This series of studies investigated affective responses to acute exercise. Studies examined the role of affect in predicting V02max, the temporal patterning of affective responses to acute bouts of exercise, and explored some individual differences which may predict .affective responses to different exercise intensities. With a sedentary male population, the first study assessed the validity of predicting V 02max in a sedentary male population during perceptually regulated trials on a cycle ergometer, and the ability of the Feeling Scale (FS) to add to the prediction of V02max. Participants successfully regulated exercise intensity in a relatively consistent manner and FS was able to account for additional variance in the prediction of V02max during trial 1, RPE range 9-17. FS responses followed previously found patterns and became more negative as exercise intensity increased. The temporal pattern of affective responses became the focus of Studies 2 and 4. Study 2 explored and contrasted the response patterns in heart rate, perceived exertion, perceived activation and affective valence to a graded exercise test in sedentary boys and men. Results showed that boys and men responded in a similar manner to exercise intensity above the ventilatory threshold evn but not below the VT. Study 3 explored the temporal dynamics of affective responses during and after prescribed and self-selected exercise in active young adolescents. During exercise, affective states were least positive in high-intensity exercise. A rebound phenomenon was obserVed across all exercise intensities post-exercise. The fourth study investigated affective responses with sedentary young adolescents, within the framework ofthe dualmode model of affect, and used a two-phase, mixed-method, sequential explanatory .. approach. Quantitative results showed affect was least positive above the VT and more positive in the self-selected condition and below the VT. Qualitative results showed positive affective responses were associated with perceived ability to cope,. perceptions of competence, and a positive interpretation of the exercise intensity. The [mal study examined the utility of the Preference for and Tolerance of the Intensity of Exercise Questionnaire (pRETIE-Q) with young adolescents, and investigated its construct validity. ConfIrmatory factor analysis did not support the original structure; ,!,;;hortened . ~ questionnaire offerec\ a stronger structure. Only the Tolerance scale of the adapted PRETIE-Q related to affective responses generated during exercise. A discussion of the research fIndings in the thesis are presented along with strengths and limitations of thestudies, conclusions, future directions and the applied implications are suggested with respect to exercise promotion.