Jet lag tips: light, heavy legs and sleep when you travel

If you fly across several time zones for a race, a training camp or work, you know the pattern: wide awake at 3 am, a wall of tiredness mid-afternoon and legs like lead. At its core, jet lag is a light problem. How light steers your body clock is explained in our main article blue light and sleep: do the glasses work. This guide is the travel version: light, legs, sleep.

What actually happens with jet lag?

After the flight your body clock is still on home time while daylight, meals and meetings are on local time. A clinical review in the New England Journal of Medicine (Sack 2010) describes jet lag as exactly this mismatch. The result is poor sleep at night, sleepiness during the day, an unsettled stomach and lower performance.

How fast the clock adjusts has been estimated in real travellers. According to a 2009 review (Eastman and Burgess), it shifts by around 92 minutes a day after westward flights and only around 57 minutes a day after eastward flights. The reason: most people's internal clock runs a little longer than 24 hours, so getting later is easier than getting earlier. London to New York is usually easier to get over than the flight home.

When to seek light and when to avoid it

Light is the strongest signal for your body clock, but it pushes in opposite directions depending on the time of day. Light late in the evening and in the first half of the night shifts the clock later; light in the early morning shifts it earlier. That gives you the plan:

The last row feels counter-intuitive. A 2019 review (Roach and Sargent) explains it: after a big jump east, the local morning still falls in your biological night, and light at that time pushes the clock the wrong way. For an eight-hour eastward shift the authors therefore suggest avoiding sunlight before midday and getting as much of it as possible in the hours after.

To avoid light, sunglasses work in the morning and tinted glasses in the evening. The red blue light glasses for hotel evenings filter 100 % of blue light from lamps, laptop and TV, according to the manufacturer. A 2021 review (Hester et al.) found signs that such lenses shorten the time to fall asleep in jet lag too. The studies are small and the evidence is thin. When red or orange lenses suit better is covered in red vs orange blue light glasses. Do not wear them to drive.

Before you fly: shift your sleep step by step

With three days' notice you can do part of the adjustment at home. In a 2003 study (Burgess et al.), 28 adults went to bed and got up an hour earlier each day for three days. Those who got bright light after waking shifted their clock by about two hours; with ordinary room light it was just over half an hour. Roach and Sargent suggest 30 to 60 minutes a day over three to four days.

• Flying east: go to bed a little earlier each day and get daylight straight after waking.
• Flying west: go to bed a little later each day, keep some light in the evening and stay in the dark longer in the morning.
• Training: if your plan allows, move hard sessions towards the new time in the days before you fly.

On the plane: what helps heavy legs

Hours of sitting, too little to drink, barely any movement: afterwards your legs feel heavy and your ankles swell. That is usually harmless. The more serious issue is the risk of a blood clot. According to a systematic review (Kuipers et al. 2007), long-distance travel raises the risk of a venous clot roughly two- to fourfold. In absolute terms it is small: about one event per 4,600 flights longer than four hours.

The NHS lists journeys of more than four hours by plane, car or train as a risk factor and advises loose clothing, plenty of water, no alcohol and moving about, for example getting up roughly every hour. The data on compression stockings are good. A Cochrane review (Clarke et al. 2021) pooled twelve trials with 2,918 passengers on flights of more than five hours. Of 2,637 people followed up, 50 had a symptomless clot: 3 wearing stockings and 47 without. Swelling was also lower with stockings, though the evidence there is weak. Whether flight socks are right for you, and which strength, is worth asking your GP or pharmacist about before you travel, especially if you have risk factors.

After landing: where compression boots fit

First, the honest view: no study has tested compression boots after flights. They do not prevent clots and do not replace moving about on the plane or wearing flight socks. What they can do: if your legs simply feel heavy and tired after travelling, with no warning signs, many people find a session pleasant. Why that is, and where the limits are, is explained in heavy legs and compression.

This is how I use them with athletes after long-haul: a walk first, then 20 to 30 minutes on a low setting at the hotel or at home, ideally in the local afternoon. The Revive Active with its rechargeable battery is portable, so you do not need a socket next to the sofa. If you have had a blood clot, have a heart condition or are pregnant, check with a doctor first. All the reasons not to use them are listed in when not to use compression boots.

How do you get your sleep back on track fastest?

• Local time straight away. Eat, sleep and get up on the new time. Set an alarm so you do not sleep until lunchtime.
• Keep naps short. Roach and Sargent suggest limiting them to an hour at most so night-time sleep does not suffer.
• Go easy on caffeine and alcohol. The NHS advises not drinking too much of either, as both can make jet lag worse.
• Wind down in the evening. Dim the lights and cut back on screens. What a set hour before bed can look like is shown in the evening recovery routine.
• No melatonin on your own initiative. The NHS does not recommend melatonin for jet lag because there is not enough evidence. If you are considering it, talk to your GP or pharmacist.

What does this mean for athletes?

For athletes, the evidence is surprisingly weak. A systematic review in the British Journal of Sports Medicine (Janse van Rensburg et al. 2020) found only twelve athlete-specific studies on jet lag, of low overall quality. What remains are the basic principles from sleep research: time your light, protect your sleep, do not overload the first days. Why sleep is the most important lever, Fabian explains in sleep and muscle recovery. For key fixtures in the east, plan one day per time zone of lead time if you can. Which season highlights are coming up in 2027, and how to plan recovery around them, is in our recovery calendar 2027.

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