02 May 2013

Jet-lag, sleep deprivation and ultramarathon endurance running

I am writing this on the airplane back to the US for my next business meeting after a few days of vacation in Paris. I can definitively say that my normal sleep-wakefulness cycle have been disrupted due to the long-haul flights over multiple meridians the past few days - even though I fear my jet lag will be even worse when I return to Sweden this weekend.

A great review paper describing the influence of sleep on physical performance was written a couple of years ago by Reilly and Edwards (Physiology & Behavior 2007; 90: 274–284). The most extreme experiments have been performed with total sleep deprivation for several days. Consistently in many studies, continuous physical activity for around 100 hours leads to marked impairment in particular in mental performance such as reaction time and short time memory already after one night followed by progressive deterioration. Over time, bizarre behavioral episodes, illusions (visual, auditory and olfactory) or hallucinations are often noted. Interestingly, the decline in mental performance is more pronounced than the one in physical parameters and a meta-analysis of sleep deprivation done by  Pilcher and Huffcutt (Sleep 1996; 19: 318–26) showed that showed that mood measures were more sensitive than cognitive tasks, which were, in turn, more sensitive than motor tasks during sleep loss. The same observations have been seen with for instance military battle combat units and long-distance sailors experiencing chronic/partial sleep loss over several days where only minimal amount of sleep each night is allowed. It appears limited loss in VO2 is seen at work rates up to 80% VO2 max, but that the effect on mood states, increasing depression, tension, confusion, fatigue and anger, and decreasing vigour were seen The data collectively can be interpreted as supporting Horne's brain restitution theory of sleep, suggesting that the primary need for sleep is located in nerve cells rather than in other biological tissues (Why we sleep. Oxford: Oxford University Press; 1988).

Reading these articles, and some of the blogs and accounts of previous TDG finishers, I know what to expect in September – however everyone is different and it is going to be interesting to see how I personally react to this amount of sleep loss. I will try to experience at least one long training run for several days with limited amount of sleep before TDG to see how I react and how I can use power naps in order to manage. The only consistent factors showing benefit in studies of prolonged sleep deprivation is napping and caffeine.

In less extreme cases of sleep deprivation, such as nocturnal shift work and traveling across time zones, I on the other hand have plenty of experience and know how I react both physically and mentally. When I started my residency in orthopaedic surgery many years ago I of course quickly noticed noticed that I had to be vigilant and be really perceptive in the ER and OR as my attention span decreased, my rate of errors increased, my performance in perceptual-motor tasks was decreased and, perhaps most notably, my mood regretfully changed quite markedly. I could, however, still go out for a run when I left my shift in the mornings and perform. Nevertheless, I quite quickly adapted and got used to working night shifts and actually enjoyed it quite much as I never experienced the constant light-headedness many of my colleagues did. I am neither too much affected by flying over the Atlantic as I do much now, however, I can certainly not say I like it. For short trips like this to the US East Coast I normally use training in order to stay as much as possible in my normal time zone as I go up very early in the morning and go the hotel gym. Sometimes it does not work, however, as I have dinners like today where I have to stay up late. I really do hope to have time for a short run on the treadmill before that.

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