Free runner athletes are aping orang-utans to help researchers investigate how the primates move through trees.
In a simulated forest habitat, the athletes are mimicking the primate's skills at leaping, vertical climbing, and "tree swaying".
Scientists hope the findings will help them understand how orang-utans and other tree-dwelling apes maximise energy efficiency.
Dr Lewis Halsey, from the Department of Life Sciences at the University of Roehampton, said: "We will study the energetic costs of orang-utan locomotion by measuring the oxygen consumption of athletic humans undertaking similar movements.
"Our subjects are a particularly appropriate model for the fluid nature and wide range of movements employed during orang-utan arboreal locomotion - professional parkour practitioners (free runners) who display elite gymnastic and athletic abilities."
Parkour, or free running, is an urban sport developed in France that uses acrobatic movements to overcome obstacles such as walls and buildings.
Besides running, it involves vaulting, rolling, climbing and jumping.
During the trials, the athletes carry instruments that record their oxygen consumption and movements.
"We focus on three key orang-utan locomotor behaviours: tree swaying, because of its role in reducing locomotion cost; vertical climbing. since this requires the animal to oppose gravity, and leaping, since while probably energetically efficient, orang-utans only leap in extremis," said Dr Halsey.
"We create simple assault courses for the athletes that mimic typical locomotor problems faced by orang-utans. Rate of oxygen consumption is measured using a portable respirometer and subjects wear an accelerometer logger to record extraneous movement."
The study could aid efforts to save the critically endangered Sumatran orang-utan by shedding light on its habitat requirements.
Scientists from the universities of Roehampton and Birmingham are conducting the study, funded by the National Environment Research Council (Nerc).
Dr Susannah Thorpe, from the University of Birmingham, said: "Methods to measure primate locomotion energetics are limited; most data are based on mathematical models.
"We propose a novel and more direct method to assess how costs of orang-utan arboreal locomotion are modulated by the environment."