By Louise Aukland, based on an interview with Professor Russell Foster.
With their final friendly played, the Lionesses will be boarding a plane and heading for Australia and New Zealand later this week. The Irish team will follow, ready to kick off the tournament against one of the hosts, Australia, on 20th July. The clock is ticking… and to celebrate the Women’s World Cup, the Football on the Brain project are releasing a special pullout for SheKicks Magazine, exploring the impact of international travel on both footballers and fans. Not only is there a considerable difference in time between here and the antipodean hosts, but the tournament itself is played over four time zones!
What does all this time zone crossing mean for teams travelling to the tournament? I put this question to Russell Foster, Professor of Circadian Neuroscience at the University of Oxford. Russell researches the natural 24-hour circadian rhythms of the body, or the internal body clock. In the brain is a master clock (within the suprachiasmatic nuclei of the hypothalamus) that coordinates billions of individual cellular clocks throughout the organ systems of the body. The clock is set mainly by light (see reference 1), and when synchronised, the circadian network allows us to optimise our biology. In terms of factors that drive sporting performance: core body temperature, coordination and reaction time, cardiovascular efficiency and muscular strength, then late afternoon or early evening is optimal (see reference 2).
To complicate things, individuals tend to have a preference for being a ‘morning person’ or ‘evening person’ depending on their genetics, age and entrainment by particular sleep patterns and habits. A person's ‘chronotype’ can be determined via a simple set of questions and can make a difference to performance at different times of day. Studies of adolescent footballers have found that morning types do perform better on motor skills tasks in the morning compared to evening types, who performed better in the evening (see references 3 and 4). Other research has identified peak performance times to be best predicted based on entrained awakening time, rather than time of day. Peak performance was found to be approximately 5.5 hours after awakening for morning types, and 11 hours after awakening for evening types; with individual variations in performance across the day as large as 26% (see reference 5). What does this mean for the performance of a team made of a mix of individual chronotypes?
Let’s get back to jetlag and travelling across the world to play in the World Cup. An individual affected by sleep and circadian rhythm disruption (SCRD for short), such as jetlag, can exhibit a rather scary list of short-term symptoms (see reference 6 and Table 1). Russell explains that this is because the circadian network becomes disconnected from the environment – with no robust timekeeping from the master clock, our internal systems (the brain, heart, gut, etc.) drift and become out of sync. Like an orchestra with a confused conductor, the wind section can fall out of time with the strings; and the result doesn’t sound good! Jetlag (travelling from the UK to the World Cup in Australia or New Zealand) or social jetlag (staying up half the night to watch live matches or analysis) doesn’t feel good for a while as our body systems struggle with the timing disruption. On the pitch this could mean poor decision making, strategies and team tactics forgotten, increased injury risk, and unhelpful emotional reactivity. Not good news for sporting performance!
Table 1: The impact of sleep and circadian rhythms disruption (SCRD) (adapted from Foster et al 2013 - see reference 6)
| Emotional responses | Cognitive responses | Somatic responses |
|
Exhaustion Increased irritability Mood fluctuations Anxiety Depressed mood Frustration Anger Increased impulsivity Decreased motor skills Increased likelihood of stimulant or sedative use |
Reduced concentration Reduced performance Reduced attention Decreased memory Reduced recall of events Reduced multitasking Reduced decision making Reduced creativity Reduced productivity Reduced socialisation Reduced communication |
Drowsiness Microsleeps Unintended sleep Bodily sensations of pain Bodily sensations of cold Reduced immunity |
Symptoms can persist until the body’s circadian clock realigns with the new time zone. For an elite football team, this could have disastrous consequences on their performance. So how long does it take to reset the circadian network? Well, that depends! If left to sort itself out, it takes approximately 1 day per time zone crossed. Travelling between London and the World Cup venues would mean about 10-12 days for full restoration. Performance is likely to be suboptimal, particularly in the early days, as the different body systems aren’t working synchronously and the biology can’t be optimised. That’s quite a long time before the World Cup begins… with considerable cost and player availability knock-on issues.
However, the rhythms can be given a nudge in the right direction. Light is the most important factor when setting the clock and the impact is felt most strongly in the morning. Adjusting light exposure can help speed up the resetting of the circadian clock after travel. Russell suggests that for the first 4 days or so in Australia or New Zealand, hiding from morning light and actively seeking out bright afternoon light (when our clock thinks it is morning time), will help advance the clock and speed up adaptation. Combine this with eating at the new, local meal times as feeding can affect the body clock, reinforce the light exposure and help realign to the new time zone.
Before we finish the interview, Russell reminds me that it isn’t just about time zones and jetlag; good sleep habits and hygiene will also reduce the impact of SCRD (sleep and circadian rhythm disruption) and have a positive effect on player performance. He then rattles off a long list of helpful, research informed advice, including: stick to sleep time and get up routines; keep the sleeping environment cool, dark, quiet and comfortable; avoid naps longer than 20 minutes and especially closer to bed time; avoid stimulants late in the day and steer clear of any sedatives; relax in the hour or so before sleep in whatever way works for the individual (meditation, reading, music, podcasts…) and avoid potentially stressful bedtime discussions (like a post-match debrief!).
So as teams or fans prepare to jet off to Australia or New Zealand, what tips can science give them to minimise the impact of jetlag?
Tip 1: Allow enough acclimatisation days to align the body clock to local time – 1 day for each time zone crossed is ideal (longer than you might think) and this will enable the body to optimise the biology for footballing performance (or fan-based activities!).
Tip 2: Help the clock realign to reduce the impact of jetlag – pack eye-masks and sunglasses to avoid the morning light and get out sunbathing in the late afternoon or evening. Adopt local meal times.
Tip 3: Prepare for good sleep – to reduce further sleep disruption, do whatever works for individual players and the team to help them sleep well (or fans). Routines, relaxation, sort the environment, pack your own pillow… and don’t forget your ear plugs if your roomie snores!
And well, if you aren’t going all the way to Australia or New Zealand, but are planning a few late-night watching sessions, then this advice applies to you too! Either way, don’t be surprised if changing your sleep patterns has more of an impact on your brain and body than you were expecting.
References:
1: Ashton A, Foster RG, Jagannath A. Photic Entrainment of the Circadian System. International Journal of Molecular Sciences. 2022; 23(2):729. https://doi.org/10.3390/ijms23020729
2: Victoria Ayala, Manuel Martínez-Bebia, Jose Antonio Latorre, Nuria Gimenez-Blasi, Maria Jose Jimenez-Casquet, Javier Conde-Pipo, Anna Bach-Faig & Miguel Mariscal-Arcas (2021) Influence of circadian rhythms on sports performance, Chronobiology International, 38:11, 1522-1536. https://doi.org/10.1080/07420528.2021.1933003
3: E. Roveda, A. Mulè, L. Galasso, L. Castelli, R. Scurati, G. Michielon, F. Esposito, A. Caumo & A. Montaruli (2020) Effect of chronotype on motor skills specific to soccer in adolescent players, Chronobiology International, 37:4, 552-563. https://doi.org/10.1080/07420528.2020.1729787
4: Ciorciari, Andrea, Mulè, Antonino, Castelli, Lucia, Galasso, Letizia, Esposito, Fabio, Roveda, Eliana, and Montaruli, Angela. "Sleep and Chronotype Influence Aerobic Performance in Young Soccer Players." Frontiers in Physiology 14 (2023). https://doi.org/10.3389/fphys.2023.1190956
5: Facer-Childs, E., and Brandstaetter, R. (2015). The impact of circadian phenotype and time since awakening on diurnal performance in athletes. Curr. Biol. 25 (4), 518–522. https://doi.org/10.1016/j.cub.2014.12.036
6: Foster, Russell G., Peirson, Stuart N., Wulff, Katharina, Winnebeck, Eva, Vetter, Céline, and Roenneberg, Till. "Sleep and Circadian Rhythm Disruption in Social Jetlag and Mental Illness." Progress in Molecular Biology and Translational Science. Vol. 119. Netherlands, 2013. 325-46. https://doi.org/10.1016/b978-0-12-396971-2.00011-7
Cover Image: Jon Tyson via Unsplash