Fig. 1

Relationships beween oxygen consumption, vertical loading rate (VLR) and percentage of running velocity at \({\dot{\text{V}}\text{O}}_{{\text{2 max}}}\). The grey dotted arrows illustrate an example: if one runs on the flat at 70% of velocity at \({\dot{\text{V}}\text{O}}_{{\text{2 max}}}\) corresponding approximately here to 12 km h⁻¹, then VLR is 337 N s⁻¹ kg⁻¹ (black solid line with black squares). The oxygen consumption is 43 ml kg⁻¹ min⁻¹ (black solid line with black rounds). Now, if one runs on a uphill at + 5% slope, for the same metabolic demand (similar \({\dot{\text{V}}\text{O}}_{{2}}\)), then VLR will be reduced to 247 N s⁻¹ kg⁻¹ (black dashed line with gray squares). SD values have been omitted for clarity