While we’re all familiar with the concept of our “body clock,” recent studies indicate that daily and annual biological clocks influence physical and emotional health more than previously believed.  In fact, our cells are strongly influenced by genes under circadian regulation and our behavior, including athletic performance, may be driven more by these “clock” genes than by external signals.

I’m certainly aware of jet lag as a circadian rhythm disorder, but I also discovered new information from a recent article in the New York Times:  “The Quest by Circadian Medicine to Make the Most of Our Body Clocks.”¹ by Kim Tingley, published July 6 of this year.  As one who is committed to physical fitness, I was happy to learn that higher levels of conditioning allow me to adjust more quickly to changes in the sleep/wake cycle.  At the same time, studies show that even professional athletes experience a hit to performance when their natural sleep/wake cycle is disrupted.

A few pertinent notes from the Times:

• “Professional athletes and their trainers…know that physical performance peaks in the late afternoon or early evening.  (Most world records are broken in the evening.)”
• Studies by physiologists suggest that physical activity is…”ideally undertaken at certain times depending on the outcomes you prioritize (weight loss, blood-sugar control, strength).”
• For elite athletes…”the slightest advantage can make the difference between a loss and a victory” and cross-country or international travel induces “tremendous circadian disruption,” which takes a toll on sports teams’ performance.

Charles Czeisler, sleep consultant for the Boston Celtics and other pros, addressed travel fatigue by persuading players to maintain consistent sleep-wake times…”practicing in the afternoon, going to bed at 3 a.m. and sleeping until 11 a.m.  When they traveled to the West Coast, he advised them to shift their schedule by three hours to keep their bodies on East Coast time.”  While Czeisler did not quantify the effect of his adjustments, a study published in the Proceedings of the National Academy of Science (PNAS) did analyze 20 years of MLB statistics, citing evidence that circadian disruptions caused being “on the road” decrease a team’s winning percentages—especially eastward travel.²

So, to better your tennis game, reduce your 10K time or make it to the top of Mount Everest, it seems that sustaining healthy circadian rhythms can help.  And that requires consistent habits like sleeping in a cool dark room, turning off the lap top an hour before sleep, and waking up and going to bed at the same time every day—all those sleep hygiene guidelines do make a difference.

And what of travel?  Are there specific strategies for athletes flying to Europe or Asia to climb a mountain or compete in the Tour de France?  In spite of recent research, it continues to be difficult to apply new knowledge to travel due to factors such as individual differences and the challenge of measuring physiological responses in the field, using markers like core body temperature (CBT) and levels of melatonin.  However, according to an article published online by the Center for Sports Knowledge and Innovation,” in Barcelona, some guidelines pertain:⁴

Researchers distinguish between travel fatigue and jet lag.  Travel fatigue, which is associated with short trips, requires relatively simple interventions that promote sleep and allow for a recovery and rest period prior to competition.  Additionally, athletes should be well hydrated, avoid caffeine and alcohol, and shift postures as frequently as possible during travel.

Jet lag results from trips that cross multiple time zones, causing “an asynchrony between “peripheral” clocks”³ like sunlight and the body clock.  It is recommended by some experts to adjust the timing of sleep and light exposure progressively before starting a trip, perhaps also ingesting melatonin or, if clinically indicated, a hypnotic medication to induce sleep.  Interventions aimed at promoting sleep (e.g., using an eye mask and noise-cancelling head-phones during flight) have been shown to improve quality of rest both during and in the days after travelling—thus reducing the adverse effects of jet lag on physical performance.  These strategies should be combined with proper hydration, avoiding heavy, high-calorie foods, and stretching during the trip.  Training should coincide with exposure to light.

The graphs below offer specific strategies:

1. “The Quest by Circadian Medicine to Make the Most of Our Body Clocks,” Kim Tingley, New York Times, July 6, 2022
2. “How Jet Lag Impairs Major League Baseball Performance,” Alex Song, Thomas Severini, Ravi Allada, PNAS, January 2017, https://www.pnas.org/doi/10.1073/pnas.1608847114
3. Managing Travel Fatigue and Jet Lag in Athletes: A Review and Consensus Statement, July 14, 2021, Abstract accessed via the National Library of Medicine (NIH), originally published in Sports Medicine, Janse vanRensburg, et al., 2021, https://www.ncbi.nlm,nih.gov/pmc/articles
4. “Strategies to Reduce the Negative Side Effects of Travelling on Athletes,” Barca Innovation Hub, The Center for Sports Knowledge and Innovation, Pedro L Valenzuela, accessed July 19, 2022, https://barcainnovationhub.com/strategies-to-reduce-the-negative-side-effects-of-travelling-on-athletes