Training the Brain: CEU Corner The Neuroscience of Aerobic Exercise
To motivate clients to adhere to fitness plans, use your brainpower—and theirs: Learn here about cutting-edge neuroscience research that demonstrates how exercise protects this vital organ across the lifespan.
For thousands of years, people have recognized the benefits that exercise confers on the body and the brain. The human body is unequivocally designed to move—and to move often. In fact, it’s estimated that our ancestors moved an average of 10–12 miles per day! Through recent scientific inquiry, we have begun to understand precisely how exercise makes us healthier. Years of evidence demonstrate how exercise lowers our risk for obesity, cardiovascular disease, cancer, diabetes—and the list goes on (Fletcher et al. 1996). However, it is only recently, with the advent of innovative neuroimaging technologies, that we have been able to investigate the effects of exercise on what is a fascinating and powerful device: the human brain.
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As humans, we spend much of our time thinking and feeling. It’s what allows us to successfully navigate what would otherwise be an impossibly complex world. Each day, we are required to plan, to make decisions, to remember, to process information and to pay attention. Just as these cognitive skills let us move through the world, so, too, do our emotions. Feelings of fear, sadness, anxiety, anger and happiness are all powerful signals we use to guide our lives. Exciting research shows that aerobic exercise—such as walking, jogging, biking, swimming and using an elliptical trainer—can have profound beneficial effects on both cognitive and emotional processes (Smith et al. 2010). The purpose of this article is to discuss.
>> how aerobic exercise benefits cognitive health,
>> how aerobic exercise benefits emotional health,
>> how specific parts of our neuroanatomy benefit from aerobic exercise, and
>> how aerobic exercise works at the neural level to provide these benefits.
Effects of Exercise on Cognitive Abilities
Perhaps the strongest evidence of the mind-body connection is in data that shows how moving our body can improve our ability to think. Copious amounts of evidence show that if we want to flex our mental muscle, we must engage in physical exercise. Exercise is such powerful brain medicine that even a single “dose” of aerobic activity (acute exercise) has important effects on cognitive abilities. One of the most consistent effects of exercise is improved executive function (Guiney et al. 2015).
Executive function is a term used to describe some of our most sophisticated thinking abilities, including our ability to plan, to develop strategies and to contemplate abstract concepts. Often, when clients feel overstressed and overscheduled, they think cutting the time they spend at the gym is a useful solution. However, neuroscience research suggests just the opposite. Stress, in fact, clouds our thinking abilities, so it is precisely in times of high stress that clients need physical activity the most. On days when your clients insist they’re “too busy” to make it to the gym, remind them that compelling evidence from the field of neuroscience suggests that even a brief run on the treadmill may yield helpful returns on their ability to think on their feet, develop innovative solutions to complex problems and manage their time wisely.
While the effects of acute exercise can be a powerful motivator, the most compelling reasons to exercise come from studies that show the protective benefits it bestows on cognitive function across the lifespan. In one of the most impressive longitudinal studies on this subject, researchers followed more than 2,700 young people (aged 18–25) for 25 years. They found that the study subjects who remained the most physically fit exhibited the strongest neurocognitive abilities when assessed after 25 years. In particular, people who maintained their cardiovascular fitness performed better on complex thinking tasks (Zhu et al. 2014). Therefore, it’s important to share with clients that early investments in exercise appear to provide protection in later years.
Also consider sharing with clients the scientific data that underscore the importance of beginning a regular exercise routine. While beginning to exercise in young adulthood is optimal, there is also good news for older clients who were not very active in their younger years: Research tells us it’s never too late to reap the cognitive rewards of exercise. Several studies have indicated that beginning to exercise even after midlife may contribute to a reduction in dementia risk, especially in people diagnosed as overweight or obese in midlife. These results suggest that exercise may help prevent dementia and improve quality of life well into a person’s senior years (Hogervorst et al. 2012).
Effects of Exercise on Emotional Health
In addition to enhancing your clients’ cognitive skills, exercise can benefit their mental health (Byrne & Byrne 1993). As a fitness professional, you won’t be surprised by the mood-boosting and mood-stabilizing effects of exercise. However, hearing an explanation of the science behind why exercise affects mood may improve buy-in among clients and increase their adherence to fitness training plans.
Consider teaching your clients what stress does to the body. Stress results in the release of a variety of chemicals, most notably catecholamines and corticosteroids (Hashiguchi et al. 1997). This “chemical cascade” prepares the body to do what the body thinks it must do: fight or flee. Today, however, when most of our stressors don’t actually require us to flee from a lion or fight off an attacker, we are often left “all revved up with nowhere to go.” Alas, it is this discrepancy—between being highly primed for action and having no physical outlet for it—that can leave people feeling irritable, on edge and jumpy. This is also why, after a rough day at the office or a particularly grueling commute in rush-hour traffic, a quick stop at the gym can have a positive impact on mood. Just as the energy generated by the stress response system can be used for fighting or fleeing, it can be directed at powering a run on the beach, a spin on the bike or a swim in the pool. In fact, channeling the energy of stress into exercise leads to the consumption of those chemicals, which ultimately relieves feelings of stress and improves mood by returning the body to its homeostatic state.
While it is useful for clients to know that one of the best quick fixes for a “meh” day is to hit the gym, it is the effects of regular aerobic exercise on emotional health that are the most compelling. As humans, we are elegantly designed to deal with acute (short-term, isolated) stressors; it is the chronic nature of stress that can have devastating and lasting impacts on our emotional lives. We live in an era when people are beset with suffering. Depression, anxiety disorders, posttraumatic stress disorder and substance abuse disorder are all common forms of psychopathology that can be related to chronic stress overload.
Several studies have indicated that exercise can be a useful therapeutic intervention. For example, researchers at Duke University assigned sedentary adults with a diagnosis of depression to one of four protocols: supervised exercise, home-based exercise, antidepressant therapy or a placebo pill. After 4 months of treatment, people in the exercise groups and the antidepressant group had higher rates of remission than did people taking the placebo. Results indicated that exercise was generally comparable to antidepressants for patients with major depressive disorder. More importantly, patients were followed, and those who, at the follow-up, reported adherence to regular exercise also had lower depression scores than their less-active counterparts. This study indicates that exercise is useful not only for treating depression but also for preventing relapse (Blumenthal et al. 2007).
Effects of Exercise on Neuroanatomy
Most clients understand what exercise can do for their core, their mood and even their heart. But they have far less knowledge about the effects of exercise on their neuroanatomy. Just as exercise can change your glutes and your biceps, so, too, can it change your brain.
NEUROPLASTICITY AND NEUROGENESIS
The brain is our most precious resource. It’s precious because, without it, all of the uniquely human things we do—talk, contemplate, love, empathize and reason—would be impossible. It is also precious because of how finite it is. While cells in other parts of the body (skin, blood, other organs) are constantly being replaced across our lifespan, cells in the brain are not nearly as renewable. In fact, it was long assumed that our entire supply of brain cells was present at birth, and that once those cells had died, they could never be replaced. But science often heralds stunning information that fundamentally changes the way we understand our biology.
These days, two of the hottest topics in neuroscience are neuroplasticity and neurogenesis. Neuroplasticity is a broad term that refers to the brain’s ability to change in response to stimuli (Fuchs & Flügge 2014). So, while brain cells are less renewable than other types of cells, we now know that the adult brain is far from being “fixed.” The list of factors that can affect neuroplasticity is long, and it includes aging, stress, injury, learning, environmental stimulation and, of course, exercise. For example, when your clients master a new skill in the gym, it’s because of the brain’s ability to change in response to stimuli; in other words, your client’s brain is neuroplastic!
We also now know that the adult human brain is, indeed, capable of neurogenesis, or the creation of new neurons. Of all the benefits that exercise confers, its relationship with neurogenesis is arguably the most exciting.
Interestingly, neurogenesis is not believed to occur broadly throughout the brain; rather, it is thought to take place in three discrete brain regions: the hippocampus, the cerebellum and the olfactory bulb (Ventura & Goldman 2007). As this is perhaps the least understood aspect of the neuroprotective benefits of exercise, let’s take a closer look at the research on two critical neuroanatomical regions that are particularly relevant to exercise: the hippocampus and the cerebellum.
THE HIPPOCAMPUS: KEEPER OF HISTORY
One of the core neuroanatomical structures of the brain affected by exercise is the hippocampus. Located within the temporal lobe—one of four lobes in the brain—the hippocampus is a key structure in the limbic system. The limbic system is sometimes referred to as the “reptilian” part of our brain because it developed earlier in our evolution (approximately 150 million years ago). But don’t assume that because it’s primitive, it’s not essential. So much of what it means to be human depends on the hippocampus. When you’re talking to your clients about the role of the hippocampus, a simple but useful heuristic can be to encourage them to think of the hippocampus as their own personal historian. This region of the brain plays a vital role in the creation and storage of memories. For example, without the hippocampus, it would be impossible for you to do any of these:
Remember your story. It’s the reason you can recall your childhood, what sparked your interest in fitness or anything that’s personally relevant to you (Viard et al. 2007).
Recall facts. It’s the reason you can remember the colors of the rainbow, the best method for doing deadlifts or why it’s important to assess body mass index (Manns, Hopkins & Squire 2003).
Navigate in space. It’s the reason you’re able to remember the way to the gym and recall where your locker is once you arrive (Broadbent, Squire & Clark 2004).
Understand chronological ordering of events. It’s the reason you can remember that you must stop at the bank before you go to Pilates—or that you became a fitness professional after you completed your AFAA or NASM certification (Eichenbaum, Yonelinas & Ranganath 2007; Howland et al. 2008; Kesner 2013).
Evidence shows that aerobic exercise increases the size and function of the hippocampus, which may result in improved memory, a lower risk of depression, better stress management and a reduced risk of dementia. In fact, the hippocampus is one of the primary neuroanatomical structures attacked in neurodegenerative diseases like Alzheimer’s (see the sidebar “Alzheimer’s Disease and Aerobic Exercise”).
THE CEREBELLUM: MASTER OF MOVEMENT
Just as clients can think of their hippocampus as their historian, they can think of their cerebellum as their master of movement. The term cerebellum means “little brain.” It is located at the very back of the brain. While recent estimates suggest there are approximately 25 billion neurons in the cerebral cortex (Pelvig et al. 2008), it is thought that there are 101 billion neurons in the cerebellum (Andersen et al. 1992)!
Like the hippocampus, the cerebellum is one of the very few sites where adult neurogenesis is thought to occur. Specifically, aerobic exercise is thought to increase the number of synapses per Purkinje cell, the main type of nerve cell in this part of the brain (Black et al. 1990). Because Purkinje cells play an enormous role in movement and are central to motor learning, exercise-induced cerebellar changes offer clients a range of powerful benefits for their workouts and their day-to-day functioning. Based on broad research into the role of the cerebellum, you can teach your clients that, thanks to the cerebellum, they are able to do the following:
Maintain balance and posture. Because of the cerebellum, your clients can make important postural adjustments, successfully balance on a BOSU® Balance Trainer or assume the appropriate stance for a weightlifting exercise.
Coordinate voluntary movements. Because of the cerebellum, your clients can do burpees, participate in Zumba® classes or execute any other series of coordinated movements. The cerebellum coordinates the timing and force of different muscle groups to produce fluid movements.
Benefit from motor learning. Because of the cerebellum, your clients can perform a sequence of movements in a vinyasa yoga class, throw a baseball, or successfully execute a clean and jerk (Morton & Bastian 2004).
Effects of Exercise On Neurochemicals
We now know that exercise can be a powerful driver of neuroplasticity—and more specifically, neurogenesis—in areas like the hippocampus and cerebellum. But how does exercise make this possible? In other words, how does running on a treadmill translate to building a healthier brain? The answer, in part, has to do with molecules known as neurotrophic factors.
Neurotrophic factors are a class of biomolecules that support the growth, survival and development of neurons (Binder & Scharfman 2004; Hennigan, O’Callaghan & Kelly 2007). While there are several neurotrophic factors, the one that will be discussed here is brain-derived neurotrophic factor.
BDNF is found in the brain, as well as in other parts of the body. It’s hard to overstate the importance of BDNF to the human brain; it’s involved in everything from thinking to feeling to moving to behaving. In fact, BDNF is a major source of the cognitive and emotional benefits of exercise (Szuhany, Bugatti & Otto 2015).
Presently, there is no exogenous way to deliver BDNF directly to the brain—in other words, there is no pill or supplement or medical technique that can increase BDNF in the brain. However, the great news for fitness pros (and their clients) is that aerobic exercise has been shown to stimulate production of BDNF (Seifert et al. 2010; Coelho et al. 2014).
Connecting the Dots for Clients
Although neuroscience is still in its infancy, exciting evidence is beginning to suggest just how powerful exercise can be for brain health. Based on recent research, here are some findings worth sharing with clients to inspire greater adherence to your training plans:
Regular exercise is best for the brain. In a meta-analysis by Szuhany, Bugatti & Otto (2015) the bulk of evidence pointed to consistent exercise being optimal.
But the occasional stop at the gym counts, too. Although the bulk of evidence points to regular exercise as delivering the best benefits, several studies have shown that even acute exercise may stimulate production of BDNF (Cho et al. 2012; Nofuji et al. 2012).
Tough workouts aren’t just good for the body; they’re good for the brain. Research suggests a linear relationship between exercise and BDNF levels: As exercise intensity increases, so do BDNF levels (Knaepen et al. 2010).
Exercise boosts BDNF, and BDNF boosts memory and mood. Plenty of research shows that exercise-induced increases in BDNF improve thinking skills (Leckie et al. 2014). Remarkably, exercise-induced BDNF activity appears to make it easier to remember things in your life (Intlekofer et al. 2013), and it has been hypothesized that BDNF places your brain in a “plastic” state, meaning the brain can learn things more easily (Cotman, Berchtold & Christie 2007).
It’s because of the boost in BDNF that you feel better after exercising. Research suggests that exercise-related improvements in mood, such as decreased feelings of anxiety and depression, are mediated by BDNF (Hopkins et al. 2012). In fact, it is thought that part of the reason antidepressant medications are effective is that they indirectly increase BDNF (Siuciak et al. 1997). Thus, exercise may offer a nonpharmacological way to protect your brain.
HIIT yields bigger BDNF gains. One study had people engage in either a continuous exercise condition (where they had to maintain a 70% maximal work rate for 20 minutes) or a high-intensity interval training protocol (where they alternated between 1-minute periods of rest and 1-minute exercise intervals at a 90% maximal work rate for a total of 20 minutes). While both protocols were effective in increasing BDNF levels, the HIIT workout yielded higher BDNF levels than the continuous exercise condition (Saucedo Marquez et al. 2015).
Work Hard, Think Smarter, Feel Better
The brain is powerful and mysterious. The pointers in this article can help you explain to your clients how exercise affects them at a neurological level. For a wide range of activities, from working to driving to having conversations with others, the importance of a healthy brain cannot be overstated. By sharing the latest developments from neuroscience, you can empower your clients to understand how working out does more than build a stronger body; it builds a stronger brain as well (Erickson et al. 2011).
What About Weightlifting?
As fitness pros know, all forms of exercise are not created equal. Different types of exercise have different effects on your clients’ health, so shouldn’t the effects on the brain be different, too? To date, the majority of studies on brain health and fitness have examined aerobic exercise. However, researchers are increasingly paying attention to other forms of exercise as well.
For example, one study examined the effects of 12 months of once- or twice-weekly resistance training on cognitive abilities in aging women. The authors reasoned that there might be plausible biological mechanisms by which resistance training improves brain function independent of aerobic exercise. Results indicated that once- or twice-weekly resistance training improved important cognitive abilities, such as attention and executive function (Liu-Ambrose et al. 2010).
Another study examined various forms of exercise on neurogenesis in rats. Although rats are obviously not human beings, there is much similarity between the brains of these two mammals. The researchers created four conditions: (1) distance running, (2) high-intensity interval training, (3) weightlifting and (4) no activity. Results indicated that distance running had the most beneficial impact on hippocampal neurogenesis. Interestingly, the rats that weightlifted demonstrated no changes in their hippocampus. In other words, in terms of this one region, the brains of these rats looked just like the brains of rats that never exercised at all (Nokia et al. 2016).
Studies like these raise numerous questions about how exercise can affect the brain. It is very important to underscore that this is a nascent literature; our understanding of how exercise affects the brain is in its very early stages. While we can confidently say that aerobic exercise is neuroprotective, much more work is needed to determine not only which other types of exercise are good for the brain but also which exercise conditions (duration, intensity and age of participant) offer the greatest neurological benefit.
Alzheimer’s Disease and Aerobic Exercise
Alzheimer’s disease is a progressive neurodegenerative disorder currently affecting more than 5 million Americans. Since 2000, deaths from heart disease have decreased by 14%, whereas deaths from AD have increased by 89%. While AD can encompass a broad array of symptoms, its hallmark feature is memory loss (APA 2013).
WHY DOES AD RESULT IN MEMORY LOSS?
The pathology of AD is related to the accumulation of two proteins, one called tau and one called beta-amyloid (Hardy & Selkoe 2002). In normal amounts, tau acts to stabilize neurons. In AD, however, there is too much tau, and it creates tangles—quite literally—within brain cells.
Plaques, another feature of the disease, occur when there is an abnormal accumulation of a “sticky” protein called beta-amyloid, which likely prevents brain cells from communicating effectively with each other. The hippocampus (which is vital for memory) is particularly susceptible to plaques and tangles, and this is why memory impairment is a hallmark symptom of AD.
HOW CAN AEROBIC EXERCISE HELP WITH AD?
Exercise offers remarkable hope for this devastating disease. It increases the production of the neurochemical brain-derived neurotrophic factor, which is neuroprotective. In particular, BDNF has been demonstrated to facilitate neurogenesis (brain cell growth) in the hippocampus.
Aerobic exercise can help in two ways: (1) In people who do not have AD, it reduces the progression of the disease (Baker et al. 2010). (2) In others, it reduces the risk of developing the disease. In fact, a meta-analysis indicated that exercise reduced the risk of developing AD by 45% (Hamer & Chida 2009).
CEU Corner QUIZ: TRAINING THE BRAIN: The Neuroscience of Aerobic Exercise
Learning Objectives: After reading the article, you should be able to:
- Identify the parts of the brain that benefit from aerobic exercise.
- Summarize how aerobic exercise benefits cognitive ability and emotional well-being.
- Discuss the neurological changes related to aerobic exercise.
- Explain which exercise strategies have proven most beneficial to neurological health
To earn 2 AFAA/0.2 NASM CEUs, purchase the CEU quiz ($35) and successfully complete it online at www.afaa.com.
- The cerebellum is best described as the site in the brain that:
a. stores memories
b. coordinates movement
c. regulates homeostasis
d. assesses fear
- Aerobic exercise is thought to improve mood because it:
a. attenuates the effects of stress chemicals, such as catecholamines
b. increases hippocampus size and function
c. stimulates production of brain-derived neurotrophic factor (BDNF)
d. all of the above
- Research has shown that aerobic exercise increases production of:
- Your clients’ ability to remember information you have taught them about their health relies on:
a. the hippocampus
b. the cerebellum
c. the amygdala
- Current scientific literature examining the effects of various forms of exercise on brain health can best be described as:
a. promising but still in its early stages
b. conclusive and certain
c. inconclusive and full of null results
d. none of the above
- How can BDNF be increased?
a. by taking certain vitamins
b. by undergoing elective surgery
c. by exercising
d. A and C
- Which of the following is the most plausible explanation for why exercise is thought to improve motor performance?
a. It improves executive function.
b. It strengthens pyramidal cells in the hippocampus.
c. It attenuates the effects of catecholamines
d. It increases the number of synapses per Purkinje cell.
- BDNF is best described as:
a. an anti-aging compound
b. a region in the cerebellum
c. a molecule that promotes neuron health
d. a neurotransmitter responsible for coordinated motor activity
- Based on the article, Purkinje cells are important to your clients because these cells enable:
c. decision making
- Which brain structure is particularly susceptible to plaques and tangles as seen in Alzheimer’s disease:
a. the cerebellum
b. BDNF production
c. the hippocampus
d. the chemical cascade
- Based on the current literature, most evidence supports _____________ as the exercise of choice for neuroprotection
a. aerobic exercise
b. resistance training
c. tai chi
d. A and B
- High amounts of tau proteins are associated with:
a. neurogenesis in the hippocampus
b. the health of Purkinje cells
c. Alzheimer’s disease pathology
d. motor movement
- Neurogenesis refers to the:
a. birth of new neurons across the lifespan
b. birth of new neurons only in utero
c. ability of the brain to acquire new information
d. ability of the brain to improve
- Neuroplastic changes can occur in the brain after which of the following?
a. aerobic exercise
c. learning new information
d. all of the above
- The effects of exercise have been scientifically demonstrated to ameliorate symptoms of which of these mental health conditions?
a. substance use disorders
b. posttraumatic stress disorder
d. all of the above
To earn 2 AFAA/0.2 NASM CEUs, purchase the CEU quiz ($35) and successfully complete it online at www.afaa.com.