Contributions of cardiac output and total peripheral resistance to inter-individual variability in peak exercise blood pressure in young adults

The mechanisms responsible for elevated exercise systolic blood pressure (SBP) in young adults remain unclear but may be influenced by cardiorespiratory fitness. The present study examined the contributions of cardiac output (Q̇) and total peripheral resistance (TPR) to peak SBP and peak SBP normalized per metabolic equivalent (∆SBP/MET). Fifty-one normotensive adults (28 females) underwent a graded maximal cycling test with brachial blood pressure measured using automated auscultation (Tango M2 Monitor). Q̇ was measured using the nitrous oxide rebreathe technique (Innocor; COSMED). Participants were analyzed across the whole cohort and compared between those with and without an exaggerated SBP (Males≥210mmHg; Females≥190mmHg) or ∆SBP/MET (≥9mmHg/MET). Higher peak SBP was related to higher peak exercise Q̇ (r=0.53, P<0.001) but not TPR (r=-0.15, P=0.29). In contrast, higher SBP/MET tended to be related to higher peak exercise TPR (r=0.26, P=0.067), but not Q̇ (r=0.07, P=0.65). Participants with an exaggerated peak SBP (n=20) had larger increases in Q̇ during exercise (∆+12.7 vs. ∆+10.2 L/min, P=0.002) and greater relative peak oxygen uptake (V̇O2peak) (P=0.03), while the reduction in TPR did not differ (∆-8.62 vs. ∆-8.85 mmHg/L/min, P=0.23). Participants with an exaggerated ∆SBP/MET (n=13) had an attenuated reduction in TPR during exercise (∆-6.47 vs. ∆-9.24 mmHg/L/min, P=0.03), while the rise in Q̇ did not differ (∆+10.4 vs. ∆+11.6 L/min, P=0.16). In normotensive young adults, a higher peak SBP during cycling exercise is associated with a larger Q̇, likely linked to higher aerobic fitness, whereas a higher ∆SBP/MET is related to attenuated vasodilation during exercise and reduced aerobic fitness.