Time to Exhaustion at Continuous and Intermittent Maximal Lactate Steady State During Running Exercise

The purpose of this study was to determine and compare the time to exhaustion (TE) and the physiological responses at continuous and intermittent (ratio 5:1) maximal lactate steady state (MLSS) in well-trained runners. Ten athletes (32.7 +/- 6.9 y, VO2max 61.7 +/- 3.9 mL center dot kg(-1) center dot min(-1)) performed an incremental treadmill test, three to five 30-min constant-speed tests to determine the MLSS continuous and intermittent (5 min of running, interspaced by 1 min of passive rest), and 2 randomized TB tests at such intensities. Two-way ANOVA with repeated measures was used to compare the changes in physiological variables during the TE tests and between continuous and intermittent exercise. The intermittent MLSS velocity (MLSSint, = 15.26 +/- 0.97 km/h) was higher than in the continuous model (MLSS. = 14.53 +/- 0.93 km/h), while the 1.E at MLSSCOfl was longer than MLSSint (68 11 min and 58 15 min, P <.05). Regarding the cardiorespiratory responses, V02 and respiratory-exchange ratio remained stable during both TB tests while heart rate, ventilation, and rating of perceived exertion presented a significant increase in the last portion of the tests. The results showed a higher tolerance to exercising during MLSSCOfl than during MLSSint in trained runners. Thus, the training volume of an extensive interval session (ratio 5:1) designed at MLSS intensity should take into consideration this higher speed at MLSS and also the lower TB than with continuous exercise.