Fly Perth to Sydney and a 7 pm final feels like 4 pm. Fly Sydney to London and your body thinks a 7 pm race is at 4 am. The body clock catches up at around an hour a day, and light speeds it up or slows it down depending on when you get it. Plan the trip below.
What the research says about travel
Australian athletes travel further than almost anyone, and the research on what that does to them is closer to home than you'd think. When 18 professional rugby league players flew 24 hours west across 11 time zones from Australia to the UK, jet lag peaked two days after landing and was still raised on day 8. Upper respiratory symptoms rose by day 6 (Fowler and colleagues, 2016).
Direction matters. In a controlled study, trained men flew 21 hours across eight time zones between Australia and Qatar. After the eastward trip home, sleep was shorter and later for four days, jet lag and fatigue were worse, and sprint and intermittent running performance dropped most in the first 72 hours (Fowler and colleagues, 2017). A study of 3,489 WNBA games from 2007 to 2024 found the same pattern in results: eastward jet lag was linked with worse home-team performance, while westward jet lag showed no link (Leota and colleagues, 2026).
The reason is the body clock. It runs on a natural day of about 24.2 hours, so delaying (flying west) comes easier than advancing (flying east). Light is the main tool for shifting it, but timing decides the direction. Light before the body's temperature low point pushes the clock later, and light after it pushes the clock earlier (Roach and Sargent, 2019).
You don't need to leave the country to feel it. Australia spans three time zones, and with Queensland, Western Australia and the Northern Territory skipping daylight saving, the gaps change twice a year. A Perth athlete racing a 7 pm final in Sydney in March is racing at 4 pm by body time. The planner below works for any trip, interstate or overseas.
True or false?
Test what you think you know before you start. Tap an answer to see what the research says.
Get as much sunlight as you can after landing.
After flying east, light before the body's low point pushes the clock the wrong way. Timing matters more than amount.
Flying east is harder on the body than flying west.
Studies of Australian athletes and of professional team results both found eastward travel costs more.
Jet lag and travel fatigue are the same thing.
Travel fatigue comes from the trip and fades after sleep. Jet lag comes from the body clock and lasts until it catches up.
A 2 or 3 hour interstate trip can change how a race feels.
A Perth athlete racing at 7 pm in Sydney (in daylight saving) races at 4 pm by body time on arrival.
Your trip
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Reading the trip card
Time shift is the gap between home and destination clocks on arrival day, taken the shorter way round the world. Over 12 hours, it's quicker to adapt the other way.
"Sleeping better" is the day the body clock's low point first falls inside the usual sleep period, which Roach and Sargent call partial adaptation. "Fully adjusted" is when the low point is back at its normal time.
Why arrival time matters
The schedules assume arrival around 1 pm. Landing early in the morning after flying east can let adaptation start a day early. Landing late at night after flying west can push it back a day, because the useful light window has passed.
Daylight saving in Australia
Queensland, Western Australia and the Northern Territory don't use daylight saving, so interstate gaps change twice a year. Brisbane and Sydney share a time in winter but are an hour apart in summer. Perth is two hours behind Sydney in winter and three in summer. The planner reads these changes from your browser.
Body clock
The dial is a 24-hour clock in destination time. The white marker is the body's low point and the green one its performance peak. Press play to watch them move into place day by day.
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What the markers mean
The white marker is the core body temperature low point, the trough of the daily cycle. It normally sits about three hours before waking. Sleepiness is highest and performance lowest in the two to three hours either side of it.
The green marker is the high point, about twelve hours later. Alertness and physical performance are best in the two to three hours either side.
Why it moves slowly
The clock can only shift a limited amount each day, so the markers creep round the dial rather than jumping. Bigger shifts move a little faster per day, and moving later (flying west) is a little easier than moving earlier.
Using it for competition
If the race falls near the low point on body time, the athlete is competing at their worst. If the trip is short, it can be better to arrive early enough to adapt, or to keep sleep and training close to home time when the race already falls in the body's peak window.
Day-by-day plan
Each bar is one day in destination time. Follow the light windows while awake and keep usual bed and wake times on local time.
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Why the light windows move
Each day the body clock's low point shifts, so the windows shift with it. Light in the five hours before the low point pushes the clock later, and light in the five hours after pushes it earlier. The planner only shows the parts that fall while the athlete is awake.
What counts as bright light
Outdoor daylight, even on a cloudy day, is far brighter than indoor lighting. Longer, brighter and bluer light has the biggest effect. After dark, bright indoor lights or a light box can stand in.
What counts as dim
Stay indoors with low lighting, keep screens dim and away from the face, or wear wrap-around sunglasses if you have to be outside. A nap of up to an hour also works, as long as it doesn't eat into night sleep.
On the plane
For long flights, time light and sleep by the body clock you're carrying, not the destination's clock.
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Why home time on the plane
When you board, your body clock is still on home time, so the right moments to seek or avoid light are set by home time too. Setting a watch to destination time on take-off feels useful but can put light at the wrong moment.
Travel fatigue on long flights
Long flights of 8 to 14 hours bring lost sleep, dehydration, low cabin air pressure, dry air and cramped seats. These cause headaches, fatigue and disorientation that fade after a good sleep, separate from jet lag.
Sleeping on the plane
Sleep quality in a seat improves the further it reclines. If the plan says dark, an eye mask, earplugs and a reclined seat give the best chance of real sleep.
The research
Ten trained men flew 21 hours across eight time zones between Australia and Qatar. After the eastward trip home, sleep was shorter and later for four days, jet lag and fatigue were worse, and 20 m sprints were slower on day 2 than after the westward trip out.
Fowler et al. (2017)The internal clock runs slightly longer than 24 hours, so it finds delaying (flying west) easier than advancing (flying east). For a 12-hour shift, adapting by delay is the usual choice.
Roach and Sargent (2019)Light schedules after a 3-hour shift give partial adaptation by day 1 and full adaptation by day 4. Six hours takes about 6 days, nine hours 7 to 8 days, twelve hours about 10.
Roach and Sargent (2019)Light in the hours before the body's low point pushes the clock later. Light in the hours after it pushes the clock earlier. Soaking up sunshine all day after flying east sends mixed signals.
Roach and Sargent (2019)An international panel set out travel toolboxes for before, during and after flights, but noted that the lack of evidence limits how strong the recommendations can be.
Janse van Rensburg et al. (2021)Travel fatigue comes from the trip itself: lost sleep, dry cabin air and cramped seats. Jet lag comes from the body clock being out of step, and mostly shows after crossing three or more time zones.
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How strong is the evidence?
The light schedules are built from laboratory phase response curves, which are well established. Field trials of light alone have had mixed results, while a review of ten field studies found melatonin effective. Combined light and melatonin plans haven't yet been tested in the field.
The Australia–Qatar study in detail
Fowler and colleagues tested countermovement jumps, 20 m sprints and the Yo-Yo intermittent recovery test at 9 am and 5 pm. They tested before travel and for four days after each 21-hour trip. The eastward return hit sleep, jet lag ratings, fatigue and motivation hardest, and performance dropped most within 72 hours of arrival.
East versus west in teams
Studies of professional team results have reported the same pattern: eastward travel tends to cost more than westward. It fits the body clock's natural day running slightly longer than 24 hours.
Toolbox
For shifts of three hours or more, move bed and wake times 30 to 60 minutes a day towards the destination in the 3 to 4 days before leaving. Flying east: earlier nights, morning light, dim evenings. Flying west: later nights, evening light, dim mornings.
Follow the on-the-plane plan above. Drink regularly, get up and move, and use an eye mask and earplugs when it's time to be dark.
Keep usual bed and wake times on local time from the first night. Train outdoors in the light window when you can, since exercise and light shift the clock the same way. If you need to avoid light in the day, stay inside, wear wrap-around sunglasses or nap for up to an hour.
When a light window falls after dark, bright indoor light or a light box helps. When a dim window falls in the evening, turn lights down and keep screens dim.
Melatonin can shift the body clock, but in Australia it's prescription-only for most people, and supplements bought online can be contaminated. It isn't part of this planner. Talk to a sports doctor before using it.
In depth: how the body clock works
The master clock
A small cluster of cells in the brain's hypothalamus sets the body's daily rhythm. Left alone, it runs at about 24.2 hours, so each day it has to be nudged back into line with the 24-hour world.
Sunlight is the strongest nudge. Social contact, meals and exercise also play a part. Organs such as the heart, liver and muscles carry their own clocks, kept in step by the master clock.
The daily timeline
For someone who sleeps from 11 pm to 7 am, melatonin starts rising around 9 pm, about two hours before bed. Core temperature bottoms out around 4 am, seven hours after melatonin onset. It peaks around 4 pm, twelve hours later.
Strength, flexibility, balance, dexterity and alertness all follow this cycle, which is why the race's body-clock time matters.
How light resets it
The same light does opposite things depending on when it lands. In the hours before the temperature low point, light shifts the clock later. In the hours after, it shifts the clock earlier. The biggest shifts come within three to six hours of the low point.
That's why "get as much sun as you can" works after flying west but sends mixed signals after flying east.
Exercise as a cue
Moderate exercise also shifts the clock, with a pattern that lines up with light: before the low point it delays, after it advances. There's no evidence yet that exercise adds to light's effect, but training in the light window does no harm and gets the athlete outdoors.
Partial and full adaptation
Full adaptation takes days, but the practical goal comes sooner: getting the low point back inside the night's sleep. Once that happens, sleep gets longer and better, daytime sleepiness drops and performance recovers.
Planning a competition trip
Work back from the race: how many days does this shift need, and does the race land near the body's low point on arrival? For big shifts, arrive early enough to at least reach partial adaptation. For short trips with small shifts, look at whether staying close to home time puts the race in the peak window anyway.
Notes and references
Light at the right time, darkness at the right time.
Sleep on local time from night one.
Know what time the race feels like.
How the planner works
The body clock's low point is set three hours before usual wake time (about 4 am for a 7 am riser) and its peak twelve hours later. After arrival the clock moves towards local time at the rate of Roach and Sargent's adaptation schedules: about 0.75 hours a day for a 3-hour shift, faster for bigger shifts, and slightly faster flying west than east. Light windows cover the five hours before the low point (to delay) or after it (to advance), shown only while awake. Shifts over 12 hours are planned the shorter way round. Daylight saving is taken from your browser's time zone data.
What this research can't tell you
The schedules come from laboratory light studies, and field trials of light alone have had mixed results. People adjust at different rates, and early birds and night owls differ. The planner can't account for poor sleep on the plane, a late night before travel or competition stress.
This is general guidance based on research. It doesn't replace advice from a doctor or your team's medical staff.
References
- Fowler, P.M., Duffield, R., Lu, D., Hickmans, J.A. and Scott, T.J. (2016) Effects of long-haul transmeridian travel on subjective jet-lag and self-reported sleep and upper respiratory symptoms in professional rugby league players. International Journal of Sports Physiology and Performance, 11(7), pp.876–884.
- Leota, J., Miller, D.J., Czeisler, M.É. et al. (2026) Home-court advantage and the associations of travel and jet lag with team performance in the Women's National Basketball Association (WNBA). Sports Medicine – Open, 12(1), 94.
- Fowler, P.M., Knez, W., Crowcroft, S., Mendham, A.E., Miller, J., Sargent, C., Halson, S. and Duffield, R. (2017) Greater effect of east versus west travel on jet lag, sleep, and team sport performance. Medicine and Science in Sports and Exercise, 49(12), pp.2548–2561.
- Janse van Rensburg, D.C., Jansen van Rensburg, A., Fowler, P.M. et al. (2021) Managing travel fatigue and jet lag in athletes: a review and consensus statement. Sports Medicine, 51(10), pp.2029–2050.
- Roach, G.D. and Sargent, C. (2019) Interventions to minimize jet lag after westward and eastward flight. Frontiers in Physiology, 10, 927.