Adults with lower‐limb amputation: Reduced multifidi muscle activity and extensor muscle endurance is associated with worse physical performance

Abstract

AbstractTrunk muscles may be an overlooked region of deficits following lower‐limb amputation (LLA). 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, that is, the Timed Up and Go (TUG), Berg Balance Scale (BBS), and 10‐m Walk Test (10mWT). Associations between trunk muscle metrics and performance were explored with regression modeling, while considering covariates known to impact performance postamputation (p ≤ 0.100). Average ultrasound‐obtained, lumbar multifidi activity was 14% and 16% for transfemoral‐ and transtibial‐level amputations, respectively, while extensor endurance was 37.34 and 12.61 s, respectively. For TUG, nonamputated‐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 LLA; reduced muscle activity and endurance may be important factors to target during rehabilitation to enhance mobility‐related outcomes.