Fitter Healthy Adults Had Arteries That Relaxed More After Blood-Flow Test

Published on March 27, 2026, the work is a cross-sectional observational study of 284 adults, average age 61, 44% of them women. Researchers at KU Leuven and partner institutions pooled baseline data from two Belgian cohorts: the PRIORITY exercise trial and the FLEMENGHO population study. Each person underwent both a cardiopulmonary exercise test and the vascular test.

The vascular test is called flow-mediated slowing, or FMS. Blood flow to the arm is briefly blocked and then released. In healthy arteries, the vessel widens in response, and the pulse wave travelling along it slows down. The test tracks that slowing between the brachial artery in the upper arm and the radial artery at the wrist. A smaller slowing may point to a vessel that is not widening well, and so to poorer endothelial function. The endothelium is the inner lining of blood vessels.

The authors describe FMS as automated and independent of the operator. They contrast it with the widely used ultrasound method, flow-mediated dilation, whose reliability depends heavily on operator skill.

Fitness was measured as peak oxygen uptake, or VO₂peak, the most oxygen a person can use during hard exercise.

The researchers also expressed it as a percentage of the value predicted for a person's age and body. Of the 284 participants, 237 had at least one cardiovascular risk factor. The other 47 were apparently healthy.

In the healthy group, a bigger fall in pulse wave velocity correlated with higher VO₂peak. The strongest associations with both VO₂peak and percent-predicted VO₂peak appeared in this group. In the at-risk group, the simple correlation was absent. After adjustment in multivariable models, a larger fall was still independently associated with higher percent-predicted VO₂peak, both in the full cohort and among at-risk participants. The researchers also sorted people by whether their response was abnormally low. An abnormally low response was associated with lower VO₂peak per kilogram and lower percent-predicted VO₂peak. The primary paper reports roughly 6% lower percent-predicted VO₂peak after full adjustment. It also reports correlation coefficients of −0.56 to −0.45 between early pulse-wave change and VO₂peak per kilogram in healthy participants.

The associations appeared stronger in women, with p-values below 0.01 for most time intervals. The difference between the sexes was not statistically significant.

The primary paper reports no statistically significant difference in FMS response between people with and without risk factors. The authors point to widespread use of blood pressure drugs and statins in the at-risk group as a possible reason. Those drugs may influence vessel responses.

The authors conclude that better macrovascular reactivity, as measured by FMS, was associated with higher fitness, particularly in women and apparently healthy people, and call FMS a promising, scalable tool for assessing cardiovascular risk. They also discuss a two-way relationship. The paper discusses how good vessel function may support exercise capacity, and regular exercise may in turn support vessel health. Because everyone was tested once, the study cannot show which direction holds.

In this group of adults, average age 61, aerobic capacity and vessel responsiveness tended to go together most clearly among the apparently healthy. The authors note that the reproducibility of arm-based FMS across clinical settings still needs to be validated against flow-mediated dilation. The healthy subgroup was small and the population was predominantly white European; residual confounding and selection bias remain possible.

Source: Renier and colleagues, Artery Research, March 27, 2026.