The metabolic costs of walking and running up a 30-degree incline: implications for vertical kilometer foot races.

Abstract

Vertical kilometer (VK) races, in which runners gain 1000m of elevation in<5000m 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. At 30°, 11 experienced runners (7M, 4 F, 30.8±7.9years, 1.71±0.08m, 66.7±9.4kg) walked and ran for 5-min trials with 5-min rest between. Starting at 0.3ms-1, we increased treadmill velocity by 0.1ms-1 for each trial until subjects could not maintain the set velocity. We measured oxygen uptake (ml O2kg-1min-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 (Jkg-1m-1). Oxygen uptake and metabolic power increased linearly with velocity. Between 0.3 and 0.7ms-1, C w<C r. At 0.8ms-1 there was no difference and extrapolation suggests that at faster velocities, running likely costs less than walking. On a 30° incline, metabolic power increases linearly with velocity. At speeds slower than 0.7ms-1, walking requires less metabolic power than running (Wkg-1) suggesting most VK racers should walk rather than run.