Intra-individual variability of sleep and nocturnal cardiac autonomic activity in elite female soccer players during an international tournament

Abstract

17 18 19 Running title: Sleep and nocturnal heart rate variability individual profiles in elite female 20 soccer. 21 22 Keywords: overnight measurements, parasympathetic system, sleep accelerometer, 23 recovery, women football 24 2 25 Abstract 26 Purpose: This study provides insights into the individual sleep patterns and 27 nocturnal cardiac autonomic activity responses of elite female soccer players during an 28 international tournament. Materials and methods: Twenty elite female soccer players 29 (aged 25.2±3.1 years) wore wrist actigraph units and heart rate (HR) monitors during 30 night-sleep throughout 9 consecutive days (6 day-time training sessions [DT], 2 day-time 31 matches [DM], and 1 evening-time match [EM]) of an international tournament. Training 32 and match loads were monitored using the session-rating of perceived exertion (s-RPE) 33 and wearable 18-Hz GPS (total distance covered [TD], training and match exposure time, 34 and high-speed running [HSR]) to characterize training and match loads. Results: 35 Individually, s-RPE, TD, exposure time, and HSR during training sessions ranged from 36 20 to 680 arbitrary units (AU), 892 to 5176 m, 20 to 76 min, and 80 to 1140 m, 37 respectively. During matches, s-RPE, TD, exposure time, and HSR ranged from 149 to 38 876 AU, 2236 to 11210 m, 20 to 98 min, and 629 to 3213 m, respectively. Individually, 39 players slept less than recommended (<7 hours) on several days of the tournament, 40 especially after EM (n=8; TST ranging between 6:00-6:54 h). Total sleep time coefficient 41 of variation (CV) ranged between 3.1 and 18.7%. However, all players presented good 42 sleep quality (i.e., sleep efficiency 75%; individual range between: 75-98%) on each 43 day of the tournament. Most of the players presented small fluctuations in nocturnal 44 cardiac autonomic activity (individual nocturnal heart rate variability [HRV] ranged from 45 3.91-5.37 ms and HRV CV ranged from 2.8-9.0%), while two players presented higher 46 HRV CV (11.5 and 11.7%; respectively). Conclusion: Overall, elite female soccer 47 players seemed to be highly resilient to training and match schedules and loads during a 48 9 day international tournament. 3 49 Introduction 50 Paragraph 1. Elite soccer players are constantly exposed to multiple high 51 physiological demands due to an elevated number of training sessions and matches played 52 in National and international competitions, often with congested match calendars [1]. In 53 some women's competitive tournaments, only one to two days of recovery are given 54 between matches [2]. In this scenario, optimizing recovery is required to reduce the risk 55 of transitioning into a state of excessive fatigue as well as to reduce the risk of injury [3]. 56 Paragraph 2. One of the most critical aspects of the recovery continuum for 57 elite athletes is obtaining a sufficient quantity and quality of sleep [4]. In fact, athletes 58 and coaches from several sports including soccer have ranked sleep as the most important 59 recovery strategy [5]. A minimum of...

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