Purpose: Vertical kilometer (VK) races, in which runners gain 1000 m of elevation in <5000 m of distance, are becoming popular. However, few studies on steep uphill running (>25°) exist. Previously, we determined that ~30° is the optimal angle for uphill running, costing the least amount of metabolic energy for a specific vertical velocity. To inform the training and strategy of VK racers, we quantified the metabolic cost of walking and running at various velocities up a 30° incline.
Methods: At 30°, 11 experienced runners (7 M, 4 F, 30.8 ± 7.9 years, 1.71 ± 0.08 m, 66.7 ± 9.4 kg) walked and ran for 5-min trials with 5-min rest between. Starting at 0.3 ms-1, we increased treadmill velocity by 0.1 ms-1 for each trial until subjects could not maintain the set velocity. We measured oxygen uptake (ml O2 kg-1 min-1) and metabolic power (W kg-1 = metabolic energy per unit time per unit body mass) and calculated metabolic costs of walking (C w) and running (C r) per unit distance (J kg-1 m-1).
Results: Oxygen uptake and metabolic power increased linearly with velocity. Between 0.3 and 0.7 ms-1, C w < C r. At 0.8 ms-1 there was no difference and extrapolation suggests that at faster velocities, running likely costs less than walking.
Conclusion: On a 30° incline, metabolic power increases linearly with velocity. At speeds slower than 0.7 ms-1, walking requires less metabolic power than running (W kg-1) suggesting most VK racers should walk rather than run.
Keywords: Cost of transport; Economy; Energetics; Uphill.