BRINGING SCIENCE TO TREATMENT

Sleeping sporting beauties: Part II – optimizing recovery and sleep

The effects of sleep on performance are well understood. In part two, Tracy Ward explores the sleep-recovery relationship and provides recommendations for improving sleep quality and quantity in female athletes.

Women’s 4 x 400m Relay – Final – Olympic Stadium, Tokyo, Japan – Allyson Felix of the United States and Sydney McLaughlin of the United States in action REUTERS/Kai Pfaffenbach

Optimizing sleep in female athletes

The average person requires approximately 7-9 hours of sleep per night to promote wellbeing and reduce morbidity and mortality(1). However, due to the demands of the sport, athletes may require more sleep. The athlete’s sleep paradox remains a challenge for clinicians, athletes, and trainers as approximately 50-78% of elite athletes report sleep disturbance(2).

Sleep deprivation may lead to numerous medical conditions such as metabolic disease, impaired immune function, depression, and anxiety(3,4). The ‘training-stress balance’ is key to performance. Sleep disturbance alters the metabolic response to training through impaired glucose sensitivity, energy intake, and protein synthesis(5).

Sleep deprivation is a multifactorial issue resulting from both sport and non-sport factors. Habitual sleep duration of fewer than seven hours, sleep dissatisfaction, and daytime fatigue characterize sleep deprivation(2,3). In addition, training after 18:00 and before 08:00 disturbs the circadian rhythm; one hour of exercise within this window can induce a 30-minute shift (6). An earlier bedtime the night prior does not offset the reduction in sleep quality and quantity(7). Additionally, electronic device usage in the evening disrupts melatonin production and disturbs the natural circadian rhythm(8).

Sleep stages

The circadian rhythm is a natural 24-hour cycle that maintains homeostasis by driving processes such as digestive activity, body temperature, hormone levels, immune function, alertness, and sleep. The circadian rhythm rises in the early morning, promoting waking and attention, and peaks in the early evening. After approximately 14-16 hours awake and the onset of darkness, the circadian rhythm drops, and the hormone melatonin is released to initiate sleep (see figure 1)(9).

Figure 1: Human 24-Hour Circadian Rhythm

Sleep consists of 90-minute cycles, with four to six cycles per night. Each cycle has four stages. The first three stages are non-rapid eye movement (NREM) sleep. Stages one to three occur predominantly in the first two cycles and consolidate learning and memory(10). The final stage is rapid eye movement (REM) sleep and occurs near the end of the sleep cycle; it is crucial for immune function (see figure 2)(10).

Figure 2: Sleep stages

Female athletes & sleep

Sleep disturbances may occur more in females due to various changes in their physiology across their lifespan.

  1. The menstrual cycle (MC)

Due to hormonal fluctuations, around 30% of women report disturbed sleep(1). Furthermore,  sleep disturbance is likely before the commencement of the MC(1). Fragmented sleep is most common during the luteal phase. The elevated progesterone levels cause a rise in body temperature, thus, interrupting sleep(11). Pre-menstrual syndrome (PMS) symptoms such as headaches, fatigue, nausea, low back pain, muscle and joint pain, and abdominal cramps, are likely to impact sleep quality and disturb sleep(1). In addition, the emotional symptoms of PMS, including increased irritability, anxiety, depression, and stress, may lead to cognitive arousal and negatively impact sleep(1).

  1. Pregnancy

As female athletes remain physically active during pregnancy, clinicians and trainers should consider the influence of pregnancy on sleep. Common symptoms characterize each trimester. For example, females frequently experience nausea and sickness during the first; position discomfort, muscle aches and cramps, heartburn, and increased urination are prevalent during the third trimester. In addition, following the infant’s birth, frequent feeding schedules and nightly care will impact sleep quantity.

  1. Menopause

Menopause is the natural cessation of ovary function and menstruation. A drop in estrogen levels initiates it. The hormonal fluctuations lead to dilatation of blood vessels, resulting in a raised body temperature, hot flushes, and night sweats.

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Caffeine – friend and foe

To battle sleep deprivation, athletes may seek supplements. Dietary caffeine comes from coffee, tea, and chocolate and stimulates arousal(12). However, over-consumption leads to increased sleep latency, reduced sleep duration, efficiency, and quality(13). The dosage and timing of caffeine consumption should therefore be reasonable and individualized.

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Sleep extension

Sleep extension is purposeful daytime napping to increase alertness, concentration, performance, and mood(14). Strategic napping may be in anticipation of replacing lost sleep, e.g., travel, competition, or training schedules, and supplementing sufficient sleep during periods of increased training frequency(14). Sleep ‘banking’ through napping before competition improves motor performance(4).

Short naps of 10-30 minutes restore alertness and improve performance metrics such as sprint time, accuracy, reaction times, and time to exhaustion(4). Short naps are transient and do not disturb the circadian rhythm. Clinicians should advise athletes to avoid naps between 45-60 minutes as this disturbs a sleep cycle and creates grogginess and reduced performance upon waking. If longer is required, it is suggested athletes aim for 90 minutes to complete an entire sleep cycle and wake refreshed. Researchers at Stanford University demonstrated that the strategic implementation of naps into an athlete’s weekly schedule to achieve 10 hours of sleep per day over five to seven weeks resulted in improved reaction and sprint times, throwing accuracy, and mood(15).

Sleep pressure, the homeostatic sleep drive, builds as the time awake increases. It typically onsets around 15:00 when your circadian rhythm detects a long awake time and core body temperature drops. Napping after lunch, however, is beneficial for relieving sleep pressure and avoiding consequences to nighttime sleep.

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Female-specific sleep strategies

  1. Menstruation
  • Sleep diary to track MC and sleep disturbances
  • Pain management
  • Good overnight sanitary protection
  • Wear breathable, comfortable clothing
  • Bedside water to manage the rise in body temperature
  1. Pregnancy
  • Bedside water to manage the rise in body temperature
  • Breathing techniques to manage leg cramps
  • Sleep in a comfortable position using pillows for support, g., side-lying with hips and knees bent
  • Avoid rich foods and eating near bedtime
  • Avoid screen time if you wake during the night
  1. Menopause
  • Use breathable clothing and bed covers
  • Air conditioning or fan to regulate room temperature
  • Cool bedside water to manage the rise in body temperature
  • Avoid heavy, spicy, or acidic foods
  • Identify coping strategies to manage negative thoughts as this impact’s cognitive arousal before and during sleep
  • Consult with a medical professional if symptoms are not manageable

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Summary

Athletes are at high risk of sleep disturbance due to multiple factors. Female athletes are further at risk due to the physiology of the MC, pregnancy, and menopause. Sleep deprivation extensively affects health and performance. Clinicians need to be aware of the health factors that are specific to female athletes. The design of training programs, competition schedules, and recovery strategies should be specific to the athlete’s needs, specifically during periods of menstruation, pregnancy, and menopause.

References

  1. The Sleep Foundation [https://www.sleepfoundation.org/articles/infographic-sleep-and-your-period]. Accessed Sep 2021.
  2. Sports Med. 2017;47:1317–33.
  3. Br J Sports Med. 2021; 55:356-368.
  4. Int J Sports Med. 2019; 40(8):535-543.
  5. Best Pract Res Clin Endocrinol Metab. 2010; 24: 687–702
  6. J Physiol. 2019; 597: 2253–2268
  7. Eur J Sport Sci. 2014;14:S310–5.
  8. Proc Natl Acad Sci USA. 2015; 112: 1232–1237
  9. Sleep Council. [https://sleepcouncil.org.uk]. Accessed Sep 2021
  10. Sleep. 2004;27:1255–73.
  11. Current Sleep Medicine Reports. 2016; 2:206–217.
  12. 2015;349:1289.
  13. Sleep Med Rev. 2017;31:70–8.
  14. J Sleep Res. 2009;18:272–81.
  15. Sleep. 2011;34:943–50.
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