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Why Exercise Is Good for the Brain

September 30, 2019

Computerized brain training games and dietary supplements will make your brain healthier, and you will get smarter—according to companies selling those products. There are many products aimed at improving brain health and cognition, but research is inconclusive regarding the benefits of many of these products. So what has been shown to enhance brain functioning? 

Exercise may lead to better cardiovascular health, stronger bones and muscles, stronger connective tissue, general fitness, athleticism, treatment of type 2 diabetes, treatment of insulin resistance, prevention of osteoporosis, and improved appearance. Better brain functioning is another possible benefit of exercise. Extensive research indicates exercise may offer an array of benefits, including physiological, behavioral, and cognitive (van Praag 2009).

Some of the earliest research showing the effects of exercise on the brain came from neuroscience pioneer Marian Diamond and colleagues (1964). Diamond’s research focused on how the brain changes (neuroplasticity). It looked at rats raised in enriched environments. The study involved three groups of rats: those raised in enriched, standard, and impoverished environments. Enriched environments are those that provide various stimuli created to promote complex sensory experiences. The rats in the enriched environment were exposed to other rats (often involving lots of play among the rats and other interactions), various toys, objects, and running wheels. The rats had the opportunity to live an activity-filled life.

rat-experiment-in-a-cage.
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The rats in the standard environment were housed in a small cage with a few other rats but with no objects or toys. For the impoverished environment, one rat remained alone in a small cage with no objects or toys. Rats raised in the enriched environment developed thicker cerebral cortexes (outer layers of the cerebral hemispheres), more blood vessels, higher levels of important chemical messengers, and increased levels of growth factors. Later studies showed similar results, as well as additional benefits, such as growth of new neurons (a type of brain cell). 

As research continued to accumulate, neuroscientists began to wonder about the influence of the different stimuli in the enriched environment: Was it exposure to the toys leading to brain changes? Was it the interaction with other rats? Was it the running wheel that was most important? After systematic study, it was discovered that the majority of changes in the brain were due to exercise. When rats were only given access to a running wheel, most of the brain changes that occurred when rats were raised in the totally enriched environments occurred. Thus, brain changes occurred without all the social interactions and exposure to various objects and toys: exercise alone was enough to induce changes. Since those early studies, many studies have revealed exercise influences the brain at cellular, chemical, behavioral, and cognitive levels (Suzuki 2015). These studies have been conducted with humans and nonhuman animals.   

People who exercise on a regular basis are less likely to suffer from cognitive decline   associated with aging. One of the key mechanisms that contribute to these benefits is the growth of cells in an area of the brain involved with learning, spatial processing, and memory (hippocampus). In addition to the growth of new nerve cells, other factors involved with how exercise changes the brain include: changes in brain connections, increased density in the receiving area of the nerve cell, growth of new blood vessels, enhancement of chemical messengers, and growth factors.

The antidepressant effect of exercise has been shown to be just as potent as some medications. In one study, after four months of aerobic exercise, individuals with major depressive disorder demonstrated a significant therapeutic benefit (Babyak et al. 2000).  After ten months, those in the exercise group had significantly lower relapse rates than those in the medication group who received sertraline therapy.  

Exercise also benefits individuals with neurodegenerative disorders. Goodwin and colleagues (2008) conducted a study reviewing randomized controlled trials (RCTs) that involved exercise interventions for people suffering from Parkinson’s Disease (PD). The results indicated that exercise was beneficial with regards to physical functioning, health-related quality of life, strength, balance, and gait speed for people with PD. Modified noncontact boxing routines are growing in popularity among people with PD. Those participating in these types of workouts report a range of positive outcomes. There is a positive association between physical activity and brain volume. Exercise has a positive impact on brain volume; these increases are good news for people with dementia-related disorders, including Alzheimer’s. The weight of evidence indicates exercise increases fitness, physical functioning, cognitive skills, and positive behavior in people with dementia and related cognitive impairments (Heyn and Abreu 2004). 

Davis and colleagues (2011) conducted a study on sedentary seven- to eleven-year-olds with the intention of investigating the effects exercise had on complex thinking. The participants were randomly assigned to an exercise program (twenty or forty minutes per day), or a control condition. Blinded, standardized psychological evaluations were used to measure complex thinking and academic achievement. Brain activity was measured using a form of brain imaging. A specific improvement on complex thinking and brain activation was seen in the kids from the exercise group. Various studies, across age categories, show exercise improves high order cognitive performance measures such as attention, processing speed, decision making, and memory.  

Research shows exercise is beneficial for people suffering from traumatic brain injury. People with such injuries were tested before and after an eight-week exercise program that consisted of performing aerobic activity twice per week (Lee et al. 2014). The exercise group was compared with a control group (no exercise). A significant improvement in mood and quality-of-life measures was found for those who were in the exercise group.    

Research indicates that anaerobic exercise can also be beneficial to the brain. In one study, learning performance was tested directly after a single bout of high impact anaerobic sprints (two three-minute sprints separated by a two-minute rest), low impact aerobic running (forty minutes), or a period of rest, in twenty-seven healthy participants (fifteen minutes) (Winter et al. 2007).  The primary findings showed that the high impact group improved significantly on measures of learning performance, while the other groups did not demonstrate increased learning.  

Michael Merzenich (a pioneer in brain plasticity research) recommends that a variety of exercises should be performed in an effort to improve brain function (Merzenich 2013).  Different movements activate different patterns of brain signaling, leading to strengthening of multiple brain connections.    

A growing body of research shows exercise of various sorts (strength training, aerobic, anaerobic endurance, stretching routines) may provide benefits for the brain. Exercise doesn’t have to be strenuous or performed for long periods to give benefits. Find an exercise program you can do consistently, and constantly strive for small improvements. The majority of research has been conducted on participants performing aerobic exercise. Future research needs to investigate different types of exercise, different durations of exercise, compare how exercise influences various populations, and examine exercise at different intensity levels. Much of the current research has been conducted in rodents; more human research needs to done.  

References

Babyak, M., et al. 2000.  Exercise treatment for major depression: Maintenance of therapeutic benefit at 10 months. Psychosomatic Medicine 62: 633–638.

Davis, C., et al. 2008. Exercise improves executive function and achievement and alters brain activation in overweight children: A randomized controlled trial. Health Psychology 30: 91–98.

Diamond, M., et al. 1964. The effects of an enriched environment of the histology of the rat cerebral cortex. Journal of Comparative Neurology 123: 111–120.

Goodwin, V., et al. 2008. The effectiveness of exercise interventions for people with Parkinson’s disease: A systematic review and meta-analysis. Movement Disorders 23: 631–640. 

Heyn, P., and B. Abreu. 2004. The effects of exercise training on elderly persons with cognitive impairment and dementia: A meta-analysis. Archives of Physical Medicine and Rehabilitation 85: 1694–1704.

Lee, W., et al. 2014. Brief report: Effects of exercise and self-affirmation intervention after traumatic brain injury. Neuro Rehabilitation 35: 57–65.

Merzenich, M. 2013. Soft-Wired: How the New Science of Brain Plasticity Can Change Your Life. San Francisco, CA: Parnassus Publishing.  

Suzuki, W. 2014. Healthy Brain, Happy Life.  New York, NY: HarperCollins Publishers.

van Praag, H. 2009. Exercise and brain: Something to chew on. Trends Neuroscience 32(5): 283–290. 

Winter, B., et al. 2007. High impact running improves learning.  Neurobiology of Learning and Memory 87: 597–609.