Researchers have investigated how the brain controls walking in humans to keep the legs coordinated. They revealed that while each leg can move independently, they remain synchronized unless they drift too far apart in their movements. This research has potential applications in enhancing treatments for those who struggle with walking due to age or neurological conditions.
Walking is an everyday action that people often overlook. Many believe they can easily multitask, such as “walking and chewing gum,” with little mental strain. In fact, each leg can move rhythmically on its own, managed by the spinal cord on its respective side. However, when faced with obstacles or uneven surfaces—like walking on a curved path—coordinating the movement to maintain an “antiphase relationship,” where the legs move half a stride out of sync, becomes challenging. Gaining more insight into how a steady walking rhythm is preserved can lead to improved rehab methods for those who have suffered from brain injuries or other neurological issues.
A recent study published in Communications Biology by researchers from Osaka University collected kinematic data from healthy participants walking on a treadmill. This treadmill had sudden speed changes that occasionally disrupted their antiphase relationship, but the subjects quickly readjusted their movements. The researchers analyzed the data using a mathematical model likened to two pendulums linked by a spring and a Bayesian inference method to determine how the brain coordinated the leg movements.
To further clarify their findings, they applied phase reduction theory, which assumes the affected system will revert to a regular cycle, referred to as the limit cycle. “Employing Bayesian inference allowed us to quantitatively assess the control of leg coordination,” explained the lead author, Takahiro Arai.
Interestingly, the study revealed that the brain does not start actively managing the leg coordination until the deviation from the antiphase alignment surpasses a specific threshold. This means the brain only intervenes when the legs are significantly out of sync. The researchers propose this reduced need for constant control enhances both energy efficiency and agility.
“Our model indicates that the brain maintains a balanced approach; it’s not overly controlling, which could hinder the ability to navigate obstacles and drain mental resources, nor too lenient, which might lead to falls when the legs become uncoordinated,” stated senior author Shinya Aoi.
This research holds importance for improving mobility in older adults or those who have experienced stroke-related neurological impairments or Parkinson’s disease. It could also contribute to the creation of mobility aids that promote more natural walking patterns.
The study, titled “Interlimb coordination is not strictly controlled during walking,” was published in Communications Biology.
