Preventing paresthesias when hiking

Appalachian trailParesthesthias commonly occur in long distance hiking, such as thru-hiking the Appalachian Trail (seen to the left) or the Pacific Coast Trail. They occur in both upper and lower extremities, and can certainly make hiking less fun. Of course, there can be serious causes to paresthesias, so care needs to be taken to not dismiss cerebrovascular accidents, toxidromes, and complications of diabetes. Once those are ruled out, the paresthesia is likely related to repetitive trauma or compression of nerves.

Shoulder straps from backpacks can cause ulnar paresthesias, and most commonly present as numbness or tingling of the ring and little fingers. Hip straps can cause numbness of the outer thigh, usually called meralgia paresthetica. It is also known as Bernhardt-Roth syndrome. Tarsal tunnel syndrome, or posterior tibial neuralgia, can be caused by footwear that compresses the area behind the medial malleous (known perhaps unsurprisingly as the tarsal tunnel). This usually causes numbness or pain of the sole, but can include the toes. If just the toes themselves are affected, then it is known as digitalgia paresthetica, and is commonly attributed to type of shoe padding.

Most of these are well known to long distance hikers, but they can happen to short distance hikers who are out of shape, as well as military recruits. Once they present, the first suggestion is to alter whatever piece of gear is the offending agent. This can mean adjusting or padding the straps of one’s pack, or changing footwear. This may stop it from getting worse, but may not makes symptoms go away.

The question is, can we prevent this? The neuropathy can last for months and be fairly debilitating. This article wasn’t trying to answer just that question, but was instead trying to determine prevalence and predictors of all injuries and illness in long distance hikers. They did this by anonymously surveying thru-hikers of the PCT and AT near the northern terminus of each trail. The responses were included if they had hiked at least 500mi in the last season, and were older than 18. Of the 143 surveys they received, only 15 were excluded.

Paresthesias were common, with 48% prevalence. The survey did allow for localization, but hikers were like most survey takers, and declined to input free text. Since the surveys did have sections asking about footwear and pack weight, the authors had enough of a sample size to analyze these factors.

Unsurprisingly, pack weight had a statistically significant affect on prevalence of paresthias, with packs between 10-20lbs having a ~30% rate of paresthesias, 21-30lbs at ~50%, and >31lbs having a nearly 70% prevalence. Obviously the take home message is to carry less with you if you want to prevent numbness or tingling. 

What is interesting is footwear. While never reaching significance, there was an obvious trend toward minimalist footwear as well. Hiking boots were worst, with ~70% paresthesias, then it drops sharply for low top hiking boots at ~40%. Running shoes were a little lower, and sandals were at the bottom with <30% prevalence of paresthesias. Maybe those guys with Chacos were doing it right all along.

So is ultralight the way to go? From this study, it seems to be a logical and healthy alternative to what many are doing.

Of note, there was also a 50% rate of wilderness-associated diarrhea, in line with earlier studies. I guess they should have washed their hands more.

The Impact of Footwear and Packweight on Injury and Illness Among Long-Distance Hikers
http://www.ncbi.nlm.nih.gov/pubmed/19737037

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