The aim of the research was, essentially, to clarify the nature and dimensionally of intrinsic motivation in competitive sport. A working definition of intrinsic motivation was established, narrowing the field of inquiry down to the feelings of subjects at the actual point of participation in a sporting event. The findings have important implications for research and practice. Firstly, it has been shown that the way in which competitive sportspeople rate their own intrinsic motivation varies according to the point in time at which they are asked about it. The in-situ questionnaire should prove to be a useful addition to the armoury of the sport psychologist in providing a means of measuring levels of intrinsic motivation in sport at the actual time of participation. Secondly, specific recommendations are provided as to the timing of questions about intrinsic motivation in a sporting context. Depending on the type of information that is being sought, asking questions at the end of an event may not provide an accurate reflection of the way subjects feel when they are actually taking part. Thirdly, the multi-dimensional model and the diagnostic IIMS will be of use in applied settings. An awareness of the motivational profiles of individual sportspeople will be invaluable in planning training and competition programmes. Finally, the research poses questions about what it is that people actually get out of sport. The findings suggest that the most important aspect of sport participation is the interaction with other people, whether they be team mates or opponents. Self-efficacy plays a less important part than was originally predicted. It is argued that this is because athletes have a particular need to have their achievements socially approved and admired.

The present thesis describes research that characterizes the mobilization of cytotoxic T cell subsets and monocyte populations in response to acute psychological stress and β-agonist (isoproterenol) infusion. Chapter two showed that γδ T cells are mobilized in response to psychological stress and isoproterenol infusion, implicating β-adrenergic mechanisms in this response. Chapter three demonstrated that γδ T cells that were tissue migrating (CD11ahi), of an effector memory phenotype (CD27 CD45RA+), and displaying NK-like features (CD94+), were most sensitive to stress induced mobilization. Chapter four showed that a perforin (pfn)+ C27 phenotype in CD4+, CD8+ and γδ T cells consistency identified cells most sensitive to stress and isoproterenol induced mobilization. However, although cytotoxicity (pfn+) was important, differentiation (CD27 ) status better predicted mobilization. Chapter five revealed that of the three major monocyte populations; CD14++CD16, C14++CD16+ and CD14+CD16+, the proinflammatory‟ CD14+CD16+ monocytes showed the largest mobilization response during stress and isoproterenol infusion. Thus, the selective mobilization of cells with a high effector ability applies to monocyte populations also. We speculate that mobilization of these leukocytes may represent an adaptive mechanism aimed at enhancing host immune defenses in times of threat. This response can have beneficial and detrimental effects depending on the inflammatory or infectious context.