The effect of short-term resistance training on hand reaction time improvement is independent of sexual dimorphism / El efecto del entrenamiento de resistencia a corto plazo en la mejora del tiempo de reacción manual es independiente del dimorfismo sexual / O efeito do treinamento resistido de curto prazo sobre a melhora do tempo de reação é independente do dimorfismo sexual

Objectiveː The aim was to evaluate the effects of four weeks of resistance training and sexual dimorphism on Manual reaction time in apparently healthy subjects.Methods: The subjects of the sample were randomly allocated in two groups, as follow: Control (CTRL) - kept 4 weeks without any systematized physical activity (Nmales= 8, age= 24±3 yrs., body weight= 76.9±15.4 kg; Nfemales= 8, age= 22.5±4 yrs., body weight= 70.8±17.5 kg); Experimental (EXP) - 4 weeks of resistance training (Nmales= 8, age= 23±3 yrs., weight= 69.6±11 kg; Nfemales= 8, age= 22.5±1 yrs., body weight= 59.77±6.8 kg). The resistance training consisted of 4 exercises for upper limbs (3 sets x 8-12 reps) and 4 exercises for lower (3 sets x 12-15 reps). Manual reaction time was evaluated in a manufactured Arduino-based reaction time device connected to a computer.Results: For men, there was a significant decrease in Manual reaction time after resistance training within EXP (p<0.0001) and between groups (p<0.0001). Women showed the same results within EXP (p<0.0001) and between groups (p<0.0001). Additionally, there was no sexual dimorphism before or after four weeks of resistance training.Conclusion: The results suggest that just four weeks of resistance training was sufficient to improve Manual reaction time, regardless of sexual dimorphism. Therefore, resistance training inclusion in the training periodization seems essential to improve or rehabilitate the fast voluntary motor response, especially for activities or sports that require it. (AU)

Objetivo: El objetivo fue evaluar los efectos de cuatro semanas de entrenamiento de resistencia y dimorfismo sexual sobre el tiempo de reacción manual en jóvenes aparentemente sanos.Métodos: Los sujetos de la muestra fueron asignados aleatoriamente en dos grupos, como sigue: Control (CTRL) - mantenido 4 semanas sin ninguna actividad física sistematizada (Nhombres= 8, edad= 24 ± 3 años, peso corporal= 76.9 ± 15.4 kg; Nmujeres= 8, edad= 22.5 ± 4 años, peso corporal= 70.8 ± 17.5 kg); Experimental (EXP) - 4 semanas de entrenamiento de resistencia (Nhombres= 8, edad= 23 ± 3 años, peso corporal= 69.6 ± 11 kg; Nmujeres= 8, edad= 22.5 ± 1 año, peso corporal= 59.77 ± 6.8 kg). El entrenamiento de resistencia consistió en 4 ejercicios para las extremidades superiores (3 series x 8-12 repeticiones) y 4 ejercicios para las inferiores (3 series x 12-15 repeticiones). El tiempo de reacción manual se evaluó utilizando una placa Arduino fabricada conectada a la computadora.Resultados: Para los hombres, hubo una reducción significativa en tiempo de reacción manual después de entrenamiento de resistencia intra EXP (p <0.0001) y entre grupos (p <0.0001). Los mismos resultados se observaron en mujeres, intra EXP (p <0.0001) y entre grupos (p <0.0001). Además, no hubo dimorfismo sexual antes y después de 4 semanas de entrenamiento de resistencia.Conclusión: Los resultados sugieren que solo cuatro semanas de entrenamiento de resistencia fueron suficientes para mejorar la tiempo de reacción manual, independientemente del dimorfismo sexual. La inclusión del entrenamiento de resistencia en la periodización del entrenamiento parece importante para mejorar o rehabilitar la respuesta motora voluntaria rápida, especialmente para actividades o deportes que lo requieran. (AU)

Objetivo: O objetivo foi avaliar os efeitos de quatro semanas de treinamento resistido e do dimorfismo sexual sobre o tempo de reação manual em jovens aparentemente saudáveis.Metodos: 32 jovens destreinados de ambos os sexos compuseram a amostra. Eles foram aleatoriamente alocados em 2 grupos: Controle (CTRL) – ficaram 4 semanas sem exercícios físicos (Nhomens= 8, idade= 24±3 anos, peso corporal= 76.9±15.4 kg; Nmulheres= 8, idade= 22.5±4 anos, peso corporal= 70.8±17.5 kg); Experimental (EXP) - 4 semanas de treinamento resistido (Nhomens= 8, idade= 23±3 anos, peso corporal= 69.6±11 kg; Nmulheres= 8, idade= 22.5±1 anos, peso corporal= 59.77±6.8 kg). O treinamento resistido consistiu em 4 exercícios para membros superiores (3 séries x 8-12 reps) e 4 para inferiores (3 sets x 12-15 reps). tempo de reação manual foi avaliado através de uma placa manufaturada de Arduino conectada ao computador.Resultados: Para os homens, houve uma redução significativa no tempo de reação manual após treinamento resistido intra EXP (p<0.0001) e entre os grupos (p<0.0001). Os mesmos resultados foram observados em mulheres, intra EXP (p<0.0001) e entre os grupos (p<0.0001). Adicionalmente não houve dimorfismo sexual antes ou após 4 semanas de treinamento resistido.Conclusão: Os resultados sugerem que apenas quatro semanas de treinamento resistido foram suficientes para melhorar o tempo de reação manual, independente do dimorfismo sexual. Portanto, a inclusão do treinamento resistido na periodização de treinamento parece importante para melhorar ou reabilitar a resposta motora voluntária rápida, principalmente para atividades ou esportes que assim necessitem. (AU)

Effects of autonomic balance and fluid and electrolyte changes on cardiac function in infarcted rats: A serial study of sexual dimorphism.

Premenopausal women are known to show lower incidence of cardiovascular disease than men. During myocardial infarction (MI), homeostatic responses are activated, including the sympathetic autonomic nervous system and the rennin-angiotensin-aldosterone system, which is related to the fluid and electrolyte balance, both aiming to maintain cardiac output. This study sought to perform a serial evaluation of sexual dimorphism in cardiac autonomic control and fluid and electrolyte balance during the development of MI-induced heart failure in rats. Experimental MI was induced in male (M) and female (F) adult (7-9 weeks of age) Wistar rats. The animals were placed in metabolic cages to assess fluid intake and urine volume 1 and 4 weeks after inducing MI (male myocardial infarction (MMI) and female myocardial infarction (FMI) groups). They subsequently underwent echocardiographic evaluation and spectral analysis of heart rate variability. After completing each protocol, the animals were killed for postmortem evaluation and histology. The MMI group showed earlier and more intense cardiac morphological and functional changes than the FMI group, although the extent of MI did not differ between groups (P > 0.05). The MMI group showed higher sympathetic modulation and sodium and water retention than the FMI group (P < 0.05), which may partly explain both the echocardiographic and pathological findings. Females subjected to infarction seem to show attenuation of sympathetic modulation, more favourable fluid and electrolyte balances, and better preserved cardiac function compared to males subjected to the same infarction model.

Acute effect of different stretching methods on isometric muscle strength / Efeito agudo de diferentes métodos de alongamento sobre a força muscular isométrica

This study investigated the acute effect of static stretching methods (SS) and proprioceptive neuromuscular facilitation (PNF) on the static muscle strength (SMS). Eleven young male subjects with strength training experience, performed 3 tests with a 48h interval between them, randomly selected, where each one subject carried out all procedures: a) hand grip without stretching; b) hand grip preceded by static stretching of wrist flexors muscles; c) hand grip preceded by PNF stretching of wrist flexors muscles. The Shapiro-Wilk test verified the normality of data, and a one-way ANOVA with repeated measures, followed by Tukey's post hoc test, evaluated the differences between the groups. The significance was set at p < 0.05. Significant differences were detected between control and static stretching protocols (35.4±11.30 vs. 30.2±9.18 kg N-1; p < 0.05). The same was observed between control and PNF stretching protocols (35.4±11.30 vs. 29.1±10.05 kg N-1; p < 0.01). However, no statistical difference was found for static and FNP stretching protocols (30.2±9.18 vs. 29.1±10.05 kg N-1; p > 0.05). In conclusion, both stretching methods had caused negative effects on isometric strength, reducing its levels.

. O presente estudo objetivou investigar o efeito agudo dos métodos de alongamento estático (AE) e facilitação neuromuscular proprioceptiva (FNP) sobre a força muscular estática (FME). Foram realizados, em 11 homens jovens com experiência prévia em treinamento de força, três testes com intervalo de 48h entre a aplicação dos mesmos, selecionados aleatoriamente, fazendo com que cada sujeito realizasse todas as técnicas, em rodízio: a) teste de preensão manual sem alongamento; b) teste de preensão manual precedido por alongamento estático dos músculos flexores de punho; c) teste de preensão manual precedido por FNP dos músculos flexores de punho. O teste de Shapiro-Wilk foi realizado para avaliar a normalidade dos dados e a one-way Anova com medida repetida, seguida por post-hoc de Tukey para análise das diferenças entre grupos. A significância adotada foi alpha p < 0,05. Conforme os resultados, entre os protocolos SA e AE, foram encontradas diferenças significativas na produção de força isométrica (35,4±11,30 vs. 30,2±9,18 kg N-1; p < 0,05). Entre SA e FNP, também foram encontradas diferenças significativas (35,4±11,30 vs. 29,1±10,05 kg N-1; p < 0,001). Todavia, diferenças significativas não foram observadas entre AE e FNP (30,2±9,18 vs. 29,1±10,05 kg N-1; p > 0,05). Os métodos de AE e FNP provocam efeito agudo sobre a FME reduzindo os níveis desta capacidade física.

Sexual dimorphism in autonomic changes and in the renin-angiotensin system in the hearts of mice subjected to thyroid hormone-induced cardiac hypertrophy.

Based on the relevance of the renin-angiotensin system and the ongoing controversy regarding the role of the sympathetic nervous system in thyroid hormone-induced cardiac hypertrophy, the aim of the present study was to establish whether the putative difference in the degree of cardiac hypertrophy exhibited by males and females might be related to differences in the sympathetic-vagal balance and/or in the cardiac renin-angiotensin system in mice of different genders. Male and female mice (n = 117) were given 0.1 mg kg(-1) of triiodothyronine or normal saline each day for 10 days consecutively. At the end of that period, study of the heart rate variability, spectral analysis and histopathological examination were performed to assess the sympathetic-vagal balance and the diameter of cardiomyocytes. The cardiac levels of angiotensin I and II were also measured. Treatment with triiodothyronine induced a greater degree of cardiac hypertrophy in male (~73%) than in female mice (~42%). This difference was attributed to greater modulation of the sympathetic nervous system and higher levels of angiotensin I and II in male than in female mice. Our data indicate that thyroid hormone-induced cardiac hypertrophy was more intense in male mice due to the synergic effect of the sympathetic nervous system and the cardiac renin-angiotensin system.