Relationship Between Step Count and the Timed Up and Go and L Test of Functional Mobility Among Adults With Transtibial Amputation.

Abstract

To explore the relationship between daily steps measured by the activPAL 3 and Fitbit Inspire 3 accelerometers and performance on the Timed Up and Go test (TUG) and L Test of Functional Mobility (L test) in adults with transtibial amputation. Observational design. Six outpatient prosthetic clinics located in the United States and the participant's home environment. Adults (n=96) with unilateral transtibial amputation. Not applicable. Each participant wore the activPAL and Fitbit concurrently for 7 days. Pearson correlation was used to assess the relationship between daily steps from each device and TUG and L test completion times. Regression was employed to control for sex, body mass index, age, and type 2 diabetes status. Moderate negative correlations were observed between daily steps recorded by the activPAL and TUG (r=-.52) and L test (r=-.51) times. Moderate negative correlations were also found between daily steps from the Fitbit Inspire 3 and TUG (r=-.55) and L test (r=-.56) times. These relationships remained statistically significant with minimal influence by the included covariates. Participants who performed well on the TUG and L test tend to have higher daily step counts, highlighting a meaningful association between clinical mobility performance and free-living physical activity. This finding provides evidence that TUG and L test completion times may reflect both functional capacity in a clinical setting and real-world ambulatory behavior. Although step counts and clinical performance measures are not interchangeable, together they offer complementary insights that can enhance the evaluation and monitoring of mobility in individuals with transtibial amputation.