Many long distance hikers suffer from a burning, tingling or feeling of numbness in their arms, legs or feet. A study of surveys from 128 hikers who either hiked the P.C.T. or A.T. and hiked at least 500 miles was conducted before the terminus of either trail. The demographics of the hikers were:
The study found that the prevalence of this illness was related to pack weight. The hikers with medium weight packs were 1.5 times as likely to suffer the above symptoms and the heaviest pack hikers were over twice as likely compared to the lowest pack weight hikers. Footwear was also co-related to this illness, but could not be separated from the effect of pack weight. It’s likely the sandals and running shoe hikers tended to have lighter packs, since this would be part of the ultralight philosophy. With the arrival of commercially available ultralight gear it’s a more practical option than making your own gear. This has likely lead to ultralight backpacking becoming more popular, but taking this to the extreme can reduce a hiker’s options and thus put the hiker at a greater risk when the unforeseen arrives. This is especially true for freshmen hikers. This study does support reducing pack weight to avoid this illness but this means giving up on items you may think are a necessity. So somewhere between a pack mule and Winton Porter's "Go Freezers" is the correct balance. Unfortunately there are so many gear lists available, and many of these aren't tailored to long distance hikers, that gear selection becomes a confusing nightmare. Even when consulting former thru-hikers, personal opinions are strongly held, even about something as seemingly simple as whether to carry maps or not. Nevertheless, I feel your pain having watched my son go through this process twice and getting it disappointingly wrong the first time.
Stewart Anderson, L., Casey M. Rebholz, Laura F. White, Patricia Mitchell, Edward P. Curcio, James A. Feldman, and Joseph H. Kahn. 2009. "The Impact of Footwear and Packweight on Injury and Illness among Long-Distance Hikers." Wilderness & Environmental Medicine 20 (3): 250-256.
Porter, Winton. 2009. Just Passin' Thru : A Vintage Store, the Appalachian Trail, and a Cast of Unforgettable Characters. Birmingham, Ala.: Menasha Ridge Press. http://site.ebrary.com/id/10395094.