Backpackers who take on the challenge of hiking in the Southern Appalachian Mountains can attest to the fact that hauling a pack up a steep mountain trail is much more difficult than carrying one on level ground, and some Western Carolina University faculty members and students have put that notion to the test.
A study that involved volunteers carrying a pack while walking on a treadmill set on an uphill grade was used to test the “energy mile” theory first proposed by the late American mountaineering legend Paul Petzoldt. Overseeing the project was Maridy Troy, an assistant professor in WCU’s health and physical education program, and Maurice Phipps, professor of parks and recreation management, who also knew Petzoldt as a friend and mentor.
Phipps first met Petzoldt and found out about his energy mile theory in 1982, when Phipps, a young immigrant from England, went on a Wilderness Education Association training trip in Wyoming’s Teton Mountains that was led by the renowned outdoorsman.
Petzoldt first proposed his theory in his 1976 book Teton Trails to help backpackers plan trips and calculate their energy needs on mountain trails. “Petzoldt defined one energy mile as the energy required to walk one mile on the flat. He recommended adding two energy miles for every 1,000 feet of elevation gain, so a person hiking one mile and 1,000 feet upward would use the equivalent of three energy miles,” Phipps said.
Petzoldt’s energy mile theory was just a reflection of the mountaineer’s “gut feeling,” Phipps said. The theory had never been tested in a laboratory before the study began in WCU’s Exercise Physiology Laboratory in the spring of 2010, Phipps said.
To determine the validity of the theory, the study measured the energy cost and perceived exertion for walking on flat ground, with and without a 44.5-pound backpack, and up an elevation gain of 1,000 feet, with and without the backpack, through the collection of metabolic data, Phipps said.
Twenty-four student, faculty and staff volunteers, including 12 males and 12 females, went through four testing sessions as the research continued into fall semester of 2010. The study results showed that the additional energy cost for ascending 1,000 feet ranged from 1.34 to 2.02 energy mile equivalents, for an average of about 1.6 miles, compared to Petzoldt’s use of two energy miles for each 1,000 feet. The range revealed by the study was due to the “hikers’” personal weight differences, Phipps said.
“It is remarkable that Petzoldt’s energy mile theory is so close to the actual energy cost measured during our study,” Phipps said. “In the field of outdoor education, it’s important for leaders to include an estimation of energy requirements during the planning of hiking trips.”
Phipps said the energy required for hiking up steep mountain trails would vary for individuals and groups, and the variables of the trail would also factor in, but he recommends that backpackers stick with Petzoldt’s idea of adding two energy miles for every 1,000 feet of elevation gain when planning trips.
Petzoldt, the founder of the National Outdoor Leadership School who is considered to be the father of outdoor education in the United States, later amended his theory, stating that 1,000 feet of elevation gain is equivalent to four miles worth of energy for trail novices with expedition packs in the Tetons. Petzoldt suggested adding three energy miles — instead of two — per 1,000 feet of elevation gain in the North Carolina mountains when he visited the WCU campus to teach a WEA expedition course in 1987, Phipps said.
An article detailing the study titled “The Validity of Petzoldt’s Energy Mile Theory” has been published in the Journal of Outdoor Recreation, Education and Leadership.