Antônio Carlos Stringhini Guimarães

Proposta metodológica para a avaliação da técnica da pedalada de ciclistas: estudo de caso

Many techniques have been used in biomechanics to describe the cycling movement. The purpose of this study is to proposal a specific methodology to evaluation the forces applied on the pedal. An experienced elite cyclist was submitted to a protocol which consisted of four different saddle positions (upward, downward, forward, and backward) assuming as reference position the one used by the cyclist in training and competition. The displacement of the saddle was of 1cm in all tests. The individuals bicycle was connected to a magnetic cycle simulator. The load was normalized by a physiological criterion (ventilatory threshold), to simulate the cyclists race rhythm. The right regular pedal was replaced by a 2D instrumented pedal to record the force normal and tangential components applied on it. Mean impulse of the angular effective force was calculated from ten consecutive pedaling cycles. The four different saddle positions have modified the effective angular pedaling impulse comparing with the reference position. Relatively small saddle adjustments may affect the effective angular pedaling impulse and supposedly cycling performance.Many techniques have been used in biomechanics to describe the cycling movement. The purpose of this study is to proposal a specific methodology to evaluation the forces applied on the pedal. An experienced elite cyclist was submitted to a protocol which consisted of four different saddle positions (upward, downward, forward, and backward) assuming as reference position the one used by the cyclist in training and competition. The displacement of the saddle was of 1cm in all tests. The individual’s bicycle was connected to a magnetic cycle simulator. The load was normalized by a physiological criterion (ventilatory threshold), to simulate the cyclist’s race rhythm. The right regular pedal was replaced by a 2D instrumented pedal to record the force normal and tangential components applied on it. Mean impulse of the angular effective force was calculated from ten consecutive pedaling cycles. The four different saddle positions have modified the effective angular pedaling impulse comparing with the reference position. Relatively small saddle adjustments may affect the effective angular pedaling impulse and supposedly cycling performance.

Temporomandibular joint dysfunction and trapezius muscle fatigability

Introduction: It has been suggested that pain increases trapezius muscle activation in patients with temporomandibular joint dysfunction (TMD). Changes in muscle activation might change muscle resistance to fatigue. The purpose of this study was to evaluate the fatigability of the trapezius muscle in patients with TMD. Method: Fourteen patients with TMD (clinically diagnosed and referred by a dentist) and eleven healthy subjects performed a fatigue test consisting of shoulder elevation performed at 70% of the maximal voluntary isometric contraction, which was maintained for 30 seconds. Electromyographic signals were obtained from the upper portion of the trapezius muscle (sampling frequency: 2000 Hz/channel). Consecutive segments of three seconds in duration each were extracted from the electromyographic signal and analyzed in the frequency domain using a Fast Fourier Transform algorithm. Linear regression analysis was applied to the consecutive median frequencies for each subject. The slope of the regression line was used to describe muscle fatigability. Results: No changes were observed in fatigability between the right and left trapezius of either group or between the left trapezius of the healthy and TMD groups. The linear regression for median frequencies in the right trapezius of the TMD group showed a slope of -0.15 ± 0.33 (mean ± SD), which was smaller than the slope for the healthy group (-0.44 ± 0.46; p= 0.049). These results suggested that the fatigability of the right trapezius was lower in the TMD group than in the healthy group.

Aplicação de força no pedal em prova de ciclismo 40 km contra-relógio simulada: estudo preliminar

O objetivo deste estudo foi analisar o comportamento das forcas aplicadas no pedal durante uma prova de ciclismo 40 km contra-relogio simulada. Avaliou-se um triatleta de nivel internacional utilizando-se uma bicicleta modelo estrada acoplada a um ciclossimulador eletromagnetico. O protocolo consistiu em completar 40 km no menor tempo possivel, utilizando estrategia de livre escolha, incluindo cadencia e relacao de marchas preferida. Utilizou-se um pedal direito instrumentado com strain gauges capaz de mensurar as componentes normal e tangencial da forca aplicada no mesmo. Foi possivel calcular a forca efetiva (componente perpendicular ao pe-de-vela, chamada de FE), a partir das forcas registradas pelo pedal. Durante todo o teste, monitorou-se o consumo de oxigenio (VO2), frequencia cardiaca (FC), potencia e velocidade. Durante a prova simulada observou-se um aumento do esforco do triatleta a partir da analise do comportamento do VO2 e da FC, bem como pelo aumento da potencia e da velocidade. A magnitude das forcas normal e tangencial ao pedal apresentou reducao no decorrer da prova, enquanto que a FE aumentou durante a fase de recuperacao. Provavelmente o triatleta mudou o direcionamento das forcas ao longo do teste na tentativa de otimizar as mesmas, influenciando dessa forma a tecnica de pedalada. A estrategia adotada pelo triatleta parece ter contribuido para aumentar a efetividade da pedalada.

Comparação das variáveis eletromiográficas e cinemáticas entre uma corrida do "triathlon" e uma corrida prolongada

A corrida e o ciclismo realizados com uma mesma duracao e intensidade podem apresentar diferentes respostas biomecânicas e metabolicas durante um protocolo de fadiga devido a sobrecarga mecânica e a especificidade tecnica de cada modalidade. O objetivo do presente estudo foi avaliar os efeitos da fadiga proveniente de uma corrida de 10 km, precedida por ciclismo ou corrida, no padrao de passada e no sinal eletromiografico (EMG). Nove triatletas do sexo masculino com tempo de pratica superior a dois anos participaram do estudo. Os testes foram realizados em duas etapas: corrida do triathlon (40 km de ciclismo seguidos de 10 km de corrida) e corrida prolongada (corrida com duracao igual ao tempo que o atleta levou para percorrer os 40 km de ciclismo, seguidos de mais 10 km de corrida). Uma analise cinematica (frequencia e amplitude de passada) e eletromiografica correspondentes as 10 passadas registradas no 5o km de cada corrida foi realizada. As curvas de EMG foram retificadas e filtradas para calculo das curvas de RMS. A partir da media das curvas de EMG foram obtidos os valores de pico de RMS para os musculos reto femoral, vasto lateral e biceps femoral. Maiores valores de frequencia de passada e do sinal EMG do musculo biceps femoral foram obtidos na corrida prolongada quando comparada com a corrida do triathlon. Esses resultados parecem estar relacionados a maior fadiga proveniente da corrida prolongada devido as maiores exigencias mecânicas.