10 October 2014

Blisters in mountain ultramarathon running

This is my 100th post at this blog. I am fairly happy with my choice of subjects for my posts so far and I have personally learnt tremendously when writing them and hope this will have benefited my running at least to some positive extent. If the posts on these subjects also have benefited other runners I am even more happy. There are however some subjects I still have not written about that constantly come to my mind when I think about what to write about next. The effects on ultrarunning on the heart, a very controversial subject, is definitively one. It is however a rather complicated subject, to put it mildly, and even though I have collected most scientific articles on the subject I have simply not had time to dig into them and write a short summary of these numerous studies and divergent findings and opinions.

Another subject I have thought long to write about is the most common problem all mountain ultramarathon runners are facing when racing – blisters. If you wonder why it is so common just look at this picture from somewhere in the Italian Alps during Petite Trotte à Léon (PTL) earlier this year – while a talus field is really beautiful for the eyes it is the darkest nightmare for your feet, at least when descending.
 
Talus fields - the worst nightmare for your feet at least when descending
It is not the amount of data that has made me hesitate to write about blisters as almost every runner writes about it and has an opinion, but rather the lack of good scientific studies on the subject.  I was therefore very happy when I came across a new scientific study about blister formation in mountain ultramarathon racing by Scheer and colleagues (Scheer et al “The enemy of the feet: blisters in ultraendurance runners” J Am Podiatr Med Assoc 2014; 104: 473). In this study, blister frequency, localization, severity and preventive measures of 50 runners of the 2010 and 2011 Al Andalus Ultra Trail, a 5-day 219 km multistage trail during the summer in high temperatures in southern Spain, were investigated.  Quite interesting, the blister formation occurred almost linearly over the first three days, with 34% having blisters after Day 1, 54% after Day 2 and 72% after Day 3. After 4 days of racing (182 km) 76% of the runners had blisters (see figure below).
 

Most of the blisters formed on the toes (65%), followed by blisters at the ball of the foot (16%), heel (14%) and sole (5%). Blisters were more painful towards the end of the race, and those of the sole and heel tended to be the most painful (although not statistically significant). Most interesting, the prophylactic measures studied (type and fabric of socks; application of antiperspirants, talcum powder, or lubricant to feet; and prophylactic taping) did not show any reduction in blister rates. The only predictive marker for reduced blister incidence was previous ultramarathon experience in men (r = -0.44, P < 0.05). I think these findings agree well with my experiences from Tor des Geants (TDG) and Petite Trotte à Léon (PTL) were my feet withstood the stress for approximately 80 hours before severe blister formation in TDG last year and around 100 hours before blister formation in PTL this year. The study also reinforces my belief that you have to find a solution to prevent blisters that works for you personally and that this solution might be different for each runner and even for each race depending on the conditions.

Looking at what others have written about blisters there exists barely an ultrarunning running blog without something about it. A really good post is by Andy Cole in his blog “Running Late” from last year entitled “Bad News and Blisters” and I can definitively recommend it. If you really want to dig into the subject “Fixing your feet. Injury prevention and treatments for athletes ”, now in its 5th edition, by John Vonhof is the reference book. It is very much written with endurance runners in mind.
 
In the scientific literature a lot has been written about friction blisters and sock fiber composition for instance, but no good prospective randomized controlled trials have been conducted to my knowledge of different types of socks, or any other intervention for that matter, in ultramarathon runners. Other studies also confirm the findings by Scheer and colleagues that blister formation is very common as they appear to represent 17-40% of injuries at continuous ultramarathons and 33-74% of injuries during multistage ultramarathons (for review see Hoffman et al “Medical services at ultra-endurance foot races in remote environments: Medical issues and consensus guidelines” Sports Med 2014; 44: 1055-1069).

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