The effect of external lateral stabilization on the use of foot placement to control mediolateral stability in walking and running
- Published
- Accepted
- Subject Areas
- Neuroscience, Kinesiology
- Keywords
- gait stability, balance, running, walking, foot placement strategy, stepping strategy
- Copyright
- © 2019 Mahaki et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2019. The effect of external lateral stabilization on the use of foot placement to control mediolateral stability in walking and running. PeerJ Preprints 7:e27244v5 https://doi.org/10.7287/peerj.preprints.27244v5
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 and 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.
Author Comment
We have balanced our conclusion section. For this, we have mentioned that both of the active control and passive dynamic coupling might play role on the correlation between ML trunk CoM state and subsequent foot placement (R^2).
The reviewer has a very good point here; indeed, we see R^2 as a quantification of the foot placement mechanism. Thus, it does not quantify stability per se, as other mechanisms may play a role. Thus, we cannot (and do not want to) make any statements about stability per-se, but only about in how far foot placement (be it passive or active) is used to control stability. To make sure that we used this correctly throughout, we searched for all instances of the use “stability”. In doing so, we realized that our title and page 4, lines 11-13, were not in line with this. Therefore, we have revised them as follows:
Title: The effect of external lateral stabilization on the use of foot placement to control mediolateral stability in walking and running.
Page 4, lines 11-13: In the current study, we set out to test the idea that running is less dependent on foot placement to control ML stability than walking.
Supplemental Information
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.
The % of nonsignificant β2's during normal and stabilized conditions in walking and running trials per each % of swing phase
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
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)
The effect of external lateral stabilization on (A) step width and (B) step width variability in walking and running
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.
The effect of external 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.
The comparsion of R2 between legs in walking and running.
(A) % of variance in ML foot placement that can be explained by ML trunk CoM state (R2) in walking and running. (B) The differences of R2 between left and right legs in walking and running.
The effect of speed on R2 in running
(A) % of variance in ML foot placement that can be explained by ML trunk CoM state (R2) in running with three different speeds [2.08, 2.50, and 2.92 m/s]. (B) The effect of running speeds (2.08, 2.50, and 2.92 m/s) on R2. The shaded regions indicate standard error of R2.
The effect of speed on step width in running
Step width was significantly decreased by increasing in running speed (F (1, 2) = 9.25, p = 0.002) (Fig. S3).
The effect of running on step width variability in running
There was no significant main effect of speed on step width variability in running (F (1, 2) = 1.48, p = 0.254) (Fig. S4).
The effect of external lateral stabilization on energy cost in walking and running
Condition effect: The effect of external lateral stabilization on energy cost in walking and running. # represents the significant differences of energy cost between normal and stabilized conditions (based on the results of Bonferroni post-hoc). Error bars represent standard deviation.