IJCS | Volume 32, Nº4, July/August 2019

344 Almeida et al. Cardiorespiratory fitness classification Int J Cardiovasc Sci. 2019;32(4):343-354 Original Article Introduction Cardiorespiratory fitness (CRF) is one of the main factors associated with general health, and a valuable predictor of cardiovascular morbidity and mortality and all-cause mortality. 1-4 Maximal oxygen uptake (VO 2 max) may be considered a “vital sign” in the CRF scenario. 2 A low CRF is associated with noncardiovascular clinical conditions such as depression, dementia, 5,6 breast cancer and digestive tract cancer. 7,8 Considering the importance of evaluating CRF, the American Heart Association (AHA) launched the principles for the construction of a national registry of the American population. 9 The gold-standart method for CRF evaluation is the direct measurement of expired gases through the cardiopulmonary exercise testing (CPET), that evaluates the VO 2 max or peak VO 2 (VO 2peak ). Since this instrument is not always available, VO 2peak may be estimated from the duration and/or maximal load reached during the treadmill or cycle-ergometer test and is expressed as metabolic equivalents (METs). 9-15 Classification of VO 2 max or VO 2peak is important in clinical practice, and may help health professionals to associate individuals’ CRF with cardiovascular risk, and to encourage the practice of physical exercise/activity. In Brazil, two classification system have been usually used in exercise test software, the Cooper 16 and the AHA systems. 17 The classification proposed by the Exercise and Sports Medicine Center ( Centro de Medicina de Atividade Física e Desporto ) of São Paulo Federal University (UNIFESP), 18 derived from a regional Brazilian sample, has been not widely used in our setting. Few years ago, Herdy and Caixeta 19 published a table from a population sample of physically active, healthy individuals from southern Brazil. In a retrospective study including 2,930 residents of Rio Grande do Sul State, Brazil, Belli et al., 20 using a treadmill test for estimating VO 2 max (Bruce protocol), observed discrepancies in the classification of CRF between Cooper, AHA and UNIFESP tables. In this context, the aims of the present study were: (1) to evaluate to evaluate the concordance between AHA, Cooper and UNIFESP systems, taking VO 2peak measured by CPET as comparison reference value, and (2) to propose a classification table, by sex and age range, based on a Brazilian sample. Methods Population A total of 11,350 individuals referred for diagnosis and assessment of functional capacitywas prospectively evaluated. CPET was performed in a referral center in Joao Pessoa, Paraiba State, Brazil, between February 2007 and December 2017. Eighty percent of the patients were residents of Paraiba State, and 16% were from other states. Flow chart of patients’ recruitment is depicted in Figure 1. A total of 4,448 subjects were excluded; 407 due to the absence of a total blood count and a echocardiogram. And the other 4,041 for the following criteria: hypertension and use of anti-hypertensive agents with cardiovascular action (36.5%), coronary artery disease (26.9%), vasculopathy (8.9%), valvular heart disease (7.1%), heart failure (8%), anemia (0.7%), chronic obstructive pulmonary disease (7.1%) and asthma (0.5%). Also, we excluded another 311 patients who did not meet the criteria of maximal CPET or due to disagreement regarding the VO 2peak value between the two observers, and 23 due to technical problems (electrical power failure). Thus, the final sample was composed of 6,568 asymptomatic individuals; none of them was using medication with cardiovascular action, and all of them had normal total blood count, resting 12-lead electrocardiogram, two- dimensional color flow doppler echocardiography, and pre-test spirometry, in addition to a CPET without any finding of pathological significance. Physical activity level was determined according to the ACSM guidelines, 11 modified by the authors, as follows: a) physically inactive subjects were those who did not practice any physical exercise regularly, those who practiced exercise less than three times a week, and those who participated in household and occupational activities that generated energy expenditure lower than 3.2 METs; b) physically active were those individuals who practiced exercise regularly three-six times a week for at least three months, and those who participated in household and occupational activities that generated energy expenditure of 3.2-10.2 METs; c) athletes were those individuals who practiced sports at a competitive level, had daily training sessions, and energy expenditure greater than 10.3 METs. Participants were classified in one of these categories, based on their answers in the pre-CPET questionnaire on past practice of physical