Correlation between ventilatory threshold and endurance capability in marathon runners

The purpose of the study was to develop an index of endurance capability i.e., "the ability to sustain a high fractional utilization of maximal oxygen uptake (VO2max) for a prolonged period of time"]. The index was based on the linear reduction of fractional utilization of VO2max with total running time greater than 7 min plotted on a log scale. The endurance index estimated from VO2max, running efficiency and the marathon performance of 18 male runners (30 +/- 7 yr old; VO2max = 66 +/- 5 ml.kg-1.min-1) ranged between -4.07 and -9.96% VO2max.1 nt-1 (mean +/- SD = -6.40 +/- 1.50) and was not related to VO2max (r = 0.107) or speed in the marathon race (r = 0.354). However, the endurance index was closely related (r = 0.853) to the fractional utilization of VO2max at ventilatory threshold (breakaway of the excess CO2 elimination curve) which occurred at 76.1 +/- 5.5% VO2max in response to a graded treadmill test. These results indicate that: (i) running time on long distance races is not, per se, an adequate measure of endurance capability because of the major contribution of VO2max to long distance running performance; (ii) the endurance index expressed as %VO2max.1n t-1 is an objective and independent index of endurance capability; and (iii) runners with a high endurance capability tend to hyperventilate at higher relative workload during a graded treadmill test.