Biology Medicine

Travelling, Running, and Starving – A New Approach To Your Circadian Rhythms (repost 2008)

For many people, long trips disturb the natural rhythms so much that normal functioning on both the physical and intellectual planes is impaired. Clearly, there is a need for some method to improve the travel experience and the race results for those on a tight schedule. First class? Sounds great, but isn’t practical and probably won’t get the job done.

Circadian rhythms may affect racing performance. Most world records have been set in the afternoon or evening rather than in the morning. It may be a matter of when the races are run, but it also may follow along with optimal body rhythms. Workouts seem easier in the afternoon, joints are stiffer in the morning, and some old lecture notes I have indicate that muscles are weakest at 8 AM & 8 PM and strongest at 5 PM. Body temperature reaches a peak around 5PM. (Spiking fevers when you are ill, do not spike in the morning, but late afternoon or evening.) Measured VO2 MAX is greater in the afternoon.



  • Start sleeping on the schedule of where you will be racing (or working).
  • If you can, train on the schedule of where you will be headed.
  • Get there early if you can, for optimal performance one day for every hour time difference. Otherwise follow all the other suggestions.
  • Melatonin
  • Bright lights for wake up time on new schedule and wake up also.
  • Eat lightly 2 days before travel, then start eating on the arrival schedule

The suggested eating change, of eating on the new arrival schedule comes as a result of a new study on circadian rhythms published in this weeks Science Magazine. The article notes that when food is readily available, circadian rhythms are greatly impacted by the light-dark cycle. If food is only available at night, the animal will shift its circadian rhythms to match the time when food is available. This led to studies of the gene clock Bmal1 and found that the dorsomedial hypothalamic nucleus seemed to impact the role of food and feeding on the circadian timing system (CTS). Light has previously been found to play a role via retinal ganglion cells containing melanopsin which generates signals to the suprachiasmatic nuclei (SCN) of the hypothalamus. The SCN then effects a tuning of the circadian rhythms via synaptic and humoral mechanisms. The studies described here were done on mice.

The authors conclusions were:

Our data indicate that there is an inducible clock in the DMH that can override the SCN and drive circadian rhythms when the animal is faced with limited food availability. Thus, under restricted feeding conditions, the DMH clock can assume an executive role in the temporal regulation of behavioral state. For a small mammal, finding food on a daily basis is a critical mission. Even a few days of starvation, a common threat in natural environments, may result in death. Hence, it is adaptive for animals to have a secondary “master clock” that can allow the animal to switch its behavioral patterns rapidly after a period of starvation to maximize the opportunity of finding food sources at the same time on following days.

The biological clock for mammals, clearly resides in the hypothalamus. In some insects and snails, the clocks seem to be located in the retina. In birds, the pineal gland has been thought to come into play, along with the hypothalamus. Photoreceptors are usually linked into the timing system, to synchronize the clock with the 24 hour day. Old studies showed light to be able to assist in resetting the clock by impacting genes, sleep patterns, alertness, and body temperature.

As we noted above, exercising on the new schedule, can also help. Recent research agrees with this as per the study “Scheduled exposures to a novel environment with a running-wheel differentially accelerate re-entrainment of mice peripheral clocks to new light–dark cycles (Yujiro Yamanaka, Sato Honma and Ken-ichi Honma Genes to Cells (2008) 13, 497-507)

A study from 2001 demonstrated the liver enzyme production could be shifted 10 hours within 2 days by altering feeding. (Science 19 January 2001: Vol. 291. no. 5503, pp. 490 – 493 Entrainment of the Circadian Clock in the Liver by Feeding. Karl-Arne Stokkan, Shin Yamazaki, Hajime Tei, Yoshiyuki Sakaki, Michael Menaker)

Larks and Owls
While we don’t have studies to cite here, others have noted that some people are better at staying up late than others, while others are happy to wake up at 5 or 6am, but can’t stay up to party, play MMORPGs, or text their buddies in the middle of the night.

Some feel that it is easier for Larks to travel west to east and for owls to travel from east to west. The larks have little trouble staying up late, and have probably already shifted in part to the western time zone.