A new study has shown that not only do racehorses cope better with jetlag than humans do, but also their performance even appears to be enhanced by it.
The research, led by academics in the University of Bristol’s Faculty of Medical and Veterinary Sciences in collaboration with colleagues from the University of Melbourne and the University of Cambridge, is published in the Journal of Neuroendocrinology.
of multiple time zones. So flying from California to the UK would have (in principle) more negative effects than flying from New York. This is certainly the case for humans. Jet lag is due to the conflict between the new cycle of light and dark and the body’s natural circadian (literally “about a day“) rhythm.
Symptoms of jetlag in humans include disturbed sleep patterns, loss of appetite, lack of concentration and lethargy. Human athletes have noticed that jetlag can impair performance. So they take time to adapt to conditions in the country where the competition is to be held.
But what about horses? This new study is the first of its kind to investigate the effects of jetlag on the physiology and performance of racehorses under tightly controlled experimental conditions. Horses are the only athletes, apart from humans, regularly flown across time zones for athletic competitions.
Dr Domingo Tortonese, Senior Lecturer in Anatomy in the School of Veterinary Sciences, who led the study, said: “We tested the hypothesis that abrupt alterations in the 24-hour light-dark cycle, such as those associated with the crossing of time-zones, would alter the molecular clockwork and neuroendocrine systems of racehorses with detrimental consequences on their athletic performance.
“In humans, air travel-associated sudden changes in the 24-hour light-dark cycle disrupt biological rhythms with negative effects on cognitive and physical performance. Indeed, jetlag has important implications for athletes who travel across time zones for competitive sporting events, particularly after an easterly flight.
“Our study shows that racehorses are different from humans in that they rely on light cues for their daily rhythms of activity, rather than for the synchronisation of an endogenously generated rhythm to the 24-hour light-dark cycle. This light dependency underlies a rapid process of adaptation with critical scientific implications and unexpected practical benefits.”
The research team took seven Thoroughbred horses with previous race training and put them through a fitness program of daily sessions of exercise on a high–speed treadmill at variable times of the day for three months. Throughout the study, the horses were kept in a light-controlled environment. The researchers then altered the lighting to mimic a sudden change in time zones - the equivalent of an easterly flight across seven time zones.
They found that the horses adapted very quickly to a shift in time zone. Importantly, this rapid adaptation was not accompanied by an increase in the level of stress, but by alterations in endocrine systems that favoured an enhancement of the horse’s physical capacity during the process.
In fact, following experimental jetlag, horses experienced improved athletic performance, being able to run at full gallop for an additional 25 seconds before reaching fatigue. The treadmill velocity at which blood lactate reached 4mmol/l was also significantly increased after the change in photoperiod.
This improved performance did not persist, however, and had returned to pre-shift values after 14 days in the new lighting conditions.
The researchers suggest that these findings have important practical implications, since equine athletes do not need to travel to be subjected to changes in daily light. Its beneficial consequences could help to reduce the level of injury in competitions.
The research was supported by a research grant from the Horserace Betting Levy Board and by a Wellcome Trust Equipment Grant.
For more details see: Experimental jetlag disrupts circadian clock genes but improves performance in racehorses after light-dependent rapid resetting of neuroendocrine systems and the rest-activity cycle, DJ Tortonese, DF Preedy, SA Hesketh, HN Webb, ES Wilkinson, WR Allen, CJ Fuller, J Townsend, RV Short.
Journal of Neuroendocrinology, published online ahead of print, 15 September 2011.