The Magnitude of RWL and RWG in Combat Sport Athletes Preparing for Competition: A Systematic Review

Combat sport athletes typically engage in a process called making-weight, characterised by rapid weight loss (RWL) and subsequent rapid weight gain (RWG) in the days preceding competition. These practices differ across each sport, but no systematic comparison of the size of the changes in body mass exists. The aim was to determine the magnitude of RWL and RWG in combat sport athletes preparing for competition. The review protocol was preregistered with PROSPERO [CRD42017055279]. In eligible studies, athletes prepared habitually with a RWL period ≤7 days preceding competition. An electronic search of EBSCOhost (CINAHL Plus, MEDLINE, SPORTDiscus) and PubMed Central was performed to July 2018. Sixteen full-text studies (total 4432 participants, 156 female, 4276 male) were included, providing data from five combat sports (boxing, judo, mixed martial arts (MMA), taekwondo and wrestling). Three studies reported RWL and fourteen studies reported RWG. Duration permitted for RWG ranged 3–32 hours. The largest changes in body mass occurred in two separate MMA cohorts (RWL 7.4 ± 1.1kg [~10%], RWG 7.4 ± 2.8kg [11.7 ± 4.7%]). The magnitude of RWG appears to be influenced by the type of sport, competition structure, and recovery duration permitted. A cause for concern is the lack of objective data quantifying the magnitude of RWL. There is insufficient evidence to substantiate the use of RWG as a proxy for RWL, and little data are available in females. By engaging in RWG, athletes are able to exploit rules to compete up to three weight categories higher than at the official weigh-in.