Physiological changes in collegiate artistic swimmers during a competition season: a prospective study

Background Female artistic swimming athletes remain understudied despite the sport’s increasing popularity and competitiveness. Since artistic swimming involves reduced gravitational forces due to water immersion, there is a concern of reduced bone mineral density (BMD) over time. Low energy availability due to dietary behaviors and long-duration practice sessions in the water may induce amenorrhea and augment BMD losses. The objective of this study was to examine female collegiate artistic swimmers’ body composition, menstruation cycle, and dietary intake throughout the competition season.Methods Twelve collegiate artistic swimmers (age: 20.5 ± 1.5 years; height: 168.1 ± 8.2 cm; weight: 65.0 ± 8.9 kg; BMI: 23.0 ± 3.2 kg/m2) completed an 8-month longitudinal assessment. Data were collected every 4 weeks (8 time points total) and included anthropometrics, body composition, resting metabolic rate, dietary intake, and menstrual cycle regularity. Anthropometrics included height (cm) and weight (kg) measured using a stadiometer and digital scale, respectively. Dual energy x-ray absorptiometry measured body composition: bone mineral density (BMD; g/cm2), bone mineral content (BMC; g), fat mass (FM; kg), and lean body mass (LBM; kg). Resting metabolic rate (RMR; kcal/d and kcal/kg/d) was assessed using a metabolic cart with canopy hood. Nutritional intake was assessed every 4 weeks using 3-day dietary recalls, analyzed through the NIH Automated Self-Administered 24-hour dietary assessment tool. Menstrual cycle regularity was monitored monthly using the Low Energy Availability in Females Questionnaire (LEAF-Q). Repeated measures ANOVA tested whether outcomes of interest changed over the competitive season.Results BMD increased over the season (p < .001, η2 = .906) from 1.09 g/cm2 to 1.12 g/cm2. FM decreased over the season (p < .001, η2 = .863) from 20.13 kg to 19.84 kg and LM decreased from 41.18 kg to 40.75 kg. (p < .001, η2 = .911). RMR increased from 1568.58 kcal/d to 1651.28 kcal/d (p = .016, η2 = .727) and RMR relative to lean body mass (RMR/kg LBM) increased (p < .001, η2 = .820) from 38.09 kcal/kg/d to 40.66 kcal/kg/d. Mean energy intake (p = .230), protein intake (p = .370), calcium intake (p = .370), and vitamin D intake (p = .688) remained constant across the 8 months. The majority (73.3%) of participants met the estimated average requirement (EAR) for calcium, while only 6.7% met the EAR for vitamin D. Forty-four percent of participants experienced irregular menstrual cycles throughout the study period.Conclusion Artistic swimmers showed significant improvements in BMD, LBM, and RMR over the season, suggesting the sport and its relative training may support bone and metabolic health despite its non-weight-bearing nature. Notably, even the modest increase in BMD may be clinically relevant, as this population is in a critical period for optimizing peak bone mass. Improvements in BMD may help mitigate long-term risk of osteopenia or osteoporosis, particularly for athletes who began the season with low Z-scores or experienced menstrual irregularities. However, low vitamin D intake and amenorrhea in athletes may compromise BMD and iron status long term. These factors may elevate risk for impaired bone accrual, increased injury risk, and compromised performance. Ongoing monitoring of menstrual function, dietary intake, and bone status are recommended as part of athlete monitoring protocols.