"Measuring Mental Toughness in Professional Sport: A Criteria-Based Psychometric Evaluation and Guidelines for an Optimized Scale"

Mental toughness is considered an important psychological characteristic in professional sport, but measuring it accurately has proven to be a challenging task. Several questionnaires have been developed over the years to assess this construct, each with different theoretical foundations and psychometric properties. This thesis critically examines four of the most commonly used mental toughness questionnaires in elite sport: the MTQ48, SMTQ, MTI, and PPI-A, evaluating their strengths and limitations from a psychometric perspective. The instruments are compared using established criteria such as internal consistency, construct validity, and factorial structure, and their content is mapped to identify gaps and overlaps in what they measure. Based on this analysis, the thesis offers guidelines for what an improved measurement tool for professional athletes could look like. No new scale is empirically tested, as this work is intended as a foundation for future research in the area.