Desempenho e pacing na prova de 200 m nado borboleta: variabilidade e relações dos tempos parciais de 50 m com o tempo final

Resumo: Objetivo: Analisar o desempenho e o pacing de prova dos semifinalistas da prova de 200 m nado borboleta do 15.° Campeonato Mundial de Natação da Federação Internacional de Natação (FINA). Método: Os dados foram obtidos da página eletrônica da FINA. Os 32 tempos da etapa semifinal, masculina e feminina, foram divididos em 4 grupos: 8 homens classificados para a final (G1M), 8 homens não classificados (G2M), 8 mulheres classificadas para a final (G1F) e as 8 mulheres não classificadas (G2F). A velocidade de nado, para cada parcial de 50 m, foi estimada pelo quociente entre 50 m e o respectivo tempo. Foram calculados os coeficientes de variação de tempo das 4 parciais de 50 m e comparados entre os grupos (ANOVA). Tamanho de efeito foi verificado com d de Cohen. Correlacionouâse o desempenho (tempo total) com o tempo de cada parcial de 50 m (r de Pearson). Resultados: O coeficiente de variação para as parciais de 50 m foi menor nos grupos dos finalistas de ambos os sexos (G1M e G1F) e menor para as mulheres. A terceira parcial de 50 m apresentou maior correlação com o desempenho final em ambos os sexos. A velocidade média caiu ao longo da prova em ambos os grupos. Conclusão: O pacing para o melhor desempenho na prova é evitar variações de tempo ao longo dos 200 m nado borboleta e os treinamentos devem ser direcionados ao aprimoramento condicionante dessa parcial (150â200 m). Resumen: Objetivo: Analizar el desempeño y pacing durante la prueba de semifinalistas de 200 m mariposa del 15.° Campeonato Mundial de Natación de la Federación Internacional de Natación (FINA). Método: Los datos fueron retirados de la página electrónica de la FINA. Los 32 tiempos de la semifinal masculina y femenina fueron divididos en cuatro grupos: ocho varones clasificados para el final de la prueba analizada (G1M), ocho varones no clasificados (G2M), ocho mujeres clasificadas (G1F) y ocho mujeres no clasificadas (G2F). La velocidad de nado para cada parcial de 50 m fue estimada por el cociente entre 50 m y su respectivo tiempo. Fueron calculados los coeficientes de variación del tiempo de los cuatro parciales de 50 m y comparadas entre los grupos (ANOVA). Se observó el tamaño de efecto con d de Cohen. Se analizó la correlación entre el rendimiento (tiempo total) y el tiempo de cada parcial de 50 m. Resultados: El coeficiente de variación para los parciales de 50 m fue menor en los grupos finalistas de ambos sexos (G1M e G1F) y menor para las mujeres. El tercer parcial de 50 m presentó mayor correlación con el rendimiento final en ambos sexos. La velocidad media disminuyó a lo largo de la prueba en ambos grupos. Conclusión: El ritmo para el mejor rendimiento en la prueba es evitar la variación del tiempo a lo largo de los 200 m mariposa y el entrenamiento debe estar dirigido a la mejora de la condición física es ese parcial (150â200 m). Abstract: Objective: To analyze performance and pacing in 200 m butterfly among the semifinalists in 15th FINA World Championship. Methods: Data were obtained from FINA website. Thirty two semifinals performances were divided in four groups: eight male classified (G1 M), eight male unclassified (G2 M), eight female classified (G1F), and eight female unclassified (G2F). Swimming velocity for each 50 m partial was estimated by the quotient between distance and time. Coefficients of variation of the four 50 m partials were compared among groups (ANOVA). Effects sizes were identified by the Cohen's d. Total time (performance) was correlated with each 50 m partial time (Pearson's r). Results: Coefficients of variation were lower for the groups with best performance in both sexes (G1F and G1 M) and in females. The third partial presented the larger correlation with overall performance. Average swimming velocity decreased along the event. Conclusion: The best pacing is to maintain swimming velocity constant within each 50 m over the 200 m and the training should be directed to the conditional improvement of this split (150â200 m). Palavrasâchave: Velocidade de nado, Natação, Cinemática, Análise de desempenho, Palabras clave: Velocidad de nado, Natación, Cinemática, Análisis de rendimiento, Keywords: Swimming velocity, Swimming, Kinematics, Performance analysi

Temporomandibular joint dysfunction and trapezius muscle fatigability Disfunção Temporomandibular e a fatigabilidade do músculo trapézio

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.<br>INTRODUÇÃO: Tem sido sugerido que a dor aumenta a ativação do músculo trapézio em pacientes com disfunção temporomandibular (TMD). Mudanças na ativação do músculo podem alterar a resistência à fadiga. O objetivo do estudo foi investigar a fatigabilidade do músculo trapézio em pacientes com TMJ. MÉTODOS: Quatorze indivíduos com TMD (diagnosticados clinicamente e encaminhados pelo especialista odontólogo) e onze indivíduos saudáveis realizaram um protocolo de fadiga que consistiu em uma contração isométrica submáxima de elevação do ombro, em um nível de 70% da contração voluntária máxima, mantida por um período de 30 segundos. O sinal eletromiográfico (EMG) foi obtido da porção superior do músculo trapézio, (taxa de amostragem de 2000Hz/canal). Três segundos consecutivos do sinal EMG foram analisados no domínio da freqüência usando a Transformada Rápida de Fourier (FFT). Uma análise de regressão linear foi aplicada para valores consecutivos da freqüência mediana (MF) de cada sujeito, e a inclinação da regressão linear foi utilizada para descrever a fatigabilidade muscular. RESULTADOS: Nenhuma diferença foi observada na fatigabilidade do músculo trapézio direito e esquerdo para ambos os grupos e entre o trapézio esquerdo do grupo saudável e com TMD. A MF do músculo trapézio direito do grupo com disfunção apresentou valores de inclinação da reta de regressão linear de -0,15 ± 0,33 (média ± SD), os quais foram menores que os valores do grupo saudável (-0,44 ± 0,46; média ± SD; p= 0,049). Esses resultados sugerem que a fatigabilidade do trapézio direito é menor no grupo com TMD do que no grupo saudável

Neuromuscular determinants of explosive torque: Differences among strength-trained and untrained young and older men

This study compared the differences in neural and muscular mechanisms related to explosive torque in chronically strength-trained young and older men (>5 years). Fifty-four participants were allocated into four groups according to age and strength training level: older untrained (n = 14; 65.6 ± 2.9 years), older trained (n = 12; 63.6 ± 3.8 years), young untrained (n = 14; 26.2 ± 3.7 years), and young trained (n = 14; 26.7 ± 3.4 years). Knee extension isometric voluntary explosive torque (absolute and normalized as a percentage of maximal voluntary torque) was assessed at the beginning of the contraction (ie, 50, 100, and 150 ms—T50, T100, and T150, respectively), and surface electromyogram (sEMG) amplitude (normalized as a percentage of sEMG recorded during maximal voluntary isometric contraction) at 0-50, 50-100, and 100-150 time windows. Supramaximal electrically evoked T50 was assessed with octet trains delivered to the femoral nerve (8 pulses at 300 Hz). Voluntary T50, T100, and T150 were higher for trained than untrained in absolute (P  0.417). Chronically strength-trained young and older men presented a greater explosive torque than their untrained pairs. In young trained, the greater explosive performance was attributed to enhanced muscular and neural mechanisms, while in older trained to neural mechanisms only.</p

Effect of 8 Weeks Soccer Training on Health and Physical Performance in Untrained Women

This study aims to analyze the physiological, neuromuscular, and biochemical responses in untrained women after eight weeks of regular participation in small-sided soccer games compared to aerobic training. Twenty-seven healthy untrained women were divided into two groups [soccer group (SG = 17) and running group (RG = 10)]. Both groups trained three times per week for eight weeks. The variables measured in this study were maximal oxygen uptake (VO2max), relative velocity at VO2max (vVO2max), peak velocity, relative intensity at lactate threshold (vLT), relative intensity at onset of blood lactate accumulation (vOBLA), peak force, total cholesterol, HDL, LDL, triglycerides, and cholesterol ratio (LDL/HDL). VO2max, vLT, and vOBLA increased significantly in both groups (12.8 and 16.7%, 11.1 and 15.3%, 11.6 and 19.8%, in SG and RG respectively). However, knee extensors peak isometric strength and triglyceride levels, total cholesterol, LDL, and HDL did not differ after eight weeks of training in both groups. On the other hand, the LDL/HDL ratio significantly reduced in both groups. In conclusion, eight weeks of regular participation in small-sided soccer games was sufficient to increase aerobic performance and promote health benefits related to similar aerobic training in untrained adult women

Neuromuscular determinants of explosive torque: Differences among strength‐trained and untrained young and older men

This study compared the differences in neural and muscular mechanisms related to explosive torque in chronically strength-trained young and older men (>5 years). Fifty-four participants were allocated into four groups according to age and strength training level: older untrained (n = 14; 65.6 ± 2.9 years), older trained (n = 12; 63.6 ± 3.8 years), young untrained (n = 14; 26.2 ± 3.7 years), and young trained (n = 14; 26.7 ± 3.4 years). Knee extension isometric voluntary explosive torque (absolute and normalized as a percentage of maximal voluntary torque) was assessed at the beginning of the contraction (ie, 50, 100, and 150 ms—T50, T100, and T150, respectively), and surface electromyogram (sEMG) amplitude (normalized as a percentage of sEMG recorded during maximal voluntary isometric contraction) at 0-50, 50-100, and 100-150 time windows. Supramaximal electrically evoked T50 was assessed with octet trains delivered to the femoral nerve (8 pulses at 300 Hz). Voluntary T50, T100, and T150 were higher for trained than untrained in absolute (P  0.417). Chronically strength-trained young and older men presented a greater explosive torque than their untrained pairs. In young trained, the greater explosive performance was attributed to enhanced muscular and neural mechanisms, while in older trained to neural mechanisms only.</p

Heliox Improves Oxygen Delivery and Utilization during Dynamic Exercise in Patients with Chronic Obstructive Pulmonary Disease

Rationale: Normoxic heliox (mixture of 79% He and 21% O 2 ) may enhance exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). It remains to be determined whether part of these beneficial effects could be ascribed to increased O 2 delivery (O 2 DEL) to locomotor muscles. Objectives: To investigate the effects of heliox on peripheral O 2 DEL and utilization during exercise in moderate to severe COPD. Methods: Twelve mildly hypoxic or nonhypoxemic men (FEV 1 5 45.0 6 13.0% predicted) underwent constant-work rate tests (70-80% peak) to the limit of tolerance while receiving heliox or room air. Near-infrared spectroscopy determined changes (D) in leg muscle deoxygenation (deoxyhemoglobin concentration [HHb], an index of fractional O 2 extraction), and surface electromyography estimated muscle fiber recruitment (n 5 5). Muscle fiber recruitment and leg effort scores were also diminished (P , 0.05). On a multiple regression analysis, reductions in dynamic hyperinflation, dyspnea, and D[HHb] were independently related to improvements in exercise tolerance with heliox (R 2 5 0.91; P , 0.01). Conclusions: Heliox increases lower limb O 2 DEL and utilization during dynamic exercise in patients with moderate to severe COPD. These effects enhance exercise tolerance in this patient population. Keywords: chronic obstructive pulmonary disease; helium; exercise tolerance; oxygen consumption; near-infrared spectroscopy There are several putative factors related to decreased exercise capacity in patients with chronic obstructive pulmonary disease (COPD). These range from pulmonary-mechanical abnormalities to impaired muscle bioenergetics (1-3). More recently, much emphasis has been given to the dynamics of oxygen delivery (O 2 DEL) to the working muscles as a contributing mechanism (1, 4-6). Reduced O 2 DEL to the lower limbs, for instance, could be related to hypoxemia (6), autonomic imbalance (7), blood flow redistribution from peripheral to respiratory muscles (8, 9), derangements in muscle vasodilatation capacity (10), and the negative effects of increased mean intrathoracic pressures and/or excessive pleural pressure swings on central hemodynamic adjustments (11-13). In fact, hyperoxia can speed the kinetics of _ VO 2 at the onset of moderate exercise in patients with COPD, suggesting a role for impaired peripheral O 2 DEL in limiting the rate of adaptation of aerobic metabolism (4). Several therapeutic strategies have been used to improve the respiratory-mechanical abnormalities during exercise in patients with COPD with potential beneficial consequences on O 2 DEL (as reviewed in Reference 14). Heliox (mixture of 79% He and 21% O 2 ), in particular, combines favorable effects on lung mechanics (e.g., faster lung emptying and reduced flow turbulence) (15), pulmonary gas exchange (16), and central hemodynamics What This Study Adds to the Field This study demonstrates that a strategy able to ammeliorate expiratory flow limitation and dynamic hyperinflation (heliox) accelerates the dynamics of peripheral muscle utilization of oxygen as a consequence of improved delivery during high-intensity exercise in patients with moderate to severe COPD. Our data provide a scientific rationale for respiratory-mechanical interventions aiming to enhance oxygen delivery to the lower limb muscles during dynamic exercise in this patient population