Despite known associations between fitness and recurrent cardiovascular events, changes in cardiorespiratory fitness (CRF) and muscle strength with long-term cardiac rehabilitation (CR) have not been extensively examined in men, and data in women is absent in the literature. The purpose of this thesis was to estimate changes in CRF and muscle strength associated with long-term CR program enrollment in men and women, and to examine the influence of baseline fitness and age on these fitness trajectories in men. Our methods and interpretations of the findings are discussed in the thesis, but in brief, using mixed model analyses we observed important fitness benefits over long-term CR enrollment in men and women and influences of baseline fitness and age on the trajectories in men. Our data provide new evidence of improved fitness trajectories in men and women after long-term CR enrollment and highlight the importance of long-term exercise-based CR after the completion of short-term programs. Larger prospective cohort studies are warranted to confirm the observations, and to identify potential mechanisms underlying these findings. / Dissertation / Doctor of Philosophy (PhD)