Changes in Aerobic Capacity and Mediterranean Diet Adherence at Group and Individual Levels During Cardiac Rehabilitation

Cardiac rehabilitation (CR) combines supervised exercise with interventions targeting long-term health behaviours, yet outcomes are often evaluated primarily through changes in aerobic capacity. This study compared the standardised magnitude of improvements in Mediterranean-diet adherence and peak oxygen uptake (VO2peak) and examined whether these changes tracked together within individual patients, and whether previous habitual physical activity was associated with subsequent aerobic response. A total of 112 patients completing an eight-week comprehensive CR programme were analysed. Pre–post changes in VO2peak and PREDIMED score were quantified using paired tests and within-subject standardised effect sizes. Associations with previous physical activity were assessed using adjusted regression models, while direct correspondence between dietary and aerobic changes was examined using Pearson correlation and equivalence testing. A four-domain exploratory analysis jointly evaluated changes in VO2peak, PREDIMED, handgrip strength, and waist circumference. VO2peak increased by 1.80 mL·kg−1·min−1 (95% CI 1.30–2.31; dz=0.67), while PREDIMED increased by 1.71 points (95% CI 1.26–2.17; dz=0.71). Their standardised effect-size estimates were similar, but individual changes were essentially unrelated (r=0.003; p=0.976), and equivalence testing supported that the association was contained within the pragmatic bounds of r=±0.20. Previous physical activity was independently associated with greater VO2peak improvement (β=1.63 mL·kg−1·min−1; 95% CI 0.53–2.72; p=0.004). The multivariate change was significant (Hotelling’s T2=152.24; F4,108=37.03; p<0.001), with all four domains providing non-redundant information. These findings indicate that behavioural and physiological improvements may coexist at the group level without parallel individual-level change, supporting a multidimensional assessment of CR response.