许多人长途旅行经历时差变化后都有疲累感觉，但英国研究人员发现，赛马在经历时差之后运动能力反而增强，能够全速奔跑的时间变得更长。
英国布里斯托尔大学等机构的研究人员在《神经内分泌学期刊》上报告说，他们针对一些受过良好训练的赛马进行了实验。这些赛马被置于光线受控制的房间中，先进行3个月的正常训练，其间光线变化遵循正常的白昼黑夜循环。随后研究人员通过改变灯光，营造出时间快了7个小时的环境，让这些赛马经历时差变化。
结果显示，与人类在经历时差后运动能力往往下降不同，这些赛马出现运动能力上升的现象。以在表现出疲劳前能够全速奔跑的时间为例，赛马在经历时差后全速奔跑的时间延长了25秒。
研究人员多明戈·托尔托内塞说，这可能是因为赛马和人适应时差的方式不同。人体生物钟的惯性较强，当生物钟与外部时间不一致时，身体需要时间来慢慢适应。而赛马对光线非常敏感，一旦光线发生变化，身体内分泌系统很快随之变化，来帮助它们适应环境的改变，运动能力提高则是内分泌变化的一个意外产物。（生物谷 Bioon.com）
doi:10.1111/j.1365-2826.2011.02222.x
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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, Domingo J.; Preedy, Danielle F.; Hesketh, Shirley A.; Webb, Hayden N.; Wilkinson, Elizabeth S.; Allen, William R.; Fuller, Catherine J.; Townsend, Julie; Short, Roger V.
Abrupt alterations in the 24-h light:dark cycle, such as those resulting from transmeridian air travel, disrupt circadian biological rhythms in humans with detrimental consequences on cognitive and physical performance. In the current study, a jetlag-simulated phase shift in photoperiod temporally impaired circadian peaks of peripheral clock gene expression in racehorses, but acutely enhanced athletic performance without causing stress. Indices of aerobic and anaerobic capacities were significantly increased by a phase-advance, enabling prolonged physical activity before fatigue occurred. This was accompanied by rapid re-entrainment of the molecular clockwork and the circadian pattern of melatonin, with no disturbance of the adrenal cortical axis, but a timely rise in prolactin, a hormone known to target organs critical for physical performance. Subsequent studies showed that, unlike the circadian pattern of melatonin, and contrary to other species, the daily rhythm of locomotor activity was completely eliminated under constant darkness, but it was restored immediately upon the reintroduction of a light:dark cycle. Resetting of the rhythm of locomotion was remarkably fast, revealing a rapid mechanism of adaptation and a species dependency on light exposure for the expression of daily diurnal activity. These results show that horses are exquisitely sensitive to sudden changes in photoperiod and that, unlike humans, can benefit from them; this appears to arise from powerful effects of light underlying a fast and advantageous process of adjustment to the phase shift.
