The Role of Sleep in High Performance

by Manav Bajaj (Sport Nutritionist & Performance Analyst) & Rishabh Jaiswal (High Performance Director)

Athletes do everything in their power to achieve high performance, from intense training to highly optimised nutrition. However, there is one simple habit that is often overlooked: getting adequate sleep.

 This brings up some relevant questions that squash players may ask, can sleep affect squash performance? How many hours of sleep is adequate? Is night sleep the same as napping frequently during the day? This article will aim to answer these questions in a precise, science backed manner.

What is more Important: Quality or Quantity of Sleep?

In last month’s blog we emphasized upon the Quantity of sleep at night bring minimum of 9 hours. While this is very important, the quality of sleep actually determines how much you recover and your readiness for the workload on the next day.  

To understand this better, we need to look at how our Sleep Cycle works.

What Happens When We Sleep? :  Importance of Deep Sleep

Sample of Sleep Cycle Monitored using a Wearable Device

Our sleep consists of different phases or stages, broadly classified and NREM (Non Rapid Eye Movement) and REM (Rapid Eye Movement) sleep.

NREM sleep is further divided into three stages: N1, N2 and N3 in which N3 is the “Deep Sleep” phase which is supposed to be the most restorative phase of the sleep. Deep Sleep typically comprises 13-23%* of your entire sleep cycle and helps you refresh and reset for the next day.

Other benefits of Deep Sleep include:

  • Energy restoration
  • Regeneration of cells and growth
  • Helping strengthen the immune system

Deep Sleep duration in each cycle typically becomes shorter as the night progresses. It is important that you maintain good sleeping habits and hygiene to ensure your sleep is not getting disrupted frequently or this could impact the recovery you are able to derive from your sleep.  

Source: MyFitnessPal

Endocrinology of Sleep

One of the main reasons linking sleep to recovery is the hormonal changes that take place during night sleep. Research shows that adequate sleep lowers levels of cortisol in the system which is the body’s stress hormone and is responsible for several catabolic functions.

 Hormones like IGF-1 (Insulin like Growth Factor-1) and HGH (Human Growth Hormone) are primarily released during sleep and mainly during the Deep Sleep phase.

 In fact, as much as 95% of HGH is released during sleep and is responsible for several anabolic functions such as bone growth, muscle protein synthesis and reduces inflammation which is caused due to exercise.

Performance Data Related to Sleep

Performance metrics such as cognitive function, reaction time and accuracy are all metrics that are known to positively influence squash performance and have been linked to sleep in current sport science research. Here are some findings which have been related to sleep and sport performance:

  • Tennis players who were allowed to sleep for 8+ hours observed a 4.2% increase in hitting accuracy compared to athletes who sleep for less than 7 hours.
  • Swimmers who slept for 9 hours showed a 17% improvement in starting times compared to swimmers who slept less than 7 hours.
  • Sleep-deprived Basketball players showed a drop by 9% in free throw and 3-point shooting accuracy.
  • Sleep loss led to an 11% reduction in time trial performance in elite cyclists.

Best Practices for Good Quantity & Quality of Sleep

Source: YLM Sport Science
  • Avoid caffeine containing products 4-6 hours pre-sleep time.
  • Avoid screens at least 30 mins pre-sleep time.
  • A glass of warm milk with almonds or Tart cherry extract can aid sleep.
  • Keep a consistent sleep/wake up time to ensure consistency.
  • Ensure meals are consumed at least 2 hours pre-sleep time.
  • Avoid late night sessions/training as this could have an impact on your sleep.


Present data allows us to conclude that sleep plays a major role in both performance and recovery in a high intensity sport like Squash. Due to variation in sleep cycles and deep sleep being a small percentage of a total sleep cycle, ~9 hours of night sleep is important for optimal performance and recovery.

Naps before 4 pm in the afternoon can supplement night sleep, however, it does not replace inadequate night sleep.

As a result, Squash players are advised to get 9 hours of night sleep to ensure they can perform optimally.


  • 95% of the body’s total growth hormone is released during sleep.
  • Adolescents who get less than 8 hours of sleep are twice as likely to get injured when playing (Milewski et al 2014).
Source: YLM Sport Science


Milewski, M., Skaggs, D., Bishop, G., Pace, J., Ibrahim, D., Wren, T. and Barzdukas, A. (2014) Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of Pediatric Orthopaedics, 34 (2), 129-133.

Mah, C., Mah, K., Kezirian, E. and Dement, W. (2011) The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep, 34 (7), 943-950.

Schwartz, J. and Simon Jr, R. (2015) Sleep extension improves serving accuracy: A study with college varsity tennis players. Physiology & behavior151, 541-544.

Thun, Eirunn, Bjørn Bjorvatn, Elisabeth Flo, Anette Harris, and Ståle Pallesen (2015) “Sleep, circadian rhythms, and athletic performance.” Sleep medicine reviews 23: 1-9.

*Reference from Pubmed Database

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s