The Influence of Exercise Intensity on Frontal Electroencephalographic Asymmetry and Self-Reported Affect

Article excerpt

The "feel better" effect of exercise has been well established, but. the optimal intensity needed to elicit a positive affective response is controversial. In addition, the mechanisms underlying such a response are unclear. To clarify these issues, female undergraduate students were monitored for ekctroencephalographic (EEG) and self-reported affective responses during the recovery period following rest, low, moderate, and high intensities of treadmill running, each lasting 30 min. Frontal EEG asymmetry and self- reported vigor scores following exercise at all three intensities were significantly elevated compared to those observed following rest. The results suggest that steady-state aerobic exercise bouts executed at varying intensities induce a similar affective response during the recovery period when assessed at both the behavioral and psychophysiological levels.

Key words: affect, brain, emotion, physical activity

**********

There is compelling evidence that exercise exerts a robust influence on health and well being. More specifically, exercise and physical activity have been consistently associated with mental health benefits (U.S. Department of Health and Human Services, 1996). Previous studies have demonstrated not only a decrease in negative affective states like anxiety, anger, tension, and depression, but elevations in positive affective states such as vigor, energy, and pleasure after acute bouts of aerobic exercise (Ekkekakis & Petruzzello, 1999; Reed & Ones, 2006). However, these positive outcomes may be related to the intensity of the work stimulus.

Accordingly, the link between exercise intensity and affect has been examined by many investigators over the last 40 years (Ekkekakis & Acevedo, 2006; Petruzzello, Ekkekakis, & Hall, 2006). Based on the absence of a significant reduction in anxiety following exercise at low or moderate intensity of short duration, Morgan, Roberts, and Feinerman (1971) initially raised the possibility of a threshold intensity in order to induce positive affect. Subsequently, various investigators suggested that the threshold of exercise intensity required to reduce anxiety was 60% of maximal oxygen uptake (V02max; Raglin & Morgan, 1985) or 70% of aerobic capacity when exercising for 20 min (Dishman, 1986). However, in a more recent study, Raglin and Wilson (1996) found that the threshold was lower than those previously proposed, as they observed that 20-min sessions of cycle ergometry at intensities of 40, 60, and 70% of V02max were all effective at reducing anxiety. On the other hand, exercise of high intensity or long duration (80-90% maximal heart rate [HRmax] and marathon running, respectively) were shown to induce adverse psychological effects (Hassmen & Blornstrand, 1991). Collectively, the findings described above are consistent with a curvilinear dose-response relationship between exercise intensity and affect (Ojanen, 1994), suggesting that there may exist a critical threshold for the elicitation of positive affect, as well as a pivotal point of higher intensity at which affect can convert to a negative state. The issue remains unresolved, however, in light of findings like those of Saklofske, Blomme, and Kelly (1992), who observed that even exercise of very low intensity and volume (e.g., 4-10 min of walking) is effective in reducing tension and increasing energy.

To clarify this issue, it may be informative to reference the intensity of work to the ventilatory threshold (VT), which is the metabolic turning point associated with increased blood lactate. Furthermore, the VT for a given individual represents an important reference point for exercise intensity, as it coincides with a similar metabolic state (i.e., the proportion of aerobic and anaerobic processes) across individuals, as opposed to percentages of [VO.sub.2]max, which may be achieved via differing degrees of aerobic and anaerobic contributions. …