Association Between Knee Extension Strength and Functional Capacity After Intensive Care Unit Discharge: A 6-Mo Prospective Cohort Study

Introduction Assessing functional improvement after intensive care unit discharge is particularly challenging. The aim of this study was to measure the association between (1) changes in knee extension muscle strength or quadriceps femoris and rectus femoris muscle thickness and (2) changes in functionality/function-related measurements in post-intensive care unit patients. Methods This prospective cohort study included adult patients without previous disability, consecutively selected after intensive care unit discharge. Some parameters, such as Short-Form 36, 6-min walking test, 1-min sit-to-stand, and Short Physical Performance Battery, were measured at baseline and 3 and 6 mos after discharge. Correlations were assessed and regression models were built to assess the association between evolution in knee extension strength or muscle thickness and evolution in functional tests. Results Thirty patients completed the follow-up. Moderate correlation was found between knee extension strength change and Short-Form 36 physical functioning (correlation coefficient [ρ] = 0.53), 6-min walking test (ρ = 0.38), 1-min sit-to-stand (ρ = 0.52), and Short Physical Performance Battery (ρ = 0.38). Baseline values and changes in knee extension strength moderately predicted evolution in Short-Form 36 physical functioning (r2 = 0.32, P = 0.006). Changes in muscle thickness were overall not associated with changes in functional variables. Conclusion Changes in knee extension muscle strength may inform on functional progression over time after intensive care unit discharge, although confirmatory studies are needed.