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The effects of a fatiguing protocol on stride-to-stride fluctuations of running
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O futebol é um desporto coletivo com atividades intermitentes e ao longo do jogo tende a instalar-se fadiga que leva a uma diminuição na performance. A fadiga parece afetar o controlo motor do indivíduo. Esse controlo motor pode ser determinado pelo tipo de flutuações existentes no sistema em análise. A complexidade fisiológica representa um estado de comportamento flexível que permite que o sistema do indivíduo se adapte às mudanças no ambiente. Existe evidencia sobre o aumento da variabilidade e diminuição da estrutura da complexidade que ocorre com atividade prolongada ou fadiga muscular. A literatura sugere que a complexidade se altera com a fadiga. Assim, o objetivo do nosso estudo consiste em investigar o efeito de um protocolo de fadiga sobre vários parâmetros de variabilidade na corrida. Dezassete adultos saudáveis (idade: 23.8 ± 2.23 anos; altura: 1.76 ± 0.05 m; massa: 71.3 ± 9.05 Kg; índice de massa corporal: 22.8 ± 2.3 Kg/m²) realizaram uma sessão composta por duas avaliações e um protocolo de fadiga. As avaliações consistiam numa corrida submáxima numa passadeira a 9 Km/h com uma duração de 10 minutos. Entre avaliações foi realizado um protocolo de fadiga que simula um jogo de futebol. Foi colocado um acelerómetro triaxial no maléolo externo para permitir a identificação do contacto com o solo de cada passada. De seguida mediu-se a magnitude da variabilidade através do coeficiente de variação e a variabilidade da estrutura temporal alcançada com o Detrended Fluctuation Analysis α (DFA). Testes t para amostras emparelhadas e o teste de Wilcoxon foram usados para determinar o efeito do protocolo de fadiga (PRE vs POS) nas medidas da variabilidade da corrida. Foi observada uma diminuição significativa do Fractal scaling do inter stride intervals (α-ISIs) após o protocolo de fadiga (t=2.138; p=0.048; d=0.519; PRE=0.85±0.18, POS=0.76±0.18). Relativamente a Coeficiente de Variação do inter stride intervals (CV-ISIs), não encontrámos nenhuma diferença estatisticamente significativa (z=-0.447; p=0.655; r=-0.108; PRE=1.47±0.51%, POS=1.41±0.51%). Foi demonstrado que a complexidade da corrida tende a diminuir, e que a magnitude do coeficiente de variação (CV) não se altera após o protocolo de fadiga. O CV é uma medida linear que não é tão sensível a flutuações como as medidas não lineares.
Soccer is a team sport with intermittent activities and throughout the game fatigue tends to set in, leading to a decrease in performance. Fatigue seems to affect the individual's motor control. This motor control can be determined by the type of fluctuations existing in the system under analysis. Physiological complexity represents a state of flexible behavior that allows the individual's system to adapt to changes in the environment. There is evidence about the increased variability and decreased structure of complexity that occurs with prolonged activity or muscle fatigue. The literature suggests that complexity changes with fatigue. Thus, the purpose of our study is to investigate the effect of a fatigue protocol on various variability parameters in running. Seventeen healthy adults (age: 23.8 ± 2.23 years; height: 1.76 ± 0.05 m; mass: 71.3 ± 9.05 Kg; body mass index: 22.8 ± 2.3 Kg/m²) performed a session consisting of two assessments and a fatigue protocol. The evaluations consisted of a submaximal run on a treadmill at 9 Km/h for 10 minutes. Between evaluations a fatigue protocol simulating a soccer game was performed. A triaxial accelerometer was placed on the external malleolus to allow identification of the ground contact of each stride. Then the magnitude of variability was measured through the coefficient of variation and the variability of the temporal structure achieved with the DFAα. Paired-samples t-tests and Wilcoxon's test were used to determine the effect of the fatigue protocol (PRE vs POS) on measures of running variability. A significant decrease in Fractal scaling from inter stride intervals (α-ISIs) was observed after the fatigue protocol (t=2.138; p=0.048; d=0.519; PRE=0.85±0.18, POS=0.76±0.18). Coefficient of Variation from inter stride intervals (CV-ISIs), we found no statistically significant difference (z=-0.447; p=0.655; r=-0.108; PRE=1.47±0.51%, POS=1.41±0.51%). It has been shown that running complexity tends to decrease, and that the magnitude of Coefficient of Variation (CV) does not change after the fatigue protocol. CV is a linear measure that is not as sensitive to fluctuations as non-linear measures.
Soccer is a team sport with intermittent activities and throughout the game fatigue tends to set in, leading to a decrease in performance. Fatigue seems to affect the individual's motor control. This motor control can be determined by the type of fluctuations existing in the system under analysis. Physiological complexity represents a state of flexible behavior that allows the individual's system to adapt to changes in the environment. There is evidence about the increased variability and decreased structure of complexity that occurs with prolonged activity or muscle fatigue. The literature suggests that complexity changes with fatigue. Thus, the purpose of our study is to investigate the effect of a fatigue protocol on various variability parameters in running. Seventeen healthy adults (age: 23.8 ± 2.23 years; height: 1.76 ± 0.05 m; mass: 71.3 ± 9.05 Kg; body mass index: 22.8 ± 2.3 Kg/m²) performed a session consisting of two assessments and a fatigue protocol. The evaluations consisted of a submaximal run on a treadmill at 9 Km/h for 10 minutes. Between evaluations a fatigue protocol simulating a soccer game was performed. A triaxial accelerometer was placed on the external malleolus to allow identification of the ground contact of each stride. Then the magnitude of variability was measured through the coefficient of variation and the variability of the temporal structure achieved with the DFAα. Paired-samples t-tests and Wilcoxon's test were used to determine the effect of the fatigue protocol (PRE vs POS) on measures of running variability. A significant decrease in Fractal scaling from inter stride intervals (α-ISIs) was observed after the fatigue protocol (t=2.138; p=0.048; d=0.519; PRE=0.85±0.18, POS=0.76±0.18). Coefficient of Variation from inter stride intervals (CV-ISIs), we found no statistically significant difference (z=-0.447; p=0.655; r=-0.108; PRE=1.47±0.51%, POS=1.41±0.51%). It has been shown that running complexity tends to decrease, and that the magnitude of Coefficient of Variation (CV) does not change after the fatigue protocol. CV is a linear measure that is not as sensitive to fluctuations as non-linear measures.
Descrição
Palavras-chave
Complexidade Controlo motor Corrida Fadiga Futebol Intervalo entre passadas Medidas não-lineares Movimento Protocolo de fadiga Variabilidade Complexity Fatigue Fatiguing protocol Motor control Movement Non-linear measurements Running Soccer Stride interval Variability