Virtual reality (VR) has become an important tool in the gamification of physical activity and has been shown to increase motivation and adherence. In-game features such as progress visualizations and feedback, alongside levels of difficulty that provide sufficient challenge, work to satisfy the psychological need for autonomy and competence and increase motivation. The purpose of this study was to examine the effects of in-game features and levels of difficulty in VR gaming on motivation, perceived exertion, and actual exertion. Enjoyment, motivation, perceived exertion (PEx), and actual exertion (AEx) were measured as participants played two versions of the VR game 'Pacebreaker' at three levels of difficulty. AEx was significantly higher than PEx at the easy and medium level of difficulty in Version 1 and 2 (p < 0.05), but there were no significant differences at the hard level for either version (p > 0.05). No significant differences were found in motivation or enjoyment between game versions or levels of difficulty (p > 0.05). Our findings suggest that greater levels of AEx and lower levels of PEx can be achieved when game difficulty is easy to optimally challenging. v Acknowledgements I first would like to thank my mentor, Dr. Anthony Mayo, for guiding and supporting me through both my undergraduate and graduate degree. Without his encouragement, I would not have stepped outside of my comfort zone and accomplished as much as I have here at San Francisco State. I thank my advisor and Committee Chair, Dr. Jimmy Bagley, for presenting me with the opportunity to lead this virtual reality research and seeing me through the Scholars Program. I would also like to show my appreciation of Dr. Rachel Flynn and Dr. Nicole Bolter for their assistance throughout this process. This research would not have been possible without the generosity of Aaron Stanton of the Virtual Reality Institute of Health and Exercise. Additionally, I am immensely grateful for my research assistant, Kelly Yu, and her dedication to this project. I would also like to express my gratitude to fellow colleagues for their contributions during piloting. Lastly, I would like to thank my friends and family for supporting me throughout this journey to my Master of Science degree. viTable of Contents List of Tables .