How humans control their bodies might seem simple—we walk, reach, or grip without thinking much about it—but scientists say the process is far from fully understood.
According to Mark Latash, a distinguished professor of kinesiology at Penn State, the way our nervous system produces movement is still an open question.
His decades of research in motor control, the study of how the brain and body interact to create movement, have shed light on how humans manage everyday actions and how subtle changes in this process could predict future neurological conditions such as Parkinson’s disease.
Latash, together with doctoral candidate Sayan Deep De, recently examined how the nervous system controls hand force.
Their findings, published in Neuroscience, provide insight into why movement feels so effortless for most people—and how this ease can start to break down in disease.
Latash explains that most of the time, people do not consciously plan every detail of a movement.
When walking, for instance, we don’t calculate exactly how long each step should be or how much force each muscle must use to handle every pebble on the ground.
The central nervous system takes care of these details automatically, adjusting muscles and joints to keep us balanced and moving forward.
This built-in flexibility allows our bodies to adapt instantly to small disturbances, such as changes in terrain, shifts in hormones, or even gusts of wind.
De describes the process as a kind of dynamic stability. Our movements are never identical, but the nervous system ensures they succeed within an acceptable range. This ability to generate a variety of solutions to complete the same task is a hallmark of healthy motor control.
When Parkinson’s disease develops, this flexibility begins to disappear. Parkinson’s is caused by the progressive loss of brain cells that produce dopamine, a neurotransmitter essential for movement.
By the time symptoms like tremors or stiffness appear, much of the brain is already severely compromised. As a result, the body loses its dynamic stability.
To illustrate this, De uses the example of a video game where players keep a spaceship at a target height by pressing two buttons with their fingers.
A healthy person can achieve the goal in many ways: pressing harder with one finger and softer with the other, then switching the balance on the next attempt.
If measured ten times, they might produce ten different force combinations—not because they’re consciously choosing variety, but because their nervous system naturally allows for flexible solutions.
In contrast, people in the early stages of Parkinson’s tend to stick to a single solution, pressing the buttons in the same pattern each time.
They can still keep the spaceship aloft, but their strategy is rigid rather than adaptable. Research from Latash’s lab has shown that this lack of flexibility can appear many years before visible symptoms of Parkinson’s disease.
This discovery suggests a new way to screen for the condition. By attaching simple force sensors to someone’s hand and asking them to perform tasks that require applying specific amounts of pressure, researchers could detect whether a person uses a wide range of solutions or just one rigid pattern.
The test takes about 15 minutes, requires inexpensive equipment, and could be performed during a routine doctor’s visit. People showing limited flexibility could then be referred for more advanced neurological tests, such as an MRI.
Early detection is critical because existing treatments can slow Parkinson’s progression if started before too much brain damage occurs. Many patients lose up to 70 percent of dopamine-producing neurons before they even notice symptoms, meaning diagnosis often comes late. While the proposed test cannot diagnose Parkinson’s directly, it could serve as a valuable early warning tool.
Latash and De emphasize that their research is part of a larger effort to understand motor control in both aging and disease. Older adults often face mobility issues due to normal aging as well as conditions like Parkinson’s. By uncovering how the nervous system controls movement, researchers hope to design better treatments and strategies to support independence and quality of life.
Recent findings from De’s doctoral work suggest that movement and force production may even be controlled through separate neurological pathways, adding another layer of complexity to the puzzle. For both researchers, each step forward brings science closer to understanding how the body moves—and how to help when it doesn’t.
“Insights into how people move have huge implications for those with movement disabilities and for everyone as they age,” Latash says. “Like other motor control researchers, we will continue to seek these discoveries.”
Source: Pennsylvania State University.
