Physiological load and breath-holding in artistic swimming: a scoping review establishing historical baselines and evidence gaps in the context of the 2022-2025 rule changes.

Background: The 2022-2025 scoring system assigns higher difficulty to complex hybrid elements and acrobatics, which consequently necessitate prolonged underwater immersion. Therefore, it is hypothesized that maximizing scores through extended underwater exertion potentially exposes artistic swimmers to increased physiological demands. Since most quantitative data predates the 2022 rules, traditional routine evidence may underrepresent current competitive stress. Objective: This scoping review systematically map literature on artistic swimmers' physiological load and apnea characteristics, establishing a historical baseline to identify critical evidence gaps introduced by the 2022-2025 regulatory changes. Methods: Following PRISMA-ScR guidelines and the PCC framework, a systematic search across four major databases identified peer-reviewed original research reporting physiological load and/or apnea-related outcomes in competitive artistic swimmers. Results: Synthesis of 36 articles revealed: (1) Routine execution triggers autonomic conflict (concurrent sympathetic/parasympathetic activation), producing broad heart rate ranges (~56.5-203.8 bpm) Additionally, chronic sport-specific training is linked to distinct cardiovascular adaptations. (2) Apnea duration in late traditional (pre-2022) routines constitutes 59%-64% of total performance time. Post-routine blood lactate concentrations are reported ~5.93-11.5 mmol/L. The revised regulations assign higher scoring weights to complex hybrid elements(officially defined as a combination of five or more lower-limb movements performed with intentional apnea),which aligns with increased underwater duration (Time Underwater, TU), higher anaerobic metabolic contributions, and instances of post-exercise hypoxemia. (3) The "Base Mark" penalty mechanism (the minimum degree of difficulty applied for non-conforming or failed elements) correlates with increased cognitive load. Studies also report stress-induced cortisol elevations and altered recovery of heart rate variability under these conditions. (4) Adolescent athletes exhibit still-developing anaerobic and cardiovascular systems. Consequently, based on legacy baselines, recent discussions hypothesize that younger athletes performing the high-frequency, prolonged underwater choreography promoted by the new scoring system may be exposed to increased acute hypoxic stress. Conclusions: Artistic swimming's exertion and prolonged apnea involve autonomic co-activation, high anaerobic demands, and specific psychophysiological responses. Based on theoretical extrapolation from established physiological baselines, it is hypothesized that the 2022-2025 scoring system increases athletes' exposure to cardiovascular and metabolic loading, presenting safety considerations for adolescents. Since most evidence predates 2022, longitudinal research under valid competitive conditions is necessary to assess the new regulations' physiological impacts. Systematic Review Registration: https://osf.io/dxapc/, identifier 10.17605/OSF.IO/DXAPC.