Why do we have more difficulty moving as we age? The answer lies, in part, in ours muscles: over time they weaken and this ends up affecting the ability to carry out even simple daily activities such as walking and standing up. But what is the reason why slow movements are added to muscle weakness? Is it a physical issue or does it (also) depend on mental abilities? Finding out is not trivial. “The reason we move the way we do, from eye movements to walking and talking, is a window into aging and diseases like Parkinson’s,” he says Alaa Ahmed, professor in the Paul M. Rady Department of Mechanical Engineering at CU Boulder. “We’re trying to understand the neural basis of it.”
Together with a team of researchers, Ahmed asked two groups of volunteers, aged 18 to 35 and 66 to 87, to complete a simple task: hit a target on a screen. The discovery was that the elderly modified theirs to achieve this movements in order to consume as little energy as possible. This suggests that as years go by, muscles work less efficiently, burning more calories to complete the same tasks than younger adults. But what happens on a mental level?
The experiment
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During the test, participants used a robotic arm to move a cursor to the target on the screen. If they succeeded, they received a small sound reward. The results revealed that both young and old people reached theobjective more quickly when they were certain they would receive the reward, but with different approaches. While the young people made quicker movements, the older people preferred to work on their (mental) reaction times. But when younger participants had weight added to the robotic arm, the differences disappeared, suggesting that the brain is able to adapt movements based on energy expenditure, regardless of age.
In short, according to the authors of the study, the energy required by physical effort is the key factor why movements during aging are slower. It’s more of a physical issue than a mental one. “Our findings suggest that the costs of physical effort to achieve the goal determine what slows down the movement of older adults,” Ahmed points out.
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Conclusions
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The researchers hope that the discovery could help doctors develop new treatments for diseases such as Parkinson’s diseasethe multiple sclerosis and others degenerative conditionsworking mainly on the body’s energy expenditure and the need for calories, even before on mental factors that count, but which in this case could have a secondary role.
