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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.

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.