Utilising different research perspectives and methodologies the primary aim of this thesis was to investigate the effects of participation in and withdrawal from physical exercise upon indices of health and psychological well-being. The first section of this thesis evaluated the effectiveness of a British corporate health and fitness club in relation to a wide range of lifestyle, physical and psychological measures. Furthermore, this thesis attempted to understand how physical self-perceptions, together with the importance individuals attach to these physical self-perceptions are related to physical fitness and physical activity levels in members of a corporate health and fitness club. Results indicated that members of the club had better psychological mood state scores and physical well-being, higher self-reported job satisfaction scores and were less absent from work than non-members. Males were also physically healthier than females, although there were no observed significant differences between males and females' mood state scores. There were no recorded gender differences in levels of job satisfaction scores or absenteeism. Additionally, results revealed a significant positive relationship between Physical Self-worth and physical activity scores in male members of the club. The second section of this thesis utilised both qualitative and quantitative research designs to consider the effects of withdrawal from exercise upon physical self-perceptions, perceived general health and mood states in physically active students. These results provide some support for the notion that exercise deprivation may negatively influence psychological well-being. Generally, it would appear that participation in physical exercise does have the potential to influence emotional well-being. Similarly, it also appears that withdrawal from habitual exercise can have a negative impact upon indices of mental health. Finally, results tend to indicate that males and females respond differentially to exercise/physical activity and exercise deprivation.