Adults with Lower-Limb Amputation: Reduced Multifidi Muscle Activity and Extensor Muscle Endurance is Associated with Worse Physical Performance.

Trunk muscles may be an overlooked region of deficits following lower-limb amputation. This study sought to determine the extent that trunk muscle deficits are associated with physical function following amputation. Sedentary adults with a unilateral transtibial- (n=25) or transfemoral-level (n=14) amputation were recruited for this cross-sectional research study. Participants underwent a clinical examination that included ultrasound imaging of the lumbar multifidi muscles, the modified Biering-Sorensen Endurance Test (mBSET), and performance-based measures, i.e., the Timed Up and Go (TUG), Berg Balance Scale (BBS), and 10-meter Walk Test (10mWT). Associations between trunk muscle metrics and performance were explored with regression modeling, while considering covariates known to impact performance post-amputation (p≤.100). Average ultrasound-obtained, lumbar multifidi activity was 14% and 16% for transfemoral- and transtibial-level amputations, respectively, while extensor endurance was 37.34 seconds and 12.61 seconds, respectively. For TUG, non-amputated-side multifidi activity and an interaction term (level x non-amputated-side multifidi activity) explained 9.4% and 6.2% of the total variance, respectively. For 10mWT, beyond covariates, non-amputated-side multifidi activity and the interaction term explained 6.1% and 5.8% of the total variance, respectively. For TUG, extensor endurance and an interaction term (level x mBSET) explained 11.9% and 8.3% of the total variance beyond covariates; for BBS and 10mWT, extensor endurance explained 11.2% and 17.2% of the total variance, respectively. Findings highlight deficits in lumbar multifidi activity and extensor muscle endurance among sedentary adults with a lower-limb amputation; reduced muscle activity and endurance may be important factors to target during rehabilitation to enhance mobility-related outcomes. This article is protected by copyright. All rights reserved.