Janssens K; St. Vincent’s Institute of Medical Research, Fitzroy, Australia.
Howden EJ; Mitchell AM; Wright L; Climie RE; Parr EB;
Haykowsky MJ; La Gerche A; Foulkes SJ

American Journal of Physiology – Heart & Circulatory Physiology.
330(6):H1841-H1852, 2026 Jun 01.

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 (Vo2peak). However,
how systolic blood pressure (SBP) responses reflect this pressure-flow
relationship, and their association with Vo2peak remain incompletely
understood. We performed cardiopulmonary exercise testing in 135 females
(51 +/- 8 yr) across a broad fitness spectrum to evaluate Vo2peak 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 Vo2peak (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
Vo2peak and COpeak and larger reductions in TPR compared with high
SBP/W-slope groups. SBPmax >=190 mmHg in isolation was associated with
higher Vo2peak 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 Vo2peak. 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.