Why we may find ourselves slowing down as we as we age

Despite our best efforts to defy the march of time, the inevitable effects of ageing eventually catch up with all of us, gradually revealing themselves as we find ourselves slowing down with each passing year.

In a quest to understand this gradual decline, researchers at the University of Colorado Boulder embarked on a journey into the mechanics of movement, their latest study offering some insight into why we might not be as quick on our feet as we age. Led by Alaa Ahmed, a professor in the Paul M. Rady Department of Mechanical Engineering, the research team set out to explore the factors influencing changes in agility among older adults. What they discovered adds a new dimension to our understanding of ageing and mobility.

“Why we move the way we do, from eye movements to reaching, walking and talking, is a window into aging and Parkinson’s,” Ahmed said.

As part of the study, subjects aged 18 to 35 and 66 to 87 were tasked with reaching for targets on a screen, akin to playing a video game. What emerged from this seemingly simple task was a complex interplay of energy expenditure and movement strategies.

Researchers uncovered that older adults may move slower due, in part, to the increased energy costs associated with their movements.

Reflecting on the study’s findings, Erik Summerside, a co-lead author of the study said, “All of us, whether young or old, are inherently driven to get the most reward out of our environment while minimising the amount of effort to do so.”

Ahmed pointed out that while declines in muscle efficiency and dopamine production with age are well-documented, their study offers a nuanced understanding of how these factors shape movement patterns. Their analysis revealed that older adults adjusted their movements to conserve energy, particularly when anticipating rewards.

Of particular interest was the difference in strategies between younger and older adults when faced with rewards. While younger adults opted for increased movement speed, older adults demonstrated improved reaction times, initiating their reaches sooner.

Robert Courter, a co-lead author of the study who earned his doctorate in integrative physiology from CU Boulder in 2023, marvelled at the brain’s adaptability.

“The brain seems to be able to detect very small changes in how much energy the body is using and adjusts our movements accordingly,” Courter said.

Ahmed added, “Putting it all together, our results suggest that the effort costs of reaching seem to be determining what’s slowing the movement of older adults.”

The implications of this research extend beyond understanding the mechanics of ageing.

Ahmed envisions potential applications in diagnosing and treating a range of illnesses, from Parkinson’s disease to depression.

By unraveling the mysteries of movement, researchers may unlock new avenues for promoting healthy ageing and enhancing quality of life.