Hiking in the Great Smoky Mountains National Park





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Ranking of Trails by the Energy Mile Theory


When setting out on a hike, clearly every hiker would love to know how hard the hike will be. This is particularly true for hikes that include substantial elevation gain (or substantial changes in elevation).  Unfortunately, there is very little empirical evidence telling us how to judge the difficulty of a hiking trail.  I have sought out the best information available to help with rank ordering the trails in this book relative to difficulty level. Initially, I considered the trails relative to the slope of the line based on distance and elevation gain. Then, I learned of “Petzoldt’s Energy Mile” theory (Petzoldt 1976) and started looking into it. Based upon years of hiking experience, Petzoldt considered the energy mile to represent the amount of energy burned when hiking one mile on flat terrain. He then suggested that it also requires two energy miles to hike up 1000 feet of elevation gain. Thus for a 1-mile hike on level ground, the energy burned would be 1 energy mile, and if there was also a 1000-foot climb, the total energy burned would be 3 energy miles.


Troy and Phipps (2010) tested this theory using male and female college students walking 2 miles on flat terrain and 2 miles with a 1000 foot gain, with and without 44 pound packs. Their findings showed that the caloric cost of a 1000-foot climb for women was 1.34 and 1.32 energy miles with or without a pack, respectively. For males, the energy equivalent was 2.02 and 1.92 energy miles, with or without a pack, respectively. Combining the data for both sexes, their findings showed that the energy equivalent is 1.69 miles and 1.64 miles with or without a pack, respectively, for a 1000-foot elevation gain.


These values based on caloric cost seem to justify the conservative use of Petzoldt’s 2 energy miles per 1000 foot gain. An additional reason to use the 2 miles/1000 foot gain is that the Troy and Phipps study examined college students walking on a stable terrain. For the purpose of this book, I’m targeting a very diverse population of men and women who might be carrying a wide variety of packs and supplies and who will be encountering all manner of trail and weather conditions. There is a valid thought that energy is expended when going downhill also, but there is no research or anecdotal information to date, so I have not been able to include a caloric cost for hiking downhill.


Follow this link to the table that lists the hikes in each area and their order of ranking based on energy (NRG) mile equivalent. It gives the hike name and number, the page it appears on, the actual miles hiked, the total elevation gain, and the NRG mile equivalent based on estimated caloric cost. The latter two values are incorporated into Tables 2 – 10 in my 4th Edition of Day Hikers Guide to all the Trails in the Smoky Mountains.



Petzoldt, P. K. 1976. Petzoldt’s Teton Trails. Wasatch Publisher’s Inc., Salt Lake City, Utah (as cited in Troy and Phipps, 2010).


Troy, Maridy M. and Phipps, Maurice. 2010. The Validity of Petzoldt’s Energy Mile Theory. J. Outdoor Recreation, Education, and Leadership. Vol. 2, No. 3, pp. 245-259.