- Email: [email protected]
Exercisers Achieve Greater Acute Exercise-Induced Mood Enhancement Than Nonexercisers
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Exercisers Achieve Greater Acute Exercise-Induced Mood Enhancement Than Nonexercisers Martin D. Hoffman, MD, Debi Rufi Hoffman, MA ABSTRACT. Hoffman MD, Hoffman DR. Exercisers achieve greater acute exercise-induced mood enhancement than nonexercisers. Arch Phys Med Rehabil 2008;89:358-63. Objective: To determine whether a single session of exercise of appropriate intensity and duration for aerobic conditioning has a different acute effect on mood for nonexercisers than regular exercisers. Design: Repeated-measures design. Setting: Research laboratory. Participants: Adult nonexercisers, moderate exercisers, and ultramarathon runners (8 men, 8 women in each group). Interventions: Treadmill exercise at self-selected speeds to induce a rating of perceived exertion (RPE) of 13 (somewhat hard) for 20 minutes, preceded and followed by 5 minutes at an RPE of 9 (very light). Main Outcome Measure: Profile of Mood States before and 5 minutes after exercise. Results: Vigor increased by a mean ⫾ standard deviation of 8⫾7 points (95% confidence interval [CI], 5–12) among the ultramarathon runners and 5⫾4 points (95% CI, 2–9) among the moderate exercisers, with no improvement among the nonexercisers. Fatigue decreased by 5⫾6 points (95% CI, 2– 8) for the ultramarathon runners and 4⫾4 points (95% CI, 1–7) for the moderate exercisers, with no improvement among the nonexercisers. Postexercise total mood disturbance decreased by a mean of 21⫾16 points (95% CI, 12–29) among the ultramarathon runners, 16⫾10 points (95% CI, 7–24) among the moderate exercisers, and 9⫾13 points (95% CI, 1–18) among the nonexercisers. Conclusions: A single session of moderate aerobic exercise improves vigor and decreases fatigue among regular exercisers but causes no change in these scores for nonexercisers. Although total mood disturbance improves postexercise in exercisers and nonexercisers, regular exercisers have approximately twice the effect as nonexercisers. This limited postexercise mood improvement among nonexercisers may be an important deterrent for persistence with an exercise program. Key Words: Affect; Fatigue; Physical fitness; Rehabilitation; Stress, psychological. © 2008 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
From the Department of Physical Medicine & Rehabilitation, Department of Veterans Affairs, Northern California Health Care System, Sacramento, CA (MD Hoffman); University of California-Davis Medical Center, Sacramento, CA (MD Hoffman); and California School of Professional Psychology, Alliant International University, Sacramento, CA (DR Hoffman). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Martin D. Hoffman, MD, Dept of Physical Medicine & Rehabilitation (117), Sacramento VA Medical Center, 10535 Hospital Way, Mather, CA 95655-1200, e-mail: [email protected]. 0003-9993/08/8902-00669$34.00/0 doi:10.1016/j.apmr.2007.09.026
Arch Phys Med Rehabil Vol 89, February 2008
EOPLE HAVE SHOWN considerable creativity in discovering ways to avoid exercise. In fact, most U.S. adults do P not regularly participate in physical activities at the minimum
recommended levels associated with health benefits.1 An important contributing factor to this problem is that approximately half of the people who begin an exercise program will fail to continue beyond 6 months.2 Given the extent of disease risk related to physical inactivity and the high associated societal cost,3 it is critically important to improve our understanding of measures that can enhance participation in regular physical activity. In addition to important physical health benefits resulting from regular exercise,4-7 there is good evidence that psychologic benefits can also be attained from exercise conditioning.8-11 Furthermore, mood can be improved acutely after even a single session of exercise.8-12 However, it is not clear if acute mood improvements occur for middle-aged nonexercisers after performing a session of exercise of appropriate intensity and duration for developing cardiorespiratory fitness. This is because previous work has primarily focused on college-aged subjects, for whom the discrepancy in fitness between exercisers and nonexercisers may be less apparent than for older adults. An important factor contributing to the difficulty of continuing an exercise program could be that nonexercisers have a blunted improvement in mood after exercise. To explore this, we measured mood state before and after a single bout of exercise of suitable intensity and duration for cardiorespiratory conditioning, and we compared the responses among middleaged adult nonexercisers and 2 groups of regular exercisers. METHODS Three groups of adult subjects (nonexercisers, regular moderate exercisers, ultramarathon runners) participated in the study, with 16 subjects (8 men, 8 women) in each group. Sample size determination based on preliminary data from our laboratory indicated that group sizes of 16 would be adequate relative to the main study variables. All participants were educated beyond high school and were free of known cardiovascular, pulmonary, and metabolic diseases. Exclusion criteria included known pregnancy, the use of tobacco or nicotine-containing products, use of mood-altering medications or drugs, and musculoskeletal disorders interfering with exercise. All subjects were required to have previously used a treadmill. They were all advised to not exercise on the day of the study before testing, to not consume food or caffeine during the 2 hours before testing, and to not take pain or anti-inflammatory medication during the 6 hours before testing. Inclusion in the group of nonexercisers required people to have engaged in 5 or fewer aerobic exercise sessions a month of no more than 25 minutes a session during the 6 months preceding the study. Criteria for the regular moderate exerciser group included performing aerobic exercise for 30 to 60 minutes, 3 to 6 times a week, most weeks during the previous 6 months. Inclusion in the group of ultramarathon runners required completion of at least 2 competitive running races of a distance of at least 50km in the preceding 24 months. Ultra-
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ACUTE MOOD CHANGES FROM EXERCISE, Hoffman Table 1: Subjects’ Selected Characteristics Characteristics
Age (y) Body mass index (kg/m2) IPAQ leisure time (MET·min·wk⫺1) IPAQ total (MET·min·wk⫺1)
Nonexercisers
Moderate Exercisers
Ultramarathon Runners
44⫾8 30.5⫾7.1*† 169⫾235* 1986⫾1821*
41⫾9 23.4⫾3.7† 1873⫾1004† 3271⫾1623†
43⫾6 23.6⫾2.0* 5173⫾3933*† 9819⫾6215*†
NOTE. Values are mean ⫾ SD. Statistical differences at P⬍.01 level present between values identified with the same superscript (*,†). Abbreviation: MET, metabolic equivalent.
marathon runners were also required to have engaged in aerobic exercise for a minimum duration of 45 minutes during each exercise session, at least 4 days a week for most weeks during the preceding 12 months. Nonexercisers and regular moderate exercisers were recruited through flyers and word of mouth in the medical center where the research was conducted, the affiliated universities, and the surrounding communities and businesses. Ultramarathon runners were recruited through mass emailing to local ultramarathon runners and through personal contact. Each participant was provided a $20 gift certificate to a local grocery store chain after completion of the study. Study participants came to the laboratory on 1 occasion. Each completed the informed consent process and signed a consent form approved by the institutional review board, and each completed the long form, last 7 days, self-administered version of the International Physical Activity Questionnaire (IPAQ).13 The IPAQ is a validated self-reported measure for assessing physical activity,14 which was used to characterize subject groups. Subjects were also acquainted with the operation of the motorized treadmilla and were informed of the study protocol, but they were not provided details about the hypotheses being tested. Height and body mass were measured. Subjects then rested in a chair for 5 minutes, completed the Profile of Mood States (POMS), and rested another 5 minutes, after which they were instructed to get on the treadmill. They were told to adjust the treadmill speed so that the intensity resulted in a rating of perceived exertion (RPE) of 9 (very light) on the Borg 6-20 scale15 for 5 minutes, followed by an RPE of 13 (somewhat hard) for 20 minutes, and then back to an RPE of 9 for the last 5 minutes. This exercise protocol was chosen because the duration and intensity fall within the range generally advised for cardiorespiratory conditioning in healthy adults.4-7 After completion of the exercise, subjects were instructed to rest in the chair, and after 5 minutes they completed the POMS again. Treadmill grade was measured and remained at 2% throughout exercise. A slight incline was used because it produces energy costs more consistent with on-ground movement, at least at running speeds.16 Treadmill speed was recorded at the end of each 5 minutes of exercise. The POMS is a 65-item self-report inventory, requiring only a few minutes to complete,17 that has been used extensively to assess the acute effects of exercise on mood.8,9,11,12 The POMS measures 6 dimensions of mood on a 5-point continuum. A total mood disturbance index is derived by subtracting the vigor-activity score from the sum of the other 5 measures of affect (tension-anxiety, depression-dejection, anger-hostility, fatigue-inertia, confusion-bewilderment). With each administration of the POMS, each subject was provided instructions to record his/her mood based on how he/she was feeling at the present time. The same investigator was present during each test but avoided interaction with subjects once the first rest period
began, at which time instructions were provided through an audio recording. Each time the intensity was to change, the instructions indicated that subjects could adjust the speed throughout the exercise period as necessary to maintain the desired intensity. Subjects were not allowed to use watches or music throughout the study, and treadmill speed, grade, and time displays were covered to prohibit viewing by subjects. The room where the exercise was performed was well lighted but had no windows and minimal distractions. An RPE chart was mounted on the wall directly in front of the treadmill. Mean ⫾ standard deviation (SD) room temperature was 21.1°⫾1.3°C. The main dependent variables in this study were the 6 dimensions of mood and total mood disturbance as measured with the POMS. Each of these variables, as well as treadmill speed, were analyzed with 2-way (group by time) repeatedmeasures analyses of variance (ANOVAs) and Bonferroni post-tests. Subject characteristics were compared with 1-way ANOVA and the Tukey-Kramer post-test. When an anticipated statistical significance was not attained, effect size (ES) was determined by dividing the between-group difference in means by the pooled SD. As proposed by Cohen,18 ES was considered small for ES less than or equal to 0.2, moderate for ES less than or equal to 0.5 and large for ES greater than 0.8. A probability value of less than .05 was accepted as significant. RESULTS Selected subject characteristics are shown in table 1. Ages ranged from 28 to 59 years and were comparable among groups. As expected, body mass index was lower (P⬍.001) among the moderate exercisers and ultramarathon runners compared with the nonexercisers. Physical activity levels (leisure time component and total) during the 7 days preceding the study, as determined by the IPAQ, were higher (P⬍.01) among the ultramarathon runners compared with the nonexercisers and moderate exercisers. Leisure time and total physical activity levels were not statistically different between nonexercisers and moderate exercisers but had ESs that were large (ES⫽2.3) and moderate to large (ES⫽.7), respectively. The subscores of the POMS are shown in figure 1. Tension showed a small but significant decrease of 3 points in all groups (95% confidence interval [CI], 1–5 for ultramarathon runners and moderate exercisers; 1– 6 for nonexercisers). The nonexercisers showed a decrease of 3 points in depression (95% CI, 1–5) and a decrease of 2 points in anger (95% CI, .3–3), whereas the ultramarathon runners and moderate exercisers showed small decreases in confusion of 2 points (95% CI, .4 –3 for ultramarathon runners; .2–3 for moderate exercisers). Group-by-time interactions were not significant for tension, depression, anger, and confusion. More evident were the changes in vigor and fatigue. Vigor increased by a mean ⫾ SD of 8⫾7 points (95% CI, 5–12) among the ultramarathon runners and 5⫾4 points (95% CI, 2–9) among the moderate exercisers, whereas fatigue deArch Phys Med Rehabil Vol 89, February 2008
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Tension
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Fig 1. Six dimensions of mood from the POMS for the nonexercisers (Œ), moderate exercisers (□), and ultramarathon runners (⌬). Significant pre-exercise to postexercise differences are indicated with dashed lines and symbols (*P<.05, †P<.01, ‡P<.001). Error bars represent 1 SD and for clarity are displayed in only 1 direction for 2 groups.
creased by a mean of 5⫾6 points (95% CI, 2– 8) for the ultramarathon runners and 4⫾4 points (95% CI, 1–7) among the moderate exercisers. Significant group-by-time interactions (P⫽.006, P⫽.008, respectively) indicate that there were differences among groups in the effects of exercise on vigor and fatigue. Postexercise total mood disturbance was decreased by a mean ⫾ SD of 21⫾16 points (95% CI, 12–29) among the ultramarathon runners, 16⫾10 (95% CI, 7–24) among the moderate exercisers, and 9⫾13 points (95% CI, 1–18) among the nonexercisers (fig 2). A nearly significant group-by-time interaction (P⫽.08) is suggestive of a trend toward less of an effect among the nonexercisers than the other groups. Treadmill speeds are displayed in figure 3. There were no differences in speeds between the ultramarathon runners and moderate exercisers. However, treadmill speeds for the nonexercisers were slower across all time points compared with the ultramarathon runners and for all time points at the higher RPE compared with the moderate exercisers. DISCUSSION This study found that a single session of exercise of appropriate intensity and duration for aerobic fitness training resulted in an increase in vigor and a decrease in fatigue among adult Arch Phys Med Rehabil Vol 89, February 2008
ultramarathon runners and regular moderate exercisers. In contrast, adult nonexercisers showed no improvement in these scores, and the effect was statistically different for this group compared with the exercisers. Although total mood disturbance improved in all 3 groups after exercise, the 2 groups of exercisers showed approximately double the effect of the nonexercisers. These findings are likely important determinants for the overwhelming difficulty people have with persistence at an exercise program. Regular exercisers probably recognize that they will feel more energized after an exercise session, making it easier for them to initiate each workout. Novice exercisers would appear to be less likely to have as strong of a motivating force. The modest improvement in total mood scores among the nonexercisers resulted from statistically significant improvements in tension, depression, and anger. For each variable, the effect was small and not statistically different from what was observed among the exercisers. Furthermore, the effect did not appear to be due to an artificial elevation of pre-exercise values due to the anticipation of an unfamiliar experience (ie, the exercise), because pre-exercise values were low, within the normative range19 and comparable among groups. Quiet rest alone is known to induce acute improvements in anxiety of similar magnitude to aerobic exercise.11,20 As such, the small
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30
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20 10 0
* -10
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-20 Pre-Exercise
Postexercise
Fig 2. Total mood disturbance for the nonexercisers (Œ), moderate exercisers (□), and ultramarathon runners (⌬). Significant preexercise to postexercise differences are indicated with dashed lines and symbols (*P<.05, ‡P<.001). Error bars represent 1 SD and for clarity are displayed in only 1 direction for 2 groups.
improvements in tension, depression, and anger that nonclinical, sedentary people receive from a session of aerobic exercise may serve as little incentive for exercise over performing other activities that yield no benefits to cardiovascular health. Few previous studies have compared acute exercise-induced mood alterations between regular exercisers and nonexercisers. From those studies21-24 in which such a comparison was made, it is difficult to reach a conclusion other than that there seems to be a greater reduction in anxiety among regular exercisers than nonexercisers. Furthermore, in each of the studies21-28 that have compared acute exercise-induced mood changes between regular exercisers and nonexercisers, subjects were young adults or students. Results from populations of young adults cannot necessarily be generalized to a middle-aged population, because young adults are likely to be more fit as a result of their youth and are engaged in a different lifestyle than the balance of the adult population. The age range of subjects in the present study was 28 to 59 years. With mean age over 40 years for each group, participants in this study represent a wide age range starting well beyond the typical college years, in which many people are more likely to maintain fitness. Hence, this study is more representative of those in middle age than the earlier studies that involved young adults and students. It was anticipated that, if the acute mood effects from exercise were different between regular exercisers and nonexercisers, the difference would be most evident among groups of very different physical activity levels. Ultramarathon runners were chosen as 1 of the groups of regular exercisers in this study because they have a much greater physical activity level than nonexercisers (see table 1). However, moderate exercisers showed mood changes comparable with those of ultramarathon runners. Previous work has shown a greater tendency toward exercise dependence for runners participating in longer-dis-
tance events.29 Whether exercise dependence is related to the acute mood effects from exercise is not clear. Nonetheless, the results of this study suggest that regular moderate exercisers have an important acute mood enhancement from exercise that probably has a favorable impact on their continuation of a regular exercise program. Many regular exercisers prefer different exercise conditions than were imposed by this study. For instance, walking or running outdoors over varying terrain and for a longer duration would likely have been preferred by some of the exercisers. As such, it would be anticipated that under more preferable exercise circumstances, the mood improvements for the exercisers might be even greater than were observed here. The mechanism accounting for the group differences in acute mood change from exercise cannot be elucidated from this study; however, possible explanations can be considered. Differences in exercise workloads between the regular exercisers and nonexercisers may have played a role. An RPE of 13 has been shown to be close to the lactate threshold for trained as well as for untrained men and women.30 However, the relationship between RPE and percentage of maximal oxygen ˙ O2max) is affected by fitness level in such a way that, uptake (V ˙ O2max is higher for those at a given RPE, the percentage of V who are trained.30 Therefore, in the present study, it is likely that ultramarathon runners and moderate exercisers were exercising at a higher absolute workload and a higher percentage of ˙ O2max than the nonexercisers. This may, at least partially, V account for the greater mood effect that was observed in the exercisers, because many of the theories of the underlying mechanisms for exercise-induced mood change8,9 are based on physiologic responses that are directly related to absolute or relative exercise intensity. Another possible explanation for the present findings may relate to individual variations in the acute mood response to exercise. Elevation in mood and reduced tension after exercise
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Time (min) Fig 3. Treadmill speeds at the end of each 5-minute period for the 3 groups. Significant differences between groups are indicated by the same letter (a, b). Error bars represent 1 SD and for clarity are displayed in only 1 direction for 2 groups.
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are recognized to be powerful motivators for continuing a running program.31,32 We would anticipate that nonexercisers who start and adhere to a regular exercise program will eventually begin to experience mood enhancement similar to that observed among the exercisers in this study. However, it is conceivable that some people may not acquire such benefits even after consistent participation in an exercise training program. For those people, the adoption of a sedentary lifestyle could be a manifestation of a blunted mood response to exercise. Given the growing evidence for genetic links to certain acute physiologic responses to exercise, adaptations to exercise training, and exercise intolerance,33 further efforts at investigating a genetic basis for exercise adherence seem important. Future research should also include longitudinal exercise training studies that explore the duration of participation in a regular exercise program that might be required for acute postexercise mood enhancement to become evident. Study Limitations Some limitations to the study are acknowledged. One limitation is that objective physiologic measurements to determine exercise intensity were not made in this study. We specifically chose to avoid heart rate and oxygen uptake measurements during the exercise to limit intrusions on subjects that might affect mood. As a result, we cannot define the exercise intensities beyond an estimation of what is typical for an RPE of 13. However, our approach was justified in that perception of effort is the typical manner in which people establish exercise intensity. An RPE of 13 (somewhat hard) falls in the middle of the range of recommended exercise intensities of approximately ˙ O2max or 60% to 90% of maximal heart 50% to 85% of V rate.34 The timing of the postexercise POMS measurement was determined based on previous studies showing exercise-induced mood enhancement at about 5 minutes after exercise.20,22,24,35-37 It could be considered a limitation by some that the POMS was measured at only 5 minutes postexercise and not repeated at a later time. However, had we performed a POMS assessment at a later time point, there would then be a potentially confounding issue of what subjects had done during the interval between completions of the POMS, because it is know that relaxation and quiet rest alone can alter mood.11,20 Another concern with performing only 1 postexercise mood assessment is that the effect could be missed because the greatest change had already dissipated or had not yet occurred at the time of assessment. It is also conceivable that mood changes could follow a different time course depending on fitness level when exercise intensity is established by RPE. One study has shown that improvements in state anxiety were found to be delayed beyond 5 minutes postexercise when the exercise was at intensities of 70% to ˙ O2max, whereas the effect was more immediate 80% of V after moderate exercise intensities.20,35 Although the exer˙ O2max likely differed cise intensity as a percentage of V among the groups in this study, an RPE of 13 typically ˙ O2max of less than 70%,34 and it would be corresponds to a V expected that unfit subjects would be at a lower percentage ˙ O2max for a given RPE than fit subjects.30 As such, it is of V unlikely that the nonexercisers were at a high enough intensity for a delayed response to have been an issue in the assessment of tension-anxiety. Furthermore, the tensionanxiety scores were low at baseline among all groups, leaving little room for further improvement beyond what was observed. Arch Phys Med Rehabil Vol 89, February 2008
CONCLUSIONS Although previous work has shown that aerobic exercise generally results in acute mood improvements, very little attention has been directed at determining whether this effect is similarly present among regular exercisers and nonexercisers. Furthermore, there has been no comparison of regular exercisers and nonexercisers who are middle-aged using exercise intensities and durations within the range that is recommended for enhancing health and fitness. The present study helps clarify that adult nonexercisers have statistically significant improvements in total mood disturbance that may have some clinical relevance. However, the mood improvement among nonexercisers is exceeded by the response among regular exercisers. The lack of an increase in vigor and decrease in fatigue among adult nonexercisers may contribute to the difficulties experienced by these people in maintaining a regular exercise program. Such information should be shared with those initiating an exercise program so that they may be more likely to persist through the initial phases of the program. References 1. Centers for Disease Control and Prevention (CDC). Adult participation in recommended levels of physical activity—United States, 2001 and 2003. MMWR Morb Mortal Wkly Rep 2005;54: 1208-12. 2. Robinson JI, Rogers MA. Adherence to exercise programmes. Recommendations. Sports Med 1994;17:39-52. 3. Anderson LH, Martinson BC, Crain AL, et al. Health care charges associated with physical inactivity, overweight, and obesity. Prev Chronic Dis 2005;2(4):A09. 4. American College of Obstetricians and Gynecologists. Exercise during pregnancy and the postpartum period. Clin Obstet Gynecol 2003;46:496-9. 5. Haskell WL, Lee IM, Pate RR, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc 2007;39:1423-34. 6. Pate RR, Pratt M, Blair SN, et al. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 1995;273:402-7. 7. U.S. Department of Health and Human Services. Physical activity and health: a report of the Surgeon General. Atlanta: Centers of Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion; 1996. Publication no. AD-A329 047/5INT. 8. Berger BG, Motl RW. Exercise and mood: a selective review and synthesis of research employing the profile of mood states. J Appl Sport Psychol 2000;12:69-92. 9. Biddle S. Exercise, emotions, and mental health. In: Hanin YL, editor. Emotions in sport. Champaign: Human Kinetics; 2000. p 267–91. 10. Hoffman MD, Hoffman DR. Does aerobic exercise improve pain perception and mood? A review of the evidence related to healthy and chronic pain subjects. Curr Pain Headache Rep 2007;11:93-7. 11. Petruzzello SJ, Landers DM, Hatfield BD, Kubitz KA, Salazar W. A meta-analysis on the anxiety-reducing effects of acute and chronic exercise. Outcomes and mechanisms. Sports Med 1991; 11:143-82. 12. Yeung RR. The acute effects of exercise on mood state. J Psychosom Res 1996;40:123-41. 13. Booth ML. Assessment of physical activity: an international perspective. Res Q Exerc Sport 2000;71:114-20.
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14. Craig CL, Marshall AL, Sjöström M, et al. International physical activity questionnaire: 12-country reliability and validity. Med Sci Sports Exerc 2003;35:1381-95. 15. Borg GA. Psychophysical bases of perceived exertion. Med Sci Sports Exerc 1982;14:377-81. 16. Jones AM, Doust JH. A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. J Sports Sci 1996; 14:321-7. 17. McNair DM, Lorr M, Droppleman L. Manual for the Profile of Mood States. San Diego: Educational and Industrial Testing Service; 1971. 18. Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. Hillsdale: Lawrence Erlbaum; 1988. 19. Nyenhuis DL, Yamamoto C, Luchetta T, Terrien A, Parmentier A. Adult and geriatric normative data and validation of the profile of mood states. J Clin Psychol 1999;55:79-86. 20. Cox RH, Thomas TR, Hinton PS, Donahue OM. Effects of acute ˙ O2max bouts of aerobic exercise on state anxiety of 60 and 80% V women of different age groups across time. Res Q Exerc Sport 2004;75:165-75. 21. Boutcher SH, Landers DM. The effects of vigorous exercise on anxiety, heart rate, and alpha activity of runners and nonrunners. Psychophysiology 1988;25:696-702. 22. Boutcher SH, McAuley E, Coumeya KS. Positive and negative affective response of trained and untrained subjects during and after aerobic exercise. Aust J Psychol 1997;49:28-32. 23. Dishman RK, Farquhar RP, Cureton KJ. Responses to preferred intensities of exertion in men differing in activity levels. Med Sci Sports Exerc 1994;26:783-90. 24. Petruzzello SJ, Jones AC, Tate AK. Affective responses to acute exercise: a test of the opponent-process theory. J Sports Med Phys Fitness 1997;37:205-12. 25. Roth DL. Acute emotional and psychophysiological effects of aerobic exercise. Psychophysiology 1989;26:593-602.
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26. Steptoe A, Cox S. Acute effects of aerobic exercise on mood. Health Psychol 1988;7:329-40. 27. Steptoe A, Kearsley N, Walters N. Acute mood responses to maximal and submaximal exercise in active and inactive men. Psychol Health 1993;8:89-99. 28. Tieman JG, Peacock LJ, Cureton KJ, Dishman RK. The influence of exercise intensity and physical activity history on state anxiety after exercise. Int J Sport Psychol 2002;33:155-66. 29. Pierce EF, McGowan RW, Lynn TD. Exercise dependence in relation to competitive orientation of runners. J Sports Med Phys Fitness 1993;33:189-93. 30. Demello JJ, Cureton KJ, Boineau RE, Singh MM. Ratings of perceived exertion at the lactate threshold in trained and untrained men and women. Med Sci Sports Exerc 1987;19:354-62. 31. Johnsgard K. The motivation of the long distance runner: I. J Sports Med 1985;25:135-9. 32. Johnsgard K. The motivation of the long distance runner: II. J Sports Med 1985;25:140-3. 33. Rankinen T, Bray MS, Hagberg JM, et al. The human gene map for performance and health-related fitness phenotypes: the 2005 update. Med Sci Sports Exerc 2006;38:1863-88. 34. Zeni AI, Hoffman MD, Clifford PS. Energy expenditure with indoor exercise machines. JAMA 1996;275:1424-7. 35. Raglin JS, Wilson M. State anxiety following 20 minutes of bicycle ergometer exercise at selected intensities. Int J Sports Med 1996;17:467-71. 36. Rehor PR, Dunnagan T, Stewart C, Cooley D. Alteration of mood state after a single bout of noncompetitive and competitive exercise programs. Percept Mot Skills 2001;93:249-56. 37. Steptoe A, Bolton J. The short-term influence of high and low intensity physical exercise on mood. Psychol Health 1988;2:91106. Supplier a. Schwinn model CI-430; Schwinn, 16400 SE Nautilus Dr, Vancouver, WA 98683.
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ORIGINAL ARTICLE
Exercisers Achieve Greater Acute Exercise-Induced Mood Enhancement Than Nonexercisers Martin D. Hoffman, MD, Debi Rufi Hoffman, MA ABSTRACT. Hoffman MD, Hoffman DR. Exercisers achieve greater acute exercise-induced mood enhancement than nonexercisers. Arch Phys Med Rehabil 2008;89:358-63. Objective: To determine whether a single session of exercise of appropriate intensity and duration for aerobic conditioning has a different acute effect on mood for nonexercisers than regular exercisers. Design: Repeated-measures design. Setting: Research laboratory. Participants: Adult nonexercisers, moderate exercisers, and ultramarathon runners (8 men, 8 women in each group). Interventions: Treadmill exercise at self-selected speeds to induce a rating of perceived exertion (RPE) of 13 (somewhat hard) for 20 minutes, preceded and followed by 5 minutes at an RPE of 9 (very light). Main Outcome Measure: Profile of Mood States before and 5 minutes after exercise. Results: Vigor increased by a mean ⫾ standard deviation of 8⫾7 points (95% confidence interval [CI], 5–12) among the ultramarathon runners and 5⫾4 points (95% CI, 2–9) among the moderate exercisers, with no improvement among the nonexercisers. Fatigue decreased by 5⫾6 points (95% CI, 2– 8) for the ultramarathon runners and 4⫾4 points (95% CI, 1–7) for the moderate exercisers, with no improvement among the nonexercisers. Postexercise total mood disturbance decreased by a mean of 21⫾16 points (95% CI, 12–29) among the ultramarathon runners, 16⫾10 points (95% CI, 7–24) among the moderate exercisers, and 9⫾13 points (95% CI, 1–18) among the nonexercisers. Conclusions: A single session of moderate aerobic exercise improves vigor and decreases fatigue among regular exercisers but causes no change in these scores for nonexercisers. Although total mood disturbance improves postexercise in exercisers and nonexercisers, regular exercisers have approximately twice the effect as nonexercisers. This limited postexercise mood improvement among nonexercisers may be an important deterrent for persistence with an exercise program. Key Words: Affect; Fatigue; Physical fitness; Rehabilitation; Stress, psychological. © 2008 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
From the Department of Physical Medicine & Rehabilitation, Department of Veterans Affairs, Northern California Health Care System, Sacramento, CA (MD Hoffman); University of California-Davis Medical Center, Sacramento, CA (MD Hoffman); and California School of Professional Psychology, Alliant International University, Sacramento, CA (DR Hoffman). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Martin D. Hoffman, MD, Dept of Physical Medicine & Rehabilitation (117), Sacramento VA Medical Center, 10535 Hospital Way, Mather, CA 95655-1200, e-mail: [email protected]. 0003-9993/08/8902-00669$34.00/0 doi:10.1016/j.apmr.2007.09.026
Arch Phys Med Rehabil Vol 89, February 2008
EOPLE HAVE SHOWN considerable creativity in discovering ways to avoid exercise. In fact, most U.S. adults do P not regularly participate in physical activities at the minimum
recommended levels associated with health benefits.1 An important contributing factor to this problem is that approximately half of the people who begin an exercise program will fail to continue beyond 6 months.2 Given the extent of disease risk related to physical inactivity and the high associated societal cost,3 it is critically important to improve our understanding of measures that can enhance participation in regular physical activity. In addition to important physical health benefits resulting from regular exercise,4-7 there is good evidence that psychologic benefits can also be attained from exercise conditioning.8-11 Furthermore, mood can be improved acutely after even a single session of exercise.8-12 However, it is not clear if acute mood improvements occur for middle-aged nonexercisers after performing a session of exercise of appropriate intensity and duration for developing cardiorespiratory fitness. This is because previous work has primarily focused on college-aged subjects, for whom the discrepancy in fitness between exercisers and nonexercisers may be less apparent than for older adults. An important factor contributing to the difficulty of continuing an exercise program could be that nonexercisers have a blunted improvement in mood after exercise. To explore this, we measured mood state before and after a single bout of exercise of suitable intensity and duration for cardiorespiratory conditioning, and we compared the responses among middleaged adult nonexercisers and 2 groups of regular exercisers. METHODS Three groups of adult subjects (nonexercisers, regular moderate exercisers, ultramarathon runners) participated in the study, with 16 subjects (8 men, 8 women) in each group. Sample size determination based on preliminary data from our laboratory indicated that group sizes of 16 would be adequate relative to the main study variables. All participants were educated beyond high school and were free of known cardiovascular, pulmonary, and metabolic diseases. Exclusion criteria included known pregnancy, the use of tobacco or nicotine-containing products, use of mood-altering medications or drugs, and musculoskeletal disorders interfering with exercise. All subjects were required to have previously used a treadmill. They were all advised to not exercise on the day of the study before testing, to not consume food or caffeine during the 2 hours before testing, and to not take pain or anti-inflammatory medication during the 6 hours before testing. Inclusion in the group of nonexercisers required people to have engaged in 5 or fewer aerobic exercise sessions a month of no more than 25 minutes a session during the 6 months preceding the study. Criteria for the regular moderate exerciser group included performing aerobic exercise for 30 to 60 minutes, 3 to 6 times a week, most weeks during the previous 6 months. Inclusion in the group of ultramarathon runners required completion of at least 2 competitive running races of a distance of at least 50km in the preceding 24 months. Ultra-
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ACUTE MOOD CHANGES FROM EXERCISE, Hoffman Table 1: Subjects’ Selected Characteristics Characteristics
Age (y) Body mass index (kg/m2) IPAQ leisure time (MET·min·wk⫺1) IPAQ total (MET·min·wk⫺1)
Nonexercisers
Moderate Exercisers
Ultramarathon Runners
44⫾8 30.5⫾7.1*† 169⫾235* 1986⫾1821*
41⫾9 23.4⫾3.7† 1873⫾1004† 3271⫾1623†
43⫾6 23.6⫾2.0* 5173⫾3933*† 9819⫾6215*†
NOTE. Values are mean ⫾ SD. Statistical differences at P⬍.01 level present between values identified with the same superscript (*,†). Abbreviation: MET, metabolic equivalent.
marathon runners were also required to have engaged in aerobic exercise for a minimum duration of 45 minutes during each exercise session, at least 4 days a week for most weeks during the preceding 12 months. Nonexercisers and regular moderate exercisers were recruited through flyers and word of mouth in the medical center where the research was conducted, the affiliated universities, and the surrounding communities and businesses. Ultramarathon runners were recruited through mass emailing to local ultramarathon runners and through personal contact. Each participant was provided a $20 gift certificate to a local grocery store chain after completion of the study. Study participants came to the laboratory on 1 occasion. Each completed the informed consent process and signed a consent form approved by the institutional review board, and each completed the long form, last 7 days, self-administered version of the International Physical Activity Questionnaire (IPAQ).13 The IPAQ is a validated self-reported measure for assessing physical activity,14 which was used to characterize subject groups. Subjects were also acquainted with the operation of the motorized treadmilla and were informed of the study protocol, but they were not provided details about the hypotheses being tested. Height and body mass were measured. Subjects then rested in a chair for 5 minutes, completed the Profile of Mood States (POMS), and rested another 5 minutes, after which they were instructed to get on the treadmill. They were told to adjust the treadmill speed so that the intensity resulted in a rating of perceived exertion (RPE) of 9 (very light) on the Borg 6-20 scale15 for 5 minutes, followed by an RPE of 13 (somewhat hard) for 20 minutes, and then back to an RPE of 9 for the last 5 minutes. This exercise protocol was chosen because the duration and intensity fall within the range generally advised for cardiorespiratory conditioning in healthy adults.4-7 After completion of the exercise, subjects were instructed to rest in the chair, and after 5 minutes they completed the POMS again. Treadmill grade was measured and remained at 2% throughout exercise. A slight incline was used because it produces energy costs more consistent with on-ground movement, at least at running speeds.16 Treadmill speed was recorded at the end of each 5 minutes of exercise. The POMS is a 65-item self-report inventory, requiring only a few minutes to complete,17 that has been used extensively to assess the acute effects of exercise on mood.8,9,11,12 The POMS measures 6 dimensions of mood on a 5-point continuum. A total mood disturbance index is derived by subtracting the vigor-activity score from the sum of the other 5 measures of affect (tension-anxiety, depression-dejection, anger-hostility, fatigue-inertia, confusion-bewilderment). With each administration of the POMS, each subject was provided instructions to record his/her mood based on how he/she was feeling at the present time. The same investigator was present during each test but avoided interaction with subjects once the first rest period
began, at which time instructions were provided through an audio recording. Each time the intensity was to change, the instructions indicated that subjects could adjust the speed throughout the exercise period as necessary to maintain the desired intensity. Subjects were not allowed to use watches or music throughout the study, and treadmill speed, grade, and time displays were covered to prohibit viewing by subjects. The room where the exercise was performed was well lighted but had no windows and minimal distractions. An RPE chart was mounted on the wall directly in front of the treadmill. Mean ⫾ standard deviation (SD) room temperature was 21.1°⫾1.3°C. The main dependent variables in this study were the 6 dimensions of mood and total mood disturbance as measured with the POMS. Each of these variables, as well as treadmill speed, were analyzed with 2-way (group by time) repeatedmeasures analyses of variance (ANOVAs) and Bonferroni post-tests. Subject characteristics were compared with 1-way ANOVA and the Tukey-Kramer post-test. When an anticipated statistical significance was not attained, effect size (ES) was determined by dividing the between-group difference in means by the pooled SD. As proposed by Cohen,18 ES was considered small for ES less than or equal to 0.2, moderate for ES less than or equal to 0.5 and large for ES greater than 0.8. A probability value of less than .05 was accepted as significant. RESULTS Selected subject characteristics are shown in table 1. Ages ranged from 28 to 59 years and were comparable among groups. As expected, body mass index was lower (P⬍.001) among the moderate exercisers and ultramarathon runners compared with the nonexercisers. Physical activity levels (leisure time component and total) during the 7 days preceding the study, as determined by the IPAQ, were higher (P⬍.01) among the ultramarathon runners compared with the nonexercisers and moderate exercisers. Leisure time and total physical activity levels were not statistically different between nonexercisers and moderate exercisers but had ESs that were large (ES⫽2.3) and moderate to large (ES⫽.7), respectively. The subscores of the POMS are shown in figure 1. Tension showed a small but significant decrease of 3 points in all groups (95% confidence interval [CI], 1–5 for ultramarathon runners and moderate exercisers; 1– 6 for nonexercisers). The nonexercisers showed a decrease of 3 points in depression (95% CI, 1–5) and a decrease of 2 points in anger (95% CI, .3–3), whereas the ultramarathon runners and moderate exercisers showed small decreases in confusion of 2 points (95% CI, .4 –3 for ultramarathon runners; .2–3 for moderate exercisers). Group-by-time interactions were not significant for tension, depression, anger, and confusion. More evident were the changes in vigor and fatigue. Vigor increased by a mean ⫾ SD of 8⫾7 points (95% CI, 5–12) among the ultramarathon runners and 5⫾4 points (95% CI, 2–9) among the moderate exercisers, whereas fatigue deArch Phys Med Rehabil Vol 89, February 2008
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ACUTE MOOD CHANGES FROM EXERCISE, Hoffman
Tension
Depression
Anger
20
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Fig 1. Six dimensions of mood from the POMS for the nonexercisers (Œ), moderate exercisers (□), and ultramarathon runners (⌬). Significant pre-exercise to postexercise differences are indicated with dashed lines and symbols (*P<.05, †P<.01, ‡P<.001). Error bars represent 1 SD and for clarity are displayed in only 1 direction for 2 groups.
creased by a mean of 5⫾6 points (95% CI, 2– 8) for the ultramarathon runners and 4⫾4 points (95% CI, 1–7) among the moderate exercisers. Significant group-by-time interactions (P⫽.006, P⫽.008, respectively) indicate that there were differences among groups in the effects of exercise on vigor and fatigue. Postexercise total mood disturbance was decreased by a mean ⫾ SD of 21⫾16 points (95% CI, 12–29) among the ultramarathon runners, 16⫾10 (95% CI, 7–24) among the moderate exercisers, and 9⫾13 points (95% CI, 1–18) among the nonexercisers (fig 2). A nearly significant group-by-time interaction (P⫽.08) is suggestive of a trend toward less of an effect among the nonexercisers than the other groups. Treadmill speeds are displayed in figure 3. There were no differences in speeds between the ultramarathon runners and moderate exercisers. However, treadmill speeds for the nonexercisers were slower across all time points compared with the ultramarathon runners and for all time points at the higher RPE compared with the moderate exercisers. DISCUSSION This study found that a single session of exercise of appropriate intensity and duration for aerobic fitness training resulted in an increase in vigor and a decrease in fatigue among adult Arch Phys Med Rehabil Vol 89, February 2008
ultramarathon runners and regular moderate exercisers. In contrast, adult nonexercisers showed no improvement in these scores, and the effect was statistically different for this group compared with the exercisers. Although total mood disturbance improved in all 3 groups after exercise, the 2 groups of exercisers showed approximately double the effect of the nonexercisers. These findings are likely important determinants for the overwhelming difficulty people have with persistence at an exercise program. Regular exercisers probably recognize that they will feel more energized after an exercise session, making it easier for them to initiate each workout. Novice exercisers would appear to be less likely to have as strong of a motivating force. The modest improvement in total mood scores among the nonexercisers resulted from statistically significant improvements in tension, depression, and anger. For each variable, the effect was small and not statistically different from what was observed among the exercisers. Furthermore, the effect did not appear to be due to an artificial elevation of pre-exercise values due to the anticipation of an unfamiliar experience (ie, the exercise), because pre-exercise values were low, within the normative range19 and comparable among groups. Quiet rest alone is known to induce acute improvements in anxiety of similar magnitude to aerobic exercise.11,20 As such, the small
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30
Score
20 10 0
* -10
‡ ‡
-20 Pre-Exercise
Postexercise
Fig 2. Total mood disturbance for the nonexercisers (Œ), moderate exercisers (□), and ultramarathon runners (⌬). Significant preexercise to postexercise differences are indicated with dashed lines and symbols (*P<.05, ‡P<.001). Error bars represent 1 SD and for clarity are displayed in only 1 direction for 2 groups.
improvements in tension, depression, and anger that nonclinical, sedentary people receive from a session of aerobic exercise may serve as little incentive for exercise over performing other activities that yield no benefits to cardiovascular health. Few previous studies have compared acute exercise-induced mood alterations between regular exercisers and nonexercisers. From those studies21-24 in which such a comparison was made, it is difficult to reach a conclusion other than that there seems to be a greater reduction in anxiety among regular exercisers than nonexercisers. Furthermore, in each of the studies21-28 that have compared acute exercise-induced mood changes between regular exercisers and nonexercisers, subjects were young adults or students. Results from populations of young adults cannot necessarily be generalized to a middle-aged population, because young adults are likely to be more fit as a result of their youth and are engaged in a different lifestyle than the balance of the adult population. The age range of subjects in the present study was 28 to 59 years. With mean age over 40 years for each group, participants in this study represent a wide age range starting well beyond the typical college years, in which many people are more likely to maintain fitness. Hence, this study is more representative of those in middle age than the earlier studies that involved young adults and students. It was anticipated that, if the acute mood effects from exercise were different between regular exercisers and nonexercisers, the difference would be most evident among groups of very different physical activity levels. Ultramarathon runners were chosen as 1 of the groups of regular exercisers in this study because they have a much greater physical activity level than nonexercisers (see table 1). However, moderate exercisers showed mood changes comparable with those of ultramarathon runners. Previous work has shown a greater tendency toward exercise dependence for runners participating in longer-dis-
tance events.29 Whether exercise dependence is related to the acute mood effects from exercise is not clear. Nonetheless, the results of this study suggest that regular moderate exercisers have an important acute mood enhancement from exercise that probably has a favorable impact on their continuation of a regular exercise program. Many regular exercisers prefer different exercise conditions than were imposed by this study. For instance, walking or running outdoors over varying terrain and for a longer duration would likely have been preferred by some of the exercisers. As such, it would be anticipated that under more preferable exercise circumstances, the mood improvements for the exercisers might be even greater than were observed here. The mechanism accounting for the group differences in acute mood change from exercise cannot be elucidated from this study; however, possible explanations can be considered. Differences in exercise workloads between the regular exercisers and nonexercisers may have played a role. An RPE of 13 has been shown to be close to the lactate threshold for trained as well as for untrained men and women.30 However, the relationship between RPE and percentage of maximal oxygen ˙ O2max) is affected by fitness level in such a way that, uptake (V ˙ O2max is higher for those at a given RPE, the percentage of V who are trained.30 Therefore, in the present study, it is likely that ultramarathon runners and moderate exercisers were exercising at a higher absolute workload and a higher percentage of ˙ O2max than the nonexercisers. This may, at least partially, V account for the greater mood effect that was observed in the exercisers, because many of the theories of the underlying mechanisms for exercise-induced mood change8,9 are based on physiologic responses that are directly related to absolute or relative exercise intensity. Another possible explanation for the present findings may relate to individual variations in the acute mood response to exercise. Elevation in mood and reduced tension after exercise
12 10
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Total Mood Disturbance
a b
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Ultramarathoners Moderate Exercisers Nonexercisers
0 0
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Time (min) Fig 3. Treadmill speeds at the end of each 5-minute period for the 3 groups. Significant differences between groups are indicated by the same letter (a, b). Error bars represent 1 SD and for clarity are displayed in only 1 direction for 2 groups.
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are recognized to be powerful motivators for continuing a running program.31,32 We would anticipate that nonexercisers who start and adhere to a regular exercise program will eventually begin to experience mood enhancement similar to that observed among the exercisers in this study. However, it is conceivable that some people may not acquire such benefits even after consistent participation in an exercise training program. For those people, the adoption of a sedentary lifestyle could be a manifestation of a blunted mood response to exercise. Given the growing evidence for genetic links to certain acute physiologic responses to exercise, adaptations to exercise training, and exercise intolerance,33 further efforts at investigating a genetic basis for exercise adherence seem important. Future research should also include longitudinal exercise training studies that explore the duration of participation in a regular exercise program that might be required for acute postexercise mood enhancement to become evident. Study Limitations Some limitations to the study are acknowledged. One limitation is that objective physiologic measurements to determine exercise intensity were not made in this study. We specifically chose to avoid heart rate and oxygen uptake measurements during the exercise to limit intrusions on subjects that might affect mood. As a result, we cannot define the exercise intensities beyond an estimation of what is typical for an RPE of 13. However, our approach was justified in that perception of effort is the typical manner in which people establish exercise intensity. An RPE of 13 (somewhat hard) falls in the middle of the range of recommended exercise intensities of approximately ˙ O2max or 60% to 90% of maximal heart 50% to 85% of V rate.34 The timing of the postexercise POMS measurement was determined based on previous studies showing exercise-induced mood enhancement at about 5 minutes after exercise.20,22,24,35-37 It could be considered a limitation by some that the POMS was measured at only 5 minutes postexercise and not repeated at a later time. However, had we performed a POMS assessment at a later time point, there would then be a potentially confounding issue of what subjects had done during the interval between completions of the POMS, because it is know that relaxation and quiet rest alone can alter mood.11,20 Another concern with performing only 1 postexercise mood assessment is that the effect could be missed because the greatest change had already dissipated or had not yet occurred at the time of assessment. It is also conceivable that mood changes could follow a different time course depending on fitness level when exercise intensity is established by RPE. One study has shown that improvements in state anxiety were found to be delayed beyond 5 minutes postexercise when the exercise was at intensities of 70% to ˙ O2max, whereas the effect was more immediate 80% of V after moderate exercise intensities.20,35 Although the exer˙ O2max likely differed cise intensity as a percentage of V among the groups in this study, an RPE of 13 typically ˙ O2max of less than 70%,34 and it would be corresponds to a V expected that unfit subjects would be at a lower percentage ˙ O2max for a given RPE than fit subjects.30 As such, it is of V unlikely that the nonexercisers were at a high enough intensity for a delayed response to have been an issue in the assessment of tension-anxiety. Furthermore, the tensionanxiety scores were low at baseline among all groups, leaving little room for further improvement beyond what was observed. Arch Phys Med Rehabil Vol 89, February 2008
CONCLUSIONS Although previous work has shown that aerobic exercise generally results in acute mood improvements, very little attention has been directed at determining whether this effect is similarly present among regular exercisers and nonexercisers. Furthermore, there has been no comparison of regular exercisers and nonexercisers who are middle-aged using exercise intensities and durations within the range that is recommended for enhancing health and fitness. The present study helps clarify that adult nonexercisers have statistically significant improvements in total mood disturbance that may have some clinical relevance. However, the mood improvement among nonexercisers is exceeded by the response among regular exercisers. The lack of an increase in vigor and decrease in fatigue among adult nonexercisers may contribute to the difficulties experienced by these people in maintaining a regular exercise program. Such information should be shared with those initiating an exercise program so that they may be more likely to persist through the initial phases of the program. References 1. Centers for Disease Control and Prevention (CDC). Adult participation in recommended levels of physical activity—United States, 2001 and 2003. MMWR Morb Mortal Wkly Rep 2005;54: 1208-12. 2. Robinson JI, Rogers MA. Adherence to exercise programmes. Recommendations. Sports Med 1994;17:39-52. 3. Anderson LH, Martinson BC, Crain AL, et al. Health care charges associated with physical inactivity, overweight, and obesity. Prev Chronic Dis 2005;2(4):A09. 4. American College of Obstetricians and Gynecologists. Exercise during pregnancy and the postpartum period. Clin Obstet Gynecol 2003;46:496-9. 5. Haskell WL, Lee IM, Pate RR, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc 2007;39:1423-34. 6. Pate RR, Pratt M, Blair SN, et al. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 1995;273:402-7. 7. U.S. Department of Health and Human Services. Physical activity and health: a report of the Surgeon General. Atlanta: Centers of Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion; 1996. Publication no. AD-A329 047/5INT. 8. Berger BG, Motl RW. Exercise and mood: a selective review and synthesis of research employing the profile of mood states. J Appl Sport Psychol 2000;12:69-92. 9. Biddle S. Exercise, emotions, and mental health. In: Hanin YL, editor. Emotions in sport. Champaign: Human Kinetics; 2000. p 267–91. 10. Hoffman MD, Hoffman DR. Does aerobic exercise improve pain perception and mood? A review of the evidence related to healthy and chronic pain subjects. Curr Pain Headache Rep 2007;11:93-7. 11. Petruzzello SJ, Landers DM, Hatfield BD, Kubitz KA, Salazar W. A meta-analysis on the anxiety-reducing effects of acute and chronic exercise. Outcomes and mechanisms. Sports Med 1991; 11:143-82. 12. Yeung RR. The acute effects of exercise on mood state. J Psychosom Res 1996;40:123-41. 13. Booth ML. Assessment of physical activity: an international perspective. Res Q Exerc Sport 2000;71:114-20.
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14. Craig CL, Marshall AL, Sjöström M, et al. International physical activity questionnaire: 12-country reliability and validity. Med Sci Sports Exerc 2003;35:1381-95. 15. Borg GA. Psychophysical bases of perceived exertion. Med Sci Sports Exerc 1982;14:377-81. 16. Jones AM, Doust JH. A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. J Sports Sci 1996; 14:321-7. 17. McNair DM, Lorr M, Droppleman L. Manual for the Profile of Mood States. San Diego: Educational and Industrial Testing Service; 1971. 18. Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. Hillsdale: Lawrence Erlbaum; 1988. 19. Nyenhuis DL, Yamamoto C, Luchetta T, Terrien A, Parmentier A. Adult and geriatric normative data and validation of the profile of mood states. J Clin Psychol 1999;55:79-86. 20. Cox RH, Thomas TR, Hinton PS, Donahue OM. Effects of acute ˙ O2max bouts of aerobic exercise on state anxiety of 60 and 80% V women of different age groups across time. Res Q Exerc Sport 2004;75:165-75. 21. Boutcher SH, Landers DM. The effects of vigorous exercise on anxiety, heart rate, and alpha activity of runners and nonrunners. Psychophysiology 1988;25:696-702. 22. Boutcher SH, McAuley E, Coumeya KS. Positive and negative affective response of trained and untrained subjects during and after aerobic exercise. Aust J Psychol 1997;49:28-32. 23. Dishman RK, Farquhar RP, Cureton KJ. Responses to preferred intensities of exertion in men differing in activity levels. Med Sci Sports Exerc 1994;26:783-90. 24. Petruzzello SJ, Jones AC, Tate AK. Affective responses to acute exercise: a test of the opponent-process theory. J Sports Med Phys Fitness 1997;37:205-12. 25. Roth DL. Acute emotional and psychophysiological effects of aerobic exercise. Psychophysiology 1989;26:593-602.
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26. Steptoe A, Cox S. Acute effects of aerobic exercise on mood. Health Psychol 1988;7:329-40. 27. Steptoe A, Kearsley N, Walters N. Acute mood responses to maximal and submaximal exercise in active and inactive men. Psychol Health 1993;8:89-99. 28. Tieman JG, Peacock LJ, Cureton KJ, Dishman RK. The influence of exercise intensity and physical activity history on state anxiety after exercise. Int J Sport Psychol 2002;33:155-66. 29. Pierce EF, McGowan RW, Lynn TD. Exercise dependence in relation to competitive orientation of runners. J Sports Med Phys Fitness 1993;33:189-93. 30. Demello JJ, Cureton KJ, Boineau RE, Singh MM. Ratings of perceived exertion at the lactate threshold in trained and untrained men and women. Med Sci Sports Exerc 1987;19:354-62. 31. Johnsgard K. The motivation of the long distance runner: I. J Sports Med 1985;25:135-9. 32. Johnsgard K. The motivation of the long distance runner: II. J Sports Med 1985;25:140-3. 33. Rankinen T, Bray MS, Hagberg JM, et al. The human gene map for performance and health-related fitness phenotypes: the 2005 update. Med Sci Sports Exerc 2006;38:1863-88. 34. Zeni AI, Hoffman MD, Clifford PS. Energy expenditure with indoor exercise machines. JAMA 1996;275:1424-7. 35. Raglin JS, Wilson M. State anxiety following 20 minutes of bicycle ergometer exercise at selected intensities. Int J Sports Med 1996;17:467-71. 36. Rehor PR, Dunnagan T, Stewart C, Cooley D. Alteration of mood state after a single bout of noncompetitive and competitive exercise programs. Percept Mot Skills 2001;93:249-56. 37. Steptoe A, Bolton J. The short-term influence of high and low intensity physical exercise on mood. Psychol Health 1988;2:91106. Supplier a. Schwinn model CI-430; Schwinn, 16400 SE Nautilus Dr, Vancouver, WA 98683.
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