Written by: W. Christopher Winter, MD
In a sport measured in grams and won by seconds, most triathletes are searching for an edge. They give meticulous attention to training methods, nutritional choices and equipment set-up. However, the triathlete’s sleep habits can greatly impact his health, training and performance during a race. With some tweaking, athletes can manipulate sleep and circadian factors to elevate their performance to new levels.
The circadian rhythm in humans is an internally driven process that helps synchronize internal biological systems with the external world. In fact, the term “circadian” translates to “about a day.” These systems are numerous and include regulation of temperature, digestion, hormone release, metabolism, immune system functioning, cognitive performance and mood. The circadian system ensures that these other systems are timed properly during the extrinsic 24-hour day/night cycle.
Circadian Rhythm and Performance
What produces the circadian rhythm? The circadian rhythm is generated in a brain structure called the suprachiasmatic nucleus (SCN). The SCN functions like a cheap watch that runs a little fast. Every day, the watch needs to undergo small adjustments to keep its owner on time. The periodic adjustments that keep our bodies on schedule with the environment are referred to as entrainment. Entrainment occurs primarily with exposure to light, but other factors such as exercise, social interactions, meals and temperature can affect an individual’s circadian rhythm. An individual’s age can play a role in circadian regulation as well.
With any process that occurs in a cycle, there exists a peak and a trough. The peaks of these processes, including athletic and performance peaks, cycle in a predictable pattern every 24 hours. Because of the extensive role these rhythms play, understanding how they work can be a valuable tool in predicting and influencing athletic performance. It has been estimated that optimizing circadian factors alone can result in as much as a 10-percent improvement in athletic performance. Stated another way, a 10-percent decline in athletic performance has been compared to competing while legally intoxicated.
A Disconnect Between External and Internal Schedules
There are two main ways an athlete’s circadian rhythm can be negatively affected. The environmental time can suddenly change due to travel or the individual’s time schedule can change. Both of these can occur in triathletes when they travel for races or suddenly change their training times.
Traveling to a race venue and the sleep and jet lag issues that go along with that travel can have a tremendously negative impact on athletic performance. For approximately two-thirds of athletes, jet lag can be a significant factor, even for relatively short transmeridian trips. For these individuals, it typically takes a full day to adapt to the local environment for every time zone crossed. This acclimation is typically even longer for travel in an eastward direction. In jet lag, the internal time clock generator is suddenly out of sync with your new time zone. Prior to travel, the body can predict actions such as eating or exercise if activities follow a constant routine. After travel, these actions continue, but there is a disconnect between the new external schedule and the internal schedule. Now, the body is forced to respond to rather than predict the presence of food in the stomach or sudden periods of intense exercise. The result in the case of eating is usually digestive problems and upset stomach, as the body is temporarily not prepared for the food it receives. These digestive problems can be devastating during a race.
An athlete does not need to travel across the country to experience the negative effects of circadian rhythm disturbances. Dramatic changes to training schedules can often result in negative circadian effects. In this case, the athlete’s internal circadian rhythm changes in the midst of a constant environment. Consider an elite athlete who has been waking up at 5 a.m. to work in longer runs before a race. During a pre-race taper, the athlete was sleeping in later, resulting in a significant change to sleep-wake cycles, meal times and obviously exercise timing. This kind of radical change to the 24-hour sleep-wake cycle can result in problems similar to those seen in jet lag, often including a measurable decline in performance.
Race Day Acclimation for Optimum Performance
Both of these scenarios—travel and schedule alterations—play out frequently in the lives of triathletes and are often unavoidable. There are, however, several ways to counteract the negative influence they may have on your stamina and performance.
• The use of light for circadian entrainment is a powerful tool. Sunlight is responsible for the majority of circadian entrainment, and athletes can use this fact to their advantage. Since athletic performance tends to peak in the late afternoon or early evening, exposure to bright light early in the morning can move this peak time earlier in the day and more in line with the timing of most races.
• Don’t exercise in the dark! The pairing of exercise and light exposure provides powerful circadian regulatory effect that can dramatically improve sleep quality, mood and cognitive performance.
• For two weeks, change nothing about the content of your diet and establish set times for breakfast, lunch, dinner and other pre- and post-exercise nutrition. By the end of the two-week period, your body will utilize the food more effectively, but beyond that you’ll be providing a solid grounding for your circadian rhythm.
• As races grow nearer, many athletes benefit from preadaptation strategies designed to slowly adjust daily schedules to better match the race day schedule and environment. In the days leading up to your race, schedule the training of your weakest event with the approximate time you will be performing it on race day. With your body more at ease, your performance will soar.
• One newer circadian adaptation strategy involves fasting during transmeridian travel. This method has been found to accelerate adaptation to the new time zone. The need for nutrition overrides the circadian rhythm, so the rhythm is suspended until the next meal arrives. By fasting during travel, an athlete can simulate this stressor and effectively suspend the circadian rhythm until the next meal in the new time zone resets the cycle in the new environment.
• New medications can also ease travel transition both traveling to and from home or the race venue. These medications can facilitate sleep when the body’s natural rhythm is geared towards wakefulness. Conversely, they can also be used to promote wakefulness in the midst of an increased drive to sleep. Make sure that all medications have been cleared by your physician and are preapproved for your race.
A triathlete’s circadian rhythm underscores and regulates virtually every biological process. Having a general understanding of its purpose and the way it functions can make an athlete aware of how circadian factors affect training and racing. Careful manipulation of these variables can often unlock dramatic pathways to performance enhancement and athletic progress.
W. Christopher Winter, MD, is the medical director of the Martha Jefferson Hospital Sleep Medicine Center in Charlottesville, Va. Currently, he is the sleep medicine specialist for Men’s Health Magazine. His current research involves sleep in the elite athlete. Dr. Winter has competed in 10 triathlons to date and looks forward to doing many more. You can contact him at William.Winter@mjh.org