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Athletes are travelling more than ever, flying across the world for competition and training. Even competing in the same country can require travelling through multiple time zones. At a time when athletes want to be in peak form, jet lag can interfere with mood and performance. Understanding of the body’s natural clock, however, can help us plan for and manage jet lag symptoms.

Jet Lag vs. Travel Fatigue
Jet lag must be differentiated from travel fatigue. Travel fatigue is the fatigue and dehydration associated with travelling that can be fairly quickly improved with rest and rehydration upon arrival. It can also represent an accumulation of physiological and psychological weariness from travels during a season that lead to loss of motivation, continual fatigue, and/or frequent illness. Jet lag, in contrast, occurs when changing time zones, and the symptoms are a result of a desynchronization of the body’s internal clock (circadian rhythms) and the new local time. The direction of travel (east vs. west), as well as the number of time zones traversed, influence the circadian mismatch. Common symptoms are gastrointestinal and sleep disturbances, decreased concentration, and loss of appetite, and usually disappear once the body adapts to the new time zone.

The Body’s Internal Clock
One of the big players that governs your daily sleep-wake cycle is the hormone melatonin. Melatonin is secreted in the brain at night, prompting lower levels of alertness and a greater desire to sleep. Because light suppresses melatonin production, by manipulating exposure to light, we can shift circadian rhythms to better match the new time zone.

The body’s core temperature also follows a cycle, peaking in the late afternoon or early evening. The lowest point is in the early morning, usually two hours before regular waking time in the home time zone. This low point, called the circadian nadir, also corresponds to the time when it is the hardest to stay awake, or the easiest to stay asleep.

  • Exposure to light before the circadian nadir delays the sleep phase.
  • Exposure to light after the circadian nadir advances the sleep phase.
  • The closer light exposure is to the nadir, the greater effect it has.

Based on those principles, this table (Table III. on page 3) outlines when the best and worst times for light exposure are when trying to adapt to a new time zone, depending on the direction of travel and the number of time zones crossed. Travelling west requires a phase shift later, whereas travelling east causes the circadian phase to shift earlier.

There are other strategies to reduce the symptoms of jet lag and promote the fastest adaptation to local time:

Before Travel

  • Reduce volume and intensity of training.
  • Adjust meal times and bedtimes 1-2h earlier if travelling east, and later if travelling west.
  • Prioritize getting adequate sleep to minimize sleep deprivation, which can impair performance.
  • Plan for at least one day per time zone to fully adapt before competition.

During Travel

  • Drink more fluids than expected to fight unnoticed dehydration from the dry air on board.
  • Isometric exercises, walking along the aisles, and stretching every couple of hours will reduce joint stiffness and help prevent “travellers’ thrombosis”.
  • Begin living – eating and sleeping – on destination local time.
    • Avoid napping unless it is night at the final destination.

After Travel

  • Modify the first few training sessions to avoid maximal exercise and risky manoeuvres.
  • As soon as possible, plan for training sessions to be at the same time of day as the competition.
  • Avoid exercising during the circadian nadir until fully adapted to the time zone.
    • After travelling east across more than three time zones, initially exercise in the early evening.
    • After travelling west across more than four time zones, initially exercise early in the morning before the circadian nadir.
  • Outdoor exercise helps the body to adjust to the temperature and humidity.
  • Take short naps (20-30 minutes) at the circadian nadir.

The most effective strategies to accelerate adaptation to a new time zone involve deliberate light exposure and avoidance. Use of melatonin supplements are also an option, but should be used under the direction of a sports medicine professional.

Bjorvatn B, Pallesen S. A practical approach to circadian rhythm sleep disorders. Sleep Medicine Reviews. 2009; 13(1): 47-60.
Reilly T, Atkinson G, Edwards B, Waterhouse J, Åkerstedt T, Davenne D, Lemmer B, Wirz-Justice A. Coping with jet lag: A position statement for the European College of Sport Science. European Journal of Sport Science. 2007; 7(1): 1-7.
Samuels CH. Jet lag and travel fatigue: A comprehensive management plan for sport medicine physicians and high-performance support teams. Clinical Journal of Sports Medicine. 2012; 22(3): 268-273.
Williams B, Clarke R, Aspe R, Cole M, Hughes J. Managing performance throughout periods of travel. Strength and Conditioning Journal. 2017; 39(4): 22-29.

About the Author: Lily is a fourth-year student in the kinesiology program at Western University, currently interning with SIRC. With a background in synchronized swimming, she continues to be actively involved in sport as a coach and varsity athlete.

The information presented in SIRC blogs and SIRCuit articles is accurate and reliable as of the date of publication. Developments that occur after the date of publication may impact the current accuracy of the information presented in a previously published blog or article.