To get a job done, find a busy person - or so the old aphorism would have it.
However, the rationale behind this idea has recently been granted scientific status by a group of researchers led by Professor of Kinesiology and Community Health, Dr.
Edward McAuley (University of Illinois, Champaign).
His team's report is one of a growing number of studies establishing a strong link between levels of physical activity and rates of depression (generally, the higher the first, the lower the second is likely to be), What is unique about Dr.
McAuley's work, however, is that it suggests a strong link between exercise and a form of positive thinking known as 'self-efficacy'.
So, just what is self-efficacy, and how is it related to both physical activity and depression? In a nutshell, self-efficacy is a belief in the effectiveness of one's one present and future actions.
Self-efficacious individuals believe that they are capable of acting in such a fashion as to achieve the goal they have in mind - a cognitive and emotional stance that depressed subjects almost completely lack.
For example, a self-efficacious individual believes intrinsically that he or she can walk to the top of the stairway without taking the elevator; a depressed individual is prone to preemptively forestall the 'harder' option, immediately supposing that such a feat is beyond his capabilities.
The McAuley team found that physically active individuals were substantially more likely to hold self-efficacious beliefs than those who are physically inactive.
Examining published data from two studies of patients with chronic illnesses (292 multiple sclerosis sufferers and 192 survivors of breast cancer), the team also invited volunteers to complete a self-report questionnaire which assessed levels of physical activity, health status, self-efficacy and levels of fatigue and depression.
Participants were asked to monitor and record their physical activity using a motion sensor (or accelerometer) over seven days during waking hours.
All participants were tested on each of these measures six months later.
The results were unambiguous: not only did the more physically active subjects report substantially lower levels of depression and fatigue, they scored appreciably higher than inactive individuals on measures of self-efficacy, too.
Dr McAuley and his colleagues concluded that the degree of physical activity influenced an individual's self-efficacy, which in turn influenced the degree of depression and fatigue, in a 'virtuous circle': the greater the physical activity, the greater the self-efficacy and as a result the lower the level of fatigue and depression.
There are important implications for the psycho-physical treatment of depression and its causes in this study.
It is possible that self-efficacy can be 'taught' to some extent through psychological methods such as cognitive behavioral therapy, but it appears to be most effective when it is physically embodied.
Exercise and physical activity seem to foster it, with self-efficacious subjects believing that they have considerably more control over their lives than those who are depressed and inactive.
Activity may indeed have anti-depressant effects, encouraging more positive patterns of thought in individuals.