The aim of this study was to analyze the effects of recovery mode (active/passive) on time spent at high percentage of maximal oxygen uptake (VO2max) i.e. above 90% of VO2max (t90VO2max) and above 95% of VO2max (t95VO2max) during a single short intermittent session. Eight endurance-trained male adolescents (15.9 +/- 1.4 years) performed three field tests until exhaustion: a graded test to determine their VO2max (57.4 +/- 6.1 ml min(-1) kg(-1)), and maximal aerobic velocity (MAV; 17.9 +/- 0.4 km h(-1)), and in a random order, two intermittent exercises consisting of repeated 30 s runs at 105% of MAV alternated with 30 s passive (IE(P)) or active recovery (IE(A), 50% of MAV). Time to exhaustion (t(lim)) was significantly longer for IE(P) than for IE(A) (2145 +/- 829 vs. 1072 +/- 388 s, P < 0.01). No difference was found in t90VO2max and t95VO2max between IE(P) (548 +/- 499-316 +/- 360 s) and IE(A) (746 +/- 417-459 +/- 332 s). However, when expressed as a percentage of t(lim), t90VO2max and t95VO2max were significantly longer (P < 0.001 and P < 0.05, respectively) during IE(A) (67.7 +/- 19%-42.1 +/- 27%) than during IE(P) (24.2 +/- 19%-13.8 +/- 15%). Our results demonstrated no influence of recovery mode on absolute t90VO2max or t95VO2max mean values despite significantly longer t(lim) values for IE(P) than for IE(A). In conclusion, passive recovery allows a longer running time (t(lim)) for a similar time spent at a high percentage of VO2max.

The purpose of our study was to compare time to exhaustion ( t(lim)) and time spent at a high level of oxygen uptake (V(.)O(2)) during two high-intensity short intermittent exercises (30 s-30 s) realized with or without series. Eleven young endurance-trained athletes [16.6 (0.4) years] took part in three field tests until exhaustion: (1) a maximal graded test to measure their maximal aerobic velocity (MAV) and maximal oxygen uptake (V(.)O(2max)); (2) and (3) two randomized intermittent exercises (30 s at 110% of MAV alternated with 30 s at 50% of MAV): one alternating repetitions non-stop (IE) and another including 4 min recovery every six repetitions (IEs). The mean t(lim) measured during IEs was significantly longer than IE [respectively 960.0 (102.0) s vs 621.8 (56.2) s]. The time spent at V(.)O(2max)( t(V(.)O2max)) and the time spent above 90% of V(.)O(2max)( t(90%V(.)O2max)) did not differ significantly according to the type of exercise: with or without series [respectively t(V(.)O2max) was 158.2 (59.7) s vs 178.0 (56.5) s and t(90%O2max) was 290.4 (84.3) s vs 345.0 (61.6) s] but when expressed as a relative value, t(90%O2max) during IEs was significantly lower than during IE [respectively 36.4 (10.4)% t(lim) vs 58.3 (8.7)% t(lim)]. Despite a significant decrease ( P<0.005) of time to achieve 90% of V(.)O(2max) at the start of each series during IEs [respectively 165.0 (43.1) s for the first series and 82.5 (15.8) s for the second series ( n=6)] the time spent under 90% of V(.)O(2max) limited the t(90%V(.)O2max) during each series. In conclusion, our results showed that intermittent exercise with series does not permit an increase in the time spent at a high level of V(.)O(2); however, the athletes performed more repetitions of short intense exercise.

In this study, we examined the effects of three recovery intensities on time spent at a high percentage of maximal oxygen uptake (t90[Vdot]O(2max)) during a short intermittent session. Eight endurance-trained male adolescents (16 +/- 1 years) performed four field tests until exhaustion: a graded test to determine maximal oxygen uptake ([Vdot]O(2max); 57.4 +/- 6.1 ml x min(-1) . kg(-1)) and maximal aerobic velocity (17.9 +/- 0.4 km x h(-1)), and three intermittent exercises consisting of repeat 30-s runs at 105% of maximal aerobic velocity alternating with 30 s active recovery at 50% (IE(50)), 67% (IE(67)), and 84% (IE(84)) of maximal aerobic velocity. In absolute values, mean t90[Vdot]O(2max) was not significantly different between IE(50) and IE(67), but both values were significantly longer compared with IE(84). When expressed in relative values (as a percentage of time to exhaustion), mean t90[Vdot]O(2max) was significantly higher during IE(67) than during IE(50). Our results show that both 50% and 67% of maximal aerobic velocity of active recovery induced extensive solicitation of the cardiorespiratory system. Our results suggest that the choice of recovery intensity depends on the exercise objective.