Relative Aerobic Load of Daily Activities in Individuals with Lower Limb Amputation: A pilot study

Individuals with lower limb amputation (LLA) often experience reduced physical capacity and increased aerobic demands during activities of daily living (ADL), which may impact participation and quality of life. Measuring the relative aerobic load of ADL is essential to set realistic rehabilitation goals, however data on short and non-steady-state ADL tasks in this population are limited.

To evaluate the feasibility of a newly developed protocol for assessing the relative aerobic load of five selected ADL tasks in individuals with LLA, and to determine the applicability of the excess post-exercise oxygen consumption (EPOC) method for these measurements.

Six individuals with unilateral LLA (mean age 59 ± 9 years; five males), including three with transtibial, one with knee disarticulation, and two with transfemoral amputation, all classified as K2-K3 ambulators, were recruited for this pilot study and underwent a cardiopulmonary exercise test (CPET) during the first assessment session. During the second assessment session, within a two-week interval, participants were asked to perform five standardized tests reflecting ADL tasks: the 6-Minute Walk Test (6MWT), Timed Up and Go Test (TUGT), Glittre ADL test, stair ascent, and stair descent. Oxygen consumption was measured using the COSMED K5 system. For each task, average oxygen consumption was computed as the total oxygen uptake during activity and recovery (EPOC) divided by total time, and relative aerobic load was defined as percentage of first ventilatory threshold (% ${\dot{V}O}_2$ -VT₁). Data analysis involved descriptive feasibility assessment and intraclass correlation to examine consistency of relative aerobic load across tasks.

The protocol showed to be feasible and no (serious) adverse events occurred during the study and 5 out of 6 participants were able to complete the protocol, demonstrating its practicality. The EPOC method was successfully applied to both short and longer-duration ADL tasks. The results showed relative aerobic loads exceeding 100% ${\dot{V}O}_2$ -VT₁ for most ADL tasks, indicating substantial physical effort. Agreement of the rankings of the different tasks between participants was observed (intraclass correlation coefficient (ICC) = 0.73, 95% confidence interval (CI) = 0.01-0.97), although the wide confidence interval indicates considerable uncertainty.

This protocol enables the assessment of relative aerobic load in a heterogeneous group of individuals with LLA and highlights the importance of individualized assessment. Given the large variability in ${\dot{V}O}_2$ peak and ${\dot{V}O}_2$ -VT₁ between participants, a generic level of physiological burden for each task cannot be given, instead individualized assessment is crucial to accurately determine physiological burden and avoid under- or overestimation of exercise intensity. The findings support the development of individualized rehabilitation programs tailored to individual capabilities and limitations, potentially improving participation and quality of life. Additionally, future studies with larger cohorts are needed to provide more robust reliability estimates and strengthen the generalizability of these findings.