In one study based on mean oxygen uptake and heart rate, researchers estimated that ascending a 15 cm (5.9 inches) step expends 0.46 kJ (0.11 kcal) for the average person, and descending a step expends 0.21 kJ (0.05 kcal). The study concluded that stair-climbing met the minimum requirements for cardiorespiratory benefits, and considered stair-climbing suitable for promotion of physical activity.