As disappointing as it may be, as we reach middle and older age, we often notice that even the simplest movements become increasingly difficult. We frequently feel sluggish and find ourselves calculating our energy levels before performing basic actions, like moving a stool or climbing a few extra stairs.
A study conducted by the University of Colorado Boulder, led by biomedical engineering professor Alaa Ahmed, explored the nature of these processes. According to the researcher, her team aimed to understand their neural basis.
The scientists divided participants into two groups. The first group consisted of individuals aged 18 to 35, while the second group included those aged 66 to 87. The team asked all volunteers to complete a simple task: reach for a specific target on a screen. During this task, the researchers measured the reaction time and the amount of energy expended, or metabolic cost, for each response.
The researchers found that older participants required more energy than younger ones to perform the same action.
When participants were promised a reward for their efforts, both groups reached the target faster—about 5 percent quicker than when the trials were conducted without a reward. However, each age group achieved the target in different ways, as reported by the Daily Mail.
While younger participants actively and quickly moved their hands toward the reward, older participants primarily improved their performance by shortening their reaction time. When the team added weight to the younger volunteers’ arms, these differences disappeared. In other words, the younger group stopped moving their hands faster and instead began to enhance their reaction time.
Why Do Scientists Need This Knowledge?
The findings of the study were published in the journal JNeurosci. It is one of the first studies to experimentally identify the reasons why older adults (specifically those over 65) move more slowly than younger individuals.
During this research, scientists quantitatively assessed the metabolic energy cost required to reach a specific target for the first time. According to the results, the effort expended by older adults is energetically more expensive.
Robert Kurter, a co-author of the study, noted, “It seems that the brain can detect very small changes in how much energy the body is using and adjust our movements accordingly. Even when moving with a few extra pounds, a quicker reaction became a more energy-efficient option for obtaining the reward, leading younger individuals to mimic older adults and do the same.”
These results could provide doctors with new tools for diagnosing a range of age-related diseases, explained Professor Alaa Ahmed.