Heart Failure (HF) is a complex clinical syndrome characterized by the heart's inability to eject blood adequately to meet the metabolic demands of peripheral tissues, or by doing so only at the expense of elevated filling pressures.^1,2 Throughout the course and progression of the disease, individuals experience multiple changes in skeletal muscle composition and function, leading to sarcopenia, dyspnea, and cardiac cachexia,³ often resulting in hospitalizations.

During hospital stays due to HF decompensation, prolonged bed rest is associated with worsening musculoskeletal depletion and reduced exercise capacity,^2,4 leading to a shift in energy metabolism with increased reliance on anaerobic pathways for energy production.⁵ These alterations may be attributed to impaired muscle perfusion and a consequent shift from type I to type II muscle fibers, which rely predominantly on anaerobic glycolytic metabolism for energy.⁶

In the early phase of physical exercise, energy production is primarily anaerobic, and this pathway may be impaired in individuals with HF, affecting short-duration daily activities and limiting autonomy. Therefore, assessing this phase of metabolism in patients with chronic conditions becomes relevant when designing short-duration, high-intensity individualized exercise programs.^7,8

One tool used to evaluate anaerobic metabolism, which can indirectly indicate adaptation to short-duration activities,⁶ is the One-Minute Step Test (1MST). The 1MST targets the energy metabolism component required for performing Activities of Daily Living (ADLs).⁷

The 1MST appears to be a promising, low-cost tool for assessing anaerobic metabolism,⁸ with the advantage of enabling continuous monitoring in a small physical space.⁹ However, to date, the test has only been used in studies involving healthy individuals and those with coronary artery disease and chronic lung disease^7,10–12 with no prior reports of its use in intensive care therapy for HF patients.

This study aimed to evaluate the safety and feasibility of performing the 1MST in hospitalized HF patients and, additionally, to assess physiological changes before and after the test.

During the data collection period, 245 patients were admitted to the CICU. Of these, 40 met the inclusion criteria. Twenty individuals were excluded based on predefined criteria (Figure 2). The study participants had a mean age of 60.9 years, were predominantly male, and had an average hospital stay of seven days. Additional clinical and demographic characteristics are presented in Table 1. The central figure summarizes the main benefits and findings of this study.

No adverse events occurred during the 1MST or the recovery period. All volunteers completed the test, and 26% used upper limb support. Evaluation required at least two physical therapists, a standardized step, and continuous monitoring equipment. The physiotherapist demonstrated the test, and vital signs and RPE were recorded before and after. The entire evaluation process, including chart review, informed consent, test execution, and data collection, took approximately 30 minutes.

Key clinical and physiological characteristics before and after the 1MST are listed in Table 2. A statistically significant increase in hemodynamic variables and perceived exertion was observed post-test, including HR, SBP, MBP, respiratory rate, and lower limb RPE. A statistically significant decrease in SpO₂ was also noted. An average of 11 step cycles was recorded, and the number of test cycles showed a weak negative correlation with age and a weak positive correlation with CICU length of stay (Figures 3A and 3B, respectively).

This study demonstrated that performing the 1MST in hospitalized HF patients is both feasible and safe, suggesting it may be a useful tool for evaluating anaerobic metabolism in clinically stable ICU patients. It is a simple test that adds to the physiotherapist's toolkit for exercise assessment and prescription in this population. This was the first study to use this tool in the ICU setting with this patient profile.

In an outpatient study with patients with Coronary Artery Disease (CAD), the 1MST was shown to be safe in over 90% of cases.⁸ No studies were found in the literature assessing the safety of the 1MST in HF patients or its use in intensive care settings.

Feasibility was determined by test adherence and practical applicability in the ICU. Laroche et al. reported that 13% of healthy individuals stumbled at least once during the test, with no falls or need to interrupt the evaluation.⁷ In Besson et al.'s study,⁸ which included patients with CAD performing the 1MST after exercise, three patients were unable to complete the test due to difficulty and poor coordination. In contrast to those studies, all volunteers in our study completed the test without reports of difficulty or stumbling. This may be attributed to prior performance for familiarization and the option to use support in case of imbalance.

During the 1MST, a significant increase in the analyzed hemodynamic variables, respiratory rate, and lower limb RPE was observed, along with a small but statistically significant drop in SpO₂. These findings show that the 1MST induces cardiovascular load, as expected during physical effort, and did not result in adverse events, suggesting it may serve as a non-invasive functional assessment tool for anaerobic metabolism.⁸ Previously, Besson et al. assessed 1MST hemodynamic variables at three different points and observed increases in HR, SBP, and Diastolic Blood Pressure (DBP), but found no significant difference between pre- and post-test periods.⁸

The number of step cycles completed in one minute has been used in clinical practice as a criterion for evaluating anaerobic metabolism.⁷ The average of 11 cycles observed in this study showed a negative correlation with age, similar to other studies involving individuals without heart disease. In those studies, younger individuals (mean age 25 years) averaged 76 cycles,²⁵ while another group (mean age 32 years) performed 52 cycles.⁷

Among cardiac patients without HF, Besson et al. reported an average of 43 cycles in patients with a mean age of 57 years.⁸ This discrepancy may be explained by the progressive musculoskeletal depletion seen in HF,² compounded by inflammation and autonomic imbalance, which contribute to physical dysfunction and reduced exercise tolerance.^2,26 Additionally, the aging process and hospitalization may further exacerbate functional decline,^27,28 impacting 1MST performance. A correlation was found between ICU length of stay and 1MST cycles, indicating that patients who stayed longer in our unit performed better on the test. This finding may be explained by the volunteers’ exposure to an individualized cardiac rehabilitation protocol, which is performed daily during their hospitalization in our unit. It is worth noting that although different populations have been evaluated regarding the measurement of anaerobic metabolism through the 1MST, there is still no cutoff point related to the performance of this test. Nevertheless, the 1MST performance appears to be a reliable and valid criterion for evaluating the short and intense demand of metabolism, being independently related to blood lactate concentration and EPOC.² The results of this evaluation can be used to support the prescription of individualized training that resembles the daily activities of individuals.⁸

The 1MST proved to be a safe and viable tool for assessing the anaerobic metabolism of patients with HF admitted to the ICU, since no participant presented any adverse events, and the exam was completed by all volunteers. In addition, a correlation was observed between the 1MST performance and age and length of ICU stay, which has never been demonstrated in the current literature. Therefore, it is expected that the 1MST will be a tool capable of assisting in the prescription of exercises, on an individualized basis, for heart disease patients, since it is easily reproducible in clinical practice.