Walking Cadence Affects the Recruitment of the Medial-Lateral Balance Mechanisms

Abstract

We have previously identified three balance mechanisms that young healthy adults use to maintain balance while walking. The three mechanisms are: (1) The lateral ankle mechanism, an active modulation of ankle inversion/eversion in stance; (2) The foot placement mechanism, an active shift of the swing foot placement; and (3) The push-off mechanism, an active modulation of the ankle plantarflexion angle during double stance. Here we seek to determine whether there are changes in neural control of balance when walking at different cadences and speeds. Twenty-one healthy young adults walked on a self-paced treadmill while immersed in a 3D virtual reality cave, and periodically received balance perturbations (bipolar galvanic vestibular stimulation) eliciting a perceived fall to the side. Subjects were instructed to match two cadences specified by a metronome, 110 bpm (High) and 80 bpm (Low), which in this experiment, led to faster and slower gait speeds, respectively. The results indicate that subjects altered the use of the balance mechanisms at different cadences. The lateral ankle mechanism was used more in the Low condition, while the foot placement mechanism was used more in the High condition. There was no difference in the use of the push-off mechanism between cadence conditions. These results suggest that neural control of balance is altered when gait characteristics, such as cadence change, suggesting a flexible balance response that is sensitive to the constraints of the gait cycle. We speculate that the use of the balance mechanisms may be a factor resulting in well-known characteristics of gait in populations with compromised balance control, such as slower gait speed in older adults or higher cadence in people with Parkinson's disease.

Interactions Between Different Age-Related Factors Affecting Balance Control in Walking

“…It was discussed later both in robotics (Kuo, 1999;Pratt et al, 2006) and human motor control (Bauby and Kuo, 2000;Hof, 2008) and is now widely accepted to be one of the dominant mechanisms for human balance control during walking (Wang and Srinivasan, 2014;Bruijn and van Dieën, 2018;Reimann et al, 2018a). The lateral shift of the left foot before heel-strike can be generated by a left hip abduction, but also by a combination of internal rotation of the stance leg knee and external rotation of the swing leg hip joint, and we have found evidence for both (Reimann et al, 2018b;Fettrow et al, 2019). We quantify the foot placement shift by calculating the difference between the perturbed foot placement and the predicted foot placement based on the CoM position and velocity at mid-swing using a linear model fitted to the unperturbed steps (for details see Wang and Srinivasan, 2014;Bruijn and van Dieën, 2018;Reimann et al, 2018b).…”

“…This mechanism was first noted in walking by Hof et al (2007) and later confirmed as an active mechanism (Hof et al, 2010;Reimann et al, 2017Reimann et al, , 2018bHof and Duysens, 2018). The roll torque is generated by an activation increase in the medial ankle muscles (tibialis anterior, gastrocnemius medialis) and a decrease in the lateral muscles (peroneus longus) (Reimann et al, 2018b;Fettrow et al, 2019). We quantify this mechanism by integrating the difference in the subtalar joint angle between the perturbed and unperturbed steps over single stance.…”

“…We observed this mechanism in healthy young humans (Reimann et al, 2018b). The increased plantarflexion in the trailing leg is preceded by increased activity in the gastrocnemius medialis in late single stance (Fettrow et al, 2019). We quantify this mechanism by integrating the difference in the ankle plantarflexion angle between the perturbed and unperturbed steps over double stance.…”

“…Here we summarize the relevant findings from this study. For details, please refer to Fettrow et al (2019). Figure 2 shows the resulting responses in the whole-body sway and the three balance mechanisms ankle roll, foot placement and push-off.…”

The Effect of a Virtual No-Step Zone on Balance Control in Walking

“…The nervous system combines these mechanisms in different ways to maintain balance, as the use of each mechanism varies on any given step (Fettrow et al, 2019b). Furthermore, the relative use of the mechanisms is altered based on internal constraints, such as the phase of the gait cycle (Reimann et al, 2019), or the stepping cadence (Fettrow et al, 2019a). This allows for a highly flexible system that can meet the goal of maintaining balance during locomotion through a variety of scenarios.…”