Ground reaction forces and muscle activities during anteriorly-loaded overground walking: Preliminary results

Anterior-load carriage is common and has been identified as a fall risk factor in occupations. However, there is a lack of investigation of how anterior-load carriage influences kinetics and muscle activities. This study examined how anterior-loading affects ground reaction forces (GRFs) and leg/trunk electromyography (EMG) during level overground walking among young adults. Thirty young adults were randomly distributed into three groups: no load, 10% bodyweight (bw), and 20% bw. Each participant walked on a walkway at self-selected speed while holding the assigned load (assembled by a fitness sandbag) with both hands and anterior to the abdomen. Dependent variables included the kinetics (the peak GRF in vertical, forward, backward directions, rate of loading, and braking and propulsive impulses) and EMG magnitudes of six leg/trunk muscles (tibialis anterior, gastrocnemius, vastus lateralis, biceps femoris, gluteus maximus, and oblique). The results did not show significant group-related differences in any kinetic parameters or the EMG magnitudes except for the gluteus maximus. Both loaded groups displayed significantly higher gluteus maximus EMG magnitude than the unloaded group during anteriorly-loaded walking. Greater activation of the gluteus maximus may reflect the body's effort to stabilize the posteriorly leaned trunk, which was the main strategy to offset the anteriorly shifted body-load system's center of mass caused by the anterior load and to maintain dynamic balance during gait. The findings of this study could contribute to reducing the risk of falls in the industrial environment by providing insight into the kinetic control of the human body during anteriorly-loaded walking.