Faculty and students test an outdoor legend’s energy theory


Backpackers who take on the steep mountain trails near WCU’s campus can confirm that hauling a pack uphill is much more difficult than carrying one on level ground, and some faculty members and students recently put that notion to the test. A study that involved 24 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 and outdoor education legend Paul Petzoldt. Overseeing the project was Maridy Troy, assistant professor in the health and physical education program, and Maurice Phipps, professor of parks and recreation management, who also knew Petzoldt as a friend and mentor.

Paul Petzoldt (bottom center) surrounded by students
including WCU faculty member Maurice Phipps (far left).
Petzoldt developed his ‘energy mile’ theory in Wyoming’s
Teton Mountains, and it was tested for the first time in
WCU’s exercise physiology laboratory (top), where
Maridy Troy monitors a research volunteer.

Phipps first met Petzoldt and learned 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 led by the renowned outdoorsman.

Petzoldt 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. The theory had never been tested in a laboratory before the study began in WCU’s exercise physiology laboratory in the spring of 2010.

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. As the study continued last fall, 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 with Petzoldt’s use of two energy miles for each 1,000 feet. Weight difference among volunteers accounted for the range, 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.

Phipps said the energy required for hiking up steep mountain trails would vary for individuals and groups, and the variables of the trail also would 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. 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.