A comparison of post-exercise mood enhancement across common exercise distraction activities.

Russell, William ; Pritschet, Brian ; Frost, Beth 等

There is a strong consensus within the exercise psychology literature that mood enhancement is a primary benefit of physical activity (Berger, 1996; Berger & McInnman, 1993; International Society of Sport Psychology, 1992; Morgan, 1997). The International Society for Sport Psychology (1992) recently described psychological benefits of physical activity and concluded that exercise has been related to desirable changes in mood. Based on a systematic analysis of self-regulation techniques, Thayer, Newman, & McClain (1994) reported that exercise was the most successful technique at changing a negative mood. Recently, the United States Department of Health and Human Services (1996) also indicated that physical activity is associated with improvements in mood states such as anxiety and depression.

Mood enhancement has resulted from both chronic (Brown, Wang, Ebberling, Fortlace, Puleo, Benson, & Rippe, 1994) and acute exercise bouts (McGowan, et al., 1996; Pierce & Pate, 1994; Roth, 1989; Steptoe & Cox, 1988), yet there is no current consensus for explanations for potential mechanisms in short or long-term exercise effects on mood state and both physiological and psychological mechanisms have been proposed (Berger & Motl, 2000). Despite common perceptions, there is little research evidence to support any individual or group factors as consistently producing mood benefits as measured by the Profile of Mood States (POMS; McNair, Lorr, & Dropplemann, 1971). Research on physiological mechanisms includes the endorphin, cortisol, monoamine, and thermogenic hypotheses (Berger & Motl, 2000). However, support for hypotheses such as the endorphin hypothesis is equivocal because the blood brain barrier is impermeable to peptides in the blood stream and endorphin levels have not been related to mood changes on the POMS (Farrell et al., 1986; Farrell, Gustafson, Morgan, & Pert, 1987). Psychological mechanisms also may influence the relationship between exercise and mood alteration. Potential psychological mechanisms include; improved self-concept, feelings of self-efficacy, enjoyment, expectancy of psychological benefits, increased sense of control, and "time-out" from daily hassles (Berger, 1996; Berger, Owen, & Man, 1993; Morgan, 1985). In particular, acute exercise has been purported to produce short-term mood improvements due to its distraction characteristics and it was recently proposed that continued research of the POMS necessitated determining whether the "time-out" hypothesis is a viable explanation for mood alteration (Berger & Motl, 2000).

Studies examining acute mood changes after a single bout of exercise have found fairly consistent beneficial changes in mood as measured by the POMS. Steptoe and Cox (1988) compared females participating in single bouts of high and low intensity exercise accompanied by either music or a metronome and found that while music did not influence post-exercise mood, beneficial mood changes were observed following low-intensity exercise. Single session activity bouts have shown exercise participants to exhibit beneficial POMS susbscale changes compared to controls during exercise compared to post-exercise (Ewing, Scott, Mandez, & McBride, 1984), in response to aerobic exercise in college students (Roth, 1989) and older women (Peirce and Pate, 1994) and for submaximal exercise (Steptoe, Kearsely, & Waiters, 1993).

Berger and Owen (1988) proposed a tentative exercise taxonomy for mood enhancement with exercise which includes an overall requirement for exercise to be (1) enjoyable, (2) aerobic, (3) noncompetitive, (4) temporally and spatially certain, and (5) repetitive and rhythmical. Suggested training requirements have included (6) 2-3 times per week, (7) moderate intensity, and (8) 20-30 minutes in duration. However, activities that are nonaerobic, but meet the other taxonomy requirements have also shown to improve mood (Berger & Owen, 1992; McGowan et al., 1996). Among additional concerns regarding short-term effects of exercise on mood are that the mechanisms for short-term change remain unclear and that expectancy effects of mood improvement, not exercise itself, may be responsible for mood improvement. Recently, Berger, Owen, Motl, and Parks (1998) examined whether expectancy of psychological benefits was related to mood changes after jogging. Despite significant acute mood benefits, expectancy of psychological benefits was not conclusively related to significant changes on the POMS subscales of tension, depression, anger, and confusion (Berger et al., 1998).

It appears then that a viable explanation for short-term mood enhancement from various exercise activities may come from the distraction characteristics of the activity. A new direction for mood research that has recently been advocated (Berger & Motl, 2000) is on environmental influences and their capacity to increase activity enjoyment and stimulate greater distractibility during exercise. Directors of many gymnasia, health clubs, university recreation centers, and other workout sites are now providing music and television for motivational reasons including the attraction of exercisers, to encourage pulsating workouts, and to distract people from the potentially negative sensations of effortful exercise. In addition, exercise modes such as elliptical machines, cycle ergometers, and stair climbing machines are often popular because they allow exercisers to engage in concomitant distraction activities during exercise.

Unfortunately, the effects of distraction activities on mood change are unclear. Steptoe and Cox (1988) examined whether lively stimulating music moderated mood changes as measured by the POMS after participation in high- and low-intensity bicycle ergometry and found no evidence that music was differentially associated with mood changes at either intensity. The effects of two other commonly engaged activities during certain physical activity, reading and television watching, and their distraction effects on mood, are unknown. The authors are not aware of any research examining the influence of exercising while either watching television or reading on the relationship between exercise and mood alteration. The potential influence of these distracting activities on the exercise -mood relationship is a needed area of investigation.

Thus, the central purpose of this study was to compare the mood alteration and perceptual appraisal of effort during exercise under standardized distraction activities (television watching and reading) with exercise in a non-distraction control condition. Subsequently, according to the "time-out" hypothesis as an underlying mechanism for mood benefits from exercise, it was hypothesized that:

1. Participants exercising in the distraction activity conditions would report greater post-exercise mood improvement compared to the exercise control condition as measured by the POMS TMD scores and individual POMS subscale scores.

2. Participants in the distraction condition would subsequently appraise exercise of a similar intensity as less effortful compared to participants in the exercise control condition.

Method

Subjects

Fifty-three (32 males, 21 females) college-age undergraduate physical education majors from a Midwest university volunteered their participation for this study. All participants reported they engaged in regular aerobic activity at least three times a week, meeting ACSM frequency requirements for regularly active adults (ACSM, 1998). Subjects were treated in accordance with the human subjects protocol and were randomly assigned to treatment conditions.

Measures

The Profile of Mood States (McNair, Lorr, & Dropplemenn, 1971) is comprised of 65 adjectives that are reflected on a 5-point scale to measure six identifiable mood or affective states and a total mood disturbance score. Scores on the six mood subscales include; tension-anxiety, depression-dejection, anger-hostility, vigor-activity, fatigue-inertia, and confusion-bewilderment. The profile has been shown to be suitable for individuals from 18 years to adulthood and internal consistency reliability has ranged from .84 to .95 (McNair & Lorr, 1964). Test-retest reliability has ranged from .65 to .74. The immediate "how do you feel right now" response was used for the current study, in order to measure psycho-physiological appraisal of effort sense throughout the ride conditions, Borg's (1982) Rating of Perceived Exertion Scale was used to evaluate subjects' perceptions of exercise.

Procedures

The experimental protocol consisted of two separate laboratory sessions. The first session was a habituation session during which subjects were explained the exercise protocol, completed informed consent, and had their resting heart rate assessed using a heart rate monitor (Polar Electro Model). The purpose of the this session was to obtain resting heart rates so experimental exercise heart rates could be obtained and to familiarize subjects with the experimental protocol to obtain more accurate pre-exercise mood. After resting heart rate was obtained, subjects were taken to a private room where they practiced riding an electronically braked bicycle ergometer at a work rate which corresponded to 60-75% of individual heart rate reserve. After obtaining individuals' work rates, subjects were scheduled for their experimental ride session.

Subjects were randomly assigned to one of three exercise conditions; (1) a video condition in which the subject was required to watch a standardized health video, (2) a reading condition in which subjects were required to read standardized health material similar in content to the video, or (3) an exercise control condition, in which subjects were not provided any external distraction. All exercise sessions consisted of a 25-minute exercise period at 60-75% of the individual's heart rate reserve and were preceded by a 5-minute warm-up and 5-minute cool-down period. Heart rate data was not available to subjects during their ride but was actively monitored by experimenters so that exercise intensity could be held constant across all conditions. Since previous research has indicated that psychological responses to exercise may vary according to circadian rhythms (Hill, Cureton, & Collins, 1988; Koltyn, Lynch, & Hill, 1998), all subjects were tested in the morning to control for time of day effects. Prior to each experimental session, subjects entered the laboratory and were fitted with a heart rate monitor and were seated in an enclosed room for a 5-minute quiet rest period. Following this rest period, subjects completed the pre-exercise POMS. During the experimental rides, participants were required to maintain a work rate corresponding with 60-75% of their heart rate reserve, and starting at five minutes into the ride, were asked to rate their perceived exertion at five minute intervals. Following the post-exercise cool-down period, participants were again instructed to rest quietly in an enclosed room and the post-exercise POMS was administered at five minutes after the cool down period ended. As an experimental manipulation check, participants in the distraction condition were asked a series of content questions regarding either the video or reading to verify that they were, in fact, attending to the distraction material during their exercise bout. Prior to experimental rides, participants were told they would be asked a series of questions about the material they were to attend during the ride. No statistical hypothesis was tested for recall response differences across distraction conditions, but participants in the distraction conditions correctly recalled all responses to post-exercise content questions asked by the investigator.

Data Analysis

In order to determine if participants in the distraction condition would report greater post-exercise mood improvement compared to exercise controls, a one-way ANOVA (exercise condition) was performed on TMD changes (pre-post exercise) scores as the dependent variable. In addition, a one-way MANOVA (exercise condition) was performed on POMS subscale change scores across exercise conditions to determine POMS subscale differences across exercise conditions. Finally, to determine whether participants' effort sense appraisal of exercise intensity was different across exercise conditions, a 3 x 5 (exercise condition x RPE assessment) repeated measures ANOVA was performed with exercise condition as the between-subjects variable and RPE as the within-subjects variable.

Results

Results of an initial dependent t-test indicated that participants had significantly improved post-exercise mood (M= 102.28, SD = 14.34) compared to pre-exercise mood (M = 110.58, SD = 26.07, t(53) =2. 71, p<.001) as measured by total mood disturbance scores. Pre-and post-exercise mood means and standard deviations across the three experimental conditions are displayed in Table 1. In order to determine pre-post exercise differences collapsed across conditions, six separate t-tests were performed for the separate subscale change scores. Results indicated significant pre-post exercise mood state decreases for tension (t(53) =2.45, p<.02) and depression (t(53)=3.09, p<.03), as well as a significant pre-post exercise increase for vigor, supporting similar pre-post exercise mood-change from previous research on affect and exercise (McGowan, Talton, & Thompson, 1996).

Results of the one-way ANOVA on TMD change scores were nonsignificant (F(2,52) =.63,p=.53) indicating that participants' TMD change scores did not differ across conditions. Results of the one-way MANOVA comparing exercise conditions on POMS subscale change scores were also nonsignificant (Wilk's Lambda =.76, F(12,40) =1.09, p=.37) indicating no significant mood change for POMS subscales across conditions. Since participants' pre-exercise mood differences may have accounted for nonsignificant MANOVA results, a oneway MANCOVA was performed on post-exercise POMS subscales, using pre-exercise POMS subscale scores as covariates. Results indicated a nonsignificant exercise effect (Wilk's Lambda =.74, F (14,74) =.87, p =.59). However, MANCOVA results did indicate an effect size that was moderate ([R.sup.2] = .27) and that there may not have been sufficient power to show a significant effect with highly correlated variables. Correlations for pre- and post-exercise mood states are shown in Table 2. The lack of power was also supported in that follow-up ANCOVAs indicated significant reductions in post-exercise TMD (F(9,52) =2.39,p<.03), depression (F(9,52) =5.12, p<.0001), anger (F(9,52) = 3.47, p<.003), and fatigue (F(9,52)=2.73, p<.009) and a significant increase in vigor (F(9,52) =2.19, p<.05), after controlling for pre-exercise mood states.

In order to examine differences across pre-and post-exercise POMS scores, separate MANOVAs were run on pre-exercise POMS scores and post-exercise POMS scores. Results from a one-way MANOVA on pre-exercise POMS scores were nonsignificant (Wilk's Lambda =.65, F(14,88) =1.57, p=.12), indicating that pre-exercise scores were equal. This allowed for a second MANOVA examining differences on post-exercise POMS scores. Results indicated no significant differences (Wilk's Lambda =.81, F(14,88) =.72, p=.75) across exercise condition on post-exercise mood. Results of a 3 x 5 (exercise condition x RPE assessment) repeated measures ANOVA resulted in a nonsignificant time x condition interaction (F(8,200) =1.56, p=. 14) as well as a nonsignificant main effect for exercise condition (F(2,50) =.20,p=.82). There was a significant main effect for time (F(4,200) =36.28,p<.0001, ES =.58), indicating participants' RPE increased significantly across time.

Discussion

The major purpose of this study was to examine whether a single bout of aerobic exercise combined with distraction activities improved post-exercise mood state, compared to an exercise bout without any external distraction activity. Results from the ore-post exercise mood state comparison indicated that a single bout of activity improved overall mood, tension, depression, and vigor, supporting previous studies that have also found acute mood benefits from single exercise bouts (Berger & Motl, 2000; Roth, 1989; Pierce & Pate, 1994). This result also supports previous literature showing acute mood changes in cycling exercise of similar duration and exercise intensities (Farrell et al., 1986; Steptoe & Cox, 1988; Steptoe et al., 1993) in members of normal populations.

The hypothesis that participants who exercised in the distraction activity condition would report greater post-exercise mood improvement compared to exercise controls was not supported. The intent of the experimental distraction was to standardize the exercise mode and content of the distraction material so that any motivational or subjective nature of the distraction content would not mask or confound the effects of mood improvements from exercise per se. However, Berger and Motl (2000) have indicated that personal enjoyment of the activity is an important criterion for encouraging short-term improvements in mood associated with exercise. The current distracting conditions, while successful in directing exercisers' attention to the content, may not have been personally enjoyable or sufficiently motivating to improve post-exercise mood. In addition, nonsignificant pre-post exercise mood differences across conditions may also have been due to ceiling effects in regard to participants' pre-exercise mood. MANCOVA result indicated that ore-exercise mood was not significantly different across conditions, yet, as Table 1 indicates, pre-exercise mood states were relatively low for these college students (Control TMD M = 119.53; Reading TMD M = 107.63; Video TMD M = 105.35) compared to previous exercise-mood research (i.e. Berger & Owen, 1992). Therefore, according to a dose-response paradigm concerning psychological benefits of exercise, lower initial mood scores may have contributed to a lack of differential pre-post exercise mood changes across conditions. In short, a ceiling effect on mood may have occurred such that since participants' moods indicated a neutral profile, subsequent exercise while engaging in task distraction may had minimal effects.

Further indirect support the contention that distractor tasks may not have been motivating was provided in that, while one-way ANOVA results comparing exercise conditions on TMD change scores were nonsignificant, mood change scores were actually more favorable in the control condition (M=13.35, SD=32.34) than reading (M=5.88, SD=17.84) or video conditions (M=-5.96, SD=14.09). Participants in the exercise control condition may have been able to engage in "time-out" dissociative strategies without being constrained to attending to distraction material that may not have been perceived as enjoyable. Thus, the video and reading passage material which contained similar standardized content may not have provided participants with the same "cognitive freedom" to choose one's own distraction activity that may have occurred during the control condition. Moreover, advantages due to "time-out" in the current study were equated across all levels of experimental manipulation. Future exercise-mood studies might create experimental conditions in which exercise distraction is either externally imposed or is self-selected by the participant.

It has recently been found that enjoyment may mediate acute mood changes associated with physical activity (Motl, Berger, & Leuschen, 2000). Berger and Owen (1986) examined the relationship between acute bouts of swimming and mood changes and found beneficial mood changes were not evident under disagreeable environmental conditions such as high water and air temperatures. Social interaction enjoyment has been as effective as meditation in lowering levels of tension (Hewitt & Miller, 1981) and enjoyable music has been related to short-term mood changes in college students (Wheeler, 1985). Individuals who have experienced enjoyment during work and leisure, operationally defined as flow, have reported higher positive affect scores than individuals who did not experience enjoyment (Csikzentmihyli & LeFere, 1989). Finally, Motl, Berger, and Lesuchen (2000) found that subjects engaged in rock-climbing displayed greater mood benefits than a health education class that included discussion of a rock-climbing video, and it was concluded that enjoyment appeared to mediate the acute mood changes associated with both activities and supported the enjoyment factor in improving mood.

Therefore, it may be that the mediating benefit for mood improvement and "time-out" efficacy during exercise may stem directly from enjoyment of the activity. If subjects within the distraction conditions had been able to select personally enjoyable video or reading material, the combined effects of aerobic exercise and distraction may have been more pronounced. Since enjoyment may mediate mood effects, future studies should allow for personal selection of distraction materials during exercise to determine the combined effects of aerobic exercise and distraction activities on acute mood change. In addition, a systematic problem with this type of research is the inability to closely control for cognitive content in the control condition. A suggestion for future research in this area might be to add structure to the control condition that requires participants to engage in a "boring" task (i.e. counting the number of specific numerals contained within number-digit strings) during the exercise control, along with a non-experimental manipulation control (let do) while participants exercise. This would allow future researchers to more accurately decipher cognitive content in the "true" control condition.

Another explanation for the nonsignificant results may have been the forced-choice of exercise mode. While current participants self-reported they were regularly active, the mode used may not have been a preferred exercise for some of the subjects. Berger and Owen (1986) found that when comparing mood responses across swimming, body conditioning, yoga, fencing, and lecture control condition, the mode of activity (yoga) significantly affected mood improvement, further supporting that mode selection mediate the effects of enjoyment on mood.

There were also no significant differences of subjective appraisal of effort across exercise conditions as measured by RPE values. Intuitively, it follows that since the distraction exercise conditions did not result in impaired mood, that the distraction components of the exercise activity were also insufficient in reducing effort sense during exercise. It has been previously proposed that in order for dissociative or "distractive" attentional strategies to be effective, there must be some motivational aspect of the distractor activity (Morgan, Horstmann, Cymermann, & Stokes, 1983; Rejeski & Kenny, 1987; Russell & Weeks, 1994; Weinberg, Smith, Jackson, & Gould, 1984). Individually-selected or self-motivating material may be more effective in not only mood improvement through increased enjoyment but also by increased dissociative aspects of exercise that would be reflected in RPE scores. The relationship between mood and reaction to situational factors (emotion) is proposed to be transactional in nature (Parkinson, Totterdell, Briner, & Reynolds, 1996). A transactional relationship would infer that general feeling states (mood) contribute to the interpretation of, and reaction to, a situation (emotion) and the subsequent emotional experience in turn contributes to mood. Therefore, the positive emotions derived from motivational distractor activities may be capable of post-exercise mood improvement. We suggest that future researchers investigate the possibility that a dissociative or distractor task with strong motivational properties may be more effective than a task with low motivational properties.

An acknowledged limitation of the present study was that the amount of distraction within the distraction conditions was not directly measured. The present manipulation check in the distraction conditions asked a series of twenty specific questions which all subjects correctly responded to, verifying that at least some dissociation was occurring. However, specific assessment regarding both associative and dissociative attentional use have been used to gauge attentional strategy use in runners (Masters & Lambert, 1989; Silva & Appelbaum, 1989) and differences in relaxation and dissociation use have shown that the methods in which attentional strategies are used are capable of influencing factors such as running economy (Smith, Gill, Crews, Hopewell, & Morgan, 1995), and may also be capable of influencing mood. The accurate assessment of attentional style in recreational exercisers appears to be needed if future research addresses the "time-out" explanation for mood enhancement of distraction activities. The Running Styles Questionnaire has shown acceptable content validity and reliability (test-retest, r =.73; alpha =.69-.88) to assess associative/dissociative strategy use, however this test was developed for marathon runners and is not appropriate to assess amount of distraction in recreational exercisers (Silva & Appelbaum, 1989). Recent research (Wright & Loftus, 2000) has attempted to measure self-reported dissociative experiences using the Dissociative Experiences Scale (DES-C), which asks subjects how often they have dissociative experiences compared to most other people. Yet this scale measures dissociative patterns as a trait measure in non-exercise situations and is also inappropriate for bout-specific measures of distraction during exercise. Future assessment of distraction amount might require a simple open-ended assessment, similar to Smith et al. (1995) in which runners were asked what they were thinking about during the run, and to rate (0 - 100%) the amount of time they attended to the attentional instructions for both the total run and the final two minutes of the run.

An additional limitation in the present study was that post-exercise mood states were only examined at 5 minutes post-exercise. Among noted limitations in the exercise and mood literature have been the discrepancies related to the timing of mood measures following exercise. For example, Steptoe et al. (1993) compared active and inactive men's' mood following maximal and submaximal exercise and found that mood scores were significantly different immediately following and 30 minutes post-exercise. In addition, increases in anxiety and mental fatigue have been shown in the first five minutes following exercise, with reductions only emerging after 15-20 minutes (Morgan, 1979; Steptoe & Bolton, 1988).

While the major hypotheses were not supported, important information regarding environmental influences on the exercise-mood relationship was obtained. The current study did provide evidence that it is not the distraction activity, per se, that leads to positive mood benefits and distraction from physical sensations of exercise (Berger & Motl, 2000). Although not directly investigated in the current study, it may be that personal enjoyment of the distraction activity may mediate any mood benefits and may be a central criterion for short-term mood improvement with exercise. Future research should focus on how environmental influences or distraction activities interact with objective measures of enjoyment (Kendzierski & DeCarlo, 1991) to determine positive mood outcomes. The use of self-selected or motivational distraction material may be a central component to supporting the "time-out" hypothesis of the exercise-mood enhancement relationship.

Address Correspondence To: William D. Russell, Ph.D., 1010 McAfee Gymnasium, Eastern Illinois University, Charleston, IL 61920. E-mail: [email protected]

Table 1
Means and Standard Deviations for Pre- and Post-exercise Mood State
Subscale and Total Mood Disturbance Scores

Group TMD Ten Dep

Exercise Control (n=17)

Pre-test 119.53 9.35 5.53
 (31.56) (7.57) (8.99)

Post-test 106.18 6.29 2.36
 (21.99) (4.84) (3.18)

Reading (n=16)
Pre-test 107.63 6.63 3.25
 (19.29) (5.04) (3.79)

Post-test 101.75 4.88 2.00
 (17.46) (3.65) (3.41)

Video (n=20)
Pre-test 105.35 6.00 3.90
 (24.89) (3.88) (7.31)

Post-test 99.40 5.15 1.75
 (18.80) (3.75) (5.14)

Group Ang Vig Fat

Exercise Control (n=17)

Pre-test 5.59 15.41 7.82
 (8.74) (6.02) (5.76)

Post-test 4.41 19.35 7.47
 (7.32) (5.77) (6.80)

Reading (n=16)
Pre-test 2.63 17.06 6.94
 (3.28) (4.85) (5.59)

Post-test 1.69 17.44 6.69
 (4.08) (6.17) (4.39)

Video (n=20)
Pre-test 4.25 16.45 3.85
 (6.24) (5.05) (3.48)

Post-test 2.90 18.40 4.30
 (4.46) (6.34) (3.53)

Group Con

Exercise Control (n=17)

Pre-test 6.65
 (4.95)

Post-test 5.00
 (3.64)

Reading (n=16)
Pre-test 5.25
 (2.54)

Post-test 3.94
 (2.21)

Video (n=20)
Pre-test 3.70
 (3.59)

Post-test 3.85
 (3.12)

Note: TMD = total mood disturbance, Ten = tension, Dep = depression,
Ang = anger, Vig = vigor, Fat = fatigue, Con = confusion.

Table 2
Intercorrelations Between Pre-and Post-Exercise Profile of Mood States
Scores

 PreTMD PreTEN PreDEP

PostTMD .55 ** .47 ** .50 **
PostTEN .39 * .42 * .37 *
PostDEP .62 ** .45 ** .68 **
PostANG .49 ** .45 ** .40 *
PostVIG -.03 .01 .01
PostFAT .44 * .43 * .40 *
PostCON .46 ** .32 * .41 *

 PreANG PreVIG PreFAT

PostTMD .54 ** -.17 .36 **
PostTEN .41 * .03 -.29 *
PostDEP .66 ** -.14 .31 *
PostANG .54 ** -.03 .53 **
PostVIG .05 .45 ** .18
PostFAT .40 * .09 .51 **
PostCON .45 ** -.15 .35 *

 PreCON

PostTMD .47 **
PostTEN .30 *
PostDEP .53 **
PostANG .66 **
PostVIG -.01
PostFAT .40 *
PostCON .44 *

* p < .05.

** p < .001.

References

American College of Sports Medicine (1998). ACSM position stand: The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness, and flexibility in healthy adults. Medicine and Science in Sports and Exercise, 30, 975-991.

Berger, B.G (1996). Psychological benefits of an active lifestyle: What we know and what we need to know. Quest, 48, 330-353.

Berger, B.G. & McInnman, A. (1993). Exercise and the quality of life. In R,N, Singer, M. Murphy, & L.K. Tennant (Eds.), Handbook of research on sport psychology (729-760). New York: Macmillan Publishing.

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.

Berger, B.G. & Owen, D.R. (1986). Mood alteration with swimming: A reexamination. In L. Vander Velden & J.H. Humprey (Eds.), Psychology and sociology of sport: Current selected research (97-113) New York: AMS Press.

Berger, B.G. & Owen, D.R. (1988). Stress reduction and mood reduction and mood enhancement in four exercise modes: Swimming, body conditioning, Hatha yoga, and fencing. Research Quarterly for Exercise and Sport, 59, 148-159.

Berger, B.G., & Owen, D.R. (1992). Mood alteration with yoga and swimming: Aerobic exercise may not be necessary. Perceptual and Motor Skills, 75, 1331-1343.

Berger, B.G., Owen, D.R., & Man, F. (1993). A brief review of literature and examination of acute mood benefits of exercise in Czechoslovakian and United States swimmers. International Journal of Sports Psychology, 24, 130-150.

Berger, B.G., Owen, D.R., Motl, R.W., & Parks, L. (1998). Relationship between expectancy of psychological benefits and mood alteration in joggers. International Journal of Sport Psychology, 29, 1-16.

Borg, G.A.V. (1982). Psychophysiological bases of perceived exertion. Medicine and Science in Sports and Exercise, 14, 377-381.

Brown, D.R., Wang, Y., Ward, A., Ebbeling, C.B., Fortlage, L., Puleo, E., Benson, H., & Rippe, J.M. (1995). Chronic psychological effects of exercise and exercise plus cognitive strategies. Medicine and Science in Sports and Exercise, 27, 765-775.

Csikzentmihalyi, M., & LeFevre, J. (1989). Optimal experience in work and leisure. Journal of Personality and Social Psychology, 56, 815-822.

Ewing, J.H., Scott, D.G., Mendez, A.A., & McBride, T.J. (1984). Effects of aerobic exercise upon affect and cognition. Perceptual and Motor Skills, 59, 407-414.

Farrell, P.A., Gustafson, A.B., Garthwaite, T.L., Kalkoff, R.K., Cowley, A.W., & Morgan, W.P. (1986). Influence of endogenous opiods on the response of selected hormones to exercise in humans. Journal of Applied Physiology, 61, 1051-1057.

Farrell, P.A., Gustafson, A.B., Morgan, W.P., & Pert, C.B. (1987). Enkephalins, catehchomaines, and psychological mood alterations: Effects of prolonged exercise. Medicine and Science in Sports and Exercise, 19, 347-353.

Hewitt, J., & Miller, R. (1981). Relative effects of meditation vs. other activities on ratings of relaxation and enjoyment of others. Psychological Reports, 48, 395-398.

Hill, D.W., Cureton, K.J., & Collins, M.A. (1988). Effect of circadian rhythm and body temperature on oxygen uptake. Journal of Sports Medicine and Physical Fitness, 28, 310-312.

International Society of Sport Psychology. (1992). Physical activity and psychological benefits: A position statement from the international society of sport psychology. Journal of Applied Sport Psychology, 4, 94-98.

Kendzierski, D., & DeCarlo, K.J. (1991). Physical activity enjoyment scale: Two validation studies. Journal of Sport and Exercise Psychology, 13, 50-64.

Koltyn, K.F., Lynch, N.A., & Hill, D.W. (1998). Psychological responses of brief exhaustive cycling exercise in the morning and the evening. International Journal of Sports Psychology, 29, 145-156.

Masters, K., & Lambert, M.J. (1989). The relations between cognitive coping strategies, reasons for running, injury and performance of marathon runners. Journal of Sport and Exercise Psychology, 11, 161-170

McGowan, R.W., Talton, B.J., & Thompson, M. (1996). Changes in scores on the Profile of Mood States following a single bout of physical activity: Heart rate and changes in affect. Perceptual and Motor Skills, 83, 859-866.

McNair, D.M., Lorr, & Dropplemann, L.F. (1971). Profile of Mood States manual. San Diego: Education and Industrial Testing Service.

Morgan, W.P. (1979). Anxiety reduction following acute physical activity. Psychiatric Annals, 9, 141-147.

Morgan, W.P. (1985). Affective beneficence of vigorous physical activity. Medicine and Science in Sports and Exercise, 17, 94-100.

Morgan, W.P. (Ed.) (1997). Physical activity and mental health. Washington, DC: Taylor and Francis.

Morgan, W.P, Horstmann, W.P, Cymermann, A., & Stokes, J. (1983). Facilitation of physical performance by means of a cognitive strategy. Cognitive Therapy and Research, 7, 251-264.

Motl, R.W., Berger, B.G., & Leuschen, P.S. (2000). The role of enjoyment in the exercise-mood relationship. International Journal of Sport Psychology, 31, 347-363.

Parkinson, B., Totterdell, P., Briner, R.B., & Reynolds, S. (1996). Changing moods: The psychology of mood and mood regulation. London: London.

Pierce, E.F., & Pate, D.W. (1994). Mood alterations in older adults following acute exercise. Perceptual and Motor Skills, 79, 191-194.

Rejeski, W.J., & Kenney, E. (1987). Distracting attentional focus from fatigue: Does task complexity make a difference? Journal of Sport Psychology, 9, 66-73.

Roth, D.L. (1989). Acute emotional and psychophysiological effects of aerobic exercise. Psychophysiology, 26, 593-602.

Russell, W.D., & Weeks, D.L. (1994). Attentional style in ratings of perceived exertion during physical exercise. Perceptual and Motor Skills, 78, 779-783.

Silva, J.M., & Appelbaum, M.I. (1989). Association-dissociation patterns of United States Olympic marathon trial contestants. Cognitive Therapy and Research, 13, 185-192

Smith, A.L., Gill, D.L., Crews, D.J., Hopewell, R., Morgan, D.W. (1995). Attentional strategy use by experienced distance runners: Physiological and psychological effects. Research Quarterly for Exercise and Sport, 66, 142-150.

Steptoe, A., & Bolton, J. (1988). The short-term influence of high and low intensity physical exercise on mood. Psychology and Health, 2, 91-106.

Steptoe, A., & Cox, S. (1988). Acute effects of aerobic exercise on mood. Health Psychology, 7, 329-340.

Steptoe, A., Kearsely, N., & Walters, N. (1993). Acute mood response to maximal and submaximal exercise in active and inactive men. Psychology and Health, 8, 89-99.

Stevens, J. (1992). Applied multivariate statistics for the social sciences. (2nd Ed.), Hillsdale, NJ: Lawrence Erlaum Associates.

Thayer, R.E., Newman, J.R., & McClain, T.M. (1994). Self-regulation of mood: Strategies for changing a bad mood, raising energy, and reducing tension. Journal of Personality and Social Psychology, 67, 910-925.

US Department of Health and Human Services (1996). Physical activity and health: A report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion.

Weinberg, R.S., Smith, J., Jackson, A., & Gould, D. (1984). Effect of association, dissociation, and positive self-talk strategies on endurance performance. Canadian Journal of Applied Sport Psychology, 9, 25-32.

Wheeler, B.L. (1985). Relationship of personal characteristics to mood and enjoyment after hearing live and recorded music to musical taste. Psychology of Music, 13, 81-92.

Wright, D.B., & Loftus, E.F. (2000). Measuring dissociation: Comparison of alternative forms of the Dissociative Experiences Scale. Australian Journal of Clinical & Experimental Hypnosis, 28, 103-126.

William Russell, Brian Pritschet, Beth Frost, John Emmett, T.J. Pelley, Judy Black, and Jill Owen Eastern Illinois University