Commingling Effects of Anterior Load and Walking Surface on Dynamic Gait Stability in Young Adults.

Treadmill walking has been used as a surrogate for overground walking to examine how load carriage affects gait. The validity of using treadmill walking to investigate load carriage's effects on stability has not been established. Thirty young adults were randomized into 3 front-loaded groups (group 1: 0%, 2: 10%, or 3: 20% of bodyweight). Participants carried their load during overground and treadmill walking. Dynamic gait stability (primary outcome) was determined for 2 gait events (touchdown and liftoff). Secondary variables included step length, gait speed, and trunk angle. Groups 1 and 2 demonstrated similar stability between walking surfaces. Group 3 was less stable during treadmill walking than overground (P ≤ .005). Besides trunk angle, all secondary outcomes were similar between groups (P > .272) but different between surfaces (P ≤ .001). The trunk angle at both events showed significant group- and surface-related differences (P ≤ .046). Results suggested that walking with an anterior load of up to 10% bodyweight causes comparable stability between surfaces. A 20% bodyweight front load could render participants less stable on the treadmill than overground. This indicates that anteriorly loaded treadmill walking may not be interchangeable with overground walking concerning stability for anterior loads of 20% bodyweight.