The purpose of this research was to investigate if various psychological wellbeing assessments can predict maximal strength performance and self-scored rating of perceived exertion (RPE) in the back squat. Fifty-eight resistance-trained males and females were recruited, and reported to the laboratory on one day. Subjects completed eight different scales and questionnaires before completing one-repetition maximum (1RM) testing of the squat, followed by two single-repetition sets at 30%, 40%, 50%, 60%, 70%, 80%, and 90% of 1RM, and a set to volitional fatigue at 70% of 1RM. Cognitive anxiety and hypersomnia were found to be positive and negative predictors (p<0.05), respectively, of 1RM performance. Further, self-confidence, grit, and perceived recovery status were significant negative predictors of RPE (p<0.05). Finally, PRS was discovered to be a positive predictor of subject-reported 1RM self-efficacy (b=0.39, t=3.14, p<0.01, R2=0.15). / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection