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).

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.

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) highintensity 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.

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