New study explains why people move slower as they age

Our bodies naturally slow down as we age. Possible explanations include a slower metabolism, loss of muscle mass, and decreased physical activity over time.

Now, researchers at the University of Colorado Boulder say that older people may move more slowly in part because it requires more energy for them than for younger people. Scientists believe this new research, published in The Journal of Neuroscience, could help develop new diagnostic tools for diseases such as Parkinson's disease and multiple sclerosis.

Older people slow down to save energy

In this study, researchers recruited 84 healthy participants, including young adults ages 18 to 35 and older adults ages 66 to 87.

During the study, participants were asked to use a robotic hand to touch a target on a screen. By analyzing how participants performed these actions, the scientists found that older adults modified their movements at certain points to save more energy than younger adults.

“As we age, our muscle cells may become less efficient at converting energy into muscle strength and movement,” explained Professor Alla Ahmed, senior author of the study. “We also become less efficient in our movement strategies, perhaps to compensate for decreased strength. We use more muscles, which requires more energy to perform the same tasks.”

Does the reward circuitry work in the brain in older people?

Ahmed and her team also wanted to find out how aging affects the brain's "reward circuitry," as the body produces less dopamine as we age.

Participants again used the robot to control a cursor on the screen, aiming for a specific goal. If they hit the target, they received an audio reward.

Scientists found that both young and old people reached goals faster when they knew they would hear a reward sound. However, they did it differently: the younger people simply moved their arms faster, while the older people improved their reaction times by starting the movement 17 milliseconds earlier.

“The fact that older adults in our study still responded to reward tells us that the reward circuitry persists with age, at least in our sample of older adults,” Ahmed said. “However, there is evidence from other studies that sensitivity to reward decreases with age. Our results show that older adults were just as sensitive to reward as younger adults, but much more sensitive to effort costs."

Potential for new diagnostics for Parkinson's disease and MS

The researchers believe their findings could help develop new diagnostic tools for movement disorders.

“Slowing down your movements as you age can have a significant impact on your quality of life,” Ahmed explained. “This can limit not only physical but also social activities. It is important to understand the underlying causes and identify potential interventions that can help slow or reverse the decline."

Ahmed emphasized that a slowdown in movements is observed not only with age, but also with a number of neurological disorders. Understanding the reasons for this could help identify better interventions, and movement tracking could become a valuable biomarker of neurological health.

More research is needed on the aging brain and movement

After reviewing the study, Cliford Segil, a neurologist at Providence Saint John Health Center in Santa Monica, California, noted the importance of encouraging physical activity in older age, even if it requires more energy.

"My rule when treating older patients as a neurologist is: 'If you don't use it, you'll lose it!'" Segil said. “I agree that encouraging older patients to move has many health benefits.”

Ryan Glatt, senior brain health coach and director of the FitBrain program at the Pacific Rim Neuroscience Institute in Santa Monica, also noted the importance of further research linking observed behavior to neurophysiological evidence.