A portable device for long-term monitoring of oxygen uptake without discomfort has been developed based on a flow-through principle. The oxygen content of the exhaust gas was kept constant by a servo-controlled blower, so that the flow rate was essentially proportional to the oxygen uptake. This system was evaluated by both a bench test and in exercising human subjects. The limiting current-type oxygen sensor used this portable device produced results which were in good agreement those obtained using a zirconia oxygen sensor (r= 0.999), and stable values were obtained for at least 15 h. The response time for a stepped oxygen change was 4 s. The air flow rate produced by the blower was proportional to the supplied voltage. The results using a time-of-flight flowmeter were highly correlated with those for a hot-wire anemometer (r=0, 999) . The oxygen uptake of exercising human subjects measured with this portable device showed good agreement with that obtained by a conventional oxygen monitor (r=0.973 for cycle ergometer, r=0, 932 for treadmill) . This portable device was able to measure oxygen uptake in subjects during daily activities, and also while driving a car, without disturbance.

A system for making prolonged measurements of oxygen uptake without the use of mask or mouthpiece is described. A subject wears a hood through which air is drawn by a exhaust pump located on the end of hoses. The flow rate of main stream is measured by a pulsed wire flowmeter located between flexible hose and rigid hose. The flow rate is essentially constant during a run. One sample pump bypasses small amount of mixed air from the main stream. The other pump draws the room air. Two sample pumps operate alternatively at 2 min interval. The sample gas is dried by passing through molecular sieve desiccant and is delivered to in-line oxygen analyzer. Both signals of flow rate and oxygen concentrations of room air and mixed air are converted to digital quantities and then stores in memory devices at 5 min interval. All measuring devices were assembled to small package which the subject carries on his back. The weight was about 7 kg. The memory chip is removed from the device after experiment and oxygen uptake is estimated by connecting the memory chip to a microcomputer. This measurement compared favorably with measurement with Douglas bag collection and gas analysis.

A simple exercise test with vertical jumping was developed for children. The vertical acceleration wave form of back was measured with strain gauge type transducer. After amplification and rectification, the signal of positive acceleration was converted to frequency with voltage-to-frequency converter (VFC) and VFC signals were decoded by a digital counter. The digital output was normalized by gravitational value and defined as physical activity rate. 10 young males and 24 schoolchildren jumped at several frequencies and oxygen uptake, physical activity rate and heart rate were measured. Also 28 children under school age jumped arbitrary and heart rate and physical activity rate were recorded. The results showed that the oxygen uptake per body weight had good correlation to the physical activity rate (r=0.95) . Although heart rate was significantly different with ages, physical activity rate which was defined as an index of exrecise test, was no significant difference with ages and weights (α<0.05) . The results indicated that this jumping test was helpful to make exercise stress test for younger children.