Jet Lag and Endurance Sports: Adapt Faster Before a Race

A flight to New York, Tokyo or Cape Town can cost you more performance than your entire last training week delivered. Jet lag does not just affect how you feel at night — it throws off your whole body clock. Heart rate, body temperature, digestion, hormones and muscle coordination suddenly run on a different beat than your surroundings. For endurance athletes this is a plannable factor: handle travel and arrival days with intent and you reach race day close to your own rhythm. Ignore them and you can lose five to ten percent of performance in a marathon.

Why jet lag really costs performance

The body drives almost every function through an internal clock, the circadian rhythm, which sits in the hypothalamus and is set by daylight. It determines when body temperature peaks, when digestion works, when your resting heart rate is lowest and when reaction time is at its best. For most people, peak performance sits in the late afternoon. After a flight across six time zones, that clock is still at home — at a 9 a.m. race start you feel as if it were 3 a.m.

Three effects are measurable. First, sleep: in the first nights you sleep shorter and lighter, and the deep-sleep deficit accumulates. Second, circulation: resting heart rate and blood pressure stay elevated for several days, and heart rate at a given pace is noticeably higher. Third, digestion: stomach and gut still work on the old schedule, which — combined with unfamiliar food — raises the risk of gastrointestinal trouble in the race. A marathon above 30 °C with dehydration makes every one of these effects worse.

How fast the body adapts

Adaptation follows a simple rule: roughly one day per time zone travelling west, about 1.5 days per time zone travelling east. Heading west you chase the day and stretch it, which the body tolerates well. Heading east you have to shorten the day — so adaptation east is much tougher.

• A few hours of difference (e.g. Vienna–London): barely noticeable, no special strategy needed.
• Three time zones (e.g. Vienna–Dubai): two to three days to adapt.
• Six time zones (e.g. Vienna–New York): five to seven days.
• Nine time zones (e.g. Vienna–Tokyo): up to two weeks — here planning decides success or failure.

That yields a clear rule for racing: with large time differences, arrive at least five to seven days before the race. The remaining days belong to easy movement outdoors and rebuilding the new sleep rhythm, not to a final hard session.

Light is the strongest lever

The fastest way to shift the internal clock runs through the eyes. Bright light in the morning advances the clock, light in the evening holds it back. Getting into daylight early in the morning accelerates adaptation east considerably — and if you are travelling west, you need light in the evening and calm and darkness in the morning.

In practice this means switching to destination time immediately. Get up at the destination morning time even if your body still asks for night. Spend at least 30 to 45 minutes outside, ideally within the first two hours after waking — daylight under a clear sky is many times brighter than any indoor lighting. In the evening dim the lights early, avoid bright screens in the last hour before sleep, and skip the sunglasses if you are travelling west and want to soak up light in the evening.

Before you fly: shift the clock step by step

Start three to four days before the trip and you lose fewer valuable days at the destination. The simple method: move sleep and meals toward destination time while still at home — heading east, go to bed 30 to 60 minutes earlier each evening; heading west, correspondingly later. It rarely works perfectly, but even a shift of one to two hours shortens adaptation on site noticeably.

On the flight itself: drink water regularly, avoid alcohol entirely (it disrupts deep sleep and dehydrates), eat light and at times that match destination time. On long-haul flights it helps to wake up at target-morning time just before landing, meaning you end a nap on board rather than stretching it to touchdown. Movement in the cabin — standing up, tensing the calves, short walks — keeps circulation going.

Training in the first days at the destination

The arrival days are adaptation days, not training days. The body needs stimuli as time cues, but not exhaustion.

• Arrival day: no hard training. A walk or 15 to 20 minutes of very easy running outdoors, preferably at a time when you should be awake at the destination.
• Day 2 to 3: one short easy session (30 to 40 minutes) and a switch to destination time. No intervals, no threshold runs.
• From day 3 to 4: first short pace stimuli once sleep stabilises — a few minutes at race pace to wake up the feel for pace without building fatigue.
• Last two days before the race: as in tapering — volume down, short sharp openers, plenty of rest.

Important for steering: in the first days, heart rate at the same pace is often five to ten beats higher than usual. Train by feel (RPE) rather than by heart rate on arrival days, and judge the load by training volume rather than the heart-rate target. This is exactly where the fitness curve helps: knowing your fitness and freshness level (TSB) shows you in black and white that you must not drift into a fatigue zone during adaptation.

Eat and drink on destination time

Digestion hangs on the internal clock more than anything else — it usually takes longer than sleep to adjust. So from day one, eat at destination times even if hunger does not show up. A light breakfast at destination morning time, main meals at the usual times, nothing heavy shortly before sleep.

For the first two days at the destination: favour familiar, carbohydrate-rich food over culinary experiments. The final fine-tuning of carbohydrate stores belongs in the 36 to 48 hours before the race — by then the body should already be eating on destination rhythm, so glycogen stores are topped up at the right internal hour. Wait until race day and you fill up at the wrong internal time.

Sample plan: arriving seven days before the marathon

• Arrival day: walk, plenty of daylight, to bed at destination time — even if it is hard.
• Day 2: 30 min easy run in the morning in daylight, look at the course. No pace work.
• Day 3: 40 min easy + 4 strides of 20 s to keep the nervous system awake.
• Day 4: rest day, fascia work, enough sleep at destination time.
• Day 5: 20 min with 3 × 3 min at marathon pace — last pace stimulus, then volume down.
• Day 6: 25 min very easy, open up the legs, check nutrition and routine.
• Race day: fresh legs, body eating and sleeping on destination rhythm.

This week adds up to just under 2.5 hours of easy running plus two short pace stimuli — enough to stay sharp and little enough not to disturb adaptation.

What else you can use

• Melatonin: when travelling east, low-dose melatonin (0.5 to 3 mg) can make falling asleep at target bedtime easier. It does not shift the clock on its own — light and bedtime remain decisive. Clear it with a doctor if you have any pre-existing conditions.
• Strategic naps: a short nap of 20 to 30 minutes in the afternoon eases the sleep dip without ruining night sleep. Longer than 45 minutes leaves you groggy and delays adaptation.
• Caffeine with intent: in the morning at destination time caffeine helps you wake up. Late afternoon and evening it delays sleep onset and worsens jet lag.
• Direction of travel: where you have a choice, west beats east. If you must head east, plan more adaptation days from the outset.

A related topic in the same depth is training on the road with its rules for heat, altitude and hotel weeks. And if the fundamentals of the final weeks before an A race are not yet second nature, you will find them in the article on tapering as well as in the threshold fundamentals in the Peakora lexicon.

Common mistakes

• Arriving too late. Land two days before an overseas marathon and you have neither adaptation nor fresh legs. The holiday days you thought you saved cost you minutes in the race.
• Training hard on arrival day. A tempo run "to see the course" is the classic self-sabotage — the body is tired and heavily loaded.
• Living on the old rhythm. Keep eating lunch on home time and staying up at night and you block adaptation completely.
• Alcohol as a sleep aid. It shortens time to fall asleep but destroys deep sleep — recovery suffers exactly where it matters.
• New tactics untested. Trying a negative-split strategy or new nutrition for the first time on race day combines two risks — pacing plan and fuelling belong in testing beforehand.

How Peakora accounts for the travel phase

In the Peakora engine you can enter a race with date and location. The plan aligns the final weeks to it and respects travel days: volume drops in good time, short pace stimuli stay in, and hard sessions never land in the adaptation phase. The recovery monitor tracks fitness (TSB) in parallel — so you can see whether the arrival days are restoring or pushing you toward a fatigue zone just before the start. On the marathon cluster you will find matching training plans and the detail articles on fuelling and race tactics.

Frequently asked questions