Effect of a previous sprint on the parameters of the work-time to exhaustion relationship in high intensity cycling.

The relationships between both metabolic (E) and mechanical (W) energy expended and exhaustion time (t(e)), was determined for 11 well-trained subjects during constant load cycloergometric exercises at 95, 100, 110, 115 % maximal aerobic power performed both from rest and, without interruption, after an all-out sprint of 7 s. These relationships were well described by straight lines: y = a + bt(e), where b was taken as the critical power (metabolic and mechanical) that can be sustained for long periods of time. b was unaffected by the exercise conditions and amounted to 82 - 94 % of maximal aerobic metabolic and mechanical power. The constant a was taken as the anaerobic stores capacity in excess of the O2 deficit. When the test was preceded by the sprint, a (metabolic and mechanical) was reduced to about 60 - 70 % of control values. This reduction was essentially equal to the corresponding E and W output during the sprint. These data support the view that the slope of linear regressions of E and W on t(e) is indeed a measure of the critical power, whereas the y intercept of these same regressions is a measure of the anaerobic capacity.

Very short (15s-15s) interval-training around the critical velocity allows middle-aged runners to maintain VO2 max for 14 minutes.

The purpose of this study was to compare the effectiveness of three very short interval training sessions (15-15 s of hard and easier runs) run at an average velocity equal to the critical velocity to elicit VO2 max for more than 10 minutes. We hypothesized that the interval with the smallest amplitude (defined as the ratio between the difference in velocity between the hard and the easy run divided by the average velocity and multiplied by 100) would be the most efficient to elicit VO2 max for the longer time. The subjects were middle-aged runners (52 +/- 5 yr, VO2 max of 52.1 +/- 6 mL x min(-1) x kg(-1), vVO2 max of 15.9 +/- 1.8 km x h(-1), critical velocity of 85.6 +/- 1.2% vVO2 max) who were used to long slow distance-training rather than interval training. They performed three interval-training (IT) sessions on a synthetic track (400 m) whilst breathing through the COSMED K4b2 portable metabolic analyser. These three IT sessions were: A) 90-80% vVO2 max (for hard bouts and active recovery periods, respectively), the amplitude= (90-80/85) 100=11%, B) 100-70% vVO2 max amplitude=35%, and C) 60 x 110% vVO2 max amplitude = 59%. Interval training A and B allowed the athlete to spend twice the time at VO2 max (14 min vs. 7 min) compared to interval training C. Moreover, at the end of interval training A and B the runners had a lower blood lactate than after the procedure C (9 vs. 11 mmol x l(-1)). In conclusion, short interval-training of 15s-15s at 90-80 and 100-70% of vVO2 max proved to be the most efficient in stimulating the oxygen consumption to its highest level in healthy middle-aged long-distance runners used to doing only long slow distance-training.

Effect of a prior intermittent run at vVO2max on oxygen kinetics during an all-out severe run in humans.

BACKGROUND: The purpose of this study was to examine the influence of prior intermittent running at VO2max on oxygen kinetics during a continuous severe intensity run and the time spent at VO2max. METHODS: Eight long-distance runners performed three maximal tests on a synthetic track (400 m) whilst breathing through the COSMED K4 portable telemetric metabolic analyser: i) an incremental test which determined velocity at the lactate threshold (vLT), VO2max and velocity associated with VO2max (vVO2max), ii) a continuous severe intensity run at vLT+50% (vdelta50) of the difference between vLT and vVO2max (91.3+/-1.6% VO2max)preceded by a light continuous 20 minute run at 50% of vVO2max (light warm-up), iii) the same continuous severe intensity run at vdelta50 with a prior interval training exercise (hard warm-up) of repeated hard running bouts performed at 100% of vVO2max and light running at 50% of vVO2max (of 30 seconds each) performed until exhaustion (on average 19+/-5 min with 19+/-5 interval repetitions). This hard warm-up speeded the VO2 kinetics: the time constant was reduced by 45% (28+/-7 sec vs 51+/-37 sec) and the slow component of VO2 (deltaVO2 6-3 min) was deleted (-143+/-271 ml x min(-1) vs 291+/-153 ml x min(-1)). In conclusion, despite a significantly lower total run time at vdelta50 (6 min 19+/-0) min 17 vs 8 min 20+/-1 min 45, p=0.02) after the intermittent warm-up at VO2max, the time spent specifically at VO2max in the severe continuous run at vdelta50 was not significantly different.

Intermittent runs at the velocity associated with maximal oxygen uptake enables subjects to remain at maximal oxygen uptake for a longer time than intense but submaximal runs.

Interval training consisting of brief high intensity repetitive runs (30 s) alternating with periods of complete rest (30 s) has been reported to be efficient in improving maximal oxygen uptake (VO2max) and to be tolerated well even by untrained persons. However, these studies have not investigated the effects of the time spent at VO2max which could be an indicator of the benefit of training. It has been reported that periods of continuous running at a velocity intermediate between that of the lactate threshold (vLT) and that associated with VO2max (vVO2max) can allow subjects to reach VO2max due to an additional slow component of oxygen uptake. Therefore, the purpose of this study was to compare the times spent at VO2max during an interval training programme and during continuous strenuous runs. Eight long-distance runners took part in three maximal tests on a synthetic track (400 m) whilst breathing through a portable, telemetric metabolic analyser: they comprised firstly, an incremental test which determined vLT, VO2max [59.8 (SD 5.4) ml.min-1; kg-1], vVO2max [18.5 (SD 1.2) km.h-1], secondly, an interval training protocol consisting of alternately running at 100% and at 50% of vVO2max (30 s each); and thirdly, a continuous high intensity run at vLT + 50% of the difference between vLT and vVO2max [i.e. v delta 50: 16.9 (SD 1.00) km.h-1 and 91.3 (SD 1.6)% vVO2max]. The first and third tests were performed in random order and at 2-day intervals. In each case the subjects warmed-up for 15 min at 50% of vVO2max. The results showed that in more than half of the cases the v delta 50 run allowed the subjects to reach VO2max, but the time spent specifically at VO2max was much less than that during the alternating low/high intensity exercise protocol [2 min 42 s (SD 3 min 09 s) for v delta 50 run vs 7 min 51 s (SD 6 min 38 s) in 19 (SD 5) interval runs]. The blood lactate responses were less pronounced in the interval runs than for the v delta 50 runs, but not significantly so [6.8 (SD 2.2) mmol.l-1 vs 7.5 (SD 2.1) mmol.l-1]. These results do not allow us to speculate as to the chronic effects of these two types of training at VO2max.