The components of the instrumented timed-up-and-go test may explain balance impairments, gait and weight-bearing asymmetries, and trunk muscle activation disorders.

Abstract

Individuals with unilateral lower-limb amputation (LLA) are exposed to conditions such as low-back pain, which limit everyday activities and trunk musculature for stability. To determine the trunk kinematics and muscle activation of lumbar-erector-spinae (LES) and rectus-abdominis during the instrumented timed-up-and-go (iTUG) test and its correlation with co-activation, muscle activation pattern, gait asymmetry, and center-of-pressure (CoP) sway measures between individuals with and without LLA. The kinematic (trunk forward and lateral flexion, and rotation) and the ratio of muscle activation of LES over rectus-abdominis (LRR) were compared between LLA (n = 26) and the control (n = 16) performing the iTUG test, gait (symmetry-index [SI], co-activation index, and muscle activation pattern), and static test (measures of CoP sway). The LLA group showed greater alterations in balance indicators than the control (iTUG duration, gait SI, weight-bearing SI, CoP-excursion, and CoP-velocity). The trunk's kinematic variables were higher during turn-to-sit than in sit-to-walk, but the LRR was higher during sit-to-walk. The turn-to-sit peak-angular-velocity significantly correlated with the LRR, co-activation index, gait SI, weight-bearing SI, and the measurements of CoP sway. The peak-angular-velocity of the turn-to-sit component indicates balance impairment and trunk muscle disorders better than the iTUG duration or turning times. Slow turning movements may be linked to increased CoP sway, gait and weight-bearing asymmetries, and muscle activation issues in the LES during daily activities, which could raise the risk of low-back pain over time.