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There is considerable support for the ability of acute bouts of exercise to influence affective states (e.g., Arent, Landers, & Etnier, 2000; Landers & Petruzzello, 1994; Thayer, 1987a). Studies have generally shown that exercise increases states of positive affect or energetic arousal (Gauvin & Rejeski, 1993; Lutz, Lochbaum, & Turnbow, 2003; Thayer, 1987a), and reduces anxiety, tension, or negative affect (Breus & O'Connor, 1998; Kennedy & Newton, 1997; Petruzzello, Jones, & Tate, 1997; Thayer, 1987a). Interestingly, research has demonstrated that exercise may be similarly effective in the treatment of depression compared with other commonly-employed modalities such as selective-serotonin reuptake inhibitors (Dunn, Trivedi, Kampert, Clark, Chambliss, 2005). A limitation exists, however, in that most studies compare postexercise affect to preexercise affect rather than daily affect. This is problematic because the magnitude of the influence of exercise on affective states may be misrepresented if baseline measures are influenced by the laboratory situation or knowledge of impending exercise engagement, or if such baselines are simply different than the affect individuals experience on a daily basis. While several studies have examined affective states in naturalistic settings (Gauvin, Rejeski, & Norris, 1996; Giacobbi, Hausenblas, & Frye, 2005; Thayer, 1987a), only one known study (Petruzzello, 1995) has yet combined the common pre-post exercise methodology with a naturalistic assessment of affective states. The present investigation, therefore, sought to examine how average daily affect compares to affective states reported before, at the mid-point, and after an exercise session.
Closely related to the present question of interest, Petruzzello (1995) examined whether commonly-reported reductions in state anxiety after exercise might be due to a "sense of relief" that exercise is over. He recruited participants for a study to assess "coping strategies and psychological control" and, upon arrival in the laboratory, two resting baselines of heart rate and state anxiety (10-item State Anxiety Inventory, SAI; Spielberger, 1983) were taken. Next, participants were told that they would be required to run on a treadmill for 15 minutes and two more resting heart rate and state anxiety baselines were taken. There was no significant change in either heart rate or state anxiety comparing the baselines taken before revelation of the exercise requirement with those taken after this revelation. Additionally, Petruzzello had participants take four SAI's during the course of a 24-hr period outside the lab. The mean levels of state anxiety taken outside the lab were in fact slightly greater (Study 1 M = 16.3, SD = 5.0 & Study 2 M = 17.7, SD = 4.5) than the mean of the baseline SAI's taken in the lab (Study 1 M = 15.4, SD = 3.99 & Study 2 M = 16.1, SD = 4.3), though these were not significant differences. Based on these results, Petruzzello stated that it is unlikely that anxiety reduction following exercise is an artificial finding, due to a sense of relief that exercise is over.
At present, the "sense of relief" phenomenon investigated by Petruzzello (1995) does not appear to be an important factor related to the anxiolytic effects of exercise. One could make this case considering Petruzzello's findings, the relatively long-lasting (up to 2 hrs or more) anxiety-reducing effects of exercise (e.g., Raglin & Wilson, 1996), and the fact that anxiety-reduction occurs after a wide range of physical activities at low to moderate intensities (see Ekkekakis & Petruzzello, 1999) which wouldn't be expected to invoke a sense of relief upon completion. Still, research has not often addressed the possibility of a sense-of-relief occurring after exercise and it should not be ignored. Even if the sense-of-relief explanation for anxiety reduction is not valid, it is important to consider how exercise influences affect considering pre and postexercise affective states and how they may differ from an individual's "average" affective states. For example, subjects in Petruzzello's research were slightly more anxious (though not significantly) outside the laboratory than in the laboratory.
Considering the question regarding whether daily affect and preexercise affect differ and Petruzzelio's (1995) study, it would be of interest to examine this question using a broader set of affective dimensions than just anxiety. Exercise appears to have somewhat different effects on positive and negative affective states (Bartholomew, 1999), so it would appear important to consider several points on the affective "circumplex" (see Carroll, Yik, Russell, & Barrett, 1999) as opposed to only one. Another potential limitation of Petruzzello's study was that there were a very limited number of measures of daily affect (four) taken, and it is unclear if they occurred randomly throughout the day.
The Importance of the Baseline
It is important to understand how affect may be influenced at the baseline time point because preexercise affect appears to influence the effects of exercise on postexercise affect. For example, O'Connor, Petruzzello, Kubitz, and Robinson (1995) found that those with higher preexercise anxiety levels exhibited larger reductions in anxiety following maximal aerobic exercise testing (r's = .27 to .65). Also, postexercise improvements in revitalization have been shown to exist only if participants' baseline scores were low or moderate (Rejeski et al., 1995). In fact, Rejeski and colleagues state that "some of the confusion in the existing literature regarding effect sizes from psychological research on exercise may have been caused by differences in level of baseline functioning" (p. 357).
Experience Sampling Method (ESM)
A problem arises, however, in determining how to best measure affective experience in participants' daily lives. One potential solution is the use of the ESM (Csikszentmihalyi & Larson, 1987; Diener & Larsen, 1984), which provides a means of collecting information about daily life in its natural setting by allowing participants to respond to repeated assessments over time. In this method, participants can be signaled with a pager or electronic device at fixed or random intervals throughout the day to complete brief self-report forms. The ESM reduces problems in research of daily life due to memory recall and it is an effective means by which to measure within-subject variance across situations and/or over time (Hektner & Csikzentrnihalyi, 2002; Scollon, Kim-Prieto, & Diener, 2003). A benefit of the ESM is that it allows for sampling of daily experience without contamination by expectancy effects that might be due to prior knowledge of the sampling period (Alliger & Williams, 1993). Thus, employing the ESM in addition to a more commonly-used exercise protocol may allow for an interesting comparison of daily vs. exercise-related affective states.
Statement of the Problem
Raglin (1997) and Morgan (1997) have suggested that behavioral artifacts (e.g., volunteerism, experimenter expectancy effects, Hawthorne effect, and participant expectancies) may be influencing the magnitude of the effects of exercise on affect. Yet, we have very little information concerning how affective states measured pre and postexercise relate to affective states experienced through the course of daily life. Understanding whether any such differences occur between daily and...
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