Stokes HE, Thompson JD, and Franz JR (2017). The neuromuscular origins of kinematic variability during perturbed walking. Nature: Scientific Reports; 7(1): 808.
Walking balance control involves coordinated adjustments in posture (i.e., head and trunk stabilization) and foot placement from step to step. Particularly in unpredictable and challenging environmental conditions, these adjustments depend on the integration of reliable sensory feedback and the planning and execution of appropriate motor responses. PBO-member Prof. Jason Franz and his students use optical flow perturbations (i.e., the visual perception of imbalance) in an immersive virtual environment to study the neuromechanical origins of balance control, adaptation, and impairment.
Kinematic variability is frequently used to quantify the magnitude and efficacy of balance corrections in the presence of perturbations. However, few studies have investigated the neuromuscular mechanisms underlying kinematic variability and thus step to step adjustments in posture and foot placement during walking. In their recently published study in Nature’s Scientific Reports, Franz and colleagues did just that. By tightly coupling electromyographic (EMG) measurements and quantitative motion capture with optical flow perturbations of different amplitudes, their findings revealed specific, highly coordinated muscular contributions to orchestrating balance corrections in human walking.
First, they found that perturbations increased EMG activity of the gluteus medius and postural control muscles in a coordinated manner during leg swing and the coactivation of antagonist lower leg muscles during limb loading in early stance. Second, they found that perturbation-induced increases in gluteus medius and postural control muscle activities positively correlated with step to step adjustments in lateral foot placement and postural sway, respectively.
Moving forward, these findings now provide an important roadmap for better understanding the onset and progression of balance impairment and falls risk due to aging and neurodegenerative disease.