New Study Reveals Why Older Adults Move Slower and How They Respond to Rewards

It’s widely known that our bodies naturally slow down as we age. Factors contributing to this include a slower metabolism, loss of muscle mass, and decreased activity levels. According to Medical News Today

Now, researchers from the University of Colorado Boulder suggest that older adults may move slower partly because it requires more energy for them than it does for younger adults.

This new research, published in The Journal of Neuroscience, could potentially lead to new diagnostic tools for diseases such as Parkinson’s and multiple sclerosis.

“The fact that the older adults in our study still responded to reward by initiating their movements faster tells us that the reward circuitry is to some extent preserved with age, at least in our sample of older adults. However, there is evidence from other studies that reward sensitivity is reduced with increasing age. What the results do tell us is that while older adults were still similarly sensitive to reward as young adults, they were much more sensitive to effort costs than younger adults, so age seems to have a stronger effect on sensitivity to effort than sensitivity to reward.”

— Alaa A. Ahmed, PhD, senior study author

Older Adults Conserve Energy by Moving Slower

For the study, researchers recruited 84 healthy participants, comprising younger adults aged 18 to 35 and older adults aged 66 to 87. Participants were asked to use a robotic arm, similar to a computer mouse, to reach for a target on a screen.

By analyzing the movement patterns, scientists found that older adults adjusted their movements at specific times to conserve energy, unlike their younger counterparts. Reported by Colorado

“With age, our muscle cells may become less efficient at converting energy into muscle force and movement,” explained Alaa A. Ahmed, PhD, professor in the Paul M. Rady Department of Mechanical Engineering at the University of Colorado Boulder and the study’s senior author.

“We also become less efficient in our movement strategies, possibly to compensate for lower strength. So we recruit more muscles, which costs more energy, to perform the same tasks.”

“A better understanding of why movement is slowing in these various disorders can provide more information about the underlying causes, which can help identify better interventions. An advantage of using movement as a biomarker is that it is an easily accessible and noninvasive measure. So tracking someone’s movements either in the lab or throughout their daily activities may at some point provide a valuable biomarker of neurological health.”

—Alaa A. Ahmed, PhD, senior study author

Impact on the Brain’s Reward Circuit

Ahmed and her team also investigated how aging might affect the brain’s reward circuitry, noting that dopamine production decreases with age.

Participants again used the robotic arm to operate a cursor on a computer screen, aiming for a target. When they hit the target, they were rewarded with a “bing” sound.

Researchers found that both young and older adults reached the targets faster when they anticipated the reward. However, they did so differently:

younger adults simply moved their arms faster, while older adults improved their reaction times, starting their reach approximately 17 milliseconds sooner on average.

This study highlights how older adults modify their movements to conserve energy and how their response to rewards remains effective, albeit through different mechanisms compared to younger adults.

“To strengthen the findings, future research should aim to directly link the behavioral data with neurophysiological evidence. Employing a broader methodological approach, including longitudinal studies and diverse population samples, could help delineate how universally these proposed mechanisms apply across different aging trajectories. Additionally, replicating the study with a larger sample size and varying conditions would be crucial to verify the robustness and generalizability of the initial result.”