Author(s): RUIZ-RIOS, M., LOSA-REYNA, J., MALDONADO-MARTIN, S., GOROSTEGI-ANDUAGA, I., CORRES, P., TOUS-ESPELOSIN, M., ETXANIZ-OSES, J., GARCIA-TABAR, I., Institution: UNIVERSITY OF THE BASQUE COUNTRY (UPV/EHU), Country: SPAIN, Abstract-ID: 341

INTRODUCTION:
Cardiorespiratory fitness (CRF) is a strong predictor of cardiovascular and all-cause mortality, with a one metabolic equivalent increase in CRF associated with substantial risk reductions [1], highlighting the central role of exercise intensity in effective exercise prescription. Although exercise intensity is often prescribed using fixed percentages of maximal anchors (e.g. percentage of peak oxygen uptake, %V̇O₂peak), high interindividual variability makes gas exchange thresholds (GETs) a more accurate approach for defining exercise-intensity domains and prescribing exercise-based training interventions [2]. Sex differences in GETs have been documented in healthy populations [3]. However, studies incorporating sex as a stratification variable for intensity domains in chronic conditions such as hypertension (HTN), schizophrenia (SP), bipolar disorder (BD), vestibular hypofunction (VH), and resistant major depression (RMD) remain scarce. Understanding sex- and diagnosis-specific differences in exercise-intensity thresholds is clinically relevant for optimizing individualized exercise prescription.
METHODS:
Data from five cohorts of individuals with chronic conditions (HTN, SP, BD, VH, and RMD) were combined for this cross-sectional study (n=530, 36% female). Cardiopulmonary exercise tests were performed using a progressive ramp protocol on a cycle ergometer to determine the first (GET1) and second (GET2) exercise-intensity thresholds (expressed in absolute and relative values), and the maximal anchors (i.e. peak power output [PPO] and V̇O₂peak). Sex differences were analyzed within each chronic health condition using a generalized linear model with sex as a fixed factor [effect size (ES) calculated as males–females].
RESULTS:
Males consistently presented significantly higher (p<0.001) absolute values of power output (PO) and oxygen uptake (V̇O2) than females in both GET1 and GET2 in all conditions (ES=0.48–1.36, small to very large). However, when thresholds were expressed relative to maximal achors (%PPO and %V̇O₂peak), males did not exhibit higher GETs than females. In GET1, %PPO values in females with HTN (ES=-0.27, small) and VH (ES=-0.54, moderate), as well as %V̇O₂peak in females with HTN (ES=-0.45, small) and SP (ES=-0.25, small), were higher compared to males. No sex differences were found in the relative values of PO or V̇O2 at GET2 across any of the clinical groups (p>0.05).
CONCLUSION:
Absolute workloads (PO, V̇O2) at the GETs were consistently higher in males than females, but relative to their individual maximal capacity (%PPO, %V̇O₂peak), sex differences were no longer evident. Considering individual variability by sex and diagnosis, these findings support an individualized exercise-intensity approach across these chronic conditions.

References:
1. Kodama et al. (2009), JAMA, 301(19):2024–35.
2. Meyler et al. (2023), Exp Physiol. 108(4):581–94.
3. Benítez-Muñoz et al. (2025), Med Sci Sports Exerc, 57(10):2269–77.