This thesis examined within-person variability and potential optimizers of mental toughness through a literature review and four central studies, three of which have been published and a fourth currently under review. Study I focused on within-person mental toughness and potential optimizers in a single elite Masters athlete across a series of endurance events (3,000 mile Race Across America, Hawaii Ironman Triathlon World Championship qualifier and a sub-3 hour marathon) over a five month period and beginning six weeks after a bike wreck resulted in eight fractures and an increased emphasis on the mental aspects of the events. Notable variability and potential optimizers were both identified via an autoethnographic approach. The second study expanded upon the first by investigating the presence of within-person variability and potential optimizers in a group of 13 elite Masters athletes. In addition to the larger group of participants, Study II also identified within-person mental toughness variability, utilizing the Mental Toughness Index (Gucciardi, 2015) to specifically track the potential variability over a 30-day period. The exploratory case study design also included collection of qualitative data regarding the potential optimizers and lead to the development of three primary higher order themes of mental toughness optimizers: Thrive, Prepare and Activate. Study III examined the influence of sleep on mental toughness, a potential optimizer identified previously within the Thrive and Prepare higher order themes. Within-person variability in mental toughness was again demonstrated and while sleep was not shown to be related to mental toughness in all participants as hypothesized, it was an influencer of mental toughness in the majority of participants. In addition, Study III provided insights into additional buoys of mental toughness utilized by participants when sleep was limited. Study IV then investigated whether self-talk (identified previously as a potential optimizer under the Prepare and Activate themes) influenced mental toughness and performance. The influence of self-talk on mental toughness and performance was demonstrated. The thesis concludes with a discussion about the findings, their implications for additional settings and applications, and future research opportunities
