ABSTRACT

There is substantial evidence that normal individuals who engage in physical activity experience positive health effects, including both psychological and physiological benefits (Bouchard et al., 1994). Interestingly, part of these positive effects on mood are observed after acute exercise, as is the case for anxiolysis (Morgan, 1987). In addition, physical exertion may also have positive effects in psychiatric patients, as illustrated by its antidepressive outcomes in mildly depressed subjects (chapter 6). Alternatively, excessive exercise (e.g., overtraining) or sudden disruption of a chronic training program may lead to mood disturbances (chapter 9). Taken together, these findings illustrate the tight, albeit complex relationships between exercise and mood. The neural bases for this interaction between exercise and mood are still unknown and only hypotheses can be advanced. Among these hypotheses, that related to a parallelism between the mechanisms underlying the antidepressant/anxiolytic effects of exercise and those involved in the therapeutic properties of “classical” antidepressant/anxiolytic drugs may prove fruitful (Ransford, 1982). In this context, the finding that central serotonergic systems are the targets for numerous antidepressant/anxiolytic compounds (Blier & De Montigny, 1994; Handley & McBlane, 1993) gives a new and promising insight into the relationships between physical activity and mood alterations. However, before assuming that central serotonergic systems play a key role (partly or totally) in the mood-improving effects of physical activity, it is necessary to show that physical activity is a paradigm that affects central serotonergic systems, and that the mood-elevating effects of physical activity can be diminished or prevented by treatments known to selectively affect central serotonergic tone. Actually, data derived from animal and human studies favor the hypothesis that central serotonergic systems are modified by physical activity (Chaouloff, 1989a), and this research literature serves as the focus of this chapter. On the other hand, studies aimed at measuring the consequences of serotonergic manipulations on mood in exercising humans are still lacking. Clearly, experiments devoted to this field of research should be encouraged because any conclusion regarding the involvement of serotonergic systems in the mood-elevating effects of physical activity requires such an experimental demonstration.