Regular leisure-time physical activity provides a boost to positive emotions: Individuals who exercise are routinely found to have lower levels of depression, anxiety, stress, and hostility. Moreover, programs of exercise have also been shown to be an effective treatment for depression, with similar findings emerging for anxiety disorders. This entry focuses on the nature of the link between exercise and emotion, explicating what is known about the range, limits, and mechanisms behind emotional responses to exercise.
Exercise Intensity and the Time Course of Emotional Responses
The positive emotional effects of exercise do not depend on high-intensity workouts. Positive mood benefits are routinely observed after moderateintensity exercise, with benefits (reductions in negative emotions and enhancement of feelings of well-being) reported within 5 to 10 minutes of completing exercise. Positive emotional responses also follow high-intensity exercise, but may be delayed by almost a half hour. This delay in positive mood may be a product of the negative moods that are induced by higher intensity or emotionally taxing workouts so that the experience of positive mood benefits from exercise must await recovery from the negative mood induction brought by intense exertion. Indeed, one prominent determinant of negative moods during exercise is exertion beyond the ventilatory threshold—commonly reached when one has difficulty talking during exercise. Also, during exercise, more negative moods in response to feelings of physical exertion are reported by sedentary individuals, those who are more sensitive exercising in front of others (secondary to concerns that others may judge their appearance negatively), and those who tend to fear sensations of emotional arousal (termed anxiety sensitivity). Mood during exercise is of particular importance for the maintenance of leisure-time physical activity; negative mood emerging during exercise appears to be a powerful predictor of exercise adherence 6 and 12 months later. In short, more feelings of pleasure during exercise translate into higher rates of exercise over the longer term.
Changes in Depression
The beneficial mood effects of exercise are reliable enough that programmed exercise has emerged as a treatment for depression. Numerous clinical trials indicate that depressed psychiatric patients, as well as individuals depressed due to medical or other stressors, can successfully use exercise as a treatment. In these treatment trials, moderate exercise (frequently walking for 30 to 40 minutes) is prescribed 4 to 5 times a week. Results of this exercise can rival that for antidepressant medications when responses are evaluated after 3 to 4 months of treatment. Exercise also appears to offer benefit to depressed outpatients who have failed to respond to previous trials of antidepressant medication. As such, programs of regular exercise can be considered an empirically supported treatment for clinical depression, as well as a strategy for nonclinically depressed individuals to boost their mood.
Changes in Anxiety
As indicated by almost 50 studies, programs of moderate exercise can also significantly reduce anxiety and stress. This evidence comes from studies of adults challenged by medical conditions or other specific stressors, studies of the elderly, studies of adults in the general population, and studies of psychiatric samples. Again, in the context of well-controlled clinical trials, results of exercise programs for anxiety rival those found for antidepressant medications. A program of regular exercise has also been shown to extend the benefits offered by cognitive behavioral treatment for anxiety.
Type of Exercise and Mood Change
The question of whether the mood benefits of exercise depend on dose (frequency, intensity, duration) or exercise type (aerobic training vs. strength training) has been examined only in a handful of studies. These studies show that there is no reason to discourage people from focusing on activities such as weight training or calisthenics for mood improvement instead of pure aerobic activity. That is, while the evidence base is strong for aerobic training, such as walking, running, or biking, the studies that have compared aerobic training to strength training have tended not to find meaningful differences. Whether more is better is also not entirely clear in the case of exercise for mood and anxiety. Results of studies examining the effects of exercise on anxiety, for example, indicate that the amount of change in anxiety reaches a peak at a dose of exercise that is roughly 1.5 times higher than the public health recommendation for exercise, which is 30 minutes of moderate exercise on 5 days of the week. At doses higher than that, the anxiety reduction benefits of exercise tended to decrease.
Exercise, Brain Physiology, and Mood Changes
Exercise brings about a cascade of brain activity, with current research supporting a number of mechanisms behind the positive mood changes with exercise. Animal studies provide reliable evidence that exercise alters some of the same neurochemical systems presumed to underlie pharmacologic treatments for depression and anxiety. Specifically, exercise appears to modulate serotonergic and noradrenergic activity in the brain, with some emerging evidence for γ-aminobutyric acid (GABA) modulation as well.
Acute aerobic exercise has been shown to increase brain-derived neurotrophic factor (BDNF) levels in both healthy individuals as well as those with psychiatric disorders. BDNF is a neurotrophin involved in brain neuroplasticity, differentiation and survival of neurons in both the central and peripheral nervous system; adequate BDNF levels appear to be an important factor in the maintenance of normal cognitive function and mood. Low BDNF has been associated with depression and anxiety, and antidepressant medications tend to enhance BDNF levels. As such, BDNF is considered as having a potential role in antidepressant activity, perhaps including the antidepressant and antianxiety effects of aerobic exercise.
Although endorphin activity has been considered a correlate of the runner’s high that may occur after prolonged exercise, at the present time there are several lines of evidence suggesting that endorphin activity does not explain the mood effects brought by moderate exercise.
Finally, atrial natriuretic peptide (ANP) is a peptide hormone that inhibits hypothalamic pituitary adrenocortical activity and may have anxiolytic properties. Importantly, submaximal and maximal exercise bouts significantly increase ANP concentrations, with early work linking these changes to anxiety reductions, raising the possibility that ANP changes may mediate some of the antianxiety effects of exercise.
Exercise to Buffer the Negative Effects of Stress on Mood and Anxiety
Among other biological and psychological processes, attention has been paid to reduced stress reactivity as an additional mental health benefit of exercise. The idea is that exercise may help individuals better modulate the kind of stressors that are so often the trigger for the development of mood and anxiety problems. Several studies have now shown that trained individuals show less physiological (e.g., heart rate, blood pressure, cortisol) and psychological (e.g., anxiety, tension, sadness) reactivity when exposed to psychological stressors as compared with their untrained counterparts. Importantly, research also shows that these protective effects are evident with single exercise sessions. That is, people tend to be less bothered by stressors when these stressors are preceded by exercise. In addition to getting protection against the development of chronic mood and anxiety problems, these observations suggest that people may notice meaningful immediate mood benefits with regular exercise.
Overexercise and Negative Mood
Although there are anecdotal reports of the emergence of depression-like conditions from overexercise in humans (and anxiety-like reactions from overexercise in rodents), there has not been systematic study of these effects. What is more certain is that strenuous exercise may lead to a plummeting mood during the exercise session, and that these mood changes may make adherence to exercise more difficult. Also, given the substantial delay between exercise and improvement in fitness or shape goals, the process of regular exercise in pursuit of weight reduction or shape improvement is a daunting enterprise. Attending to the emotional benefit brought by exercise offers exercisers a more contingent (tightly time-linked) positive outcome for their exercise efforts.
Evidence from a variety of sources provides justification for prescribing exercise as a mood and anxiety management strategy. The mood and anxiety benefits of exercise are apparent immediately following exercise bouts, particularly among individuals who experience significant distress. For these people in particular, exercise training programs that help them establish a habit of repeated (moderate intensity) exercise sessions every week can provide long-term mood benefits that rival those provided by established pharmacological and psychological treatments.
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