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How long does jetlag affect physical performance?

September 4th, 2011

Athletes have to fly to competitions — it’s an inevitable part of international sport. But flying long distances can hurt performance. There are lots of “rules of thumb” that people use to plan travel and competition (e.g. allow one day of recovery for each time zone crossed), but not a lot of hard evidence. Australian researchers have just published a neat study in the European Journal of Applied Physiology that sheds a little light on this question.

The study looked at five members of the Australian skeleton team before and after a flight to a training camp in Canada that took 24 hours and involved four different flights (so a pretty brutal travel schedule, but not that rare for athletes). Two days before they left, they did a bunch of power tests: box drop jumps, squat jumps, and countermovement jumps. Once they arrived in Canada, they repeated these measurements daily for 11 days. Some Canadian skeleton athletes (who didn’t have to fly) also did some of the tests as a control.

The data, frankly, is pretty messy. Performance clearly drops after the flight, but the various measurements aren’t perfectly consistent about when the biggest drops come and how quickly performance returns. Here’s a bit of sample data, showing the squat jump height. The two squares (instead of circles) are the Canadian controls — they basically just show that there’s not much day-to-day variation in the measurements for non-jetlagged athletes:

So what’s going on? The researchers believe that it’s not just being cooped up in a plane for a day that causes the problems:

We would contend that a symptom of jet lag is circadian misalignment and as such the performance declines that we are reporting are the result of circadian misalignment due to trans-meridian flight.

Seems fairly reasonable. The solution:

This research highlights that where possible, athletes performing explosive short duration efforts as part of a competitive environment should time their arrival in the destination country following long haul travel at least five days prior to the competition.

This I’m a little more skeptical about. Looking at the data, it’s hard to see any particular break point after five days. That being said, in the balance between leaving too little time to recover versus arriving too early and being out of your element for too long, five days does seem like pretty good common sense.

  1. BMan
    September 5th, 2011 at 00:22 | #1

    I assume days 5 and 8 produced lesser results as a result of having done the tests the day before (it would have been proper for the Canadian Controls to do the tests on all the same days… as it is the controls appear to offer nothing). So you can throw out days 5 and 8. As such, it roughly looks like not a whole lot of change from days 4, 7, & 10 (maybe day 10 is higher… don’t have the numbers, so I don’t know… and if so, possibly because the athletes improved regardless of adjusting to jetlag). So I see a maximum of 4 days from this graph, or greater than 10 to get back to the -2 day level.

    The fact that the athletes do not get back to their -2 day level in 10 days perhaps brings up another 2 questions:
    - have the athletes really not adjusted in 10 days to the time change (my experience is that this could be possible).
    - if they have adjusted, what other influences of being in a foreign environment have significant affects on performance (and how can one minimize these effects)?

  2. alex
    September 5th, 2011 at 01:43 | #2

    Thanks for the comments, BMan. I should caution that we shouldn’t read too much into the single graph I posted. There are actually nine graphs in the paper (representing different kinds of jumps, and comparing height, peak power, velocity, and “eccentric utilization ratio,”) and they all have slightly different trends. As I noted above, the data is pretty messy and doesn’t lend it self to straightforward conclusions.

    I definitely agree that it’s strange that they don’t get back to “max” after 10 days. The error bar on the -2 day test is also suspiciously large — why is there so much variation compared to the subsequent tests? Another thing to bear in mind is that these are national team athletes who have flown all the way to Canada for a training camp. This little study is just a minor little detail that they agreed to cooperate with. As a result, I expect they’re training extremely hard during the training camp — that’s, after all, what training camps are all about. So maybe the -2 day measurements are pretty much irrelevant.

    The study does say: “All athletes maintained similar training, nutrition and sleeping schedules as they completed similar training sessions at the same time of day; ate at the same venues at the same time of day and shared accommodation.” But presumably that just applies AFTER the flight — and it’s still possible that cumulative fatigue is mounting during the 10 days, superimposing a gradual decline in performance on top of the gradual increase as they recover from jetlag.

    So all in all… hard to know exactly what’s happening, beyond the fact that there’s a steep decline for the first two days.

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