A man is as old as his arteries.--Thomas Sydenham, English physician, 1624English physician, -1689 This comment, made almost four centuries ago, absolutely conforms to the contemporary suggestion that arterial stiffness, which reflects the effects of aging, high blood pressure, and other cardiovascular (CV) risk factors on the arterial wall, is an independent predictor of CV morbidity and CV and all-cause mortality. 1 Therefore, current therapeutic strategies aim towards the management of traditional CV risk factors, such as hypertension, dyslipidemia, diabetes mellitus, and metabolic syndrome in the effort to turn back the clock of vascular age.2-5 Nevertheless, the astute physician has to use every weapon of the therapeutic armamentarium in order to either attenuate arterial stiffening or "destiffen" the arterial wall.In this issue of the Journal, Gando and colleagues 6 tested the hypothesis that higher cardiorespiratory fitness (CRF) would be associated with less progression of age-related arterial stiffening in healthy adults. The investigators recruited 470 healthy Japanese adults and conducted a 2-year follow-up study to examine the association between CRF and arterial stiffness progression. Study participants were distributed into tertiles based on their peak oxygen uptake (VO 2max ) levels during a graded cycle exercise test. Brachial-ankle pulse wave velocity (baPWV) was measured at baseline and 2 years later for the assessment of arterial stiffness. Anthropometric measures, body composition determined by dual-energy radiography absorptiometry, and exercise habits were recorded for each participant. The daily physical activity was evaluated by a triaxial accelerometer, which was worn during the day. In addition, the levels of glucose and glycated hemoglobin, total cholesterol, high-density lipoprotein cholesterol, and triglycerides were determined in blood samples.The 2-year changes in baPWV were significantly higher in the low CRF group compared with those in the highest CRF group. Therefore, higher CRF was associated with slower progression of age-related arterial stiffening (measured by baPWV). In addition, CRF was inversely associated with 2 years of baPWV progression. Stepwise multiple regression analysis demonstrated that the inverse association between CRF and arterial stiffness was independent of other factors traditionally related to arterial stiffness. This is the first study to investigate the relationship between CRF and the rate of progression of baPWV in healthy adults in a longitudinal study. Previous crosssectional studies have shown that a high level of CRF was associated with arterial stiffness. Thus, there is still only limited knowledge about the longitudinal relationship between CRF and the changes in baPWV. The main strengths of the study were the large sample size, the adequate follow-up period (2 years), and the use of maximal exercise testing for estimation of CRF levels, which has high accuracy and remains the gold standard for the measurement of CRF.On the other hand, there a...