The ventilatory cost of activity.

The energy cost of activity, depending on its intensity, varies between 6 and 50 kJ min-1 with average values for essential daily tasks and for hard work respectively of 12 and 28 kJ min-1. The levels of ventilation required to sustain these activities are, on average, 15 and 33 1 min-1 with an overall range of +/- 30%. Additional ventilation is needed for speech. The requirements for individual activities are reviewed.