Adaptive control of dynamic balance in human gait on a split-belt treadmill

Abstract

Human bipedal gait is inherently unstable, and staying upright requires adaptive control of dynamic balance. Little is known about adaptive control of dynamic balance in reaction to long-term, continuous perturbations. We examined how dynamic balance control adapts to a continuous perturbation in gait, by letting people walk faster with one leg than the other on a treadmill with two belts (i.e. split-belt walking). In addition, we assessed whether changes in mediolateral dynamic balance control coincide with changes in energy use during split-belt adaptation. In 9 min of split-belt gait, mediolateral margins of stability and mediolateral foot roll-off changed during adaptation to the imposed gait asymmetry, especially on the fast side, and returned to baseline during washout. Interestingly, no changes in mediolateral foot placement (i.e. step width) were found during split-belt adaptation. Furthermore, the initial margin of stability and subsequent mediolateral foot roll-off were strongly coupled to maintain mediolateral dynamic balance throughout the gait cycle. Consistent with previous results, net metabolic power was reduced during split-belt adaptation, but changes in mediolateral dynamic balance control were not correlated with the reduction of net metabolic power during split-belt adaptation. Overall, this study has shown that a complementary mechanism of relative foot positioning and mediolateral foot roll-off adapts to continuously imposed gait asymmetry to maintain dynamic balance in human bipedal gait.

Handrail Holding During Treadmill Walking Reduces Locomotor Learning in Able-Bodied Persons

“…Motor learning occurs when long-lasting adjustments in movement control are made in response to discrepancies between intended and actual task performance [22], [23]. During split-belt walking, a control problem emerges because of an inefficient, asymmetric gait pattern [9], [20]. This study shows that altered balance demands are an important aspect of this control problem, as the asymmetry that is typically seen in early split-belt adaptation [8], [9], [20] was reduced when participants were externally supported.…”

“…A suitable paradigm to study locomotor learning in a controlled environment is split-belt treadmill walking [7], [8]. During split-belt walking people are exposed to asymmetric left and right belt speeds, by which they are initially perturbed, and in response to which they adapt their step lengths, double support times [8] and balance control [9], [10]. After approximately ten minutes of split-belt walking, the perturbation is removed by setting the belts at symmetric belt speeds.…”

“…These after-effects are considered indicative of locomotor learning [11]. Previous research has shown that split-belt walking may enforce changes in balance control [9], [10], [12], [13]. Holding on to handrails stabilizes the body, as it increases the base of support, allows the generation of corrective forces [14], and increases somatosensory input through touch of the handrails [15].…”

Motorized shoes induce robust sensorimotor adaptation in walking

“…In other words, subjects with the motorized shoes placed the foot closer to the body than with regular shoes. This distinct behavior might be explained by the fact that the balance is perturbed in the beginning of the split condition (Buurke et al, 2018; Iturralde and Torres-Oviedo, 2019) and it might be further challenged when stepping with the motorized shoes by augmenting the center of mass’ height, increasing even further gait instabilities while walking.…”

Inertial sensor-based centripetal acceleration as a correlate for lateral margin of stability during walking and turning

“…The relationship between the XcoM and the base of support (BoS) reveals the instantaneous mechanical stability of the system; if the XcoM falls outside the BoS, balance cannot be recovered with joint torque alone -a stepping response or external force / torque is required. Since the spatial distance between the XcoM and the BoS was defined as the margin of stability (MoS) [7,8], the MoS has been widely used to assess gait stability [6,[9][10][11][12][13][14][15], and gait controllers have been proposed with objectives of maintaining constant MoS, or constant offset, through foot placement [16,17].…”