Ventilatory thresholds during short- and long-term exercise.

The ventilatory (anaerobic) threshold for short-term exercise was defined as the work rate or O2 uptake (VO2) immediately below the work rate at which ventilation increased disproportionately relative to work rate or VO2, and the ventilatory threshold for long-term exercise as the work rate or VO2 immediately below the work rate at which ventilation continued to increase with time rather than attain a steady state. The purpose of the present study was to investigate how both thresholds relate to each other and how they relate to other measures of physical performance capacity. The subjects were eight healthy males, 20-53 yr of age. Maximal performance capacity was estimated by measurements of maximal O2 uptake (VO2 max) and by endurance performance during a 12-min distance run. A high interrelationship was found between the two thresholds (r = 0.84), and each threshold expressed in VO2 (ml X min-1 X kg-1) correlated highly with VO2 max (r = 0.87 and r = 0.75, for short-term and long-term exercise, respectively). When the two thresholds were expressed as a percentage of VO2 max, neither threshold showed a significant relationship with VO2 max. Endurance performance was significantly correlated with both the ventilatory threshold for short-term and long-term exercise (r = 0.73 and 0.82, respectively). A stepwise multiple regression analysis indicated that the distance run in 12 min was best predicted by VO2 max (R2 = 0.66) or the ventilatory threshold for long-term exercise (R2 = 0.63). It is concluded that the ventilatory threshold for long-term exercise is a more specific measure to explain running performance than is the threshold during graded exercise.