Helms, EricStorey, AdamRoberts, BrandonKwan, Kedric2026-01-272026-01-272025http://hdl.handle.net/10292/20545Rapid weight loss (RWL) is widely practiced in weight-class restricted sports to enable athletes to compete in a lower weight category, typically through strategies that reduce body mass via dehydration (e.g., fluid manipulation, sauna/sweating) and/or non-dehydration methods that reduce gut content and glycogen (e.g., reduced carbohydrate intake, low food volume, fibre restriction). Although RWL is often perceived to confer competitive advantage, it can also compromise health, cognitive function, and physical performance, with risk generally increasing as the magnitude of weight loss increases and as the post–weigh-in (PWI) recovery window shortens. Existing RWL research has largely focused on combat sports, yet RWL is highly prevalent in weight-class restricted strength athletes (WRSA), including powerlifters, weightlifters, and strongman competitors. Differences in sport demands, recovery opportunities, and performance determinants suggest that findings from combat sports may not translate directly to WRSA, creating uncertainty around best practice. This thesis aimed to expand the evidence base on RWL in WRSA by integrating: (1) a synthesis of current literature on RWL magnitudes, methods, and health/performance outcomes, and the extent to which combat sport data can be extrapolated to WRSA; (2) observational data describing the prevalence, magnitude, and methods of RWL in world-class powerlifters and the relationship between RWL and competitive performance; (3) changes in validated subjective wellness measures across the seven days prior to weigh-in and their associations with weight loss magnitude, competitive calibre, and biological sex; (4) an experimental evaluation of a three-day low-gut-volume (LGV) dietary strategy, assessing the magnitude and within-subject repeatability of body mass loss and potential sex differences; and (5) an experimental investigation of passive dehydration via heat exposure at different time points (evening prior vs morning of testing) on WRSA-relevant strength and power outcomes across baseline, dehydrated, and rehydrated states. Collectively, this thesis addresses key gaps by providing WRSA-specific descriptive data, testing practical RWL strategies, and evaluating performance and wellness implications under conditions relevant to strength sport competition. The findings are intended to inform evidence-based, context-specific RWL guidelines for WRSA and to guide future research on safer and more effective weight-making practices.enThesisOpenAccess