By Aurora Eastwood.
The positive effects of jet lag for polo ponies.
Research conducted at the University of Bristol Faculty of Medical and Veterinary into the effects of travelling horses across different time zones threw up some startling results.
Dr Domingo Tortonese, an Argentine vet who moved to the UK in the early 90’s, was the lead scientist. A life-long fan of polo, his primary interests lay in reproductive endocrinology so this latest study is a somewhat different line of work, which relates to his concern with the neuroendocrine control of biological rhythms.
Humans, when crossing time zones, suffer from jet lag; that is, our circadian rhythms (our natural 24 hour cycles) are disrupted. We have all had sleepless nights (especially when flying East) as although local time may be 10 pm, it may be only 3pm back home. This is bad enough for business travellers, but for athletes there are serious negative effects on performance.
Domingo’s research results were a surprise, not least to him:
“This was part of a series of studies over many years, and the results were the opposite to what we expected to find.
“We observed that although horses are extremely sensitive to abrupt changes in the 24-hour light-dark cycle, they adapt very quickly to phase shifts, such as those experienced after a transmeridian flight. This relates to a light-dependency of this species for the expression of a circadian rhythm of activity rather than for the entrainment (i.e. synchronisation) of a rhythm to the 24-hour light-dark cycle as is the case for humans”.
“The fast process of adaptation involves alterations in endocrine systems that facilitate an acute increase in physical capacity”.
“These results relate to a weakness in the endogenous control of the horse’s circadian rhythms of activity, which could be observed, for example, in the lack of a defined sleep-wake cycle, as horses sleep for short periods scattered throughout day and night. However, horses display very strong circannual (i.e. yearly) biological rhythms. Thus, they respond extremely slowly to a change in North/South hemispheres and require 12 months to fully adjust to new winter/summer cycles and this has a very detrimental effect on performance”.
The full press release is later in this article, but in a nutshell, the findings are relevant in polo for several reasons.
1) Horses are highly sensitive to light and this must be considered when moving ponies.
2) Athletic performance could be enhanced through the appropriate manipulation of the 24-hour light-dark cycle.
3) A polo pony flown across time zones will temporarily have enhanced athletic performance. Therefore, high goal ponies should be flown to the UK as close as possible to their first game (ie a matter of days before) to benefit from this.
4) Horses suffer loss in performance when crossing the equator; therefore, point three is especially relevant in high goal polo given that many ponies fly from South to North America for the high goal season (and vice versa).
For optimum athletic performance, ponies should be flown to the UK from Argentina just days before the first high goal game to exploit the enhanced performance that the crossing of time zones will trigger, and to avoid the onset of reduced athletic performance that the crossing of hemispheres will cause.
The original press release:
Light dependency underlies beneficial jetlag in racehorses
A new study has shown that racehorses are extremely sensitive to changes in daily light and, contrary to humans, can adapt very quickly to sudden shifts in the 24-hour light�?dark cycle, such as those resulting from a transmeridian flight, with unexpected benefits on their physical performance.
The research led by academics in the University of Bristol’s Faculty of Medical and Veterinary Sciences is published in the Journal of Neuroendocrinology.
This is the first study 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.”
Thoroughbred horses with previous race training were housed in light-controlled rooms and put through a fitness program of daily sessions of exercise on a high�speed treadmill at variable times of the day for three months. They then experienced a shift in the 24-hour light-dark cycle that mimicked an easterly flight across seven time zones.
The 24-hour patterns of four clock genes, together with neuroendocrine systems involved in a variety of functions, including time measurement, homeostasis and the response to stress, were investigated before and after the shift. The aerobic and anaerobic capacities were measured by standardised performance tests. Locomotor activity was also assessed continuously, under photoperiodic conditions and in the absence of light cues (constant darkness), to determine the expression and robustness of a 24-hour rest?activity cycle. The speed of re-adaptation to a new light?dark cycle was also investigated.
Contrary to the prediction based on human and rodent data, the results show that whereas horses are extremely sensitive to sudden changes in the 24-hour light-dark cycle, they can adapt very quickly to a phase shift. Importantly, this rapid adaptation is not accompanied by an increase in the level of stress, but by alterations in endocrine systems that favour an enhancement of the horse�s physical capacity during the process.
The improvement in athletic performance following experimental jetlag resulted in the animals being able to run at full gallop for an additional 25 seconds before reaching fatigue. This differs from humans who show a slow adjustment, particularly after an eastbound flight, with detrimental consequences on performance. The difference between the two species can be attributed to the powerful masking effect of light on the horse’s daily locomotor activity, which, together with the absence of a robust sleep?wake cycle, can be a part of a mechanism of adaptation to sudden changes in the environment.
The results of this study have important practical implications, since equine athletes do not need to travel to be subjected to changes in daily light, and its beneficial consequences could help to reduce the level of injury in competitions.
The research by the University of Bristol, in collaboration with academics from the University of Melbourne and the University of Cambridge, was supported by a research grant from the Horserace Betting Levy Board and by a Wellcome Trust Equipment Grant.
Paper: Experimental jetlag disrupts circadian clock genes but improves performance in racehorses after light-dependent rapid resetting of neuroendocrine systems and the rest-activity cycle, Tortonese D J, Preedy D F, Hesketh S A, Webb H N, Wilkinson E S, Allen W R, Fuller C J, Townsend J, Short R V. Journal of Neuroendocrinology
In the weeks following the press announcement of the findings, Domingo Tortonese has been inundated with interest from media all over the world – from the Equestrian press to The Telegraph, CNN and the Discovery Channel – the latter are both flying to the UK to film programmes about the studies. This is truly groundbreaking research.