RESUMO
This study aimed to investigate the reliability of 1) the key parameters of cycling ergospirometry (maximum power output [Pmax] and oxygen uptake [VÌO2peak], ventilatory thresholds 1 [VT 1] and 2 [VT 2], and cycling efficiency [CE] and gross efficiency [GE]), 2) the commonly used parameters to quantify exhaustion (maximum heart rate [HFmax], respiratory quotient [RQmax], blood lactate concentration [BLAmax], and ratings of perceived exhaustion [RPEmax]), and 3) the kinetics of exercise induced gas exchange measurements (oxygen uptake [VÌO2], carbon dioxide output [VÌCO2], and minute ventilation [VÌE]) using the PowerCube-Ergo metabolic system in consideration of international statistical recommendations. 12 women and 12 men (28â±â4 years; 23.2â±â2.4âkg/m(2)) performed two cycling tests (20 watt/min) separated by one week. The reliability was calculated based on differences in means (t test and effect sizes), retest correlation (intraclass correlation coefficient [ICC]), and within-subject variation (standard error of measurement [SEM]). Of the key parameters of cycling ergospirometry, an excellent reliability (ICC ≥â0.969; pâ=â0.000) and high accuracy (%SEM ≤â4.6) were found for Pmax, VÌO2peak, and VT 1. Of the most commonly used parameters to quantify exhaustion, an excellent reliability (ICCâ=â0.922; pâ=â0.000) and high accuracy (%SEMâ=â1.0) existed only for HFmax. The gas exchange measurements (VÌO2, VÌCO2 und VÌE) of the PowerCube-Ergo were all excellently reliable (ICC ≥â0,991; pâ=â0.000) and the accuracy of VÌO2 (SEMâ=â0.10âl/min) and VÌE (SEMâ=â3.13âl/min) fulfilled the quality guidance of exercise physiology laboratories. For future studies and practical purposes, the results are vital for the decision as to whether a difference between two tests represents a true intervention effect or just a measurement error and for the estimation of required sample sizes.
Assuntos
Teste de Esforço/instrumentação , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Troca Gasosa Pulmonar/fisiologia , Ventilação Pulmonar/fisiologia , Espirometria/instrumentação , Adulto , Desenho de Equipamento , Análise de Falha de Equipamento , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The aim of this study was to examine the effects of strength and endurance training on myostatin mRNA in the vastus lateralis muscle of healthy and physically active humans. 21 healthy and physically active sports students (static and dynamic knee extensor strength 33 ± 4.5 N/kgBW; 1 185 ± 170 W, respectively; maximum oxygen uptake 52.5 ± 8 ml/kgBW/min) were recruited and randomly assigned to a moderate endurance training group (n=7), a strength training group (n=7) and a control group (n=7). Muscle biopsies were taken from the vastus lateralis muscle 3-5 days before the start as well as at the end of the 12 weeks' training period. Exercise-specific functional improvements after moderate endurance training and strength training were measured for submaximal endurance and for static and dynamic strength of the knee extensor muscles. None of the myostatin mRNA values showed significant pre-post differences or group-specific differences. These results are in contrast to data with sedentary subjects, suggesting that myostatin is necessary for adaptations of skeletal muscle to exercise stress. We conclude that functional improvements after moderate endurance training and strength training can occur without alterations in myostatin mRNA in physically active humans.