**2.2 The endorphin and endocannabinoid hypotheses**

Perhaps the most popular explanation for the positive impact on mood that results from exercise is the endorphin hypothesis. This hypothesis is based on the observation that following vigorous exercise of one half hour or more, there is an elevation of a special endogenous opiate (*B*, or beta, endorphin). This endogenous or body produced opiate is released through exercise and is said by some to be responsible for the "runners high," an elevation of mood following running or jogging or extended periods. The endorphin hypothesis is not without its critics who have carefully examined the data from empirical studies.

One such study compared a jogging group to a relaxation group that did not engage in exercise to a group that did back stretches. The moods that were examined were anger, tension, energy level, calmness, positive mood, depression and others. While all groups produced positive emotional changes there were no differences among the groups. If beta-endorphin is released through exercise, the non-exercise groups should not have shown positive changes and yet they did. Clearly something other than, or in addition to endorphins must be responsible for positive emotional effects of exercise.

A further critique of the endorphin hypothesis is that circulating endorphin levels are not reflective of brain endorphin levels and endorphins cannot cross the blood brain barrier. So even if circulating or peripheral endorphin levels increased, this should not have an impact on brain mediated emotional states. A further critique of the endorphin hypothesis is that when the endorphin blocking substance naloxone, an opiate antagonist, is provided to those experiencing the runners high, the elevation in mood is not diminished. If endorphins were causal to exercise induced mood changes, one would expect a significant deterioration in mood following naloxone injection.

It may be of some significance to note here that a recent alternative to the endorphin hypothesis has come to be known as the *endocannabinoid hypothesis*. Endocannabinoids are bodily produces substances that are similar in action to that of tetrahydrocannabinol (THC), the active constituent in marijuana. Using trained male college students running on a treadmill or cycling on a stationary bike for 50 minutes at 70–80% of maximum heart rate, elevations of endocannabinoids were detected in blood plasma. Because activation of the endocannabinoid system reduces pain sensations, it has been suggested that this might be what is behind the runners high and alterations of mental and emotional processes [10]. Owing to the presence of cannabinoid receptors in the skin, lung, and muscle, it has been suggested that there may be a role for endocannabinoids in producing analgesic effects through exercise. Unlike the endorphin hypothesis where it was noted that endorphins do not cross the blood brain barrier, cannabinoids do appear to operate both centrally (i.e., in the central nervous system) and in the peripheral nervous system. Cannabinoids are reported to reduce anxiety, alter attention, and impair working memory, much like THC does. So, although research is in the early phases, endocannabinoids have been proposed as an alternative to endorphins as the possible mediator of the runners high, analgesic effects and beneficial psychological effects of exercise. The

endocannabinoid hypothesis is of comparatively recent development and is not anywhere near as widely accepted as the apparently doubtful endorphin hypothesis.

### **2.3 Monoamine hypothesis**

This hypothesis is somewhat similar to the endorphin and endocannabinoid hypotheses in that is proposes that exercise produces chemical changes in the body and these are what causes mood changes in exercise. The monoamine hypothesis proposes that exercise results in increased brain availability of brain neurotransmitters such as serotonin, dopamine, and norepinephrine and that these result in reductions in depression and other negative emotional states. Available studies show that while exercise does result in monoamine elevations as assessed in plasma and urine, the question remains as to whether there similar elevations in the brain take place. In fact testing of biochemical hypotheses is difficult in humans because it often involves invasive procedures such as spinal taps for cerebrospinal fluid samples. Further, biochemical samples obtained from blood or other body fluids may not necessarily reflect the availability of similar biochemical samples in the brain. Animal studies suggest that exercise increases serotonin and norepinephrine in the brain but reliable and replicable studies in humans have not been demonstrated.

Another line of reasoning that further clouds the issue of whether biochemical changes following exercise is causal of positive mood enhancement is that all mental activity is in essence chemical activity of the nervous system, especially the central nervous system. So, as will soon be discussed, it may be possible that positive mood states arise from perceptions of having successfully completed some form of strenuous activity, and the positive mental state is what drives the biochemical changes, rather than the other way around. The issue is, what is responsible for causing what? Which came first?

#### **2.4 Distraction hypothesis**

This hypothesis suggests that psychological or environmental changes are what are responsible for changes in emotional states following exercise and that biochemical mediators play an ancillary role. The hypothesis proposes that when one is engaged in vigorous physical activity it is difficult to simultaneously entertain depressive thoughts and negatively tinged depressive ruminations. We only have so much attention to go around and when one is busy exercising there is little available attention for depressive rumination. It is usually when one is inactive, immobile, and has few demands on one's time that there is time and space available to engage in depressive thoughts. And, as we saw earlier, negative thinking and cognitive distortions are the basis for negative emotional states according to CBT perspectives.

In some studies exercise has been compared to control groups such as relaxation training, or waiting list controls, where one is distracted yet not involved in physical activity. The results of these studies are varied with some showing reductions in depression following distracting activity and some not. However, when one examines mood elevation and not simply reduction in depression, usually exercise shows greater changes than non-exercise interventions. So, it is possible that distraction serves as a means through which one moves away from depressive rumination, but that for mood elevation to occur, distraction may not be a sufficiently effective means.

#### **2.5 Self-efficacy theory**

Self-efficacy perceptions refer to one's self-view of their capabilities to accomplish certain objectives. The originator of self-efficacy theory [11], claims

**75**

*The Role of Exercise in Reducing PTSD and Negative Emotional States*

that people who are depressed are comparatively lacking in a healthy sense of self-efficacy. Those who are clinically depressed see themselves as relatively incapable of setting goals and accomplishing hoped for objectives. These negative self-perceptions eventuate in depressive rumination on, for example, perceived inadequacies, and these perceptions decrease the possibility of engaging in self-

The studies that have been conducted do in fact show that when one engages in physical exercise they feel more accomplished and more capable of achieving various exercise related goals. Their self-efficacy perceptions, i.e., their view of themselves setting specific exercise targets and accomplishing them has been found to increase following a planned sequence of exercise. The research however, on whether these enhanced views of exercise competence can produce reductions in clinical depression is less clear-cut. It does seem clear that exercise is associated with reductions in depression and elevation in mood. Whether these outcomes are due to

alterations in one's self-perceptions of their capabilities is less obvious.

At this point it is unclear as to whether biochemical or psychological factors mediate the positive effects of exercise on mood states such as depression. Depression and anxiety are significant factors in PTSD and the alleviation of the emotional distress that they cause would be a productive step in treating PTSD. It may very well be that we are making an error in seeking out unitary causes for the beneficial effects of exercise and that a combination of biochemistry, psychology, and perhaps even socialization, and in some instances, spiritual issues come into play, and maybe these vary in importance depending on at what point in one's cycle of emotional distress one chooses to intervene. What we can derive from the avail-

Why this is so is, as of this writing, unclear. However, from a practical point of view, it does seem that exercise produces biochemical alterations in the nervous system, even if the specific nature of these biochemical events is unclear, and it is these biochemical changes that improve negative emotional states. Perhaps a biochemical and self-efficacy interpretation in combination is the most useful model of the

Those clinicians who have treated individuals suffering from PTSD, anxiety, and depression know that it is a real challenge to get them to engage in exercise, despite its beneficial effects. The American College of Sports Medicine recommends that those between the ages of 18–65 should engage in moderate intensity exercise for 30 minutes 5 days a week. Moderate exercise intensity is defined as 60–80% of maximum heart rate. In general maximum heart rate has been calculated as 220 minus age multiplied by .6 to .8 So, for an individual who is 50 the calculation would be 220 − 50 = 170; 170(.6) = 102; 170(.8) = 136. Therefore the 50 year old should exercise in such a way that they maintain a heart rate of 102–136 for half an hour,

The numbers presented above, exercising 5 days a week for a half hour at moderate intensity are, for all intents and purposes, unrealistic, to say the least, for many and especially for those who are depressed. Getting a depressed patient to do anything, other than that which is absolutely necessary to get on with their lives, is often a real challenge. So what is realistic? In many instances just getting them to go for a walk for 10 minutes or so maybe twice a week might be a major

**2.6 Conclusion on causal hypotheses of exercise effects**

able literature is that exercise alleviates emotional distress.

beneficial effects of exercise.

5 days a week. Is this reasonable?

**2.7 From research to clinical perspectives**

*DOI: http://dx.doi.org/10.5772/intechopen.81012*

validating behaviors.

#### *The Role of Exercise in Reducing PTSD and Negative Emotional States DOI: http://dx.doi.org/10.5772/intechopen.81012*

*Psychology of Health - Biopsychosocial Approach*

**2.3 Monoamine hypothesis**

Which came first?

**2.4 Distraction hypothesis**

**2.5 Self-efficacy theory**

endocannabinoid hypothesis is of comparatively recent development and is not anywhere near as widely accepted as the apparently doubtful endorphin hypothesis.

This hypothesis is somewhat similar to the endorphin and endocannabinoid hypotheses in that is proposes that exercise produces chemical changes in the body and these are what causes mood changes in exercise. The monoamine hypothesis proposes that exercise results in increased brain availability of brain neurotransmitters such as serotonin, dopamine, and norepinephrine and that these result in reductions in depression and other negative emotional states. Available studies show that while exercise does result in monoamine elevations as assessed in plasma and urine, the question remains as to whether there similar elevations in the brain take place. In fact testing of biochemical hypotheses is difficult in humans because it often involves invasive procedures such as spinal taps for cerebrospinal fluid samples. Further, biochemical samples obtained from blood or other body fluids may not necessarily reflect the availability of similar biochemical samples in the brain. Animal studies suggest that exercise increases serotonin and norepinephrine in the brain but reliable and replicable studies in humans have not been demonstrated. Another line of reasoning that further clouds the issue of whether biochemical changes following exercise is causal of positive mood enhancement is that all mental activity is in essence chemical activity of the nervous system, especially the central nervous system. So, as will soon be discussed, it may be possible that positive mood states arise from perceptions of having successfully completed some form of strenuous activity, and the positive mental state is what drives the biochemical changes, rather than the other way around. The issue is, what is responsible for causing what?

This hypothesis suggests that psychological or environmental changes are what are responsible for changes in emotional states following exercise and that biochemical mediators play an ancillary role. The hypothesis proposes that when one is engaged in vigorous physical activity it is difficult to simultaneously entertain depressive thoughts and negatively tinged depressive ruminations. We only have so much attention to go around and when one is busy exercising there is little available attention for depressive rumination. It is usually when one is inactive, immobile, and has few demands on one's time that there is time and space available to engage in depressive thoughts. And, as we saw earlier, negative thinking and cognitive distortions are the basis for negative emotional states according to CBT perspectives. In some studies exercise has been compared to control groups such as relaxation training, or waiting list controls, where one is distracted yet not involved in physical activity. The results of these studies are varied with some showing reductions in depression following distracting activity and some not. However, when one examines mood elevation and not simply reduction in depression, usually exercise shows greater changes than non-exercise interventions. So, it is possible that distraction serves as a means through which one moves away from depressive rumination, but that for mood elevation to occur, distraction may not be a sufficiently effective means.

Self-efficacy perceptions refer to one's self-view of their capabilities to accomplish certain objectives. The originator of self-efficacy theory [11], claims

**74**

that people who are depressed are comparatively lacking in a healthy sense of self-efficacy. Those who are clinically depressed see themselves as relatively incapable of setting goals and accomplishing hoped for objectives. These negative self-perceptions eventuate in depressive rumination on, for example, perceived inadequacies, and these perceptions decrease the possibility of engaging in selfvalidating behaviors.

The studies that have been conducted do in fact show that when one engages in physical exercise they feel more accomplished and more capable of achieving various exercise related goals. Their self-efficacy perceptions, i.e., their view of themselves setting specific exercise targets and accomplishing them has been found to increase following a planned sequence of exercise. The research however, on whether these enhanced views of exercise competence can produce reductions in clinical depression is less clear-cut. It does seem clear that exercise is associated with reductions in depression and elevation in mood. Whether these outcomes are due to alterations in one's self-perceptions of their capabilities is less obvious.
