13 June 2014

The limits of human running endurance

It has been another good week from a running perspective. I have shifted focus from building on my aerobic capacity with hill repeats to longer distances and a lot of long back-to-back runs. The reasons for this are two-fold. Firstly, I got a muscle strain last week in an abdominal muscle when doing core exercises; actually quite annoying as I now really feel how much you use also the abdominal muscles when running on technical paths. In order to give the muscle time to heal I decided to refrain not only from directly hurtful activities, like further core training and sit-ups, but also from mildly uncomfortable activities like trail and downhill running. And, the muscle appear to quickly be getting better. Secondly, I would like to prepare better for the difficult task of starting a run when feeling really stiff and sore. During Tor des Géants last year it was sometimes really hurtful to go out in the cold and darkness after having slept for a short period of time and it took a while until the muscles had getting used to running again. With longer back-to-back runs I imagine I will prepare myself a little bit for this before PTL.

However, compared to what waits the 14 runners starting The Sri Chinmoy Self-Transcendence 3100 Mile Race on Sunday, my longer back-to-back runs seem like sprint distances. For those of you who have not heard about this almost 5000 kilometer long race I can strongly recommend the book “Running Beyond the Marathon: insights into the longest footrace in the world” by Grahak Cunningham. The runners are given 18 hours a day between 6:00 am to midnight, seven days a week, for 51 days to complete 5649 laps around an 883 meter block in Queens, New York. They need to run a minimum of 60 miles (96 km) a day to complete the distance. Grahak’s book is a really great and fascinating account of both the physical and mental struggles to complete this race and it is really inspirational. It also gives good practical tips about blisters, chaffing and other ailments that will be experienced at magnitude at such an extreme ultra event like this. To me, what is really fascinating about this race is that it really shows what the human body and mind is capable of. Interestingly, there are not many runners not finishing the race and those who are forced to a DNF appear quite often to be suffering from issues with infected blisters.

In reading the literature about what limits human endurance I came across the papers “The limits of human endurance: what is the greatest endurance performance of all time? Which factors regulate performance at extreme altitude?” and “The limits of endurance exercise”  by Tim Noakes in Adv Exp Med Biol 2007; 618: 255-76 and Basic Res Cardiol 2006; 101: 408-417. In these papers he discusses the energy expenditure of ultra endurance activities and classifies endurance performances based on the required energy consumption. That would make Robert Falcon Scott's Polar party during the 1911/12 British Antarctic Expedition the greatest endurance performance of all days as, for most of 159 consecutive days, Scott's team man-hauled for 10 hours a day to the South Pole and back covering a distance of 2500 km with a predicted total energy expenditure per individual of about 1 million kcal.

However, in line with the histories of runners in Grahak’s book on the Self-Transcendence 3100 Mile Race it appears not to be primarily the negative energy  balance which limits the endurance performance for these long races, even though that it partly determines the possible running pace during these herculean runs.  I have previously mentioned the findings from the 4487 km long Trans Europe Foot Race 2009 (TEFR 2009) for instance in a blog post about the effects caused by this race in the 44 participants on the brain and the pain perception and personality traits of the runners. This race has now been described in a number of fascinating scientific articles and confirm that most runners complete the race despite the massive negative energy balance  that they lost more than half of their adipose soft tissue and even lean tissue volume decreased (mainly skeletal muscle tissue). For further reading I can recommend the articles listed below, most of them actually freely available through Pubmed. I certainly think we will learn much more about human physiology from studies of longer races like this in the future.

·      Schütz et al “The TransEurope FootRace Project: longitudinal data acquisition in a cluster randomized mobile MRI observational cohort study on 44 endurance runners at a 64-stage 4,486 km transcontinental ultramarathon” BMC Med  2012 10:78

·      Freund et al “Substantial and reversible brain gray matter reduction but no acute brain lesions in ultramarathon runners: experience from the TransEurope-FootRace Project” BMC Med 2012; 10:170.

·      Freund et al “Ultra-marathon runners are different: investigations into pain tolerance and personality traits of participants of the TransEurope FootRace 2009” Pain Pract 2013; 13: 524-32

·      Schütz et al “Characteristics, changes and influence of body composition during a 4486 km transcontinental ultramarathon: results from the TransEurope FootRace mobile whole body MRI-project” BMC Med 2013; 11: 122

·      Freund et al “Regionally accentuated reversible brain grey matter reduction in ultra marathon runners detected by voxel-based morphometry” BMC Sports Sci Med Rehabil. 2014; 6:4

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