Changes in VO2 Kinetics After Elevated Baseline Do Not Necessarily Reflect Alterations in Muscle Force Production in Both Sexes

A link between muscle fatigue, decreased efficiency and the slow component of oxygen uptake (VO2sc) has been suggested. However, a cause-effect relationship remains to be elucidated. Although alterations in VO2 kinetics after elevated baseline work rate have previously been reported, to date no study has observed the effect on muscle force production (MFP) behavior considering physiological differences between male and female subjects. This study investigated the effect of elevated baseline work rate on the VO2 kinetics and MFP in 10 male and 10 female healthy subjects. Subjects performed 4 transitions of very-heavy (VH) intensity cycling in a randomized order after unloaded (U-VH) or moderate (M-VH) exercise. Maximal isokinetic efforts (MIE) were performed before and after each condition at two different cadences (60 or 120 rpm). Whereas baseline VO2 and time constant (τ) were significantly higher in M-VH compared to U-VH, the fundamental amplitude and the VO2 slow component (VO2sc) were significantly lower in M-VH (p < 0.05) in both sexes. Blood lactate concentration ([La]) and rate of perceived exertion (RPE) were not influenced by condition or sex (p > 0.05). The MFP post-exercise was not significantly influenced by condition in both sexes and cadences (Δtorque for males: at 60 rpm in U-VH = 13 ± 10 Nm, in M-VH = 13 ± 9 Nm; at 120 rpm in U-VH = 22 ± 14 Nm, in M-VH = 21 ± 12 Nm; for females: at 120 rpm in U-VH = 10 ± 9 Nm, in M-VH = 12 ± 8 Nm; p > 0.05), with the exception that female subjects presented smaller decreases in M-UH at 60 rpm compared to U-VH (11 ± 13 vs. 18 ± 14 Nm, respectively, p < 0.05). There was no correlation between the decrease in torque production and VO2 kinetics parameters (p > 0.05). The alterations in VO2 kinetics which have been suggested to be linked to changes in motor unit recruitment after elevated baseline work rate did not reflect alterations in MFP and fatigue in both sexes

Thigh Ischemia-Reperfusion Model Does Not Accelerate Pulmonary VO2 Kinetics at High Intensity Cycling Exercise

Background: We aimed to investigate the effect of a priming ischemia-reperfusion (IR) model on the kinetics of pulmonary oxygen uptake (VO2) and cardiopulmonary parameters after high-intensity exercise. Our primary outcome was the overall VO2 kinetics and secondary outcomes were heart rate (HR) and O2 pulse kinetics. We hypothesized that the IR model would accelerate VO2 and cardiopulmonary kinetics during the exercise.Methods: 10 recreationally active men (25.7 ± 4.7 years; 79.3 ± 10.8 kg; 177 ± 5 cm; 44.5 ± 6.2 mL kg−1 min−1) performed a maximal incremental ramp test and four constant load sessions at the midpoint between ventilatory threshold and VO2 max on separate days: two without IR (CON) and two with IR (IR). The IR model consisted of a thigh bi-lateral occlusion for 15 min at a pressure of 250 mmHg, followed by 3 min off, before high-intensity exercise bouts.Results: There were no significant differences for any VO2 kinetics parameters (VO2 base 1.08 ± 0.08 vs. 1.12 ± 0.06 L min−1; P = 0.30; τ = 50.1 ± 7.0 vs. 47.9 ± 6.4 s; P = 0.47), as well as for HR (MRT180s 67.3 ± 6.0 vs. 71.3 ± 6.1 s; P = 0.54) and O2 pulse kinetics (MRT180s 40.9 ± 3.9 vs. 48.2 ± 5.6 s; P = 0.31) between IR and CON conditions, respectively.Conclusion: We concluded that the priming IR model used in this study had no influence on VO2, HR, and O2 pulse kinetics during high-intensity cycling exercise

Effects of priming exercise on the oxygen uptake kinetics and muscle fatigue during high-intensity cycling

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Desportos, Programa de Pós-Graduação em Educação Física, Florianópolis, 2018.Acredita-se que os mecanismos que determinam a cinética do consumo de oxigênio ("V" ?O2) refletem a fadiga muscular esquelética e uma consequente redução na eficiência muscular. Assim, o principal objetivo deste estudo foi verificar a relação da fadiga muscular com a cinética de "V" ?O2, analisando se o exercício prévio influenciaria essa relação durante o ciclismo de alta intensidade em indivíduos fisicamente ativos. Este trabalho foi dividido em três estudos, cada um buscando responder uma questão específica. No estudo um e dois, 13 homens saudáveis desempenharam testes para determinar o máximo consumo de "V" ?O2 ("V" ?O2peak), a potência crítica (CP) e a W' (capacidade finita de trabalho acima da CP) e seis cargas constantes até três ou oito min, ou até a exaustão (estudo dois). Cada uma destas numa taxa de trabalho para depletar 70%W' em 8 min, com um esforço isocinético máximo (MIE) realizado antes e depois das condições sem (VHCON) e com exercício prévio (VHEXP), para medir o decréscimo no pico de torque. No estudo três, 20 sujeitos (10 mulheres) saudáveis desempenharam quatro transições de exercício de intensidade muito pesada (VH) em ordem randomizada depois do exercício sem carga (U-VH) ou moderado (M-VH). O MIE foi desempenhado antes e depois de cada condição em duas diferentes intensidades (60 ou 120 rpm). No estudo um a magnitude do componente lento de "V" ?O2 ("V" ?O2SC) (VHCON = 0,280 ± 0,234, VHEXP = 0,116 ± 0,109 L.min-1; p=0,04) no 3º min e a trajetória do "V" ?O2SC foram significativamente menores na condição VHEXP (VHCON = 0,108 ± 0,042, VHEXP = 0,063 ± 0,031 L,min-2; p0,05). Em conclusão, considerando que os efeitos do exercício prévio no "V" ?O2SC não foram acompanhados pelo padrão de força muscular, esses achados não evidenciam a hipótese de uma relação de causa-efeito entre o curso de tempo da fadiga muscular e o "V" ?O2SC¬. O exercício prévio VH diminui a performance de ciclismo de alta intensidade. Sugere-se que esse prejuízo é influenciado por distúrbios fisiológicos ligados a depleção da W'. As alterações na cinética de "V" ?O2 depois do exercício de baseline elevado não refletem alterações na produção de força muscular em ambos os sexos.Abstract : It is believed that the mechanisms that determine the oxygen uptake ("V" ?O2) kinetics reflect skeletal muscle fatigue and a consequent reduction in muscle efficiency. Thus, the main purpose of this study was to verify the relation of muscular fatigue with the "V" ?O2 kinetics, analyzing whether prior exercise would influence this relationship during high intensity cycling in physically active individuals. This work was divided into three studies, each one seeking to answer one specific question. In the study one and two 13 healthy male subjects performed tests to determine the maximal "V" ?O2 ("V" ?O2peak), critical power (CP) and W' (fixed amount of work above CP) and six square-wave bouts until 3 or 8 min, or until exhaustion (study two). Each of them at a work rate set to deplete 70%W' in 8 min, with an maximal isokinetic effort (MIE) before and after the conditions without (VHCON) and with prior exercise (VHEXP), to measure the cycling peak torque decrement. In the study three 20 healthy subjects (10 female) performed 4 transitions of very-heavy (VH) intensity cycling in a randomized order after unloaded (U-VH) or moderate (M-VH) exercise. The MIE was performed before and after every condition at two different cadences (60 or 120 rpm). In the study one the "V" ?O2 slow component ("V" ?O2SC) magnitude at 3 min (VHCON = 0.280 ± 0.234, VHEXP = 0.116 ± 0.109 L.min-1; p=0.04) and the "V" ?O2SC trajectory were significantly lower for VHEXP (VHCON = 0.108 ± 0.042, VHEXP = 0.063 ± 0.031 L.min-2; p0.05). In conclusion, considering that priming effects on the "V" ?O2SC were not accompanied by the muscle force behavior, these findings do not support the hypothesis of a causal relationship between the time-course of muscle fatigue and "V" ?O2SC. Prior VH intensity exercise impairs high-intensity cycling performance. It is suggested that these impairments are mediated by physiological disturbances linked to W' depletion. The alterations in "V" ?O2 kinetics after elevated baseline did not reflect alterations in muscle force production in both sexes

Physiological characteristics, evaluation and prescription of aerobic training in Futsal

DOI: http://dx.doi.org/10.5007/1980-0037.2015v17n6p753   Futsal has intermittent characteristics with different requirements of displacements and changes of direction, requiring simultaneously aerobic and anaerobic capacities of athletes. So, during counter-attacks and returns to defense or fast movements to get rid or perform marking, there is maximum mobilization of specific capabilities of the sport and the ability to perform high-intensity intermittent exercise is a key factor of performance. The aim of this study was to perform an expositive review on the physiological characteristics, high-intensity interval training and aerobic evaluation methods that have been used and suggested in scientific literature in original studies. A search in scientific portals Google Scholar, Scopus®, SciELO®, ScienceDirect® (Elsevier) and PubMed® was conducted to find articles with publication date since 2000 using the following terms in different combinations: “Futsal”, “performance”, “aerobic evaluation”, “high-intensity interval training”, “field tests” and their variations in English. Analysis of physiological indexes related to game performance can help in the knowledge about the aerobic fitness of Futsal players and improve training assessment, prescription and monitoring, also serving as reference to assist professionals of this sport in the preparation of high intensity interval training programs to meet the particular needs of the sport. Field tests with specific features of the sport were created as a means of assessment and also training prescription and are recommended due to their specificity and ecological validity

O efeito do “FIFA 11+” na performance de saltos verticais em atletas de futebol

DOI: http://dx.doi.org/10.5007/1980-0037.2015v17n6p733   O objetivo do estudo foi verificar o efeito do treinamento de nove semanas de um programa de aquecimento “FIFA 11+” na performance de saltos verticais (SV) de jogadores de futebol. Participaram do estudo 20 atletas da categoria sub-20 de uma equipe da série A do campeonato brasileiro (idade: 18,3 ± 1,6 anos; tempo de prática 8,2 ± 1,3 anos; massa corporal de 74,0 ± 7,1 kg; estatura 177,8 ± 6,5 cm e percentual de gordura 10,7 ± 1,9 %), separados em grupo intervenção (G11+; n=10) e grupo controle (GC; n=10). Os Atletas foram avaliados antes (Pré) e após (Pós) a intervenção por meio dos saltos Countermoviment Jump (CMJ) e Squat Jump (SJ), realizados em uma plataforma de força, sendo os valores máximos da altura dos saltos adotados para análise. Foi realizada uma ANOVA modelo-misto para verificar os possíveis efeitos tempo x grupo. Nível de significância adotado de p < 0,05. Ambos os grupos foram submetidos à mesma rotina de treinamento (físico, técnico e tático), diferindo apenas o aquecimento proposto, que foi realizado três vezes por semana para o G11+. O GC não apresentou alteração significativa na performance dos saltos, porém o G11+ apresentou melhora significativa para ambos os tipos de saltos (CMJ: F= 26,23, p<0,01; %mudança= 11,3; SJ: F= 23,16, p<0,01, %mudança= 9,8). Desta forma, as nove semanas de intervenção com o programa de aquecimento “FIFA 11+” na rotina de treinamento promoveu um aumento significativo no desempenho dos saltos

The effects of priming exercise on the VO2 slow component and the time-course of muscle fatigue during very-heavy intensity exercise in humans.

We hypothesized that prior exercise would attenuate the muscle fatigue accompanied by the VO2SC behavior during a subsequent very heavy (VH) intensity cycling exercise. Thirteen healthy male subjects performed tests to determine the critical power (CP) and W′ and six square-wave bouts until 3 or 8 min, each at a work rate set to deplete 70 % W′ in 8 min, with an maximal isokinetic effort (MIE) before and after the conditions without (VHCON) and with prior exercise (VHEXP), to measure the cycling peak torque decrement. The VO2SC magnitude at 3 min (VHCON = 0.280 ± 0.234, VHEXP = 0.116 ± 0.109 L.min-1; p=0.04) and the VO2SC trajectory were significantly lower for VHEXP (VHCON = 0.108 ± 0.042, VHEXP = 0.063 ± 0.031 L.min-2; pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Maximal power output during incremental cycling test is dependent on the curvature constant of the power-time relationship

The aim of this study was to investigate whether the maximal power output (Pmax) during an incremental test was dependent on the curvature constant (W') of the power-time relationship. Thirty healthy male subjects (maximal oxygen uptake = 3.58 ± 0.40 L·min(-1)) performed a ramp incremental cycling test to determine the maximal oxygen uptake and Pmax, and 4 constant work rate tests to exhaustion to estimate 2 parameters from the modeling of the power-time relationship (i.e., critical power (CP) and W'). Afterwards, the participants were ranked according to their magnitude of W'. The median third was excluded to form a high W' group (HIGH, n = 10), and a low W' group (LOW, n = 10). Maximal oxygen uptake (3.84 ± 0.50 vs. 3.49 ± 0.37 L·min(-1)) and CP (213 ± 22 vs. 200 ± 29 W) were not significantly different between HIGH and LOW, respectively. However, Pmax was significantly greater for the HIGH (337 ± 23 W) than for the LOW (299 ± 40 W). Thus, in physically active individuals with similar aerobic parameters, W' influences the Pmax during incremental testing