CPT Sports Performance Recovery

Circadian Rhythm and Performance

Stacey Penney
Stacey Penney

Do you know which NFL team has better odds of winning Monday night? Chances are it could be determined by circadian rhythm.

What is Circadian Rhythm and what does it have to do with football?

Circadian rhythm is our daily clock-when we wake and when we sleep, but also includes frequency of eating and drinking, body temperature, blood pressure, release of certain hormones, and even sensitivity to certain medications. The typical adult human cycle is about 24 hours. Starting in the morning, our lowest body temperature is around 4:30 a.m., and peaks around 7 p.m. We are highly alert around 10 a.m., our best coordination is mid-afternoon around 2:30 p.m., followed by peak reaction time at 3:30 p.m. and, here’s the important one—greatest cardiovascular and muscle strength is around 5 p.m. (1).

Using circadian rhythm has been a better predictor of Monday night NFL wins than Las Vegas odds (2). One study evaluated 25 NFL seasons to see if performance on Monday night was affected by time zone. Because gamtime was typically 9 p.m. ET during this review, the East Coast team was playing much later than their peak cardiovascular and strength time of 5 p.m., while the West Coast teams had the clock advantage. Even when the West Coast teams traveled to the East’s field, the home team still lost to the circadian clock advantage.


Melatonin is released by the pineal gland, which is located deep in the brain. Melatonin plays a role in the sleep-wake cycle. Its production is triggered by darkness and inhibited by light. Melatonin is thought to help cause sleepiness by reducing core temperature and shifting brain activity. Melatonin supplements have been shown to be helpful for reducing jet lag symptoms and other sleep disorders related to circadian rhythm. Though usually safe for the short term, melatonin supplements can have side effects such as nausea, headache, dizziness, or drowsiness. These may affect a client’s or athlete’s ability to exercise so be aware of the possibility of a residual effect of the supplement (3).

Jet Lag and Circadian Rhythm

Daylight saving time will end for most of us this weekend on November 5th, giving us back the hour we lost in spring, but it also puts us back on a more natural schedule. (How many people ever complain about that extra hour of sleep they get starting in the fall?) Circadian rhythms can be affected by outside influences including light exposure and time zones (4). Athletes, and clients, need time to adjust to their current or upcoming time zones to synchronize their internal clocks with times of peak performance demands. Interestingly, elite athletes who traversed five time zones or more for competitions also had a two to three times higher rate of illness compared to when they competed on their home turf (5). Some approaches to combating jet lag include gradually adjusting the current sleep schedule by 30 to 60 minutes every few days, using a light box to adjust melatonin release, or melatonin supplementation (6).

Humans follow an internal clock that influences multiple physiological functions, including the sleep-wake cycle.  This cycle, the circadian rhythm, also influences physical performance and melatonin production. When this cycle is disturbed, as seen with daylight saving time, jet lag, or even shift work, there can be impacts on health and performance.

Did You Know? This year, the 2017 Nobel Prize in Physiology or Medicine was awarded jointly to Jeffrey C. Hall, Michael Rosbash and Michael W. Young for their discoveries of molecular mechanisms controlling the circadian rhythm


  1. Smolensky M, Lamberg L. The Body Clock Guide to Better Health: How to Use your Body's Natural Clock to Fight Illness and Achieve Maximum Health 1st edition. New York: Henry Holt and Co; June 14, 2000.
  2. Smith Roger S.,  Guilleminault Christian, Efron Bradley. Sport, Sleep, and Circadian Rhythms Circadian Rhythms and Enhanced Athletic Performance in the National Football League.Feb. 1997. Date accessed 7 Oct. 2012  http://www.journalsleep.org/Articles/200507.pdf.
  3. Sharecare Desk Reference: Melatonin http://fitness.sharecare.com/library/common.aspx?id=9293
  4. Psychology Today Circadian Rhythm Body Clock, Sleep Cycle, Jet Lag - Accessed on 7 Oct. 2012. http://www.psychologytoday.com/basics/circadian-rhythm.
  5. Schwellnus MP, Derman WE, Jordaan E, et al. Elite athletes travelling to international destinations >5 time zone differences from their home country have a 2–3-fold increased risk of illness.  8 Aug. 2012. Accessed 7 Oct. 2012. Br J sports med http://bjsm.bmj.com/content/early/2012/07/27/bjsports-2012-091395.abstract.
  6. Peters, Brandon. How Can I Treat Jet Lag? Learn How to Shift Your Circadian Rhythm. 26 Mar. 2009. Accessed on 7 Oct. 2012. About.com http://sleepdisorders.about.com/od/sleepdisorderstreatment/a/Treat_Jet_Lag.htm.


The Author

Stacey Penney

Stacey Penney

Stacey Penney, MS, NASM-CPT, CES, PES, CNC, is the Content Strategist with NASM and AFAA. A 20+ year veteran of the fitness industry, she's worked with the top certification and continuing education groups. At NASM and AFAA she drives the content for American Fitness Magazine, blog and the social media platforms. Stacey received her degree in Athletic Training/PE from San Diego State University and an MS in Exercise Science from CalU, plus credentials in Health Promotion Management & Consulting (UCSD), Instructional Technology (SDSU), group fitness and yoga. Previous San Diego Fall Prevention Task Force Chair, she’s developed continuing education curriculum for fitness organizations in addition to personal training, writing, and co-coaching youth rec soccer.