Since the 1950s and the "interval-training" made popular by Emil Zatopek, an emblematic figure of this method, intermittent training, by opposition to continuous effort, has kept on expanding. Various purposes can be correlated to such a development, but the so-called intermittent training is most commonly associated to the development of athletes' aerobic potential. In this frame, several authors have proved that intermittent effort was more efficient than continuous effort. Indeed, Gorostiaga et al. (1991) demonstrated that the VO2max increase was significantly higher after 24 sessions of intermittent training (30s~30s at 100% of VO2max) than after a continuous effort at 50% of VO2max. In the same way, Billat et al. (2000), comparing two continuous and discontinuous sessions performed at the same mean strength, revealed that the discontinuous session enabled to make use of VO2max three times as longer as the continuous one. The efficiency of intermittent effort does not seem to be questionable. However, the multiple forms deriving from this training basis can vary depending on the sequence intensity or duration and the recovery time length. The experimental work proposed aims at characterising the sessions in relation to certain modalities of the sequence duration and intensity. We intentionally oriented our study towards the trainer's perspective, in order to compare: one session of VO2max development on slopes, and two flat race sessions. One of these two sessions repeats the duration of the slope training effort (i.e. 1 min30), the other corresponds to a "classic" session of short intermittent effort (30s~30s). Methods: 9 high level middle-distance runners (specialised in 800 to 10000m) took part in the experiment. They were all very well and regularly trained, among others, for the three considered forms of sessions. They accepted to partake in the following protocol: 1) VO2max and MAS evaluation test (adapted TUB 2) 2) VO2max development session on slopes (4 to 5 %), which consisted in running 500m, 6 times, at 85% of the estimated MAS on the flat; Recovery time of 1min30. 3) VO2max development session on the flat / long intervals, which consisted in 6 times 600m at 102% of MAS, with the goal of reproducing as closely as possible the slope session. 4) VO2max development session on the flat / short intervals, which consisted in a 20min run with 30s fractions in turns, respectively, at 105% and at 50% of VO2max. The rhythm of the sessions is imposed and graded thanks to a sound bip and plot generator device every 50m. Sessions 3 and 4 are carried out in arbitrary order. All subjects of the experience are equipped with a portable gas analyser (K4, Cosmed, Italy) which enables to record the ventilatory parameters, among which VO2, as well as with a heart rate monitor. Two cameras (50Hz) allow to characterise the strides frequency and amplitude at the beginning (50m after the starting point) and at the end (50m before the end point) for each fraction. The ground contact duration is estimated within about 10ms. For each session, a blood sample is taken when the effort is stopped, as well as 3min after the last fraction. The total time lengths spent at more than 95 and 98% of VO2max during the effort sequences were chosen in order to compare the energetic impact of the various sequences. The average VO2max (effort sequences + recovery sequences) is also presented as an element of comparison between sessions. Results: VO2max Evaluation: the TUB2 test enabled to assess an average VO2max for this group of 73 + 4.7 mlO2.mn-1.kg-1. The maximal aerobic speed (MAS) was estimated for all subjects at 21 or 22 km.h-1, based not on the VO2 actually recorded but on the VO2 estimated from the last stage speed. Discussion: We must notice that the estimated MAS values are significantly different from those calculated by the K4 (minimal speed requiring VO2max). This difference was particularly overestimated for the 800m runners who were more capable of using their anaerobic metabolism towards the end of the test. It appears that the 6*600m flat, at 102% of MAS was the most demanding session (45 vs. 2 vs. 9% of the effort fractions were spent at more than 95% of VO2max for, respectively, 6*600mflat, 6*500mslope, and 30s~30s). Gorostiaga et al. (1991) as well as Millet et al. (2000) had established that a 30s~30s session at 100% of MASmax could not allow to reach VO2max. It turns out, according to Millet et al. (2000), that it is the same for a session at 105% at MAS, what our study confirms for a total effort of 20min. Nevertheless, if we take into account the total duration of the session (effort + recovery), the mean impact of this session (30s~30s) is superior to the other assessed sessions': 59,3 mlO2.mn-1.kg-1, 49,5 (6*500mslopes) 55,07 (6*600mflat). It also appears that the lactate blood concentration towards the end of the session is higher for the 6*600flat compared to the others': 12.7 mmol.l-1 against 8 mmol.l-1 for both the other sessions. Finally, the bio-mechanical parameters of the stride vary with the sessions: the ground contact duration is longer for the 6*500mslope, the amplitude greater for the 6*600mflat and the frequency more important for the 30s~30s.
© Copyright 2002 Expertise in Elite sport. 2nd International Days of Sport Sciences, 12.-15. November 2002, INSEP, Paris (France). Veröffentlicht von INSEP. Alle Rechte vorbehalten.