Optimizing exercise intensity in coronary artery disease: why ‘moderate and continuous’ prevails

This invited commentary refers to ‘Effect of exercise intensity and volume on mortality and hospitalization in patients with coronary artery disease: a systematic review and pairwise and exploratory network meta-analysis’, by J. Dong et al., https://doi.org/10.1093/eurjcn/zvaf233. Coronary artery disease (CAD) remains one of the leading causes of hospitalization, morbidity, and global mortality, even in the context of contemporary advances in pharmacotherapy and secondary prevention.1,2 Scientific evidence consistently demonstrates that structured cardiac rehabilitation (CR) programmes based on physical exercise reduce clinically relevant events, including cardiovascular mortality and hospital readmissions, with particularly robust evidence for moderate-intensity protocols and continuous aerobic training.2,3 However, an important gap persists regarding the specific role of different exercise intensities (moderate, vigorous, and high) and training formats (continuous and interval) in modulating outcomes such as hospitalization and mortality, a gap reinforced by the predominance of studies evaluating functional capacity rather than hard clinical endpoints.4,5 In this context, the study by Dong et al.6 provides a comprehensive synthesis by systematically evaluating how different exercise intensities and volumes influence mortality and hospitalization in patients with CAD. The study synthesizes evidence that exercise-based CR programmes reduce total and cardiovascular hospitalizations in patients with CAD, with consistent estimates and low heterogeneity. When comparing training modalities, the authors identify that continuous aerobic training, particularly at moderate intensity, presents the most robust clinical benefit signal, whereas interval or higher-intensity interventions remain limited by a small number of studies and greater imprecision.6 In the network analysis, moderate- and vigorous-intensity continuous training formats outperform usual care in reducing hospitalizations, although the apparent superiority of higher intensities depends on sparse evidence and wide estimator variability. Overall, the findings reinforce that structured exercise delivered in a continuous format remains the strategy with the most consistent evidence for reducing hospital admissions in patients with CAD.6 Interpretation of these findings should consider that contemporary literature consistently supports the central role of structured exercise as a cornerstone of CR, particularly in reducing mortality and major events in CAD. Classic and updated meta-analyses demonstrate significant reductions in all-cause and cardiovascular mortality associated with exercise-based CR, with particularly robust effects for moderate-intensity continuous programmes, which constitute the core of current practice.2,3 Comprehensive studies demonstrate consistent reductions in all-cause and cardiovascular mortality associated with supervised exercise, with an effect of ∼25% in stable coronary populations and post-event settings.3,7 Population-based studies reinforce this pattern: greater adherence to the programme and higher session dose are associated with lower risk of major events, with no evidence of a minimum threshold or ceiling, indicating a linear relationship between dose and reduction in major adverse cardiovascular events, including mortality.8 Large cohort data and population-level analyses also show that higher levels of physical activity, including moderate and vigorous modalities, are associated with lower all-cause and cardio-cerebrovascular mortality in individuals with CAD, reinforcing that the clinical benefit of exercise extends beyond functional capacity to include hard outcomes.9 European guidelines, in turn, consolidate this evidence by positioning exercise-based rehabilitation as a central intervention to reduce morbidity and mortality, recommending structured prescription and continuous follow-up after coronary events.10 These same guidelines reinforce that exercise recommendations must prioritize safety, gradual progression, and adequate stimulus to improve functional capacity and risk factors, maintaining moderate intensity as the most widely supported standard.10,11 In this context, the results of the target article deepen a relevant gap by comparing different intensities and volumes, an area scarcely explored in previous studies, which focused primarily on functional capacity, safety, or metabolic responses. There is evidence that high-intensity interval training can induce greater gains in cardiorespiratory fitness in selected populations,4,5 but such interventions remain limited by small samples, short duration, strong selection of low-risk participants, and primary focus on peak oxygen consumption or haemodynamic behaviour rather than hard clinical outcomes. Thus, the synthesis presented by the study stands out by directing the discussion towards hospitalizations and mortality, offering a level of clinical applicability superior to what is typically observed in the high-intensity exercise literature. The practical implications of the findings also align with recent guidelines emphasizing the need for feasible, scalable programmes tailored to individual risk. The European position reinforces that moderate-intensity continuous exercise remains the structural axis of CR, whereas vigorous or interval-based approaches should be employed with caution, considering safety criteria, clinical stability, and team expertise.10,11 This converges with the interpretation of the findings in the article under discussion: despite the physiological potential of higher intensities, the robustness of the evidence still favours continuous training as the primary strategy to reduce hospitalizations in CAD. From an organizational standpoint, the results reinforce the need to expand coverage and adherence to traditional exercise models, a topic widely discussed in implementation studies and population registries.8,12 The linearity of benefit observed in the target article also parallels dose–response data, indicating that greater exposure to supervised or structured exercise appears to be associated with lower risk of events, with no clearly defined minimum threshold.8 These findings suggest that strategies that increase frequency and engagement, such as hybrid models, supervised home-based sessions, and workflow optimization, may have relevant clinical impact. Important gaps, however, remain. The available literature is still insufficient to determine with confidence the superiority of higher-intensity exercise for hard clinical outcomes, particularly considering the variability of interventions, protocol heterogeneity, and the small number of dedicated trials. Furthermore, existing studies on high-intensity interval training, although promising with regard to safety in highly controlled environments, are insufficient for broad extrapolation to routine programmes that handle more diverse risk profiles.4,5 It is also important to highlight the scarcity of trials directly comparing different volumes within the same intensity, limiting more refined inferences about optimal dose. In conclusion, the findings presented by Dong et al.6 reinforce the centrality of structured exercise, especially moderate-intensity continuous aerobic training, as the strategy most consistently associated with reduced hospitalizations in CAD. By comparing different intensities and volumes, the study fills a relevant gap in the literature and provides a solid foundation for clinical decision-making aligned with contemporary guidelines, while also demonstrating that vigorous or interval-based approaches still require robust trials to confirm benefit in hard clinical outcomes. From the perspective of CR, the results outline research priorities, including identifying subgroups that may benefit from higher intensities, evaluating hybrid models that balance efficiency and safety, and defining the ‘minimum effective dose’ capable of maximizing adherence without compromising clinical effects. Taken together, the work advances the field by consolidating continuous exercise as the foundation of modern rehabilitation and by guiding future investigations into the optimization of exercise dose and format in patients with CAD. Luíza Caetano Vieira Custodio (Conceptualization [lead], Writing—original draft [lead], Writing—review & editing [supporting]), Luciano Fonseca Lemos de Oliveira (Conceptualization [supporting], Writing—original draft [supporting], Writing—review & editing [supporting]), Marilita Falangola Accioly (Conceptualization [supporting], Writing—original draft [supporting], Writing—review & editing [supporting]), and Eduardo Elias Vieira Carvalho (Conceptualization [lead], Supervision [lead], Writing—original draft [lead], Writing—review & editing [lead]) None declared. This commentary does not contain new data.