Absolute and workload-indexed exercise blood pressure responses: associations with cardiac output, vascular resistance, and cardiorespiratory fitness in females.

During exercise, vascular resistance, the ratio of arterial pressure to blood flow [i.e., cardiac output (CO)], is an important component of the hemodynamic response determining peak oxygen uptake (V̇o2peak). However, how systolic blood pressure (SBP) responses reflect this pressure-flow relationship, and their association with V̇o2peak remain incompletely understood. We performed cardiopulmonary exercise testing in 135 females (51 ± 8 yr) across a broad fitness spectrum to evaluate V̇o2peak and SBP responses. SBP responses were stratified by maximal SBP (SBPmax <190 mmHg or ≥190 mmHg) and workload-indexed SBP (SBP/W-slope; low vs. high based on sex- and age-specific median values). Peak CO (COpeak) was quantified from exercise cardiac magnetic resonance imaging. SBPmax ≥190 mmHg occurred in 74 participants (55%), high SBP/W-slope in 41 (30%), and 26 (19%) had both. A high SBP/W-slope was associated with lower V̇o2peak (1.7 ± 0.4 vs. 2.1 ± 0.6 L/min; P < 0.001) and COpeak (12.8 ± 2.3 vs. 15.7 ± 3.5 L/min; P < 0.001) and higher total peripheral resistance (TPRpeak; 11.2 ± 2.3 vs. 9.0 ± 2.0 mmHg·min/L; P < 0.001). In contrast, a low SBP/W-slope despite SBPmax ≥190 mmHg had the highest V̇o2peak and COpeak and larger reductions in TPR compared with high SBP/W-slope groups. SBPmax ≥190 mmHg in isolation was associated with higher V̇o2peak and COpeak, although it also identified females with low fitness and COpeak. Thus, SBP/W-slope provides a framework for interpreting SBP relative to flow, with higher slopes indicating an unfavorable pressure-flow profile characterized by higher vascular resistance, lower COpeak, and reduced V̇o2peak. In contrast, SBPmax reflects both flow and resistance. Incorporating SBP/W-slope may therefore improve identification of females with impaired pressure-flow regulation.NEW & NOTEWORTHY In females, a higher workload-indexed systolic blood pressure (SBP/W)-slope during exercise was associated with greater peripheral vascular resistance, lower cardiac output, and lower cardiorespiratory fitness, irrespective of maximal systolic blood pressure (SBPmax). In contrast, an exaggerated SBPmax alone reflected differing contributions of increased flow (i.e., cardiac output) or increased vascular resistance across individuals. Evaluating the SBP/W-slope provides a more physiologically informed interpretation of exercise blood pressure and may improve identification of females with impaired pressure-flow regulation and reduced cardiovascular reserve.