MEASUREMENT OF VENTILATORY THRESHOLD BY RESPIRATORY FREQUENCY

SronmaY.-This study was conducted to assess whether respiratory frequency can be used as a valid parameter €or estimating ventilatory threshold and for examining differences in exercise modes such as a cycle ergometer and a treadmill. 24 men and 12 women performed an incremental exercise test to exhaustion on a cycle ergometer and on a treadmill. Oxygen uptake, carbon dioxide output, pulmonary ventilation, ventilarory frequency, and heart rare were measured continuously every 30 sec. during the test. Three d~fferent and independent reviewers detected the ventilatory threshold point and break poinr of respiratory rate, which were then compared. Analysis indicated that (1) venulatory threshold was well correlated with break poinr of respiratory rate for both cycle (r = .88, p< ,001) and treadmill exercise (r = .96, p< ,001). However, on the average, ventilatory threshold was only 71% (cycle) or 88% (treadmill) of break point of respiratory rate. (2) The regression equation for treadmill exercise was more accurate than that for cycling, bur the detected data samples were smaller. The break poinr of respiratory rate was more easily detected €or the cycle ergometer test (33 of 36 subjects) than for the treadmill test (only 15 of 36). The cycle ergometer test identified the break point of respiratory rate more easily than did the treadmill test. (3) There was an association benveen physical fitness and whether the break point of respirarory rate was detectable, and the more fir the subject (above average), the more likely the break point was to be underected. Our study demonstrates that the break point of respiratory rate is closely associared with ventilarory threshold and that the cycle ergometer test is more conducive than the treadmill test to the detectability oE break poinr of respiratory rate.