Comparison of physiological strain and muscular performance of athletes during two intermittent running exercises at the velocity associated with VO(2)max

The purpose of this study was to examine physiological strain and muscular performance responses of well trained athletes during two intermittent runn ing exercise protocols at the velocity associated with (V) over dot O(2)max . Ten national level middle-distance runners ((V) over dot O(2)max 69.4 +/- 5.1; mean +/- SD) performed in random order two 28 min treadmill running e xercises: 14 bouts of 60 s runs with 60 s rest (IR60) and 7 bouts of 120 s runs with 120 s rest between each run (IR120). During IR120 peak oxygen upt ake (12 %), peak heart rate (3 %) and peak blood lactate (79 %) were signif icantly higher than during IR60 (P < 0.001) and almost the same as in the ( V) over dot O(2)max test. In IR120 the relative aerobic energy release calc ulated on the basis of the accumulated oxygen deficit during the running bo uts was significantly higher than in IR60 (81.5 +/- 2.7 vs. 70.2 +/- 2.6 %, P < 0.001) likewise the sum oxygen consumption during the 14 min running ( P < 0.001), while during the 14 min recovery it was as much lower (P < 0.00 1). There were no changes either during or between the IR60 and IR120 proto cols with regard to the muscular performance parameters, stride length or h eight of maximal vertical jumps. In conclusion, during intermittent running at the velocity associated with (V) over dot O(2)max doubling the duration of work and rest bouts from 60 s to 120 s increased the physiological stra in of well trained athletes to the same level as at exhaustion in the (V) o ver dot O(2)max test but the muscular performance variables were not influe nced.