Regular physical exercise provides many powerful short-term benefits ranging from improved stamina to greater muscle strength to weight management. In addition, prolonged regular physical exercise has been shown to be protective (and restorative) with regard to many chronic health conditions including heart disease, stroke, lung disease, cancer and diabetes to name a few.
But did you know that exercise also helps protect our brains against cognitive and physical decline as we age? So concludes a new research study published last month online ahead of print in the journal Behavioral Brain Research, which demonstrated that physically active seniors exhibited brain activity more closely related to young adults than sedentary seniors. 
This study’s results echo previous research findings examining the benefits of exercise and brain function as the study authors noted in the introduction of their article:
“Exercise has been associated with increases in overall brain volume, preserved gray matter density, and may contribute to increased density in brain white matter. Recent work has even indicated that the beneficial effect of exercise on the mass and integrity of neural substrates can be shown in healthy preadolescent participants. Findings from studies employing cognitive tasks during functional magnetic resonance imaging (fMRI) have revealed differences in patterns of cortical activity in older adults as a function of physical fitness. That is, older adults with higher levels of cardiovascular fitness evidence better performance and patterns of recruitment in the frontal lobes more similar to young adults than sedentary age cohorts during attentionally demanding executive function tasks. Recent evidence has shown that patterns of motor-related neural activity in older adults may also be altered by regular engagement in physical exercise.”
To better understand the connection between physical exercise and brain function, it is useful to take a step back and describe what happens to the brain as we age. First, the two main types of tissue that dominate our brains are “grey matter” and “white matter.” Grey matter is essentially what we think of as the cells that receive, store and respond to input that occurs inside and outside of our bodies. In this way, grey matter drives our thoughts and actions. White matter cells, by contrast, form the connections between grey matter and our central nervous system (CNS). They are the messengers that deliver information and commands between the rest of our bodies and the grey matter in our brains.
As we age, we tend to lose both grey matter and white matter. Over time, as the losses of these tissues mount, the brain begins to behave differently in response to stimuli. For example, you may recall that the left side of our brain controls the physical actions of the right side of our bodies and vice versa. So when we want to move our right hands, the grey matter in the left side of the brain that controls right side body motor function (motor cortex) sends signals via white matter and the CNS to instruct our hand muscles to move.
Normally, when the left side of your brain sends a signal to the right hand to move, the right side of your brain remains inactive (a state referred to by neuroscientists as an “ipsilateral silent period,” meaning that the opposite side of your brain’s motor cortex doesn’t react to physical actions dictated by the side of the brain originating the action). But as we age and start to lose both grey and white matter, for reasons scientists don’t fully understand, more and more ipsilateral motor activity begins to occur (meaning both sides of the brain start to react to actions on one side of the body).
When neuroresearchers examine elderly people with severely degraded physical and cognitive function they find a significant amount of this cross-talk happening in the brain. By contrast, when examining young, healthy adults, researchers find very little of this cross-talk and, therefore, they speculate that increasing levels of ipsilateral brain activity must be associated with aging and the loss of grey and white matter.
But interestingly, it appears that elderly people who engage in regular physical exercise experience far less of this brain cross-talk compared to sedentary seniors. In fact, on a number of measures, very active seniors seem to have brain response patterns more closely akin to young adults than their sedentary counterparts as was evident in the research study discussed here.
In that study, 36 people were enrolled (12 active elderly, 12 sedentary elderly and 12 young adults). The average age of the two elderly groups was approximately 70, while the average age of the young adult group was 24. The active elderly group was comprised of individuals who were currently engaged in an aerobic exercise program three times each week for at least 30 minutes a session and who had been in such a program for at least five consecutive years. Sedentary seniors in the study were categorized as such if they acknowledged engaging in aerobic exercise for less than 45 minutes per week. The young adult group was not segregated based on physical activity level.
The researchers put each group through baseline physical tests to assess their relative level of physical condition including tests to judge their aerobic exercise capacity, reaction time and hand strength. Not surprisingly, the young adult group performed the best on all three tests with the active elderly group registering greater capacity on all tests in relation to the elderly sedentary group.
To assess how much brain function differences were at play in these results the researchers conducted a diagnostic evaluation known as the “finger tapping test.” In this test, subjects rest their right palm on a computer keyboard and tap on a designated key with their right index finger for 60 seconds while doing nothing else (isolating both the physical and brain activity as much as possible). While tapping, the subjects were connected to two different medical devices that evaluate brain activity — functional magnetic resonance imaging device (fMRI) and trans magnetic stimulation (TMS) device. These devices detect patterns of blood flow and electrical/magnetic currents in targeted areas of the brain.
The researchers pointed the devices to detect changes in activity in the left and right sides of the participants’ motor cortex where hand-related commands are known to take place (approximately two inches above and slightly forward of the top of your ears). These sensors were used to evaluate if there were differences in ipsilateral brain activity between the groups undergoing the finger tapping test. From the TMS device readings, it was clear that the young group had the least amount of ipsilateral brain activity as expressed by the duration of the “silent period” between cross-talk events between the two sides of the motor cortex. In fact, the cross-talk silent period in young adults was 90% longer than sedentary seniors while only 35% longer than the active elderly group. Granted, we’re talking milliseconds here, but the differences were significant nonetheless. The results from most of the other specific data analysis from these two devices revealed similar findings.
While offering no definitive cause/effect reasons for their findings, the study authors concluded, “These results indicate that the long-term maintenance of high levels of physical activity could delay or reverse losses of inter-hemispheric inhibition associated with chronological aging.
While previous work has indicated that aerobic exercise could serve to mitigate age-related cognitive decline, less is known of the potential effect of physical fitness on the human motor system. We found that older adults who engage in regular bouts of volitional exercise exhibit greater inter-hemispheric inhibition in ipsilateral M1, in contrast to their sedentary counterparts.”
In other words, a long-term commitment to aerobic exercise seems to dilute the impact of aging on the brain’s motor skill functions. Combined with previous research that has shown a higher degree of cognitive function among physically active seniors, it would seem that a regular program of exercise might just be the most effective natural remedy one can find to preserve youth of mind, body and spirit.
 McGregor KM, et al. Physical Activity and Neural Correlates of Aging: A Combined TMS/fMRI Study. Behav Brain Res. 2011 March 24 [Epub ahead of print].