The aim of this study was, validation of slope of the lines between selected physiological variables (VO2, VCO2, VE, HR) for evaluation of cardio-respiratory fitness in Iranian boys. So we investigate cardiorespiratory fitness without exhaustive protocol and below the lactate threshold, measured. For that purpose, middle and high school students were randomly selected and number of 72 healthy adolescent boys with a mean age 13.95 ± 1.84 (years) and body mass index of 19.91 ± 3.4 (kg/m2), weight 51.64±13.15 (kg) voluntarily participated in an aerobic exhaustive test. Also, VO2max value using gas analyzer method (VE, VO2, VCO2 values) was measured with a breath by breath style. Then its correlation with slope of the line of the physiological parameters (VO2, VCO2, VE, HR) were analyzed. Results showed a high validity evaluating of the performance of children's cardio-respiratory functional reserve exists for OUES (R=0.95, SEE=292.2) and index slope of the lines between selected physiological variables was high too (R=0.74-0.81). Also there are moderate correlation between VO2max and index slope of the lines between selected variables in time %80 of test (R=0.70 – 0.94) and in Lactate threshold (R=0.31–0.86). Overall, results showed that slope of the lines between variables (VO2,VCO2,VE,HR) and OUES can be new indicators to measure of the cardiorespiratory system in Iranian teenage boys respiratory and diseases of screening studies or sports talent, especially when the activity is in lactate threshold (in %56 time test), used ofthis findingaresignificant and outstanding.
