Activity of group III-IV muscle afferents: implication for the neuromuscular and cardiovascular responses to exercise in humans

Changes in activation of muscle III-IV afferents has shown to lead to impaired cardiovascular and neuromuscular responses to exercise. The mechanisms underlying these alterations has been attributed to changes in sensitivity of the muscle afferents that associated with muscle inflammation, ageing and pathological conditions. In the first three experimental chapter (chapter 4 to 6), we collected data from healthy moderately active young male performing an exercise induced muscle damage protocol (EIMD), that induced muscle inflammation and changes in muscle afferent activation (i.e., mechano and nociceptors) 48h post EIMD. These changes were associated to alterations in blood pressure regulation, cardiovascular responses, peripheral blood flow, neuromuscular function, and exercise performance. Following these experiments, we tested the association of blood pressure responses and exercise performance in a master athletes’ cohort (Chapter 7), showing links between increased blood pressure responses and lower exercise performance. In the last chapter (chapter 8), we conducted a systematic review with meta-analysis to determine cardiorespiratory fitness and neuromuscular function of people with Chronic fatigue and Fibromyalgia syndromes compared to healthy individuals. From the 99 studies selected we found a large decreased in cardiorespiratory fitness, neuromuscular function, and fatigability within increased in perceived exertion in patients. In conclusion, the data collected showed the physiological relevance of the changes in muscle afferents activation, becoming relevant for future studies in chronic pain and fatigue conditions

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The association of elevated blood pressure during ischaemic exercise with sport performance in Master athletes with and without morbidity

Background An exaggerated exercise blood pressure (BP) is associated with a reduced exercise capacity. However, its connection to physical performance during competition is unknown. Aim To examine BP responses to ischaemic handgrip exercise in Master athletes (MA) with and without underlying morbidities and to assess their association with athletic performance during the World Master Track Cycling Championships 2019. Methods Forty-eight Master cyclists [age 59±13yrs; weekly training volume 10.4±4.1 h/week; handgrip maximum voluntary contraction (MVC) 46.3±11.5 kg] divided into 2 matched groups (24 healthy MA and 24 MA with morbidity) and 10 healthy middle-aged non-athlete controls (age 48.3±8.3 years; MVC 40.4±14.8 kg) performed 5 min of forearm occlusion including 1 min handgrip isometric contraction (40%MVC) followed by 5 min recovery. Continuous beat-by-beat BP was recorded using fnger plethysmography. Age-graded performance (AGP) was calculated to compare race performances among MA. Healthy Master cyclists were further grouped into middle-age (age 46.2±6.4 years; N:12) and old-age (age 65.0±7.7 years; N:12) for comparison with middle-aged non-athlete controls. Results Healthy and morbidity MA groups showed similar BP responses during forearm occlusion and AGP (90.1±4.3% and 91.0±5.3%, p>0.05, respectively). Healthy and morbidity MA showed modest correlation between the BP rising slope for 40%MVC ischaemic exercise and AGP (r=0.5, p<0.05). MA showed accelerated SBP recovery after cessation of ischaemic handgrip exercise compared to healthy non-athlete controls. Conclusion Our fndings associate long-term athletic training with improved BP recovery following ischaemic exercise regardless of age or reported morbidity. Exaggerated BP in Master cyclists during ischaemic exercise was associated with lower AGP during the World Master Cycling Championships

Saberes históricos na educação infantil: alguns apontamentos e necessidades

As reflexões contidas neste texto são resultantes de uma pesquisa que se desenvolveu no âmbito do Grupo de Investigação sobre o Ensino e as Necessidades Formativas de Profissionais da Educação – CNPq/UFMT, a qual buscou identificar a representação de necessidades que professoras da Educação Infantil têm acerca da construção de saberes históricos junto as crianças. O tema em questão foi escolhido em função da emergência de conhecimentos sobre a perspectiva do ensino e de práticas pedagógicas relacionadas a construção de saberes históricos junto as crianças bem como de precisar necessidades formativas a partir da voz dos sujeitos. A metodologia utilizada para a realização da pesquisa de cunho empírico assenta-se no método de Discrepância utilizado para analisar necessidades formativas, o qual consiste em evidenciar discrepâncias entre o real e o ideal. A análise dos dados permite afirmar que a pluralidade existente na formação dos saberes docentes interfere na concepção de História das docentes, induzindo suas práticas pedagógicas. Apontamos a conscientização das lacunas e carências evidenciadas como condição para promover práticas educativas experienciais, voltadas à construção de conhecimentos históricos, condizentes com a aprendizagem na infância

Effect of nitrate supplementation on skeletal muscle motor unit activity during isometric blood flow restriction exercise

Background Nitrate (NO3-) supplementation has been reported to lower motor unit (MU) firing rate (MUFR) during dynamic resistance exercise, however its impact on MU activity during isometric and ischemic exercise is unknown. Purpose To assess the effect of NO3- supplementation on knee extensor MU activities during brief isometric contractions and a 3-min sustained contraction with blood flow restriction (BFR). Methods Sixteen healthy active young adults (six females) completed two trials in a randomized, double-blind, crossover design. Trials were preceded by 5 days of either NO3- (NIT) or placebo (PLA) supplementation. Intramuscular electromyography was used to determine the m.vastus lateralis MU potential (MUP) size, MUFR and near fibre (NF) jiggle (a measure of neuromuscular stability) during brief (20 s) isometric contractions at 25% maximal strength and throughout a 3 min sustained BFR isometric contraction. Results Plasma nitrite (NO2-) concentration was elevated after NIT compared to PLA (475±93 vs.198±46 nmol·L-1, p0.05), MUP duration was shorter with NIT compared to PLA during brief isometric contractions and the sustained ischemic contraction (p<0.01). Additionally, mean MUP duration, MUP area and NF jiggle increased, and MUFR decreased over the 3 min sustained BFR isometric contraction for both conditions (all p<0.05). Conclusion These findings provide insight into the effect of NO3- supplementation on MUP properties and reveal shorter MUP duration after short-term NO3- supplementation which may have potential positive implications for skeletal muscle contractile performance

Mapeamento genético de marcadores AFLP ligados ao gene de resistência do híbrido de timor à Hemileia vastatrix.

A ferrugem alaranjada do cafeeiro causada por Hemileia vastatrix é tida como a mais devastadora doença do cafeeiro. Este trabalho objetivou estudar a herança gênica e a identificação de marcadores moleculares ligados ao gene que confere resistência a esta doença. Para este estudo foram utilizados a população F2 (160 indivíduos), o retrocruzamento resistente (RCr, 20 indivíduos) e o suscetível (RCs, 135 indivíduos), derivados do cruzamento entre o Híbrido de Timor UFV 427-15, genitor resistente e o suscetível Catuai amarelo UFV 2143-236. A análise da segregação das populações, em estudo, indicou que um único gene dominante, presente no acesso do Híbrido de Timor UFV 427-15, é responsável pela resistência. Foram utilizadas as metodologias de BSA (Bulked Segregant Analysis) e AFLP, e analisadas 852 combinações de primers, que permitiram identificar três marcadores ligados ao gene de resistência localizados flanqueando ambos os lados, e distantes a 8.69, 20.50 e 25.10 cM. Estes são os primeiros marcadores identificados para o gene de resistência a ferrugem presente no Híbrido de Timor, e auxiliarão na seleção em programas de melhoramento para a resistência a ferrugem no Brasil

Effects of exercise induced muscle damage on cardiovascular responses to isometric muscle contractions and post-exercise circulatory occlusion

Purpose: The aim of the present study was to investigate whether exercise-induced muscle damage (EIMD) influences cardiovascular responses to isometric exercise and post-exercise circulatory occlusion (PECO). We hypothesized that EIMD would increase muscle afferent sensitivity and, accordingly, increase blood pressure responses to exercise and PECO. Methods: Eleven male and nine female participants performed unilateral isometric knee extension at 30% of maximal voluntary contraction (MVC) for 3-min. A thigh cuff was rapidly inflated to 250 mmHg for two min PECO, followed by 3 min recovery. Heart rate and blood pressure were monitored beat-by-beat, with stroke volume and cardiac output estimated from the Modelflow algorithm. Measurements were taken before and 48 h after completing eccentric knee-extension contractions to induce muscle damage (EIMD). Results: EIMD caused 21% decrease in MVC (baseline: 634.6 ± 229.3 N, 48 h: 504.0 ± 160 N), and a 17-fold increase in perceived soreness using a visual-analogue scale (0–100 mm; VASSQ) (both p < 0.001). CV responses to exercise and PECO were not different between pre and post EIMD. However, mean arterial pressure (MAP) was higher during the recovery phase after EIMD (p < 0.05). Significant associations were found between increases in MAP during exercise and VASSQ, Rate of Perceived Exertion (RPE) and Pain after EIMD only (all p < 0.05). Conclusion: The MAP correlations with muscle soreness, RPE and Pain during contractions of damaged muscles suggests that higher afferent activity was associated with higher MAP responses to exercise

Age-related declines in muscle and respiratory function are proportionate to declines in performance in Master Track Cyclists

Purpose Respiratory and musculoskeletal function decline with age, irrespective of physical activity levels. Previous work has suggested that the age-related rate of decline in function of these two systems might be similar, but it is not known to what extent each system contributes to decreasing performance in ageing master cyclists. Therefore, the purposes of this study are (1) whether the age-related rate of decline in respiratory function, respiratory muscle strength, muscle architecture, muscle function, haemoglobin concentration, haematocrit and performance in master cyclists is uniform and (2) which parameters contribute most to the reduction in performance with age. Methods Master cyclists were recruited during the Track Cycling Masters World Championship 2019 in Manchester. Respiratory function and respiratory muscle strength were determined using spirometry and a mouth pressure device, respectively. Muscle architecture was determined using ultrasonography, and muscle function by countermovement jump. Results Forced expiratory volume in the frst second, forced vital capacity, fascicle length, muscle thickness, take-of velocity, jump power, jump power per body mass, handgrip strength, haemoglobin concentration and performance correlated negatively with age (p≤0.043). The age-related rate of decline did not difer signifcantly between parameters (p=0.124), but it was slower for haemoglobin concentration (p=0.041). Take-of velocity was the major determinant of performance in 200, 500 and 2000 m track cycling disciplines (R2 adj=0.675, 0.786 and 0.769, respectively; p<0.001). Conclusion Age-related decline in respiratory and muscle system is accompanied by a similar rate of decline in performance. The major contribution to the age-related decline of performance is reduced muscle function, specifcally take-of velocity

Superior Physiological Adaptations After a Microcycle of Short Intervals Versus Long Intervals in Cyclists

Purpose: To compare the effects of a 1-week high-intensity aerobic-training shock microcycle composed of either 5 short-interval sessions (SI; n = 9, 5 series with 12 × 30-s work intervals interspersed with 15-s recovery and 3-min recovery between series) or 5 long-interval sessions (LI; n = 8, 6 series of 5-min work intervals with 2.5-min recovery between series) on indicators of endurance performance in well-trained cyclists. Methods: Before and following 6 days with standardized training loads after the 1-week high-intensity aerobic-training shock microcycle, both groups were tested in physiological determinants of endurance performance. Results: From pretraining to posttraining, SI achieved a larger improvement than LI in maximal oxygen uptake (5.7%; 95% confidence interval, 1.3–10.3; P = .015) and power output at a blood lactate concentration of 4 mmol·L−1 (3.8%; 95% confidence interval, 0.2–7.4; P = .038). There were no group differences in changes of fractional use of maximal oxygen uptake at a workload corresponding to a blood lactate concentration of 4 mmol·L−1, gross efficiency, or the 1-minute peak power output from the maximal-oxygen-uptake test. Conclusion: The SI protocol may induce superior changes in indicators of endurance performance compared with the LI protocol, indicating that SI can be a good strategy during a 1-week high-intensity aerobic-training shock microcycle in well-trained cyclists