakon eksperimentalnih sesija praćena je koncentracija različitih biohemijskih i hematolo&scaron;kih markera: guanidinosirćetna kiselina (GAA); kreatin (Cr); kreatinin (Crn); laktat (Lac); interleukin-6 (IL-6); kreatin kinaza (CK); kortizol (Cor). Rezultati prvog eksperimentalnog tretmana su utvrdili statistički značajne promene u koncentraciji GAA, Cr i Crn u ktvi pre i nakon pojedinačne epizode aerobnog i anaerobnog vežbanja maksimalnim intenzitetom. Utvrđena je i statistički značajna povezanost između vežbanjem-indukovanih promena u cirkulatornim vrednostima GAA, Cr, Crn za vreme pre, tokom i nakon drugog eksperimentalnog tretmana. Uočena je statistički značajna povezanost između promena koncentracije GAA, Cr, Crn u serumu sa tradicionalnim biomarkerima perifernog zamora (IL6, Cor, Lac, CK). Dobijeni rezultati ukazuju na mogućnost primene biomarkera metabolizma kreatina u krvi prilikom praćenja i evaluacije stanja organizma tokom maksimalnih intenzivnih fizičkih aktivnosti kod mladih mu&scaron;karaca i žena.</p> / <p>The use of biomarkers of cellular bioenergetics in exercise science appears more prevalent in recent years, where these outcomes perhaps describe changes in creatine metabolism during strenuous exercise. The aim of this study was to determine the effects of individual episodes of strenuous aerobic and anaerobic exercise on several biomarkers of peripheral fatigue and cellular bioenergetics in young men and women. The study recruited physically active men and women, and active athletes. In the first experiment, physically active men (n = 12) and women (n = 11) were subjected to strenuous aerobic and anaerobic exercise. During the aerobic test, subjects ran to exhaustion while during the anaerobic test, subjects performed repetitive bench press exercise. The second experimental treatment consisted of a pre-experimental testing of cardiorespiratory fitness, and an experimental protocol of a strenuous running session to exhaustion at constant individual running speed at the anaerobic threshold; active athletes (n = 10) were included in this experimental treatment. The blood levels of various biochemical and hematological markers were monitored before, during and after the experimental sessions, including guanidinoacetic acid (GAA); creatine (Cr); creatinine (Crn); lactate (Lac); interleukin-6 (IL-6); creatine kinase (CK); cortisol (Cor), and plethora of other physiological outcomes. We found statistically significant changes in serum GAA, Cr and Crn before and after a single session of strenuous aerobic and anaerobic exercise. A significant correlation was found between exercise-induced changes in serum GAA, Cr and Crn before, during and after the second experimental intervention. A statistically significant association was observed between changes in serum GAA, Cr, Crn and traditional biomarkers of peripheral fatigue (IL6, Cor, Lac, CK). The results of the present study suggest that biomarkers of creatine metabolism might be used as innovative tools in monitoring strenuous exercise in young men and women.</p>

A presente tese investigou o efeito da ingestão de cafeína no desempenho no ciclismo, no recrutamento muscular, na contribuição energética, no lactato sanguíneo, nas respostas fisiológicas e perceptivas e no desenvolvimento de fadiga central e periférica em diferentes modelos de exercício aeróbio de alta intensidade. Nove ciclistas do sexo masculino (32,3 ± 6,0 anos de idade, 79,3 ± 6,8 kg, 181,2 ± 7,9 cm e VO2máx 55,2 ± 5,7 mL.kg-1.min-1) completaram 11 sessões experimentais. Os participantes foram submetidos a testes contrarrelógio de 4.000 m, testes com carga constante até a exaustão realizados na potência média do contrarrelógio (313 ± 41 W e 100 ± 10 rpm), e ainda testes com carga constante com tempo fixo correspondente a 60% do tempo sustentado no teste de carga constante até a exaustão (237,2 ± 56,0 s). Os participantes ingeriram cápsulas contendo placebo ou cafeína (5 mg.kg-1 de massa corporal) 60 minutos antes da realização dos testes, em ordem contrabalançada e em um modelo duplo-cego. Respostas cardiorrespiratórias e perceptivas foram mensuradas durante os testes. Lactato sanguíneo foi coletado antes e após o exercício. Avaliações neuromusculares foram realizadas através de estimulação elétrica no nervo femoral nos momentos Baseline (previamente à ingestão da cápsula), Pré-EX (uma hora após a ingestão, antes do exercício), e Pós-EX (2 min após o exercício). A ingestão de 5 mg.kg-1 de cafeína melhorou o desempenho no teste contrarrelógio de 4.000 m de ciclismo (-6,9 ± 7,4 s; p = 0,024), devido a um aumento na contribuição anaeróbia. O desempenho no teste com carga constante até a exaustão também foi melhor após a ingestão de cafeína (+134,3 ± 81,5 s; p = 0,001), mas neste caso acompanhado por maior contribuição aeróbia. A ingestão de cafeína previamente a realização do exercício proporcionou efeito ergogênico no teste contrarrelógio de 4.000 m e no teste de carga constante até a exaustão, sem alterar o limiar de fadiga periférica. Entre os componentes periféricos avaliados, a taxa máxima de desenvolvimento de força reduziu significativamente menos após o teste de carga constante até a exaustão na condição cafeína, mesmo como o tempo de exercício prolongado, e também reduziu significativamente menos após o teste de carga constante e tempo fixo, o que sugere que a cafeína pode ter alterado o processo acoplamento excitação-contração, o que resultou em atraso da fadiga periférica. Além disso, no teste com carga constante até a exaustão, a disposição e a sensação de prazer foram maiores após a ingestão de cafeína, sugerindo que neste modelo de exercício estas variáveis perceptivas também podem ter contribuído para o efeito ergogênico da cafeína observado no desempenho. Em conclusão, este estudo demonstrou que a cafeína melhorara o desempenho no ciclismo em ambos os modelos de exercício aeróbio de alta intensidade, sendo no contrarrelógio devido ao aumento da quantidade total de energia anaeróbia e no carga constante até a exaustão nas variáveis perceptíveis e alteração no acoplamento excitação-contração, sem alterar o limiar de fadiga periférica / The present thesis investigated the effect of caffeine on cycling performance, muscle recruitment, energetic contribution, blood lactate, physiological and perceptual responses and the development of central and peripheral fatigue in different models of high-intensity aerobic exercises. Nine male cyclists (32.3 ± 6.0 years old, 79.3 ± 6.8 kg, 181.2 ± 7.9 cm and VO2max 55.2 ± 5.7 mL.kg-1.min-1) completed 11 experimental sessions. The participants performed 4,000 m cycling time trial, constant-load to exhaustion in the average power output of the time trial (313 ± 41 W and 100 ± 10 rpm), and also performed constant-load with fixedtime corresponding to 60% of the time sustained in the constant-load to exhaustion (237.2 ± 56.0 s). Participants ingested capsules containing placebo or caffeine (5 mg.kg-1 body weight) 60 minutes prior to the tests, in a counterbalanced order and in a double-blind model. Cardiorespiratory and perceptual responses were measured during the tests. Blood lactate was collected before and after exercises. Neuromuscular assessments were performed via electrical femoral nerve stimulation at Baseline (prior to capsule ingestion), Pre-EX (one hour after capsules ingestion, before exercise), and Post-EX (2 min after exercise). 5 mg.kg-1 of caffeine improved their performance in the 4,000 m cycling time trial (-6.9 ± 7.4 s; p = 0.024), due to an increase in anaerobic contribution. The performance in the constant-load to exhaustion was also enhanced after caffeine intake (+134.3 ± 81.5 s; p = 0.001), but in this case accompanied by greater aerobic contribution. Caffeine intake prior to cycling performance provided an ergogenic effect in the 4,000 m time trial and in the constant-load to exhaustion, without altering the critical threshold of peripheral fatigue. Among the peripheral components evaluated, the maximum rate of force development significantly reduced less after the constant-load to exhaustion in the caffeine condition, even as the prolonged exercise time, and also reduced significantly less after the constant-load with fixed-time, which suggests that caffeine may have altered the excitation-contraction coupling, which resulted in delayed peripheral fatigue. In addition, during the constant-load to exhaustion test, the felt arousal and feeling were higher after the caffeine, suggesting that in this exercise model these perceptions may also have contributed to the observed ergogenic effect of caffeine on the cycling. In conclusion, this study demonstrated that caffeine improved the cycling performance in both models of high-intensity aerobic exercise, being in the time-trial due to the increase of the total amount of anaerobic energy and the constant load until the exhaustion due to alteration in the perceptible variables and in the excitation-contraction coupling, without change the peripheral fatigue threshold

A presente tese investigou o efeito da ingestão de cafeína no desempenho no ciclismo, no recrutamento muscular, na contribuição energética, no lactato sanguíneo, nas respostas fisiológicas e perceptivas e no desenvolvimento de fadiga central e periférica em diferentes modelos de exercício aeróbio de alta intensidade. Nove ciclistas do sexo masculino (32,3 ± 6,0 anos de idade, 79,3 ± 6,8 kg, 181,2 ± 7,9 cm e VO2máx 55,2 ± 5,7 mL.kg-1.min-1) completaram 11 sessões experimentais. Os participantes foram submetidos a testes contrarrelógio de 4.000 m, testes com carga constante até a exaustão realizados na potência média do contrarrelógio (313 ± 41 W e 100 ± 10 rpm), e ainda testes com carga constante com tempo fixo correspondente a 60% do tempo sustentado no teste de carga constante até a exaustão (237,2 ± 56,0 s). Os participantes ingeriram cápsulas contendo placebo ou cafeína (5 mg.kg-1 de massa corporal) 60 minutos antes da realização dos testes, em ordem contrabalançada e em um modelo duplo-cego. Respostas cardiorrespiratórias e perceptivas foram mensuradas durante os testes. Lactato sanguíneo foi coletado antes e após o exercício. Avaliações neuromusculares foram realizadas através de estimulação elétrica no nervo femoral nos momentos Baseline (previamente à ingestão da cápsula), Pré-EX (uma hora após a ingestão, antes do exercício), e Pós-EX (2 min após o exercício). A ingestão de 5 mg.kg-1 de cafeína melhorou o desempenho no teste contrarrelógio de 4.000 m de ciclismo (-6,9 ± 7,4 s; p = 0,024), devido a um aumento na contribuição anaeróbia. O desempenho no teste com carga constante até a exaustão também foi melhor após a ingestão de cafeína (+134,3 ± 81,5 s; p = 0,001), mas neste caso acompanhado por maior contribuição aeróbia. A ingestão de cafeína previamente a realização do exercício proporcionou efeito ergogênico no teste contrarrelógio de 4.000 m e no teste de carga constante até a exaustão, sem alterar o limiar de fadiga periférica. Entre os componentes periféricos avaliados, a taxa máxima de desenvolvimento de força reduziu significativamente menos após o teste de carga constante até a exaustão na condição cafeína, mesmo como o tempo de exercício prolongado, e também reduziu significativamente menos após o teste de carga constante e tempo fixo, o que sugere que a cafeína pode ter alterado o processo acoplamento excitação-contração, o que resultou em atraso da fadiga periférica. Além disso, no teste com carga constante até a exaustão, a disposição e a sensação de prazer foram maiores após a ingestão de cafeína, sugerindo que neste modelo de exercício estas variáveis perceptivas também podem ter contribuído para o efeito ergogênico da cafeína observado no desempenho. Em conclusão, este estudo demonstrou que a cafeína melhorara o desempenho no ciclismo em ambos os modelos de exercício aeróbio de alta intensidade, sendo no contrarrelógio devido ao aumento da quantidade total de energia anaeróbia e no carga constante até a exaustão nas variáveis perceptíveis e alteração no acoplamento excitação-contração, sem alterar o limiar de fadiga periférica / The present thesis investigated the effect of caffeine on cycling performance, muscle recruitment, energetic contribution, blood lactate, physiological and perceptual responses and the development of central and peripheral fatigue in different models of high-intensity aerobic exercises. Nine male cyclists (32.3 ± 6.0 years old, 79.3 ± 6.8 kg, 181.2 ± 7.9 cm and VO2max 55.2 ± 5.7 mL.kg-1.min-1) completed 11 experimental sessions. The participants performed 4,000 m cycling time trial, constant-load to exhaustion in the average power output of the time trial (313 ± 41 W and 100 ± 10 rpm), and also performed constant-load with fixedtime corresponding to 60% of the time sustained in the constant-load to exhaustion (237.2 ± 56.0 s). Participants ingested capsules containing placebo or caffeine (5 mg.kg-1 body weight) 60 minutes prior to the tests, in a counterbalanced order and in a double-blind model. Cardiorespiratory and perceptual responses were measured during the tests. Blood lactate was collected before and after exercises. Neuromuscular assessments were performed via electrical femoral nerve stimulation at Baseline (prior to capsule ingestion), Pre-EX (one hour after capsules ingestion, before exercise), and Post-EX (2 min after exercise). 5 mg.kg-1 of caffeine improved their performance in the 4,000 m cycling time trial (-6.9 ± 7.4 s; p = 0.024), due to an increase in anaerobic contribution. The performance in the constant-load to exhaustion was also enhanced after caffeine intake (+134.3 ± 81.5 s; p = 0.001), but in this case accompanied by greater aerobic contribution. Caffeine intake prior to cycling performance provided an ergogenic effect in the 4,000 m time trial and in the constant-load to exhaustion, without altering the critical threshold of peripheral fatigue. Among the peripheral components evaluated, the maximum rate of force development significantly reduced less after the constant-load to exhaustion in the caffeine condition, even as the prolonged exercise time, and also reduced significantly less after the constant-load with fixed-time, which suggests that caffeine may have altered the excitation-contraction coupling, which resulted in delayed peripheral fatigue. In addition, during the constant-load to exhaustion test, the felt arousal and feeling were higher after the caffeine, suggesting that in this exercise model these perceptions may also have contributed to the observed ergogenic effect of caffeine on the cycling. In conclusion, this study demonstrated that caffeine improved the cycling performance in both models of high-intensity aerobic exercise, being in the time-trial due to the increase of the total amount of anaerobic energy and the constant load until the exhaustion due to alteration in the perceptible variables and in the excitation-contraction coupling, without change the peripheral fatigue threshold

Tyrimo aktualumas - yra žinoma, kad sportininkams rungtyniaujant rinktinių čempionatuose ar turnyruose yra gaunamas labai didelis fizinis krūvis. Kartais tenka sužaisti 2-3 rungtynes per dvejas, trejas dienas. Dėl šios priežasties, šiame tyrime bus analizuojamas dviejų dienų varžybinis laikotarpis plačiau ir įvertinama jėgos, greitumo, reakcijos, dėmesio sutelktumo rodiklių kaita. Tai padės geriau įvertinti krepšininkių pasirengimą kelių dienų varžybiniam laikotarpiui. Pasiruošimo krepšinio čempionatams metu, treneriai turės daugiau informacijos kokių fizinių savybių tobulinimui skirti didesnį dėmesį, atsižvelgdami į mūsų tyrimo gautus rezultatus. Tikslas – nustatyti Lietuvos jaunių merginų krepšinio rinktinės žaidėjų fizinio pajėgumo, dėmesio sutelktumo ir reakcijos laiko pokyčius rungtyniaujant dvi dienas iš eilės. Uždaviniai: 1. Nustatyti krepšininkių fizinį pajėgumą, dėmesio sutelktumą ir reakcijos laiko pokyčius prieš, per ir po pirmųjų rungtynių. 2. Nustatyti krepšininkių fizinį pajėgumą, dėmesio sutelktumą ir reakcijos laiko pokyčius prieš, per ir po antrųjų rungtynių. 3. Palyginti krepšininkių fizinio pajėgumo, dėmesio sutelktumo ir reakcijos laiko pokyčius tarp pirmųjų ir antrųjų rungtynių. Išvados: 1. Iškart po pirmosios dienos rungtynių sumažėjo 20 m bėgimo greitis ir maksimalios valingos jėgos momentas. 2. Antrosios rungtynės reikšmingai sumažino tik sudėtingosios reakcijos laiką. 3. Lyginant pirmųjų ir antrųjų rungtynių rezultatus antros dienos rungtynių... [toliau žr. visą tekstą] / The purpose of this study – there is known, that there is produced very high physical activity for sportsmen participating in championships or tournaments of squads. At times they have to play 2-3 competitions in two-three days. Because of this reason, there will be more fully analyzed two-days competition period strength, speed, reaction and attention concentration change of rates estimated. This will help to evaluate better the bakstetball players preparation for a few days competition. Our analysis results will give more information for coatches to which physical properties needs to concentrate in period of prepartion for championship of basketball. The aim – determine the changes of physical fitness, concentration of attention and reaction time of Lithuanian junior girls’ basketball squad players, playing two days in a row. Tasks: 1. To determine the changes for basketball players of physical fitness, concentration of attention and reaction time before, at and after the first competition. 2. To determine the changes for basketball players of physical fitness, concentration of attention and reaction time before, at and after the second competition. 3. To compare the changes for basketball players of physical fitness, concentration of attention and reaction time between the first and the second competitions. Conclusions - 1. At once after the firts competition 20 m runing speed and maximum voluntary conraction force moment decreased. 2. The second competition... [to full text]

Resumo: O objetivo principal desta tese foi investigar a causa e a conseqüência da fadiga em countermovement jumps realizados em diferentes razões de esforço e pausa. Esses objetivos foram testados utilizando dois estudos experimentais. O primeiro estudo comparou as causas da fadiga em protocolos de fadiga de curta (=10 min) e longa duração (=20 min), manipulando as durações da pausa entre countermovement jumps. Os resultados indicaram que, após a realização do protocolo de fadiga de curta duração, houve redução da contração isométrica voluntária máxima para extensão do joelho acompanhada por fadiga central e periférica. Por outro lado, após a realização do protocolo de fadiga de longa duração, a redução da contração isométrica voluntária máxima para extensão do joelho foi associada apenas à fadiga periférica. No segundo estudo foi utilizado um protocolo de fadiga para o sistema neuromuscular similar ao primeiro estudo, tendo como objetivo investigar o padrão de movimento sob fadiga. O tempo e a seqüência da relação inter-segmental do movimento e da ativação muscular permaneceram inalteradas sob a condição de fadiga. Entretanto, alguns ajustes no controle de countermovement jumps realizados sob a condição de fadiga foram observados, provavelmente na tentativa de manter a altura do salto vertical. Entre alguns ajustes, é possível destacar um aumento na flexão das articulações e na duração do salto vertical. Esses resultados foram similares independentemente da razão de esforço e pausa utilizada para induzir fadiga em countermovement jumps. Considerando ambos os estudos experimentais, os resultados da presente tese sugerem que a causa da fadiga em countermovement jumps é tarefa-dependente. Isso significa que dependendo do protocolo de indução de fadiga utilizado, a causa da fadiga pode ser alterada de central para periférica, por exemplo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This thesis explored the cause of fatigue in countermovement jump performed under different intensities and its influence upon movement pattern. These aims were tested using two experimental studies. The first one aimed to compare the causes of fatigue development during a short- (=10 min) and a long-term (=20 min) countermovement jump protocols through the manipulation of resting interval. The results indicated that after short-term fatigue protocol, maximal voluntary isometric contraction reduction was accompanied by central and peripheral fatigue. On the other hand, after long-term fatigue protocol, maximal voluntary isometric contraction reduction was accompanied by peripheral fatigue. The second study used similar exercise protocol to induce fatigue on neuromuscular system. It was aimed to investigate the movement pattern of countermovement jump throughout fatigue exercise protocols. The timing and sequencing of inter-segmental movement and of muscle activation remained relatively unaltered under fatigue. However, in order to sustain required jump height, few adjustments were performed on control and on coordination of fatigued jumps, such as increased joint flexion and earlier initiation of joint extension. This result was quite similar irrespective of fatigue-induced exercise intensities. Considering both experimental studies, the results of present thesis suggest that the cause of fatigue in countermovement jump is task-dependent in which depends on what fatigue protocol is used, thereby the cause of fatigue can move from one site to another. Even with the neuromuscular system impaired, there was not change on the movement pattern of countermovement jump, irrespective of exercise duration and cause of fatigue. However, adjustments on control and coordination of countermovement jump were performed in order to compensate the force loss and to maintain the targeted jump height. / Orientador: Eduardo Kokubun / Coorientador: José Angelo Barela / Banca: André Luiz Félix Rodacki / Banca: Ana Maria Forti Barela / Banca: Carlos Ugrinowistch / Doutor