• Identify the relationship between exercise and psychological health variables.
• Explain the correlation between aerobic and anaerobic exercise and depression, anxiety, stress, mood state, self-esteem and body image.
• Provide general guidelines for exercise prescription, where applicable, for improving psychological health.

It is commonly acknowledged that physical activity and exercise have a positive impact on many aspects of health, including protection against coronary heart disease, high blood pressure, some cancers, diabetes and osteoporosis (Kesaniemi et al., 2001). A growing body of research over the last 10 years substantiates that physical activity also improves psychological well-being (Dubbert, 2002). This article reviews the effects of physical activity on the mental health variables of stress, mood state, depression, anxiety, self-esteem and body image based on recent research. It is meaningful to clarify that much of the research presented here is correlational research, which means that the scientists studied the associations that exist between exercise and mental health variables, and not the causal relationships. Because of this, the exercise prescriptions for improving these psychological health variables are better viewed as suggested guidelines to follow rather than the more precise recommended guidelines for physical benefits, which are based on a greater body of experimental research.

EXERCISE AND STRESS
Published investigations conclude that individuals with improved levels of fitness are capable of managing stress more effectively than those who are less fit (Hassmen, Koivula & Uutela, 2000). The data suggest an inverse relationship: higher physical fitness is associated with lower levels of stress. It appears that the mode of exercise that most affectsstress reduction is aerobic exercise. Studies describe the role of exercise as a preventive intervention in managing stress as opposed to a corrective intervention. The research indicates that moderate intensity exercise, performed three times a week (sessions lasting over 20 minutes) for up to 12 weeks, has the most influence on stress management. Although the specific mechanisms explaining the improved stress levels from aerobic exercise are unclear at this time, it appears that possible theories include the involvement of physiological, biochemical and psycho-social factors (Fox 1999).
Key point: Aerobic exercise for up to 12 weeks following ACSM guidelines for developing and maintaining cardiorespiratory fitness appears to have the most influence on the prevention of stress.

EXERCISE AND MOOD STATE
Frequently, health and fitness professionals hear clients say that they exercise because it "feels good." Because mood state is influenced by psychosocial, psychophysiological, environmental and pharmacological factors, explaining the exercise-induced mechanism is quite difficult. However, it appears that aerobic and anaerobic exercise can positively affect different mood states including tension, fatigue, anger and vigor (a psychological variable defining vitality or energy) in normal and clinical populations (Lane & Lovejoy, 2002; Fox, 1999; Scully et al., 1998). In addition, even acute bouts of exercise (single sessions) may improve a person's present mood state (Lane, Crone-Grant, & Lane, 2002). It has been shown that a single bout of 25-60 minutes of aerobic exercise (at low, moderate or high intensities) increases positive mood feelings while also decreasing negative mood feelings. Implications from these data denote the incorporation of regular exercise in a person's lifestyle for the enhancement of a positive mood state. The use of resistance training to improve mood state requires further research. For the chronic management of mood state, interpretations from the research appear to indicate that following ACSM guidelines is a most suitable exercise prescription.
Key point: Aerobic and anaerobic exercise can acutely and chronically enhance a person's mood state. Aerobic exercise following ACSM guidelines appears to be most effective.

EXERCISE AND DEPRESSION
The antidepressant action is one of the most commonly accepted psychological benefits of exercise. Individuals with clinical depression tend to be less active than healthy average adults and have a reduced capacity for physical exertion (Fox, 1999). As such, it is challenging for the fitness professional to introduce physical activity to this population, as people suffering from depression are not predisposed to participating in exercise. However, patients diagnosed with depression have credited exercise as being a most important element in comprehensive treatment programs for depression (Dunn et al., 2002). Aerobic and anaerobic exercise seem to be equally effective in producing antidepressive effects (Brosse, Sheets, Lett, & Blumenthal, 2002). Therefore, the inclusion of resistance exercise, circuit training, calisthenics, as well as different modes of aerobic exercise should be encouraged.

It also appears that both acute exercise bouts and chronic exercise training programs (over a period of time) have a positive effect on people with clinical depression (Dunn et al., 2002). The research does imply, though, that the greatest antidepressive effects seem to occur after 17 weeks of exercise, although observable effects begin after 4 weeks (Scully et al., 1998). In addition, the effects of exercise on depression seem equivalent in both genders and are uninhibited by age or health status. Although no research guidelines exist for an actual exercise prescription, the evidence suggests following the ACSM guidelines for the recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness and flexibility in healthy adults (Pollock et al., 1998).
Key point: Various modes of aerobic exercise and resistance training following ACSM guidelines, completed over a continuous period of 17 weeks, appear to have a positive influence on individuals (of both genders and all ages and fitness levels) with depression.

EXERCISE AND ANXIETY
According to Webster's Unabridged Dictionary, anxiety is "distress or uneasiness of mind caused by fear of danger or misfortune." It is a stage of apprehension. The results of over 30 published papers substantiate a link between acute and chronic exercise and the reduction of anxiety (Scully et al., 1998). Most of the research on exercise and anxiety involved aerobic training regimens. The few studies involving resistance training and flexibility have also shown a slight decrease in anxiety, but additional research in this area is needed. However, the data does indicate that aerobic exercise is more beneficial for the reduction of anxiety. In regard to the actual aerobic exercise prescription, there appears to be much debate about whether low-intensity (40-50% maximum heart rate [MHR]), moderate-intensity (50-60% MHR), or high-intensity (70-75% MHR) exercise is most beneficial. For participant adherence, exercise intensity should be set at an adjustable level agreed upon by the individual in consultation with a physician or health practitioner. It appears that even short bursts of 5 minutes of aerobic exercise stimulate antianxiety effects. The research also indicates that individuals who train for periods of 10 to 15 weeks receive the greatest beneficial effects.
Key point: Anaerobic and aerobic exercise positively influence anxiety, with aerobic activity at an individualized level of intensity having slightly more benefits in reducing anxiety. Optimal benefits appear after 10 to 15 weeks of regular exercise.

EXERCISE AND SELF-ESTEEM
As with the other psychological health variables, exercise has a positive influence on improving self-esteem (McAuley et al., 2000). The effect of exercise also appears to be more potent in those who have lower self-esteem (McAuley et al., 2000). Studies indicate that aerobic exercise may have a more pronounced effect than anaerobic exercise, but that may be because there is little research available on resistance training exercise and self-esteem. However, self-esteem is quite complex and studies suggest that certain subcomponents contribute to a person's self-esteem including perceived sport competence, physical condition, body image and strength (Scully et al., 1998). Because of the many variables that influence self-esteem, it is important to note that a person may highly value his/her physical condition and yet have a negative evaluation of his/her body. Current research provides little direction regarding the mode or dose recommendation of exercise for improved self-esteem. More recent data suggest that important factors influencing a person's self-esteem are perceptions of their body attractiveness and physical condition (McAuley et al., 2000).
Key point: Evidence suggests that individuals with low self-esteem benefit more than others from aerobic exercise. An optimal exercise prescription is uncertain at this time.

EXERCISE AND BODY IMAGE
Body image is a complex construct that involves feelings, thoughts and perceptions about one's physique (Scully et al., 1998). Females tend to have a less positive body image than males and can become preoccupied with losing weight (Hausenblas & Fallon, 2002). Females also tend to focus on their body from an aesthetic viewpoint whereas males tend to view their body in respect to strength, speed and coordination (Franzoi, 1995). Franzoi suggests that women are more likely to engage in activities that are noncompetitive, such as aerobics, with the goal of keeping fit.

Disturbances in body image appear to be strongly implicated in the development of eating disorders and clinical depression. When diet and exercise become too dominant in a female's lifestyle, she is susceptible to a set of disorders referred to as the female athlete triad. The female athlete triad includes disordered eating, amenorrhea, and premature osteoporosis. In addition, the eating disorders of anorexia nervosa and bulimia are more prevalent in this population. The sufferer is usually someone who is driven to excel and who equates leanness with improved performance.

More recent research suggests that even a relatively short period of 6 weeks of circuit weight training positively influenced the body image of college-aged males and females (Williams & Cash, 2001). Both men and women subjects reported greater body satisfaction, reduced social physique anxiety, and enhanced physical self-efficacy.

Research suggests that health and fitness professionals should be very attentive to the design of fitness facilities in order to make women feel more comfortable with their body image (Scully et al., 1998). For instance, private changing facilities are recommended for helping reduce body image dissatisfaction. In addition, fitness professionals need to be aware that exercise participation may accentuate a person's body image dissatisfaction, enhancing a person's drive for leanness. The suggestion that everyone can attain the "elite model look" may perpetuate psychological disorders in some female clients. Caution is necessary for all health practitioners in guiding clients, especially females, toward healthy physical activity to avoid the development of eating disorders and an obsession with thinness.
Key point: Body image is a complex construct that involves feelings, thoughts and perceptions about one's physique. Females tend to have a less positive body image then males and can become preoccupied with thinness, which may lead to unhealthy diet and exercise practices. Recent research suggests that a brief (6-week intervention) circuit weight training significantly improved the evaluation of body appearance by college-aged men and women.

PROMOTION OF PSYCHOLOGICAL HEALTH BENEFITS
From this brief review, it is clear that health and fitness professionals may confidently declare the psychological health advantages of exercise in addition to the well-established physiological health benefits. Certainly, for several mental conditions, exercise serves a therapeutic role. The fitness professional now has research-based information with which to develop and prescribe realistic exercise programs for clients who seek to improve their psychological well-being.

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