Chapter 5 health- enhancing behaviors

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In addition to mood effects, regular exercise appears to reduce stress, anxiety, and depression (plante & rodin, 1990). It should be noted that exercise is not a panacea for a poor personality (plante & rodin, 1990). Rarely have any long-term personality changes been reported in conjunction with regular exercise. Rather, exercise seems to be associated with a more subtle lift in mood and feelings of well- being.
Some have maintained that exercise has a beneficial effect or cognitive processes by focusing attention and concentration. However, the evidence on this point is mixed (plante & rodin, 1990; Blumenthal et al., 1991a), furnishing no answer one way or the other. Exercise may initially facilitate attention, but as its intensity increases, these effects may be cancelled out by the debilitating effects of muscle fatigue (tomporoski & ellis, 1986).
There may be economic advantages to exercise. A resent review of employee fitness program, witch are now a part of over 50,000 U.S. businesses, suggests that such program can reduce absenteeism, increase job satisfaction, and reduce health care costs, especially among women employees (see J.Rodin & Plante, 1989, for a review). Exercise may also buffer people against the adverse health effects of stress. J.D. brown and siagel (1988) conducted a longitudinal study to see if adolescents who exercised were better able to cope with stress and avoid illness than those who did not. Result indicated that the negative impact of stressful life event of health declined as exercise levels increased. Thus, exercise may be a useful resource for combating stress (J. D. Brown, 1991; rejeski, Thompson, Brubaker, & Miller, 1992).
One possible mechanism whereby exercise may buffer certain adverse health effect of stress involves the impact of exercise on the immune system. In one study ( Fiatarone et al., 1988), exercise produced a rise in natural killer cell activity and an increase in the percentage of lymphocytes bearing natural killer cell surface markers. And increase in endogenous opioids (natural pain inhibitor; see Chapter 11) stimulated by exercise may play a role in the modulation of immune activity during periods of psychological stress.
One puzzle is way exercise, witch produces the release of adrenalin and other hormones, has a beneficial effect on heart functioning, whereas stress, witch also produces these hormones, has and adverse effect, associated with lesions in the heart tissue (Wright, 1988). One theory maintains that in frequent activation and discharge of adrenalin may have beneficial effect, whereas chronically enhanced discharge of adrenalin may not. Another possible is that adrenalin discharged under conditions for with in was intended (such as running of fighting) is metabolized differently from adrenalin that occurs in response to stress, witch is not expressed physically in the some ways. That is, hormones may be metabolized differently depending or whether one is engaged in large-muscle or small- muscle activity.

Determinants of regular exercise
Although the health and mental health benefits of exercise have been established, most people’s participation in the exercise programs is erratic. Evaluations of exercise programs indicate that 6- month participation levels range from 11 to 87%, averaging at about 50%( Dishman, 1982). That is, on the average, only half of those who initiate a voluntary exercise programs are still participating in that program after 6- month.