Title: Workload Demands during Ball-in-Play Periods: A Comparative Study of Locomotive and Contact Metrics in Professional Male for Female Rugby Union Players. Purpose: Rugby Union is a high collision-based sport demanding the best physical, technical, tactical and decision-making capabilities of players to influence success on the field. Various factors affect the ability of females and males to perform and meet the demands of match-play. This thesis was developed as a pilot study and employed an innovative design that examined and compared contact and workload metrics between female and male professional rugby players, aiming to explore differences in match play. Methods: Data were collected from 60 professional male and female rugby players, from two professional 2023 New Zealand National Provincial Rugby teams. All participants wore GPS units (Apex Pro Pod, STATSport, Newry, NIR). Each match was filmed and coded using a Sportscode video analysis software package (Sportscode 12.4.3, Sportstec, Australia), where contact and GPS metrics during Ball-in-Play periods were identified and recorded throughout the match. GPS and Sportscode data for each Ball-in-Play period for each match were combined in a bespoke software package. Differences between the sexes for each metric were analysed using Welch’s t-test with the level of significance set at P<0.05 and the magnitudes of the standardised differences were calculated using effect sizes determined by Cohen’s d (Hopkins, 2009, 2017). Tests for equality of variances, normality, and the examination of outliers were conducted in IBM SPSS Statistics (Version 27) and the few metrics that failed normality testing were log-transformed. Results: Males locomotive metrics (GPS measures) and impacts (accelerometer measures) were typically significantly greater than females showing large to moderate magnitude differences. On the other hand, contacts were often significantly higher for females with small to large magnitude differences. Conclusion: The differences between males and females were likely a combination of genetic differences, and differences in how the respective games were played, and the males in this study typically had greater full-time professional training support and resources. Due to these differences, altering female threshold standards for specific intensive locomotion metrics to suit the physical capabilities of females, may give more of an accurate representation of game demands. On the other hand, providing greater resources to female rugby union players for similar periods to the males may reduce the differences observed in this study.