Association between energy availability and sleep quality in elite female and male swimmers: a brief report

Background There is a high prevalence of poor sleep quality and low energy availability (EA) in athletes during phases of intensive training, which poses significant risks for overreaching, improper recovery, and compromised training adaptations. To mitigate these risks, there is a need to explore the relationship between EA and sleep quality. To determine the interrelationships between EA and sleep quality, we assessed EA and sleep quality (sleep durationhrs, sleep debthrs, percent and hours of: slow-wave sleep (SWShrs/%), and rapid-eye movement (REMhrs/%)).Methods The participants included 26 elite male (n = 10; 83.8 ± 8.6 kg; BMI: 24.1 ± 1.9 kg/m2) and female (n = 16; 68.0 ± 5.6 kg; BMI: 22.5 ± 1.6 kg/m2) collegiate swimmers (aged 18–22 years). The descriptive data collected included age, weight, height, training data, and body composition measures. Using a wearable device and a dietary recording cell phone application, the collection of EA was matched to sleep data over a two-week period of heavy training. Pearson correlations were utilized to determine relationships between variables. When effects of sex were observed, linear regression analyses were utilized to control for sex-differences.Results Among all swimmers, 69% exhibited sub-optimal EA (<45 kcal/kg FFM/d). Male swimmers exhibited greater EA and SWS versus females (p < 0.05). EA was positively correlated with REMhrs (R = 0.64; p= 0.001) but not related to sleep debthrs. Regression analyses revealed that when controlling for sex, EA positively predicted SWShrs (R2 = 0.448; F = 9.35, p < 0.001), where higher EA predicted longer SWS durations. Controlling for sleep durationhrs, EA positively predicted REMhrs (R2 = 0.425; F = 8.509, p < 0.002) and negatively predicted sleep debthrs (R2 = 0.261; F = 4.055, p < 0.031), such that higher EA was predictive of longer durations of REM, and fewer hours of sleep debt. There was a trend toward a correlation between EA and sleep durationhrs in all swimmers (R = 0.33; p = 0.06).Conclusion Higher EA was significantly associated with greater REM and SWS durations, and with lower sleep debt in elite male and female college swimmers. Although cause and effect were not established, these findings provide preliminary evidence that adequate EA may support better sleep quality in elite collegiate swimmers. If this is confirmed, our results may suggest that athletes should get adequate sleep and consume adequate calories to support energy expenditure needs and optimize training and recovery. Future research should explore the underlying mechanisms and whether low EA causally impacts sleep quality.