THE METABOLIC COSTS OF WALKING AND RUNNING UP A 30 DEGREE INCLINE; IMPLICATIONS FOR VERTICAL KILOMETER FOOT RACES

Purpose: Vertical Kilometer (VK) races, in which runners gain 1000 m of elevation in \u3c5000 m of total distance, are becoming popular, yet there are few studies on steep uphill running. Previously, we determined that ~30° is the optimal angle for uphill running, costing the least amount of energy for a given vertical velocity. In the present study, we quantified the metabolic cost of walking and running at various velocities at a 30° incline. Method: At a 30° incline, eleven experienced runners (7M, 4F, 30.8 +/- 7.9 years, 1.71 +/- 0.08m, 66.7 +/- 9.4 kg) walked and ran for 5 minute trials with 5 minute rest between. Starting at 0.3 m/s we increased treadmill velocity by 0.1 m/s for each successive trial until subjects were unable to maintain the set velocity. We measured oxygen uptake (mlO2/kg/min) and metabolic rates (W/kg) and calculated the costs of walking (Cw) and running (Cr) (J/kg/m). Result: Oxygen uptake and metabolic power increased linearly with velocity (W/kg walk= 1.452 + 21.848V, W/kg run=5.351 + 17.586V). At the five slowest velocities (0.3, 0.4, 0.5, 0.6, and 0.7 m/s), Cw was less than Cr. However, at 0.8 m/s there was no difference between the two, and extrapolation suggests that at faster velocities, running likely cost less than walking. Conclusion: Running quickly up steep inclines requires more energy than running slowly does. Furthermore, at slower speeds, walking costs less than running. Thus, VK racers should pick a specific gait based on their racing speed