Sleeping towards medals? The difference in qualitative sleep between elite and non-elite gymnasts Dumortier J, Mariman A, Boone J, Delesie L, Tobback E, Vogelaers D, Bourgois JG
INTRODUCTION
Performance of athletes depends on the optimal symbiosis of training and recovery. Quantity and quality of sleep are essential components to facilitate the recovery process. The goal of this study is to identify differences in objective sleep characteristics between elite and non-elite female artistic gymnasts. We hypothesize that elite gymnasts will show better sleep quality than non-elite gymnasts because of the higher physical loads.
METHODS
Twelve elite (international competition level) and twelve age-matched non-elite female gymnasts (regional competition level) (15.1 ± 1.5 vs. 15.4 ± 1.6 years old; 31 ± 2 vs. 10 ± 2 hours of training per week; VO2peak: 53.2 ± 5.1 vs. 42.1 ± 3.5 ml·min-1·kg-1) underwent a nocturnal polysomnography (PSG) after a regular training day. For the PSG measurements, the gymnasts were equipped with electroencephalography, electrooculography, electrocardiography, electromyography (chin, right and left leg), posture detector, pulse oximeter (assessing oxygen saturation: SAO2), breathing detectors (on thorax and abdomen) and a manometer (measurement of oronasal pressure). Total sleep time (TST) and sleep efficiency (SE, proportion of time effectively asleep to time in bed) as well as proportion (relative to TST) of non-rapid eye movement sleep phase 1 (NREM1) and 2 (NREM2), slow wave sleep (SWS) and REM sleep during a night were compared between the elite and the non-elite gymnasts using Independent Samples T-Tests. Data are expressed as mean ± SD.
RESULTS
Both groups showed an equal amount of TST (elite: 437 ± 27 min vs. non-elite: 437 ± 21 min, P = 1.000) and SE (elite: 89.5 ± 4.1 % vs. non-elite: 90.1 ± 4.3 %, P = 0.768). Of the qualitative sleep measurements, no inter-group differences were found for NREM1 and NREM2 (elite: 5.1 ± 3.5 % vs.
non-elite: 3.9 ± 1.8 %, P = 0.440; elite: 38.7 ± 10.2 % vs. non-elite: 47.8 ± 4.4 %, P = 0.056). The proportion of SWS was highest in the elite gymnasts (36.9 ± 11.4 % vs. 25.1 ± 5.2 %, P = 0.030) while REM sleep was elevated in the non-elite gymnasts (23.3 ± 4.4 % vs. 19.3 ± 3.9 %, P = 0.031).
CONCLUSION
Although SE did not differ between elite and non-elite gymnasts, the higher SWS in elites indicates an improved sleep quality. SWS is an important phase within the sleep cycle with regards to physical recovery since growth hormone secretion peaks during this phase. Therefore, athletes with substantially low SWS, may be at risk for inadequate physical recovery and thus lower performance levels.
