The reason why people walk more slowly as they age is explained by new study.

 As individuals age, their physical movements tend to naturally decelerate. Recent studies indicate that older adults may experience slower movements due to the higher energy expenditure compared to younger adults. This discovery has the potential to contribute to the development of novel diagnostic instruments for conditions like Parkinson's disease and multiple sclerosis. It is widely acknowledged that as we grow older, our bodies naturally exhibit a decrease in movement speed. This decline can be attributed to various factors including a reduced metabolic rate, loss of muscle mass, and decreased physical activity over time. The University of Colorado Boulder researchers have now revealed that older adults may move at a slower pace due to the increased energy cost associated with their movements, as compared to younger adults. This groundbreaking research, recently published in The Journal of Neuroscience, holds promise in advancing the field of disease diagnosis, particularly for Parkinson's disease and multiple sclerosis.                                             Older individuals decelerate their movements in order to conserve energy.                                                                                                                                   For this investigation, a total of 84 healthy individuals were enlisted by the researchers. The participants consisted of two groups: younger adults aged between 18 and 35, and older adults aged between 66 and 87. Throughout the research, the participants were tasked with reaching for a target displayed on a screen while utilizing a robotic arm held in their right hand. The robotic arm functioned in a manner similar to that of a computer mouse. Upon scrutinizing the patterns of how the participants executed their reaches, the researchers observed that older adults made adjustments to their movements at specific instances in order to conserve their more limited energy levels, in contrast to the younger adults. Alaa A. Ahmed, PhD, who serves as a professor in the Paul M. Rady Department of Mechanical Engineering within the College of Engineering and Applied Science at the University of Colorado Boulder, and is the senior author of this study, elucidated to Medical News Today, "As we age, our muscle cells may become less effective in converting energy into muscle force and subsequently movement. Additionally, our movement strategies become less efficient, potentially as a means to compensate for reduced strength. Consequently, we engage more muscles, which results in higher energy expenditure to accomplish the same tasks."                                                                                               Is the reward circuit in the brain still operational in elderly individuals?                                                               Ahmed and her team were interested in investigating how aging could impact the brain's "reward circuitry." This is because the body tends to produce less dopamine as we age.

Participants were once again instructed to use the robotic arm to control a cursor on a computer screen with the goal of reaching a specific target. Upon successfully hitting the target, they were rewarded with a "bing" sound. The researchers observed that both young and older adults were able to reach the targets more quickly when they anticipated hearing the "bing." However, scientists noted a difference in how this was achieved - younger adults simply moved their arms faster, while older adults improved their reaction times by initiating their reach with the robotic arm approximately 17 milliseconds earlier on average.                                                                                                                            “The fact that the older adults in our study still responded to reward by initiating their movements faster tells us that the reward circuitry is to some extent preserved with age, at least in our sample of older adults. However, there is evidence from other studies that reward sensitivity is reduced with increasing age. What the results do tell us is that while older adults were still similarly sensitive to reward as young adults, they were much more sensitive to effort costs than younger adults, so age seems to have a stronger effect on sensitivity to effort than sensitivity to reward.”

— Alaa A. Ahmed, PhD, senior study author