Wed, 10 Oct. 2012 - 2:28 a.m. MT
Credit: ARA Staff - American Running Association
The connection between regular exercise and reduction of depression symptoms has been frequently reported in the literature. Exercise raises serotonin levels, lowers the production of stress hormones like cortisol, and—at least when undertaken outdoors—even increases the skin’s vitamin D production. It therefore can be an effective combatant against winter-related mood problems like seasonal affective disorder (SAD). Moderate—though not intense—exercise can also reinforce your immune system and so aid in staving off respiratory infection during cold and flu season.
Now, the link between exercise and depression takes on a new twist: depression just may change the way the body responds to exercise.
Exercise-recovery and depression. A study of 886 healthy adults published in November in Psychophysiology suggests that clinical depression may hamper the body’s ability to recover from physical activity, prolonging the amount of time it takes for a depressed person’s heart rate to slow down and return to normal after a workout. Poor cardiovascular recovery after exercise is indicative of “dysfunctional autonomic control of the cardiovascular system,” the researchers write, and it predicts cardiovascular events and death.
In the study, the first of its kind, 51 subjects had received a diagnosis of major depression. All of the subjects were given stress tests on a treadmill, and their blood pressure and heart rates were measured both at rest and during the exercise test, as well as at intervals of one to five minutes afterward. Over all, compared with the subjects without depression, it took significantly longer for the depressed subjects’ heart rates to slow down to normal after the stress test. The difference was about 3.7 beats per minute. Some research suggests that a difference of just these few beats during post-exercise recovery is associated with a shorter life span. A 2001 Stanford study of over 2,000 men, for example, found that the men who died during the seven-year follow-up had recorded on average heart-rate recoveries of 3 beats per minute slower than the other subjects.
The new findings may help shed light on the well-known link between depression and heart disease. Depression sufferers have a significantly increased risk of cardiovascular mortality, including from myocardial infarction. Heart patients who develop depression die sooner than heart patients without depression. Now, it seems, depressed individuals have a slow parasympathetic recovery from exercise.
The researchers speculate that people with major depression perhaps have a dysfunctional stress response. During a stressful event, there is an arc that is considered normative during which adrenaline flows, heart rate increases, and pupils dilate—all of which return to normal after a given amount of time once the stress is removed. Something about being depressed could very well have some influence on the circuitry of the brain that causes the stress response to not return from high alert as quickly as it should.
The implications are unclear as of now, but should not be taken to mean that patients with depression should refrain from physical activity. Exercise, after all, treats depression. The present study used an unusually acute exercise test to purposely stress the subjects. Single moderate bouts of exercise are not presently considered harmful to depression sufferers, and in the long run are likely to improve the heart’s response time on the way back down to normal after stressful or threatening events.
Exercise and memory. Other recent research underscores a long-thought connection between exercise and improved memory function. At UCLA, researchers found that rats produced more brain-derived neurotrophic factor (BDNF) when allowed to run at will for a week, as opposed to rats who remained sedentary. BDNF molecules are increasingly seen as essential to memory function. For example, in another recent study, of 144 airline pilots (aged 40 to 69 years) who operated a cockpit simulator three separate times over the course of two years, those with a common genetic variation that is believed to reduce BDNF activity lost their ability to perform this complicated flight-simulator task at nearly double the rate of the other pilots.
Putting it together, it seems BDNF molecule activity may be crucial to memory function and skilled manual task performance. When taking into account the results of the rat study—and numerous others that seem to similarly confirm exercise’s role in increased BDNF activity—we see evidence that exercise can slow memory- and skilled manual task-decline by raising BDNF levels.
Other studies of exercise and memory on the brains of both humans and animals have been conducted in Ireland and Brazil in recent years, with similar findings. Ever-increasing understanding of the relationship between brain functions as diverse as mood and memory, and that of exercise, continue to remind us of the essential mind-body connection, and of the reality that we by no means evolved to remain sedentary.
Psychophysiology, 2011, Vol. 48, No. 11, pp. 1605-1610, http://www.ncbi.nlm.nih.gov/pubmed/21806634
Translational Psychiatry, Oct. 25, 2011, http://www.nature.com/tp/journal/v1/n10/full/tp201147a.html
Mech. Aging Dev., Oct. 1, 2011, http://www.ncbi.nlm.nih.gov/pubmed/21983475
Neuroscience, 2011, Vol. 192, Sep. 29, pp. 773-780, http://www.ncbi.nlm.nih.gov/pubmed/21756980
Physiol. Behav., 2011, Vol. 104, No. 5, pp. 934-941, http://www.ncbi.nlm.nih.gov/pubmed/21722657
(RUNNING & FITNEWS® November / December 2011 • Volume 29, Number 6)
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