Shorter training time, same impact? Encouraging evidence for short-term, high-intensity interval inspiratory muscle training in chronic heart failure

This invited commentary refers to ‘Home-based, short-duration, high-intensity interval inspiratory muscle training improves exercise capacity of patients with chronic heart failure: a double-blind study’, by Y.-C. Wu et al., https://doi.org/10.1093/eurjcn/zvaf130 The study by Wu et al.,1 with a robust methodological design, offers a valuable contribution to the literature by demonstrating that a short-term (<10 min) home-based protocol based on high-intensity interval inspiratory muscle training (H-IMT) can significantly improve exercise capacity, inspiratory muscle strength, and quality of life in patients with chronic heart failure (CHF). The study stands out for addressing and trying to overcome, albeit in a secondary way, one of the main challenges of cardiac rehabilitation (CR): low adherence to treatment. Although the benefits of CR are widely documented in the literature, the programmes remain underutilized worldwide.2,3 This scenario reinforces the relevance of studies such as this one, whose design aims to minimize frequently reported barriers, such as difficulties with transportation, low motivation, and reduced engagement. In this context, the proposed protocol is interesting not only because it suggests home-based, high-intensity interval training, but also because it associates it with a short-duration approach (<10 min), contrasting with current evidence, which recommends training with a load corresponding to 60% of maximal inspiratory pressure (MIP), lasting 30 min, six times a week, for 12 weeks.4 The H-IMT protocol, consisting of six sets of five respiratory incursions at 60% of MIP, with a 1 min interval between sets, proved to be safe, feasible, and effective. The results reveal an increase of 82% in MIP after 12 weeks of intervention, in addition to significant improvements in peak oxygen uptake (VO₂peak), with an increase of 8%, and in the distance covered in the 6 min walk test (6MWD), with an increase of 12% in relation to baseline values. Furthermore, more than 70% of participants in the H-IMT group exceeded the minimal clinically important difference at 6MWD, with an average post-intervention increase of 52 m. Another notable finding was the improvement in the quality of life of the H-IMT group, with significant reductions in the physical dimension and in the total score of the questionnaire used. The 55% reduction in the overall score suggests benefits that go beyond physiological variables, reflecting a subjective perception of improvement in daily life, a highly relevant outcome in a clinical context often marked by fatigue, dyspnoea, and functional limitations. In addition, the authors compared their findings with those of conventional protocols, reinforcing the idea that, when barriers to implementing traditional programmes are identified, adopting interval-based, short-duration, home-based IMT can be a beneficial alternative. This strategy is particularly relevant for individuals with chronic conditions who not only need to adopt new habits, such as regular physical activity, but also maintain them autonomously and sustainably over the long term. In summary, interventions with these characteristics may promote self-motivation, an essential component for voluntary and continuous engagement in training programmes, which is fundamental to delivering the benefits of CR. The present study reported a high adherence rate in the H-IMT group (94%), with more than half of participants fully adhered to the programme. These findings point to a promising alternative outside hospital and outpatient settings, which is particularly important given the limited availability of CR programmes worldwide and the high dropout rates.2 Several studies have shown that only ∼30% of eligible patients participate in CR programmes,1 with the distance to the CR programme being one of the main predictors of non-participation.5 Thus, the importance of valuing and investing in home-based rehabilitation strategies becomes even more clear. Despite the encouraging results, the study has limitations that should be considered in the interpretation of the data. The inclusion of participants with different heart failure subtypes can be seen as a limitation, as the relatively small sample size does not allow subgroup analyses. It is also worth noting that more than half of the participants had improved ejection fraction, which opens the door to future investigations that explore the effects of training in a stratified way among the different clinical profiles of CHF. By choosing to compare the proposed protocol with a sham intervention without load, the authors were able to isolate the specific effects of short-duration, high-intensity interval IMT. However, this methodological decision precludes a direct comparative analysis with traditional protocols widely recommended in clinical guidelines and meta-analyses.4–6 Such an approach would have increased the value of the study, allowing professionals to consider replacing or adapting well-established protocols with more support. In addition, although the study demonstrated an improvement in the oxygen uptake efficiency slope, suggesting an increase in the efficiency of oxygen uptake and utilization, possibly related to the conditioning of inspiratory muscles, this hypothesis still needs to be further investigated, since the IMT, in this study, did not promote significant changes in ventilatory efficiency, measured by the VE/VCO₂ slope. Another aspect that could have been better explored is the evaluation of participants’ engagement and motivation. Including specific tools to assess these dimensions, as well as a more detailed description of strategies for monitoring attendance and adherence, would enrich the analysis and strengthen the validity of the findings, and contribute to the comparison of the results in similar studies. The findings presented in this study are relevant and highly applicable to contemporary clinical practice. They reinforce the effectiveness of inspiratory muscle training as a complementary therapeutic tool in the management of heart failure, especially when performed with high intensity, short duration and in a home-based setting. By presenting evidence that relevant clinical outcomes can be achieved through a simple, accessible, and well-accepted protocol, the authors pave the way for integrating this strategy into CR programmes. Future multicentre studies with larger sample sizes that consider the different subtypes of heart failure and including direct comparisons with well-established IMT protocols, are needed to better elucidate the prognostic value of this intervention and the potential benefits of integrating high-intensity, short-duration protocols into a home-based setting for this population. Jéssica Malek da Silva (Conceptualization [lead], Data curation [lead], Writing—original draft [lead], Writing—review & editing [lead]), Leandro Cruz Mantoani (Conceptualization [supporting], Data curation [supporting], Visualization [supporting], Writing—original draft [supporting], Writing—review & editing [supporting]), and Luiz Carlos Marques Vanderlei (Conceptualization [supporting], Data curation [supporting], Visualization [supporting], Writing—original draft [supporting], Writing—review & editing [supporting]) None declared. No data was used to generate this publication.