Motivation and emotion/Book/2014/Exercise and mood

From Wikiversity
Jump to navigation Jump to search
Exercise and mood:
How does exercise effect mood?
Figure 1. Exercise provides many benefits including mood enhancement

Overview[edit]

The effects of exercise on mood and mood disorders have long been a topic of interest and research. What are the benefits of exercise? Does it improve mood? Can it treat mood disorders? The relationship between exercise and mood is an interesting topic as numerous studies have found the more active people are, the more of a reduction in negative mood and depressive symptoms will be felt compared to those who are sedentary (Brosse, Sheets, Lett & Blumenthal, 2002). Exercise has been found to enhance mood, so does this mean exercise can reduce symptoms of mood disorders? Exercise could be an alternative treatment offered to people suffering from depression and anxiety. Mood disorders, especially depression are usually poorly treated (Lawlor & Hopker, 2001) because of the unpleasant side effects of pharmacological treatments as well as the low rates of compliance. Exercise could be beneficial as it's free unlike psychological and pharmacological treatments but will this work for everyone?

Mood[edit]

People experience moods on a daily basis, [grammar?] mood is an individual's affective (feeling) state, and differs from emotion as emotions are shorter and more intense (Salovey & Mayer, 1989). Moods refer to changing affective states that are related to how a person feels at a particular point in time (Berger & Motl, 2000). Affective states can be both positive and negative. Positive affect includes pleasurable emotions such as happiness and negative affect includes unpleasant emotions such as sadness or anger (Berger & Motl, 2000). Moods are not only asserted through emotions but can be seen through body language including posture, facial expressions and tone of voice. Mood can be linked to both physical and psychological health, positive affect can reduce the risk of developing illness and disease as well as mood disorders (Berger & Motl, 2000). So when a person experiences negative moods and emotions, could that mean mood disorders such as depression or anxiety have a high risk of developing?

Depressive mood or depression according to the DSM-5 usually includes feelings of worthlessness, lack of energy, helplessness, irritability, changes in sleep patterns and weight gain/loss (American Psychiatric Association, 2013). Another prevalent mood disorder is anxiety. There are numerous types of anxiety disorders such as panic attacks, obsessive compulsive disorder, post traumatic stress disorder, generalised anxiety and so on. Generalised anxiety is characterised by excessive worry and anxiety, in which the individual cannot control as well as other symptoms such as restlessness, difficulty sleeping, irritability and trouble concentrating (American Psychiatric Association, 2013).

The impact of exercise on mood[edit]

Physical activity is defined as movement of the body which expends energy using skeletal muscles (Caspersen, Powel & Christenson, 1985). Exercise has been said to be a category of physical activity which is structured and ongoing as a means of physical fitness (Caspersen et al., 1985). The effects of exercise have been studied due to the physical and psychological benefits it produces. Individuals engage in exercise and physical activity not only for the fitness benefit but because it is enjoyable. Exercise is enjoyable because it improves mood. When mood is measured before and after exercising, in almost all cases mood is enhanced (Salmon, 2001). When looking at the effects of exercise on mood there are three types of exercise regimes used, aerobic, muscular strength and flexibility training. Aerobic exercise uses energy and oxygen, and includes exercises such as running/jogging or swimming at a comfortable pace (Byrne & Byrne, 1993). Muscular strength focuses on energy use without the use of oxygen, such as weightlifting and flexibility training aims to improve the range of motion in one's body, which can include stretching and yoga (Brosse et al., 2002). The type of exercise someone engages in determines the effect it has on their mood. Aerobic exercises produce clear mood enhancements either immediately or shortly after completing the regime, whereas muscular strength and flexibility training don't produce clear effects on mood, meaning it's difficult to determine if these exercise types effect mood at all (Salmon, 2001).

Research has compared the effects of exercise on mood with other mood regulation techniques such as relaxation and meditation. Exercise was as equally effective as relaxation techniques in the regulation of mood in the short-term and reduced feelings of anger, stress and depression (Berger & Motl, 2000). Further evidence suggests that walking/running at a steady pace is linked to positive affect (Berger & Motl, 2000). These findings provide evidence that exercise enhances mood and positive emotions, could this be applied to mood disorders? Exercise may prove to be an effective alternative treatment for depression and anxiety patients in aim to enhance mood and reduce symptoms.

Table 1.
The effect exercise has on mood

Why does exercise enhance mood? Explanation
Social Interaction Exercising in a group environment can offer social support and interaction which can allow people suffering from mood disorders to feel less isolated.
Positive feedback Positive feedback from others can help improve self-esteem and improve feelings of self-worth and therefore reducing depressive symptoms.
Distraction Physical activity can be an effective way to distract people from thinking about negative memories/thought.
Physiological Effects Exercise can regulate stress and mood, therefore decreasing negative affect, depressive and anxiety related symptoms (Ross &Thomas, 2010).


(Lawlor & Hopker, 2001).

Exercise and mood disorders[edit]

Exercise is suggested to have a positive effect on mental health[factual?]. Research suggests that individuals who are physically active are three times less likely to suffer from depression than inactive individuals (Armstrong & Oomen-Early, 2009). Exercise has been compared with antidepressants as a treatment for depression[factual?]. Clinically depressed patients were asked to exercise which included running on a treadmill three times a week for 16 weeks, another group were asked to comply with a medication program and the last group exercised and took antidepressant medication (Blumenthal et al., 1999). After the intervention all groups displayed a reduction in depressive symptoms but treatment impacted patients differently (Blumenthal et al., 1999). People with severe depression responded better to medication whereas patients with less severe depression responded quickly to the combination of exercise and medication (Blumenthal et al., 1999). This finding demonstrates that exercise has a positive impact on mood, in particular depressive symptoms, but that individual differences are apparent. Individuals each respond differently to treatment, exercise enhances mood in some but not in others. The type of exercise used in this study, like many others, is aerobic exercise which, usually improves mood.

Salmon (2001) states that aerobic exercise indeed does significantly enhance mood as research has shown that running programs which last for about 12 weeks enhance mood more significantly than other exercise types. However muscle strengthening and flexibility training type regimes have had much less attention than aerobic exercise for improving mood.

Figure 2. Depressive symptoms can be reduced with exercise

Research has suggested that exercise used as a treatment for clinically depressed patients can act as a better treatment option than psychotherapy (Klein et al., 1984). Clinically depressed patients were assigned to one of three groups, a running group, a psychotherapy group or meditation-relaxation therapy group (Klein et al., 1984). It was found that all treatment groups produced significant reductions in depressive symptoms and interestingly there were no significant differences found between groups (Klein et al., 1984). This suggests that exercise is just as effective as psychological/relaxation treatments for depression. Exercise could be an alternative treatment option as it's free and the reductions in depressive symptoms were apparent after nine months (Klein et al., 1984).

The effects of exercise on anxiety are extremely [grammar?] less studied than depression, [grammar?] this may be because anxiety disorders differ tremendously and results cannot be generalised to all anxiety sufferers (Ströhle, 2008). The research that has been conducted on anxiety and exercise has produced controversial conclusions. Research has found that physical activity reduces anxiety related symptoms and lowers the risk of a range of phobias (Ströhle, 2008). Reducing anxiety has been tested with all exercise types. Muscle strengthening and flexibility training have produced slight decreases in symptoms of anxiety but aerobic exercise has been the most effective in symptom reduction (Scully, Kremer, Meade, Graham & Dudgeon, 1988). Although this finding is controversial, as reduction in anxiety related symptoms and reduced risk of developing anxiety is apparent in a healthy population, but not in people who have been diagnosed with anxiety (Ströhle, 2008)[grammar?]. Some studies have found that anxiety is heightened due to the exercise regime and exercise may even induce panic attacks (Ströhle, 2009). It is apparent that research on anxiety and exercise is inconclusive as there is no plausible evidence to suggest exercise does or doesn't improve mood.

Most research on exercise and mood disorders demonstrates an increase in positive affect and reduced mood-related symptoms, however limitations of these studies must be addressed. Nearly all studies examining the exercise and mood relationship used short-term exercise programs, [grammar?] there is little evidence to suggest exercise can improve mood long-term or permanently. This provides complications for suggesting exercise as a treatment for mood disorders because it's unknown whether it would be effective long-term. Researchers haven't investigated whether exercising for differing durations such as 10 minutes, 40 minutes or an hour or different intensities effects mood or symptoms of mood disorders differently (Yeung, 1996). In real-world situations it's unrealistic that people will exercise as often as participants did in these studies, meaning these results may be biased. There is limited research and conclusions on the effects of exercise on anxiety, meaning it is difficult to draw the conclusion that exercise improves anxiety related symptoms. Further research is needed to determine if there is a connection between exercise and anxiety and whether exercise can be used as a treatment option for people suffering from anxiety.

Case Study[edit]

Jane was a clinically depressed patient who failed in attempting suicide. Jane is 26 years old, overweight and has a history of self-injury in which she has received psychological and pharmacological treatment for [grammar?] (Wallenstein & Nock, 2007). In aim [grammar?] to prevent Jane from self-injuring and attempting suicide again Mathew Wallenstein and Matthew Nock (2007) provided Jane with an exercise program to determine whether this could help her.

Jane was provided with an exercise video that ran for 60 minutes telling her how often to exercise (3 times a week) and she was instructed to exercise when she feels like self-injuring (Wallenstein & Nock, 2007). In conjunction with this Jane filled out a mood and self-injury questionnaire on a daily basis (Wallenstein & Nock, 2007). Jane did this routine for 8 weeks and was assessed by the researchers afterwards.

During exercising periods self-injury urges were much lower than non-exercise periods and increase in positive mood was found after exercise compared to before exercise (Wallenstein & Nock, 2007). This exercise program seemed to be effective in reducing Jane’s urges to self-injure as after she exercised she no longer felt the need to self-harm (Wallenstein & Nock, 2007). This case study demonstrates that exercise can be beneficial not only for mood but it can be used to reduce self-harm and suicidal urges by enabling people to enhance their mood through exercising.

Physiological explanations[edit]

Why does exercise effect mood? There have been a number of explanations to explain [Rewrite to improve clarity] the relationship between exercise and mood, many of which have centred around the physiological effects of exercise. Depression is related to imbalances of neurotransmitters in the brain, including serotonin, dopamine and norepinephrine (Ross & Thomas, 2010). Neurotransmitters are chemicals that send messages within the brain (Ross & Thomas, 2010). According to the monoamine hypothesis exercise can help restore balance to these neurotransmitters and therefore reduce depressive symptoms (Peluso & Andrade, 2005). Endorphins also play important role in the relationship between depression and exercise, in particular the β-endorphin. β-endorphins are endorphins that help people cope with pain, are released when pain is felt, and are also related to elevated mood (Brosse et al., 2002). Pain is felt during exercise so therefore exercise increases the release of the β-endorphins which in turn elevates mood (Brosse et al., 2002). A problem with this study and many others is that the endorphins and monoamine levels haven't been measured before and after exercise. Researchers only offer the hypotheses as explanations and don't have any real evidence to suggest they are correct. Salmon (2001) states that exercise does improve mood and offers the endorphin and monamine hypotheses to explain why but in his studies he didn't test these hypotheses. Nevertheless these hypotheses are the two main physiological mechanisms that have been said to underlie the exercise and mood relationship but it must be noted that research is needed to confirm or reject these explanations.

Monoamine hypothesis[edit]

The monoamine hypothesis proposes that exercises leads to balanced levels of dopamine, serotonin and norepinephrine, which is important because neurotransmitters are usually imbalanced in people suffering from depression (Peluso & Andrade, 2005). Anti-depressants, medication to treat depression, are used to regulate neurotransmitters, therefore the monoamine hypothesis suggests that exercise can work in a similar way to anti-depressants. A number of studies have determined whether running or swimming affect levels of neurotransmitters within the brain. Results were mixed, [grammar?] some studies found that exercise only slightly affected levels of neurotransmitters and other studies found no change at all (Meeusen & Meirleir, 1995). Further experiments are needed to determine whether the monamine hypothesis is a plausible explanation as to why exercise impacts on mood.

Endorphin hypothesis[edit]

The endorphin hypothesis suggests that exercise can reduce depressive symptoms as it increases the release of endorphins, [grammar?] endorphins can be associated with positive moods and therefore reduce feelings of depression (Peluso & Andrade, 2005). Research has supported the endorphin hypothesis, as it is commonly known that exercise increases the release of endorphins into the body, in particular the β-endorphin, to cope with pain produced by engaging in exercise (Brosse et al., 2002). These β-endorphins seem to be related to elevated mood, as studies have demonstrated that after exercise participants show an increase in positive mood and decreases in negative affect or depressive symptoms (Brosse et al., 2002). But do these elevated mood effects last forever? Brosse and colleagues (2002) state that endorphins only produce elevated moods in people for a short period of time and there is no evidence to suggest that endorphin release in relation to exercise can elevate mood and reduce depressive symptoms permanently. Therefore a combination of physiological and psychological explanations could demonstrate why exercise enhances mood.

Psychological explanations[edit]

Psychological and physiological mechanisms of the relationship between exercise and mood have not been widely studied. Research that has examined the role of physiological and psychological mechanisms in explaining the effect of exercise on mood has produced results that are inconclusive (Craft, 2005). One study conducted by Craft (2005) looked at whether psychological mechanisms such as distraction and self-efficacy explain why exercise influences mood. Participants in this study included two groups of women who were depressed, one group participated in exercise 3 days a week ranging from jogging, cycling, and stretching, whereas the other group did not participate in any exercise program (Craft, 2005). After nine weeks researchers found that women in the exercise group displayed reductions in depression, [grammar?] before the experiment they were moderately depressed whereas after the intervention they were only minimally depressed (Craft, 2005). Results also showed that self-efficacy was improved as well as coping efficacy for dealing with depression, [grammar?] exercise was a distraction for participants as women reported less negative thoughts after the intervention than before (Craft, 2005). This study demonstrated that the distraction hypothesis and self-efficacy hypothesis could be plausible explanations as to why exercise improves mood. These hypotheses will be explained in further detail.

Distraction hypothesis[edit]

Exercise can be a means of distraction, [grammar?] distraction is especially important for people who are feeling down, showing depressive or anxiety related symptoms. The distraction hypothesis proposes that exercise distracts people from depressive thoughts, feelings, worries and fears (Peluso & Andrade, 2005). The distraction hypothesis states in relation to anxiety that exercise offers a distraction from stressful or worrying thoughts/situations which in turn leads to anxiety reduction (Petruzzello et al., 1991). When people are distracted from their moods through activities such as exercise, they will experience more positive emotions compared to people who aren't distracted (Morrow & Nolen-Hoeksema, 1990). Many researchers believe that exercise provides individuals with a distraction from distressing or sad thoughts (Morrow & Nolen-Hoeksema, 1990). Exercise can offer a distraction as people usually focus on their breathing, heart rate, sore body parts, instead of negative thoughts and feelings (Craft 2005).The distraction hypothesis can offer a reasonable explanation as to why exercise enhances mood, although some researchers ignore the physiological effects of exercise (Morrow & Nolen-Hoeksema, 1990). Morrow and Nolen-Hoeksema (1990) believe that exercise doesn't always act as a distraction and can facilitate time for thinking negative thoughts. It is apparent that research has found conflicting results regarding the distraction hypothesis, suggesting further investigation is needed to determine if this hypothesis can sufficiently explain why exercise enhances mood.

Practical Example

Dave had been feeling down for a few weeks and heard that exercising could be a way to feel better. Dave decided to join a jogging group which exercised four times a week around the local parks and lakes. Dave started his jogging and made some new friends within the group. While attending these jogging session Dave would catch up with his new friends have a chat about his day, as well as trying to improve his personal best jogging times. Dave realised that while he was exercising he was no longer thinking about negative things or events and he began to feel more happier. This is an example of how distraction may provide benefits for people feeling down, depressed or anxious.

Self-efficacy hypothesis[edit]

Self-efficacy is defined as an individual's belief in their ability to achieve a goal or perform a task (Peluso & Andrade, 2005). There is a relationship between depressive moods/depression and negative self-evaluations, including low self-efficacy (Brosse, et al., 2002). Increasing one's self-efficacy could reduce depressive symptoms. People who are 'healthy' are able to successfully regulate their feelings, moods, thoughts and goals (Bandura, 1997). Someone with low self-efficacy may be more vulnerable to feeling anxious during situations where they feel they cannot achieve the desired goal (Craft, 2005). Low self-efficacy can play a role in increasing negative thoughts and evaluations in depressed people (Craft, 2005). The self-efficacy hypothesis states that exercise can give people confidence and improved self-efficacy to cope with depression or anxiety (Peluso & Andrade, 2005). Albert Bandura (1993), proposes low self-efficacy leads to depression as well as anxiety in three ways. Firstly low self-efficacy can be due to people setting high standards that they cannot realistically fulfil, secondly low self-efficacy in relation to social relationships, as people who don't have social support are at a higher risk of negative affect and depression (Bandura, 1993). Finally low self-efficacy can be due to the individual constantly thinking negatively (Bandura, 1993). Exercise can target each of these aspects that lead to low self-efficacy and in turn depression and anxiety. Exercise can allow people to master a skill such as learning to run properly and then mastering running so running a marathon can be achieved, improving self-efficacy. According to Craft (2005) mastery of a skill or exercise seems to be the best way to improve self-efficacy, when a person feels confident they have mastered running/swimming for example they are likely to feel highly efficacious. Improving self-efficacy in relation to mastering running for example, can lead to enhanced self-efficacy in coping and overcoming depression and anxiety (Peluso & Andrade, 2005). Exercise acts as a distraction and this can prevent the individual from thinking negatively, which will increase self-efficacy. A meta-analysis has found support for the self-efficacy hypothesis, stating that after an exercising program participant's self-efficacy significantly increased (Netz, Wu, Becker & Tenenbaum, 2005). This finding is exciting as higher ratings of self-efficacy could possibly help people cope with their mood disorders and also gives evidence to suggest that self-efficacy is an underlying psychological mechanism that can explain why exercise enhances mood.

Conclusion[edit]

There has been a large amount of research suggesting that exercise enhances mood and could possibly be used as a treatment for mood disorders such as depression and anxiety. Exercise as a treatment for regulation of mood and mood disorders have been emphasised by health professional [grammar?] (Petruzzello et al., 1991). From the evidence, it can be concluded that exercise does enhance mood and could possibly reduce symptoms of mood disorders. More research is needed to gain clearer results on this relationship between exercise and mood. The psychological and physiological hypotheses that have been proposed have gained very little research, meaning it is difficult to determine whether they do in fact explain why exercise enhances mood. It could be a combination of both physiological and psychological mechanisms that explain why exercise enhances mood but it will remain unknown until further research is conducted. In conclusion the relationship between mood and exercise is an exciting one as exercise could possibly be an effective treatment for both depression and anxiety. It is clear that more research is needed to determine if exercise can influence mood and mood disorders in the long-term and also to determine if it can reduce depressive and anxiety related symptoms permanently. Overall exercise is beneficial for humans both psychologically and physically, and everyone should aim to exercise regularly.

Quiz[edit]







  

1

How does mood differ from emotion?

Mood is more intense than emotions
Emotions are more intense than mood
Mood and emotions are the same
None of the above

2

Which of the following is a symptom of depression according to the DSM-5?

Crying
Anger
Irritability

3

Which of the following is an example of aerobic exercise?

Weight lifting
Swimming
Stretching

4

What type of exercise is most commonly used in mood and exercise research?

Aerobic
muscle strengthening
flexibility training
All of the above

5

What are the two psychological mechanisms that explain the exercise-mood relationship?

Self-efficacy and monoamine hypothesis
Self-efficacy and distraction hypothesis
Distraction and endorphin hypothesis


See also[edit]

References[edit]

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Washington, DC.

Armstrong, S., & Oomen-Early, J. (2009). Social connectedness, self-esteem, and depression symptomatology among collegiate athletes versus nonathletes. Journal Of American College Health, 57, 521-526. Retrieved from humanresourcefulness.net 1Kristina1 (discusscontribs)

Bandura, A. (1993). Perceived self-efficacy in cognitive development and functioning. Educational Psychologist, 28, 117–148. doi:10.1207/s15326985ep2802_3

Bandura, A. (1977). Self-efficacy: Toward a unifying theory of behavioural change. Psychological Review, 84, 191–215. doi:10.1037/0033-295x.84.2.191

Berger, B. G., & Motl, R. W. (2000). Exercise and mood: A selective review and synthesis of research employing the profile of mood states. Journal of Applied Sport Psychology, 12, 69–92. doi:10.1080/10413200008404214

Blumenthal, J. A., Babyak, M. A., Moore, K. A., Craighead, W. E., Herman, S., Khatri, P., … Krishnan, K. R. (1999). Effects of exercise training on older patients with major depression. Arch Intern Med, 159. doi:10.1001/archinte.159.19.2349

Brosse, A. L., Sheets, E. S., Lett, H. S., & Blumenthal, J. A. (2002). Exercise and the treatment of clinical depression in adults. Sports Medicine, 32, 741–760. doi:10.2165/00007256-200232120-00001

Byrne, A., & Byrne, D. G. (1993). The effect of exercise on depression, anxiety and other mood states: A review. Journal of Psychosomatic Research, 37, 565–574. doi:10.1016/0022-3999(93)90050-p

Caspersen, C. J., Powell, K. E., & Christenson, G. M. (1985). Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research. Public health reports, 100, 126. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1424733/pdf/pubhealthrep00100-0016.pdf

Craft, L. L. (2005). Exercise and clinical depression: examining two psychological mechanisms. Psychology of Sport and Exercise, 6, 151–171. doi:10.1016/j.psychsport.2003.11.003

Klein, M. H., Greist, J. H., Gurman, A. S., Neimeyer, R. A., Lesser, D. P., Bushnell, N. J., & Smith, R. E. (1984). A comparative outcome study of group psychotherapy vs. exercise treatments for depression. International Journal of Mental Health, 13, 148-176. Retrieved from http://www.jstor.org/discover/10.2307/41344367?uid=3737536&uid=2&uid=4&sid=21104961040663

Lawlor, D. A., & Hopker, S. W. (2001). The effectiveness of exercise as an intervention in the management of depression: systematic review and meta-regression analysis of randomised controlled trials. BMJ, 322, 763. doi: 10.1136/bmj.322.7289.763

Meeusen, R., & De Meirleir, K. (1995). Exercise and brain neurotransmission. Sports Medicine, 20, 160–188. doi:10.2165/00007256-199520030-00004

Morrow, J., & Nolen-Hoeksema, S. (1990). Effects of responses to depression on the remediation of depressive affect. Journal of Personality and Social Psychology, 58, 519–527. doi:10.1037/0022-3514.58.3.519

Netz, Y., Wu, M.-J., Becker, B. J., & Tenenbaum, G. (2005). Physical activity and psychological well-being in advanced Aae: A Meta-Analysis of Intervention Studies. Psychology and Aging, 20, 272–284. doi:10.1037/0882-7974.20.2.272

Peluso, M. A. M., & Andrade, L. H. S. G. de. (2005). Physical activity and mental health: the association between exercise and mood. Clinics, 60, 61–70. doi:10.1590/s1807-59322005000100012

Petruzzello, S. J., Landers, D. M., Hatfield, B. D., Kubitz, K. A., & Salazar, W. (1991). A meta-analysis on the anxiety-reducing effects of acute and chronic exercise. Sports Medicine, 11, 143–182. doi:10.2165/00007256-199111030-00002

Ross, A., & Thomas, S. (2010). The health benefits of yoga and exercise: A review of comparison studies. The Journal of Alternative and Complementary Medicine, 16, 3–12. doi:10.1089/acm.2009.0044

Salmon, P. (2001). Effects of physical exercise on anxiety, depression, and sensitivity to stress. Clinical Psychology Review, 21, 33–61. doi:10.1016/s0272-7358(99)00032-x

Salovey, P., & Mayer, J. D. (1989). Emotional intelligence. Imagination, Cognition and Personality, 9, 185–211. doi:10.2190/dugg-p24e-52wk-6cdg

Scully, D., Kremer, J., Meade, M. M., Graham, R., & Dudgeon, K. (1998). Physical exercise and psychological well being: a critical review. British Journal of Sports Medicine, 32, 111–120. doi:10.1136/bjsm.32.2.111

Ströhle, A. (2008). Physical activity, exercise, depression and anxiety disorders. Journal of Neural Transmission, 116, 777–784. doi:10.1007/s00702-008-0092-x

Wallenstein, M. B., & Nock, M. K. (2007). Physical exercise as a treatment for non-suicidal self-injury: evidence from a single-case study. American Journal of Psychiatry, 164, 350–351. doi:10.1176/appi.ajp.164.2.350-a

Yeung, R. R. (1996). The acute effects of exercise on mood state. Journal of Psychosomatic Research, 40(2), 123–141. doi:10.1016/0022-3999(95)00554-4