Respiratory valve for oxygen uptake measurements during swimming

A detailed description of a respiratory valve to measure oxygen uptake while swimming is given. The effect on body drag of the addition of this equipment was measured in four subjects swimming over a range of speeds (0.9-1.9 m s-1). The respiratory valve has a low airflow resistance (29 Pa at an airflow of 8 l X s-1) and a small deadspace (30 ml). Total body drag when swimming while wearing the respiratory equipment did not differ significantly from that when swimming without the equipment. It is concluded that this respiratory valve is ideal for making valid and reliable measurements of oxygen uptake during swimming.