The impact of travel on performance is a growing focus of research for sports scientists. Peta Bee reports on their latest findings
Joint stiffness, dehydration and sleep deprivation, loss of appetite and a body clock sent haywire. These are some of the common side effects of long distance travel and yet, according to sports scientists, they are factors often overlooked by the growing number of athletes making lengthy journeys to training camps and competitions.
Reporting in the Strength and Conditioning Journal recently, a team of researchers from the sports and exercise departments of the University of Gloucestershire and Birmingham City University described how many athletes travel with little planning for the potential impact it might have on their physical and mental wellbeing.
Although many of the unwanted side effects of long haul flights are impossible to avoid altogether, a better understanding of the precautions that can be taken can only bring benefits.
“Minimising the potential decrement in athletics performance caused by travel requires comprehensive management by athletes and coaches,” writes Richard Clarke, a senior lecturer in strength and conditioning at the University of Gloucestershire.
“But awareness of the fundamental mechanisms of fatigue associated with travel and implementing recommended coping strategies can provide favourable outcomes.”
So what can be done to alleviate the problems?
Avoiding sleep deprivation
“Sleep deprivation can have negative effects on athletics performance,” Clarke says. “And it can occur both from sleep loss on overnight flights and from jet lag.”
Preflight practices such as adjusting bedtime by 1-2 hours for 1-2 days before travel are recommended so that you partially adapt to a new time zone. “If possible, plan early morning or afternoon arrivals which will enable the next night’s sleep sooner compared with evening departures and early morning arrivals,” Clarke says.
“And to reduce the negative effects of travel, get as much sleep as possible on the plane.”
Keeping the cabin window shades down and turning off the overhead lights until an hour before arrival are recommended.
“Avoiding caffeine, too much food and brain stimulating activities will reduce travel fatigue,” he adds. If you have travel fatigue on arrival, Clarke suggests athletes adopt a napping strategy.
“Naps of less than 30 minutes are not susceptible to sleep inertia, the fatigued state you can experience upon waking from longer sleeps,” he says. “Short naps have also been reported to improve alertness and cognitive performance following restricted night time sleeps.”
Coping with jet lag
Our human body clock works roughly to a 24-hour cycle and is controlled by a master clock in the brain. But it’s also influenced by peripheral clocks in other parts of the body that respond to cues such as changes in light and dark.
Changing the schedule of daylight and darkness confuses the pineal gland in the brain, which produces sleep hormones such as melatonin. Clarke and his team suggest different coping strategies depending on how long you are staying in a destination. If the length of your stay is short – less than three days – they suggest sticking to the patterns of your original ‘home’ time.
“Because the normal cycle of the human circadian rhythm is slightly longer than 24 hours, we have a natural tendency to accommodate lengthening of time zone (westward travel) than shrinking (eastward),” Clarke writes.
At least one day per time zone should be allowed prior to intense training or competition to allow for resynchronisation of the internal body clock, studies show.
Consume cherry juice
Professor Glyn Howatson, a researcher at the sport, exercise and rehabilitation department of Northumbria University, discovered that tart-tasting Montmorency cherry juice significantly increases the levels of melatonin in the body, the hormone which regulates sleep, and may help to prevent jet lag.
His research showed that when participants drank cherry juice for a week there was a significant increase in their urinary melatonin (15-16%) compared with control condition and placebo drink samples. “On long haul flights crossing more than 3-4 time zones, I would be inclined to take it just before you fly to promote sleep on the flight and then when you intend to rest or sleep at the destination take again about an hour before,” Howatson says.
“A good number of athletes are now routinely using cherry juice to overcome jet lag when traveling to competitions.”
A dose of 30ml of cherry concentrate is recommended.
Try compression clothing
Studies have linked lower leg compression garments with less discomfort through prolonged sitting in a cramped position and a significant reduction in blood pooling. Using electro-stimulation, or Tens equipment, during and after a flight might also be helpful.
“Recently, nerve stimulation has also been looked at and has been shown to increase blood flow to the lower leg,” Clarke says.
“It’s been shown to be more effective than both water-aerobic exercise and passive rest at reducing muscle pain in young soccer players.”
One study showed that athletes reported enhanced energy levels and enthusiasm when they combined electro-stimulation with compression clothing. “Few specific studies have looked at the effects of electro-stimulation during flights on subsequent performance. It’s logical to assume it would have both physiological and psychological benefit,” Clarke wrote.
Plan your nutrition
On a flight, the air circulated in cabins can be as dry as the Sahara, increasing the risk of dehydration.
Figures from the Aerospace Medical Organisation recommend drinking around 225ml of water for every hour in the air, but you might need more. To avoid the risk of gastrointestinal disease, Clarke urges athletes to “avoid drinking local water, including ice cubes and water for brushing teeth, and the consumption of raw foods or those that might have been washed in water”.
Scheduling meals on your flight to eat in sync with your new time zone can determine how well your body clock adjusts. In a recent study Dr Jonathan Johnston and Dr Sophie Wehrens, chronobiologists at the University of Surrey, recruited 10 male volunteers. Each participant was given breakfast 30 minutes after waking, and then had lunch and dinner at five hour intervals.
Immediately after they had eaten each meal, the participants had blood samples and fat biopsies taken in the special laboratory that simulated in-flight conditions – there was dim lighting, limited physical activity and no sleep – and allowed the researchers to keep tabs on their body clocks.
For the second stage of the trial, the experiment was repeated but with breakfast provided five hours after the subjects had woken instead. Results, published in the journal Current Biology, showed that moving mealtimes forward by five hours delayed changes to the rhythms of blood sugar by the same amount of time.
“We think that changing the meal times reset some peripheral clocks without affecting the master body clock,” says Johnston.
Manage light exposure
Arrive at your destination and, depending on the timing, exposure to bright light (especially natural light) can be helpful in resetting your circadian rhythm, or body clock.
Clarke explains that secretion of the sleep hormone melatonin is slowed on exposure to bright light and increased during darkness.
“Allowing or restricting light exposure would seem an ideal way to manipulate melatonin secretion to suit the circadian phase,” he says. Some researchers have shown that fluorescent and blue light can be used to suppress melatonin as they stimulate the same environmental responses as daylight.
Others have recently shown how intermittent transcranial light therapy, where bright light is shone through the ear canal for 4x12min a day has a positive effect on jet lag symptoms after cumulative days of treatment.
However, it is the timing of light exposure that’s crucial and eastwardly travellers crossing several time zones should consider dark ‘blue blocker’ goggles to reduce exposure to light and boost melatonin secretion, the study found.