Frequency band analysis of muscle actiwation during cycling to exhaustion

• Published in: Brazilian Journal of Kinanthropometry and Human Performance Vol. 14; no. 3; pp. 243 - 253
• Main Authors: Diefenthaeler, F, Bini, R R, Vaz, MA
• Format: Journal Article
• Language: Portuguese
• Published: 01.01.2012
• Subjects: Aerobic power; Analysis; Bicycling; Exercise; Fatigue; Muscles; Muscles (activity); Muscles (fatigue); Work load
• ISSN: 1415-8426

Lower limb muscles activation was assessed during cycling to exhaustion using frequency band analysis. Nine cyclists were evaluated in two days. On the first day, cyclists performed a maximal incremental cycling exercise to measure peak power output, which was used on the second day to define the workload for a constant load time to exhaustion cycling exercise (maximal aerobic power output from day 1). Muscle activation of vastus lateralis (VL), long head of biceps femoris (BF), lateral head of gastrocnemius (GL), and tibialis anterior (TA) from the right lower limb was recorded during the time to exhaustion cycling exercise. A series of nine band-pass Butterworth digital filters was used to analyze muscle activity amplitude for each band. The overall amplitude of activation and the high and low frequency components were defined to assess the magnitude of fatigue effects on muscle activity via effect sizes. The profile of the overall muscle activation during the test was analyzed using a second order polynomial, and the variability of the overall bands was analyzed by the coefficient of variation for each muscle in each instant of the test. Substantial reduction in the high frequency components of VL and BF activation was observed. The overall and low frequency bands presented trivial to small changes for all muscles. High relationship between the second order polynomial fitting and muscle activity was found (R super(2) > 0.89) for all muscles. High variability ( similar to 25%) was found for muscle activation at the four instants of the fatigue test. Changes in the spectral properties of the EMG signal were only substantial when extreme changes in fatigue state were induced.Original Abstract: A ativacao dos musculos do membro inferior foi avaliada durante a pedalada ate a exaustao utilizando bandas de frequencia. Nove ciclistas foram avaliados em dois dias. No primeiro dia, os ciclistas realizaram um teste de carga incremental para a determinacao da maxima potencia aerobia, sendo esta utilizada como carga de trabalho para o teste de carga constante ate a exaustao durante o segundo dia de avaliacoes. Foi adquirida durante o teste de carga constante a ativacao dos musculos vastus lateralis (VL), porcao longa do biceps femoris (BF), porcao lateral do gastrocnemius (GL), e tibialis anterior (TA) do membro inferior direito. Uma serie de nove filtros digitais do tipo passa-banda Butterworth foi utilizada para a determinacao da amplitude do sinal obtido de cada banda de frequencia. As ativacoes musculares oriundas das nove bandas, das bandas de alta frequencia e das bandas de baixa frequencia foram definidas para a analise dos efeitos da fadiga muscular por meio da magnitude das alteracoes. O padrao da ativacao global das nove bandas durante o teste de carga constante foi determinado utilizando um polinomio de segunda ordem, enquanto a variabilidade da ativacao foi avaliada por meio do coeficiente de variacao. Reducoes substanciais nas bandas de alta frequencia foram observadas para os musculos VL e BF ao longo do teste. A ativacao das nove bandas e das bandas de baixa frequencia apresentou alteracoes triviais. Uma elevada capacidade preditiva do padrao de ativacao muscular foi observada utilizando o polinomio de segunda ordem (R super(2) > 0,89). Uma elevada variabilidade ( similar to 25%) foi observada para a ativacao muscular ao longo do teste. Alteracoes substanciais nas caracteristicas da ativacao muscular foram observadas apenas quando mudancas extremas no estado de fadiga muscular foram induzidas.