Alterations in peak torque occur without hematological changes after muscle fatigue / As alterações no pico de torque ocorrem sem modificações em parâmetros hematológicos após fadiga muscular / Los cambios en el pico de par ocurren sin modificaciones en parámetros hematológicos después de fatiga muscular

ABSTRACT Introduction: Muscular fatigue during voluntary muscle contractions is a complex and multifactorial phenomenon associated with central changes and adaptations of the neuromuscular system. Objective: The aim of this study was to analyze the changes in both peak torque and hematological parameters in active and inactive healthy subjects following a muscular fatigue protocol. Methods: Twenty-one healthy adult males performed a muscle fatigue protocol (10 sets, 10 repetitions of knee extension at 75% of the maximal isometric torque (MIT), 120º s-1 and 40 seconds of rest). Hematocrit (Ht), red blood cells (RBC) and leukocytes (L) analysis were evaluated before (B) and after (A) a fatigue test. Results: The inactive group presented impairment only in concentric muscular action of -41±4% in relation to the active (-23±3%) group. No differences were found in hematological parameters in inactive group (Ht, B: 45.00±0.01 vs. A: 47.00±0.01; RBC, B: 442±40 vs. A: 487±41; L, B: 7,565±2,878 vs. A: 8,015±4,224) and the active group (Ht, B: 45.00±0.63 vs. A: 47.00±0.01; RBC, B: 477±30 vs. A: 559±37; L, B: 6,418±3,557 vs. A: 6,632±4,460). Conclusion: Differences were found only in concentric actions between groups. Additionally, there were no relationships found in hematological parameters between groups.

RESUMO Introdução: A fadiga muscular durante as contrações musculares voluntárias é um fenômeno complexo e multifatorial associado a alterações centrais e adaptações do sistema neuromuscular. Objetivo: O objetivo deste estudo é analisar as alterações do pico de torque e dos parâmetros hematológicos em indivíduos saudáveis ativos e inativos depois de realizar um protocolo de fadiga muscular. Métodos: Vinte e um adultos saudáveis do sexo masculino realizaram um protocolo de fadiga muscular (10 séries, 10 repetições de extensão do joelho a 75% do torque isométrico máximo (TIM) a 120ºs-1 e 40 segundos de repouso). Hematócrito (Ht), glóbulos vermelhos (GV) e leucócitos (L) foram analisados antes (A) e depois (D) do teste de fadiga. Resultados: O grupo inativo apresentou deterioração apenas na ação muscular concêntrica (-41 ± 4%) com relação ao grupo ativo (-23 ± 3%). Não foram encontradas diferenças nos parâmetros hematológicos no grupo inativo (Ht, A: 45,00 ± 0,01 vs. D: 47,00 ± 0,01; GV, A: 442 ± 40 vs. D: 487 ± 41; L, A: 7.565 ± 2.878 vs. D: 8.015 ± 4.224) e no grupo ativo (Ht, A: 45,00 ± 0,63 vs. D: 47,00 ± 0,01; GV, A: 477 ± 30 vs. D: 559 ± 37; L, A: 6.418 ± 3.557 vs. D: 6.632 ± 4.460). Conclusão: Foram encontradas diferenças apenas em ações concêntricas entre os grupos. Além disso, não foram encontradas relações quanto aos parâmetros hematológicos entre os grupos.

RESUMEN Introducción: La fatiga muscular durante las contracciones musculares voluntarias es un fenómeno complejo y multifactorial asociado con cambios centrales y adaptaciones del sistema neuromuscular. Objetivo: El objetivo de este estudio es analizar los cambios del par máximo y los parámetros hematológicos en sujetos sanos activos e inac-tivos después de un protocolo de fatiga muscular. Métodos: Veintiún adultos sanos del sexo masculino realizaron un protocolo de fatiga muscular (10 series, 10 repeticiones de extensión de la rodilla en el 75% del par isométrico máximo (PIM) a 120ºs-1 y 40 segundos de descanso). Hematocrito (Ht), glóbulos rojos (GR) y leucocitos (L) fueron evaluados antes (A) y después (D) de la prueba de fatiga. Resultados: El grupo inactivo presentó deterioro sólo en la acción muscular concéntrica (-41 ± 4%) con respecto al grupo activo (-23 ± 3%). No se encontraron diferencias en los parámetros hematológicos en el grupo inactivo (Ht, A: 45,00 ± 0.01 vs. D: 47,00 ± 0,01; GR, A: 442 ± 40 vs. D: 487 ± 41; L, A: 7.565 ± 2.878 vs. D: 8.015 ± 4.224) y en el grupo activo (Ht, A: 45,00 ± 0,63 vs. A: 47,00 ± 0,01; GR, A: 477 ± 30 vs. D: 559 ± 37; L, A: 6.418 ± 3.557 vs. D: 6.632 ± 4.460). Conclusión: Se encontraron diferencias sólo en las acciones concéntricas entre los grupos. Además, no hubo relaciones con respecto a los parámetros hematológicos entre los grupos.

Relationships between Cardiorespiratory and Muscular Fitness with Cardiometabolic Risk in Adolescents.

This study examined the independent relationships between cardiorespiratory and muscular fitness with cardiometabolic risk in adolescents. Subjects were 192 adolescents (118 boys), aged 15-17.5 years. The 2 m multi-stage fitness test assessed cardiorespiratory fitness and the counter movement jump assessed muscular fitness. Additional measures included interleukin-6, C-reactive protein, adiponectin, fibrinogen and plasminogen activator inhibitor-1. Regression analysis revealed that cardiorespiratory fitness was negatively related to cardiometabolic risk (ß = -0.014, p < 0.001). With additional adjustment for muscular fitness the relationship remained significant (ß = -0.015, p < 0.001). Muscular fitness was negatively related to cardiometabolic risk (ß = -0.021, p < 0.001) and remained significant after adjustment for cardiorespiratory fitness. Participants in the least-fit quartile for both cardiorespiratory and muscular fitness had significantly poorer cardiometabolic risk scores than those in the other quartiles. Findings revealed that muscular and cardiorespiratory fitness are significantly associated with cardiometabolic risk independently of one another.

Novel risk factors of cardiovascular disease and their associations between obesity, physical activity and physical fitness.

The prevalence of cardiovascular disease (CVD) is increasing around the globe and is the leading cause of death around the world. Though once thought of as an adult problem, it is now recognised that the early manifestations of disease may occur during childhood. Numerous risk factors have been linked to CVD with much of the research focusing on understanding the prevalence and relationship of traditional risk factors such as dyslipidemia, smoking, diabetes mellitus, hypertension, obesity, psychosocial stress, poor diet, physical inactivity and alcohol consumption to the early etiology of disease. While this line of investigation has greatly enhanced our understanding of the relationship between these risk factors and disease, they do not fully explain all cardiovascular events. To enhance our understanding and help with the management of CVD, investigations that involve the measurement of traditional as well as novel risk factors may be necessary. Public health strategies that aim to reduce the prevalence of obesity and overweight encourage youth to increase their physical activity levels as a means of protecting against poor cardiometabolic profiles. Interventions that increase physical activity levels and improve cardiorespiratory fitness cause a reduction in certain CVD risk factors but the lack of agreement between findings makes it impossible to give precise recommendations that will ensure CVD risk reduction. Yet it is important that research continues in order to establish the most appropriate means of improving the health and well-being of those at most risk of future CVD.

The effects of time and intensity of exercise on novel and established markers of CVD in adolescent youth.

OBJECTIVES: This article examines the effects of brief, intense exercise in comparison with traditional endurance exercise on both novel and traditional markers of cardiovascular disease (CVD) in youth. METHODS: Forty seven boys and ten girls (16.4 ± 0.7 years of age) were divided into a moderate (MOD), high intensity (HIT), or a control group. The MOD group (12 boys, 4 girls) and HIT group (15 boys, 2 girls) performed three weekly exercise sessions over 7 weeks. Each session consisted of either four to six repeats of maximal sprint running within a 20 m area with 20-30 s recovery (HIT) or 20 min continuous running within a 20 m area at ∼70% maximal oxygen uptake (VO(2) max). RESULTS: Total exercise time commitment over the intervention was 420 min (MOD) and 63 min (HIT). Training volume was 85% lower for the HIT group. Total estimated energy expenditure was ∼907.2 kcal (HIT) and ∼4410 kcal (MOD). Significant improvements (P ≤ 0.05) were found in systolic blood pressure, aerobic fitness, and body mass index (BMI) postintervention (HIT). In the MOD group, significant (P ≤ 0.05) improvements were noted in aerobic fitness, percentage body fat (%BF), BMI, fibrinogen (Fg), plasminogen activator inhibitor-1, and insulin concentrations. CONCLUSIONS: These findings demonstrate that brief, intense exercise is a time efficient means for improving CVD risk factors in adolescents.

The influence of a high intensity physical activity intervention on a selection of health related outcomes: an ecological approach.

BACKGROUND: Cardiovascular disease (CVD) is the main cause of mortality throughout the world. With accumulating evidence suggesting that CVD has its origins in childhood, it is unsurprising that research into obesity prevalence within school aged youth is burgeoning. Within this study our primary objective will be to examine whether high intensity interval training (HIT) improves the CVD risk profile of secondary school aged adolescents. Our secondary objective will be to identify the prevalence of CVD risk factors and examine factors associated with these in adolescents aged 15-18 years. METHOD/DESIGN: A South Lanarkshire school of low socioeconomic status (SES) was selected to participate in the study intervention. Participants from secondary 5 (15-17 years) and 6 (16-18 years) will be recruited for this study. Participants from secondary 6 will be randomly assigned to Group A (HIT) or Group B (moderate-vigorous) and will perform each protocol three times weekly. The secondary 5 participants will act as the control group. Data collection will take place during the Physical Education (PE) lessons and on school premises and will include: anthropometrical variables (height, weight, waist and hip circumferences, skinfold thickness at two sites), physiological responses (blood pressure, aerobic fitness, heart rate (HR) response, vertical jump performance, 10-metre (m) sprint, 50-m sprint and 505-agility test), diet (self-reported seven-day food diary), physical activity (Physical Activity Questionnaire for Adolescents (PAQ-A)) and blood tests (fasting glucose, insulin, total cholesterol (TC), high-density lipoprotein (HDL), high-sensitivity C-reactive protein (hs-CRP), fibrinogen (Fg), interleukin-6 (IL-6), adiponectin (high molecular weight), triglyceride and plasminogen activator inhibitor-1 (PAI-1). An environmental audit of the secondary school and the health related quality of life (HRQOL) of the participants will also be measured. Finally, all exercise sessions will be video recorded and rate of perceived exertion (RPE) and mood states will also be taken after each exercise session. DISCUSSION: Our study may be able to demonstrate a time efficient means of reducing CVD risk factors in adolescents. TRIAL REGISTRATION: NCT01027156.