Comparison of overhead harness configurations for measuring trunk kinematics during treadmill disturbances

Background: Research has shown that postural perturbation training reduces falls. Trunk kinematics, at recovery step, are key outcome measures. Fall prevention training programs are being developed for routine clinical care. In these programs, the subject is positioned on a treadmill and subjected to forward and backward disturbances which simulate trips and slips. The patient wears a safety vest attached to an overhead harness to create a secure environment. Motion capture is used to measure trunk kinematics.

Research question: It is important to verify that trunk kinematics are independent of harness configuration. The purpose of this study was to compare the trunk flexion angle and angular velocity at recovery step after forward and backward disturbances on a treadmill measured by motion capture with the harness in both a fixed and free position.

Methods: Ten healthy young adults (5/10 female, age: 29.2 ± 6.3 years, BMI: 24.2 ± 2.4) participated in this study. The subjects had retro-reflective markers placed on key anatomical landmarks to measure trunk kinematics. The participants experienced forward and backward disturbances, which incrementally increased in intensity until the harness clearly supported the subjects for three disturbances in both directions. The order of harness configurations was randomized across subjects and each subject participated in two consecutive rounds of disturbances, one round for each harness configuration. Equivalence testing was performed to demonstrate that the harness configurations were equivalent (α = 0.05).

Results and significance: The Equivalence Test demonstrated that the trunk angle (TA) and angular velocity (TAV) were equivalent for the different harness configurations. The 95% Confidence Intervals (TA: [-2, 1], TAV: [-18, 16]) were within the equivalence interval (TA: [-3, 3], TAV: [-20, 20]) and the p-Values (TA: 0.008, TAV: 0.034) were less than alpha. Trunk kinematics are independent of overheard harness configurations during treadmill induced disturbances for clinical postural perturbation training.