Feasibility of Activity Monitors to Assess Physical Capacity After Critical Illness: An Observational Study Nested Within a Randomized Clinical Trial.

Objective: To determine if daily physical performance measures collected remotely through a wrist-worn activity monitor (AM) could serve as a reliable alternative to the clinic-based 6-minute walk test (6MWT) for assessing physical capacity after critical illness. Patients and Methods: Participants were recruited from a group of critically ill adults aged ≥18 years with moderate-to-severe anemia as they enrolled in a parallel-group, single-center randomized clinical trial assessing the impact of a multifaceted anemia prevention and treatment strategy vs standard care at intensive care units at a large US medical center. The nested prospective observational study was conducted from September 2022 to October 2025. Participants were instructed to wear a wrist-worn AM for 4 days in their free-living environments at 1 month and 3 months post-hospitalization to coincide with their clinic-based 6MWTs. Mean daily step counts and maximum daily cadences were calculated from the AM. Results: Fifty-two participants (median [interquartile range] age, 66 [60-71]; 29 men) were enrolled. Over 80% of participants completed monitoring and provided valid data. Mean daily step count (r Conclusion: Home-based wrist-worn AM use is feasible after critical illness with high retention and adherence rates. The strong correlation between daily maximum cadence and 6MWT distance suggests this device can effectively evaluate physical performance and recovery in intensive care unit survivors remotely. These findings provide valuable preliminary data to guide the design of large clinical trials. Trial Registration: ClinicalTrials.gov Identifier: NCT05167734 (2021-12-09).