The effect of external lateral stabilization on the use of foot placement to control mediolateral stability in walking and running

Abstract

It is still unclear how humans control mediolateral (ML) stability in walking and even more so for running. Here, foot placement strategy as a main mechanism to control ML stability was compared between walking and running. Moreover, to verify the role of foot placement as a means to control ML stability in both modes of locomotion, this study investigated the effect of external lateral stabilization on foot placement control. Ten young adults participated in this study. Kinematic data of the trunk (T₆) and feet were recorded during walking and running on a treadmill in normal and stabilized conditions. Correlation between ML trunk CoM state and subsequent ML foot placement, step width, and step width variability were assessed. Paired t-tests (either SPM1d or normal) were used to compare aforementioned parameters between normal walking and running. Two-way repeated measures ANOVAs (either SPM1d or normal) were used to test for effects of walking vs. running and of normal vs. stabilized condition. We found a stronger correlation between ML trunk CoM state and ML foot placement and significantly higher step width variability in walking than in running. The correlation between ML trunk CoM state and ML foot placement, step width, and step width variability were significantly decreased by external lateral stabilization in walking and running, and this reduction was stronger in walking than in running. We conclude that ML foot placement is coordinated to ML trunk CoM state to stabilize both walking and running and this coordination is stronger in walking than in running.

Keywords: Balance; External lateral stabilization; Foot placement strategy; Gait stability; Running; Stepping strategy; Walking.

Figure 1. Schematic representation of the experimental set up.

(A) Schematic representation of the experimental set up. Inset (B) shows the stabilization in more detail. (1) frame; (2) springs; (3) height-adjustable horizontal rail; (4) ball-bearing trolley freely moving in anterior-posterior direction; (5) slider freely moving in vertical direction; (6) vertical rail; and (7) rope attached to frame.

Figure 2. Flow of data processing adopted in this study.

Figure 3. The % of nonsignificant β₂’s during normal and stabilized conditions in walking and running trials per each % of swing phase.

Figure 4. The ability of ML trunk CoM state to predict subsequent ML foot placement (R²) during normal (solid) and stabilized (dashed) conditions in walking (blue) and running (green).

The shaded regions indicate standard error of R².

Figure 5. The differences of R² between normal walking and running.

The shaded areas indicate significant effects in the corresponding portion of the swing phase (based on the results of SPM paired t-test).

Figure 6. The effect of external lateral stabilization on (A) step width and (B) step width variability.

Condition effect: The effect of external lateral stabilization on (A) step width and (B) step width variability in walking and running. # represents the significant differences of step width and step width variability between normal and stabilized conditions (based on the results of Bonferroni post-hoc tests). * represents the significant differences of step width and step width variability between normal walking and running (based on the results of paired t-test). The error bars represent the standard deviation.

Figure 7. The effect of lateral stabilization on R² in walking and running.

(A) Condition effect: The effect of external lateral stabilization on R² in walking and running. (B) Locomotion mode effect: The differences of R² between walking and running in both conditions (normal & stabilized). (C) Interaction effect (condition × locomotion mode effect): The differences of external lateral stabilization effect on R² between walking and running. The shaded areas indicate significant effects in the corresponding portion of the swing phase.