Current consensus has highlighted collegiate athletes commonly experience poor sleep quality and quantity, provoking daytime sleepiness and potentially negatively impacting academic and athletic performance [1]. Moreover, recent evidence has revealed female collegiate soccer players have an increased odds for experiencing sleep dysfunction [2]. Female collegiate soccer players require sustained and elevated cardiorespiratory, musculoskeletal and cognitive performance during training and competition [3]. This is of great importance for female soccer players, as decrements in sleep quality can elicit mental fatigue, an effect that has shown to be negatively associated with maximal cardiorespiratory performance, maximal soccer ball shot speed and accuracy [4]. Such physiological demands necessitate ample time between exercise bouts in the effort to mitigate injury as well as mental and physical fatigue. Typical North American collegiate soccer schedules involve competing in two matches within a 24–72-hr window, placing considerable psychophysiological strain on athletes. Moreover, student athletes are required to excel in both the classroom and on-field, often experiencing academic and athletic stressors simultaneously [5]. Student athletes may therefore experience habitual fatigue and under-recovery, highlighting the importance for maximizing recovery through sleep. This evidence is of clinical and athletic importance for coaches and practitioners as poor sleep quality has been associated to reductions in match performance and a greater risk for injury in soccer players [6].

Alterations in cardiovascular function follows the circadian rhythm displaying significant changes throughout the sleep cycles, with declines in nocturnal heart rate and arterial blood pressure in non-rapid eye movement (REM) sleep, and elevations in REM sleep [7]. Interestingly, during sleep, the brain appears to heighten protection against transient increases in blood pressure, such as those occurring during transition from non-REM to REM sleep [8]. Conversely, the cerebral autoregulation for hypotension may in fact be blunted [9]. In non-REM, which corresponds to approximately 80% of the total sleep duration, cerebral ischemia may result when the reduction in arterial blood pressure causes cerebral blood flow to fall beyond a critical limit [10]. Hypotensive individuals, specifically females, have demonstrated significant reductions in sleep quality and quantity, an outcome thought to be the consequence of spontaneous awakening due to a lack cerebral blood flow [11]. As such, the relationship between cardiovascular function and sleep quality should be a primary concern for practitioners when establishing the health of their athletes as well findings technique to maximize sleep and recovery. This is especially important given the interplay between sleep quality and cardiovascular function and overall health [12].

Regular exercise has shown to improve sleep quality [13]. However, exercise should be delineated from athletic training and competition, where the psychological demands are vastly different. The effect of accumulated exercise stress on sleep in female athletes remains ambiguous, with current literature revealing both insignificant [14] and significant associations [15]. This ambiguity may be attributed to the underlying physiological functioning of the athlete. Wearable technology has provided practitioners an efficient and integrative approach to examining exercise stress in athletes using heart rate and GPS monitors. These data now allow examining indices of internal and external work completed and its association to sleep quality. The potential influence of exercise, when examined as quantifiable measure, on sleep quality, would empower coaches to design periodized training programs knowing the potential ramifications of altered sleep and physiological recovery. Recent evidence utilizing internal and external measures of exercise stress, has demonstrated varying associations between both ratings of perceived exertion (sRPE) and total distanced covered with sleep in male semi-professional soccer players [16]. However, the use of a sleep specific questionnaire was not incorporated to thoroughly examine sleep quality.

To date, there remains a paucity of inquiry into resting cardiovascular function and its association to sleep quality in female athletes. Longitudinal research permitting fluctuations in exercise volume, academic and athletic obligations, as well lifestyle alterations, is required to provide a robust analysis of the influence of cardiovascular function and sleep quality. As such, the primary purpose of this investigation was to examine the association between sleep quality and cardiovascular function in healthy female collegiate soccer players during a six-month period. Additionally, a sub-analysis was conducted to examine the association between sleep quality and accumulated exercise stress from on-field training over a two-month period. It was hypothesized that sleep quality would be greater in individuals with superior cardiovascular function, optimal blood pressure and lower accumulated exercise stress.