Contribution of the 6–minute Walking Test (6mwt) to the Definition of Exercise Intensity in Cardiac Rehabilitation

Abstract The target heart rate (THR), calculated using the Karvonen formula after a maximal exercise test (ET), defines the correct exercise intensity for each patient (pt). However, some pts referred for cardiac rehabilitation (CR) may not have undergone a ET yet due to clinical or organisational delays. Until an ET is available, it is common practice to empirically set the THR between 30 and 50 % above the resting heart rate (HR). However, while this method has been shown to meet safety criteria, there is a risk of underestimating the intensity of the training. We wanted to verify whether the HR achieved at the end of the 6MWT (a test that physiotherapists can conduct independently) can be used to guide the choice of correct exercise intensity in the early stages of CR. Patient and methods the study took into consideration 124 pts (108 male and 16 female; mean age: 61.85 ± 9.8 years) who were enrolled in an outpatient CR programme between September 2024 and August 2025. Of these, 80 (64,5%) had experienced acute coronary syndrome, 28 (22,6%) had undergone cardiac surgery, 14 (11,3%) had heart failure, 1 (0,8%) had suffered a massive pulmonary embolism and 1 (0,8%) had obstructive peripheral artery disease. All pts underwent both the 6MWT and the ET on a cycle ergometer, with an interval of no more than two weeks between the two tests. No changes had been made to the β–blocker therapy in the meantime. The THR was defined as 50–80% of the HR reserve, as calculated using the Karvonen formula. It was therefore verified whether the HR achieved at the end of the 6MWT fell within the THR range of ± 5 beats per minute (bpm). In fact, a difference of ± 5 b.p.m. is not considered significant for training planning. Results in our case series 89 pts (71.77%; 95% CI: 62–79%) had a HR at the end of the 6MWT that fell within the THR range ± 5 bpm. A maximum HF at the 6MWT below the THR range was observed in 21 pts (16.93%). Only 14 pts (11.29%) had a maximum HR at 6MWT above the THR range. Conclusions due to its selfpaced natuta, it is possible that the 6MWT sometimes underestimates functional capacity. Less frequently the 6MWT and ET results can differ significantly because some pts find walking more suitable than cycling. However, it is likely that the 6MWT can correctly and safely guide the initial sessions of CR programme, especially if supplemented by another assessment tool, such as the Borg Scale of Perceived Exertion.