Beyond sex differences: equivalent adaptations across the O 2 transport chain after exercise-based cardiac rehabilitation in women and men with coronary heart disease
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Background
Exercise-based cardiac rehabilitation (CR) improves peak oxygen uptake (V̇O 2 peak) in patients with coronary heart disease (CHD); however, whether women and men exhibit similar adaptations across the steps of O 2 transport remains unknown. We aimed to compare the ventilatory and circulatory determinants of V̇O 2 peak changes between women and men with CHD following a structured exercise training program.
Methods
A total of 28 women (27%) and 75 men (73%) with CHD, matched for age, body mass index, and V̇O 2 peak (% predicted), underwent maximal cardiopulmonary exercise testing (CPET) before and after 12 weeks of CR. V̇O 2 peak and minute ventilation (V̇E) were measured breath by breath. Heart rate and cardiac output (Q̇c)were assessed non-invasively using impedance cardiography. Exercise efficiency (ΔV̇O 2 /ΔW), alveolar ventilation (V̇A), ventilatory efficiency (OUES), O 2 pulse, arteriovenous oxygen content difference (C(a-v̄)O 2 ) and gross muscular efficiency (ηW) were calculated using standard equations. Mixed model analyses (sex∈time) were used to compare training-induced changes between sexes.
Results
At baseline, values of V̇O 2 peak (absolute and normalized by fat free mass), V̇E, V̇A, O 2 pulse, C(a-v̄)O 2 , ΔV̇O 2 /ΔW, ηW were significantly lower in women than in men with CHD (group effect, p<0.01). V̇O 2 peak normalized by fat-free mass improved similarly in both sexes after CR (p<0.0001, no significant sex x time interaction). Pulmonary convection (V̇E, V̇A), ventilatory efficiency (OUES), circulatory convection (Q̇c, cardiac index, O 2 pulse), and peripheral gross muscular efficiency (ηW) all improved similarly after CR in women and men (effect size∈time effect, p<0.05, no significant group∈time interaction). The prevalence of responder categories did not differ between sexes (p=0.826).
Conclusion
Women and men with CHD demonstrated equivalent O 2 transport phenotype adaptations after CR, with comparable improvements across the O 2 transport chain (pulmonary, circulatory, and peripheral determinants of V̇O 2 peak).
