Osaka University research indicates that the brain efficiently manages walking coordination, intervening only when leg misalignment is significant, with potential applications in rehabilitation and aid design.
Walking is an activity that is often taken for granted. People typically assume they can multitask by “walking and chewing gum” simultaneously with minimal taxation of their mental effort. Indeed, each leg can move rhythmically independently of the other, controlled by its side of the spinal cord.
However, the ability of the human brain to coordinate the gait such that a walker’s legs are half a stride out of phase with each other, the “antiphase relationship,” is not so trivial when an obstacle or asymmetry occurs, such as a curve in the path.
A new study by Osaka University sheds light on how a normal walking cadence is maintained, providing insights that could improve rehabilitation techniques for patients who have experienced brain trauma or other neurological problems.
Insights from Recent Walking Study
In the study, recently published in Communications Biology, the researchers captured kinematic data from healthy patients walking on a treadmill that was occasionally perturbed by a sudden change in speed. This led to a momentary loss of the antiphase relationship, but it was quickly restored as the subjects reoriented their walking movements.
The data from this experiment was analyzed using a mathematical model of two coupled oscillators – similar to two pendulums connected by a spring – along with a Bayesian inference method. The approach allowed the researchers to calculate the most probable function that represents how the brain applied its control to coordinate the leg motions.
To simplify the problem further, phase reduction theory was applied, which assumes that the perturbed system is returning to a regular periodic solution, called the limit cycle. “Using Bayesian inference enabled us to infer the control of leg coordination in a quantitative way,” says the lead author of the study, Takahiro Arai.
Brain Efficiency in Walking Coordination
Surprisingly, the researchers found that the relative phase is not actively controlled by the brain until the deviation from correct the antiphase orientation exceeds a certain threshold. That is, the brain does not actively intervene to coordinate the relative position of the legs until they are a certain amount out of lockstep. They suggest that not requiring the constant application of control improves both energy efficiency and maneuverability.
“Based on our model, we see that the brain is neither overly controlling, which would limit our ability to negotiate obstacles and also consume a lot of brainpower, nor overly lax, which could lead to falling over when the legs become too uncoordinated,” says senior author, Shinya Aoi.
Implications for Rehabilitation and Mobility Aids
This research may be important to help improve the walking of elderly people or individuals who have experienced the neurological effects of a stroke or Parkinson’s disease. It may also lead to the development of physical aids that help people walk more naturally.
Reference: “Interlimb coordination is not strictly controlled during walking” by Takahiro Arai, Kaiichiro Ota, Tetsuro Funato, Kazuo Tsuchiya, Toshio Aoyagi and Shinya Aoi, 20 September 2024, Communications Biology.
DOI: 10.1038/s42003-024-06843-w
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.