Decreasing high intensity intervals are showing promising results that could make this format a popular option for high intensity training among cyclists.
If your competition shows up with a maximal oxygen uptake of 85 ml/min and your uptake is 60, chances are you will gett beaten.
Of the many training intensities that may drive development of your VO2 max, high intensity intervals are a popular choice. And to that end, decreasing high intensity intervals may be an interesting choice.
Photo credit: Shutterstock.com / Radu Razvan
What are decreasing high intensity intervals?
Decreasing high intensity intervals are what the name implies – bouts of high intensity efforts sequenced in such a way that your effort and recovery duration decreases for each bout.
4 min, 3 min, 2 min, 1 min and so on.
Vaccari and colleagues published the results from a study on decreasing high intensity intervals in the European Journal of Applied Physiology back in 2020 (1).
Their results are indeed intriguing.
What did they do?
The authors wanted to compare three different formats of high intensity interval training.
- long intervals (3 min work, 2 min recovery)
- short intervals (30 sec work, 20 sec recovery)
- decreasing intervals (* 3 min to 30 sec, 3:2 work:recovery ratio)
* decreasing intervals applied the following effort durations (recovery durations in brackets): 3 min (2 min), 2 min (1 min 20 sec), 60 sec (40s), 45 sec (30 sec), 30 sec (20 sec). The 30:20 sec effort was then repeated until exhaustion.
All three workout formats were performed until exhaustion. Importantly, they all applied the same ratio between work and recovery. They were all executed at the same constant power output (approx. 117% of critical power).
Specifically, the authors were interested in how much time cyclists accumulated at VO2 values > 90% of VO2 max. The reasoning behind this is the suggestion that spending time close to VO2 max is effective for improving your maximal aerobic capacity (1).
It has been shown that, to improve VO2 max, a training protocol should prolong the time at which the oxygen uptake remains close to the maximum (within 5-10% of VO2 max).Vaccari F et al. Eur J Appl Physiol 2020
Additional outcomes were time to exhaustion, blood lactate and rate of perceived exertion measured at time of exhaustion.
Participants executed each of the three workouts (in randomised order) with 2 days between each workout.
Who did they test?
Twelve amateur cyclists aged 29-62 years (mean age 41) partook in the experiment. They all reported at least 3 training sessions per week in the previous 6 months.
Their average VO2 max was 56,8 ml/kg/min indicate that they were a good bit below elite, and probably also below top amateur level. For comparison, Chris Froome has documented a VO2 max of 84 ml/min/kg few weeks after winning the Tour de France (2).
What did they find?
The decreasing high intensity intervals accumulated more time above 90% of VO2 max (312 sec) than did long (179 sec) and short intervals (183 sec). This difference (decreasing intervals vs. the other two) was statistically significant.
Interestingly, both the decreasing and long intervals resulted in the cyclists reaching 90% of their VO2 max quicker than did the short intervals. However, a notable difference was that decreasing intervals allowed riders to more effectively remain above 90% of VO2 max. Whereas during the long intervals, riders would more often fall below the 90% mark (during the recovery periods and initially during next effort).
It is also worth noting that at the end of the session, the athletes rated the 3 workouts as equally tough. Indeed, there were no differences in blood lactate, rate of perceived exertion, heart rate or VO2 when measured at complete exhaustion. Time to exhaustion, which illustrates the duration of each workout was also similar between the three workouts.
Why does decreasing intervals yield higher time >90% of VO2 max?
The authors does present some thoughts on this.
They argue that muscle oxygen consumption is related to depletion of phosphocreatinine (PCr) in working muscle.
Very briefly explained, PCr is involved in making energy (ATP) available to working muscles. During muscular work, PCR is reduced. The authors argue that the faster the depletion of PCr, the higher the oxygen consumption (VO2).
The idea is that by starting with a longer interval, you will more quickly deplete your PCR. And therefore more quickly reach a higher oxygen consumption (VO2) than if the first interval is a short one.
Secondly, PCr is replenished during recovery. So if you want to promote PCr depletion, it makes sense to keep the recovery periods short (as opposed to long).
All this presents an obvious practical question:
Modifying your interval and recovery durations to promote PCr depletion (and thereby oxygen consumption) is all well and good. As long as you are still able to carry out the remaining workout at the targeted intensity.
And that is precisely what makes this study interesting.
Furthermore, the decreasing high intensity interval format allowed for a longer time to exhaustion than the long and short intervals. In short, riders could keep their interval session going for longer before bonking.
This would of course also contribute towards the higher time on >90% of VO2 max.
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As always, you should soberly consider potential limitations of a study.
For starters, this study was performed on trained subjects only. So probably not the strongest weekend warriors, and definitely not pros. So we cannot conclude if the results would look different in a more highly trained group.
Secondly, the sample size of twelve riders is not massive. This is customary to many experiments in sports science – it is challenging to recruit a large number of relevant subjects. So we need to interpret the results with some caution.
That being said, the same authors repeated a similar experiment on nine track runners (3). Again, time above 90% of VO2 max was significantly longer with decreasing high intensity intervals (998 sec) than with long (673 sec) and short intervals (678 sec). The fact that they repeated the same results with different subjects, and in a different sport, makes it less likely that their results were a one off.
Finally, keep in mind that these studies had no follow-up period. As such, we cannot conclude that this workout leads to superior performance in the long run. Instead, based on existing knowledge about mechanisms and adaptation, we can speculate that the high duration on high VO2 max values could be beneficial in the long run.
An additional perspective is that some colleagues in the sports science world has pointed out that the association between time at close-to-VO2 max and performance improvements may not necessarily be super strong. Which again suggests that we’re relying on a bit of an assumption in terms of mechanisms and effect here. So do take this into consideration when applying these results.
This study adds to the research I have previously discussed on fast-start intervals and short intervals. Collectively, these studies adds to your knowledge of how you can manipulate duration, intensity and recovery periods in search of your desired training stimulus.
Summary of take-aways
It is commonly accepted that cycling at a high percentage of VO2 max (above 90% of VO2 max) is an effective way of stimulating a higher maximal oxygen consumption.
Two recent studies indicate that descending intervals may be an efficient format to maximise the time you spend above 90% of VO2 max during high intensity training.
The long-term effect of this interval session has yet do be demonstrated in the literature. However, the be an interesting one to experiment with if you’re in the market for higher VO2 max – or if you simply need some variation from your regular interval formats.
- Vaccari F et al. High-intensity decreasing interval training (HIDIT) increases time above 90% of VO2 peak. European Journal of Applied Physiology, 2020;120:2297-2405
- Bell PG et al. The physiological profile of a multiple Tour de France winning cyclist. Medicine & Science in Sports & Exercise, 2017;49(1):115-123
- Vaccari F et al. High-intensity interval training: optimizing oxygen consumption and time to exhaustion taking advantage of the exponential reconstitution behaviour of D’. European Journal of Applied Physiology, 2023;123:201-209