The years that pass by have inevitable effects on our body. There skin becomes less elastic and firm, the hair turns white, eyesight diminishes and can give rise to problems such as a cataract or glaucoma… Our whole organism evolves over time, and our mobility also takes a hit. And for good reason, the older we get, the more slowly and difficult we move, whether to go get a baguette at the bakery or to get up from bed The morning. American scientists were interested in this phenomenon and sought to know why does the body take longer to make its movements over the years. Their study was published in the journal JNeurosci.
A speed test to measure body speed
With this research, scientists from the University of Colorado at Boulder wanted to understand the reasons why people aged over 65 are no longer as quick as before in their movements. To carry out their study, the researchers analyzed people aged 18 to 35 on the one hand, and subjects aged 66 to 87 on the other. Everyone had to accomplish the same task: grab a robotic arm and hit a target on a screen thanks to the movement of a cursor, in the same vein as a video game. As soon as it was hit, the target made a ringing sound. If they succeeded, the candidates received a reward, intended to positively stimulate their brain.
Then, the scientific team analyzed the movement patterns of each participant. According to his observations, older people seemed to modify their movements in certain circumstances, in order tosave their more limited energy reserves.
Rising energy costs as we get older
All participants reached their targets faster when they heard the sound of a reward than without the sound. Nonetheless, the two groups achieved the goal differently, so the younger groups generally moved their arms faster toward the reward. On the other hand, for their part, older adults improved their reaction times by starting to move their arm sooner. Secondly, the scientists complicated the test for the youngest, who had to carry out the exercise with a weight of 3.5 kilos on the robotic arm. By adding additional weight to them, the differences between the two groups disappeared. The younger group stopped moving their arms faster and began to improve their reaction times.
Clearly, according to the researchers, whether young or old, adults did not seem to have difficulty perceiving rewards, but their brain slows down movements in tiring circumstances. Thus, older people have need more energy to perform their movements than the youngest.
How the brain saves energy
“The brain appears to be able to detect very small changes in the amount of energy used by the body andadjust our movements accordingly“, explains Robert Courter, co-lead author of the study and doctor in integrative physiology. And continues: “Even when moving around with a few extra kilos, reacting quickly has become the least expensive option in terms of energy to reach the reward, so the young adults imitated the older ones and did exactly the same thing.“
According to scientists, their “results suggest that the cost of effort to achieve a goal appears to determine what slows movement in older adults“, adds Alaa Ahmed, co-author and professor of biomedical engineering and robotics. According to the specialist, these results could one day provide new tools for diagnose a range of illnessesincluding Parkinson’s disease, multiple sclerosis as well as depression and schizophrenia.
Sources :
- Slowing of Movements in Healthy Aging as a Rational Economic Response to an Elevated Effort Landscape – JNeurosci
- Why do we move slower the older we get? New study delivers answers – University of Colorado Boulder
