Correlation between the 6-minute walk test and the 6-minute stepper test in individuals who have been hospitalized in an intensive care unit.

The number of survivors following an intensive care unit (ICU) stay is steadily increasing, driven by a rise in ICU admissions and improved survival rates (Boulet et al., 2023; Spragg et al., 2010). This trend is accompanied by the admission of older patients with a higher burden of comorbidities (Bagshaw et al., 2009; Zampieri et al., 2021). Together, these factors contribute to an increasing number of patients at risk of developing physical, psychological, and/or cognitive impairments related to ICU hospitalization, now collectively referred to as post–intensive care syndrome (PICS). This condition is frequent and has major repercussions on functional exercise capacity, autonomy, quality of life, and socio-professional reintegration. Early screening, recently identified by the French National Authority for Health as a major public health issue, allows timely referral to appropriate care pathways. In this context, post-ICU follow-up clinics have been implemented. Functional assessment after an ICU stay is essential, particularly to enable early identification of physical limitations and to guide rehabilitation strategies. The 6-minute walk test (6MWT) is considered the reference standard for assessing functional exercise capacity even if it does not allow determination of the underlying origin of deconditioning, which may be cardiac, respiratory, or muscular. Moreover, its implementation is often challenging in routine clinical practice, limiting its use in post-ICU follow-up consultations (Agbakou et al., 2024). There is therefore a need to identify tests that provide similar information to the 6MWT while being more accessible and easier to perform, in order to optimize post-ICU follow-up. The 6-minute stepper test (6MST) may represent a reliable alternative. Indeed, it has demonstrated a strong correlation with the 6MWT in patients with chronic obstructive pulmonary disease and sarcoidosis (Ribeiro et al., 2022; Zeren et al., 2023). However, this test has never been evaluated in a post-ICU population. Therefore, the primary objective of this study is to assess the correlation between the 6MWT and the 6MST in individuals who have been hospitalized in an ICU, approximately three months after hostpital discharge. The marked decline in functional exercise capacity frequently observed after intensive care unit hospitalization is likely multifactorial, combining peripheral muscle weakness, muscle atrophy, and cardiorespiratory dysfunction. Consequently, functional tests such as the previously described 6MWT and 6MST are unable to disentangle the respectiv contribution of these underlying mechanisms to the observed functional limitations. Exploring the relationship between these functional tests and specific markers of skeletal, lower limb muscle function and morphology may help clarify the underlying determinants of reduced functional capacity in this population. Therefore, the main secondary objectives will be to assess the relationship between the 6MWT and 6MST and more specific markers of lower-limb muscle performance: the five-times sit-to-stand test (5STS) and muscle ultrasound to measure the cross-sectional area (CSA) of the rectus femoris (RF) and vastus lateralis (VL), providing information on muscle trophicity. The primary objective of this study will be to assess the correlation between the 6MWT and the 6MST in individuals who have been hospitalized in an ICU, approximately three months after hostpital discharge. Th secondary objectives will be to assess the relationship between the 6MWT and 6MST and more specific markers of lower-limb muscle performance: the five-times sit-to-stand test (5STS) and muscle ultrasound to measure the CSA of the RF and VL muscles, providing information on muscle trophicity. The inclusion of standardized self-administered questionnaires will allow evaluation of the impact of functional and motor capacity on quality of life.