Background & Aims: In large populations, the level of cardiorespiratory fitness (CRF) can be evaluated by estimating non-exercise models with the least amount of time and money. In this study, we present non-exercise equations for predicting CRF and also investigate the effect of socio-environmental factors on it. Materials & Methods: 2490 male and female subjects aged 25-65 years old from different cities of Iran participated in this study. Rockport and Bruce (10% in each age category and gender) exercise test measured VO2max, a global standard for evaluation of CRF. Three non-exercise equations including, VO2masStep, VO2maxIPAQ-s, and VO2maxIPAQ-l were estimated using Stepwise Linear Regression. Variables for estimating these models are physical activity (PA) (obtained by pedometer and short and long-form of the International Physical Activity Questionnaire (IPAQ), separately), Body Mass Index (BMI) , Waist-Hip Ratio(WHR), Body Adiposity Index (BAI ), age, gender, and VO2maxROC. For comparison between measured and predicted VO2max values based on age, gender, level of education and city of residence Repeated Measures Analysis with Bonferroni Compare Main Effect test was used. Results: There were significant relationships between measured and estimated VO2max (p<0.05) (VO2maxIPAQ-l: R2 adj=0.671 and SEE=4.381, VO2maxStep: R2 adj=0.543 and SEE=5.331 and VO2maxIPAQ-s: R2 adj=0.621 and SEE=4.823). Also, there were significant differences between VO2max values in males and females in different age categories and city of residence (p<0.05). Conclusion: The results of this study demonstrated that predicted VO2max models with SC, IPAQ-s, and IPAQ-l can be used as nonexercise models for estimating VO2max in Iranian society, and socio-environmental factors are influential variables on PA and level of CRF
