We can see that there were two people who seemed to respond really well to the progressively decreasing design. However, for all other participants, the effect was more modest, and in fact there were 4/12 participants where the progressively decreasing interval design wasn’t the most favourable.
Another limitation is that the intensity used in the ‘recovery’ intervals was really quite high (roughly 83% critical power, which would translate to nearly 90% FTP). This was chosen in order to keep oxygen consumption high while still allowing some recovery and ‘re-charging’ of W’.
So while at first glance, this study appears to compare the progressively decreasing design to two fairly classic VO2max sessions, the abnormally high intensity used for the recoveries limits the comparability with these well-used interval designs.
Indeed, as the authors of the study acknowledge, other research, has shown short ‘microburst’ type intervals to be more favourable than long intervals in increasing time to exhaustion and time above 90% VO2max, which is in disagreement with the findings of the present study. The present study also used a 3:2 work:recovery ratio rather than the 2:1 ratio that’s normally used for short microburst intervals, which may also account for some of the differences seen.
Finally, it’s worth noting that this study only looks at time spent training close to VO2max, and doesn’t investigate which interval design actually results in the best improvements in VO2max. It’s often assumed that spending time near VO2max is a good way to develop this key fitness attribute. However, we also know that other types of training – such as long, low-intensity riding – are also great ways to build VO2max. So it doesn’t necessarily follow that more time at VO2max = better improvements in VO2max.
Our Take-Aways
1. Evidence is promising for progressively-decreasing efforts
The progressively decreasing interval design is one we’ve seen suggested on a few occasions previously. In particular, the concept of shortening your recovery interval to only as much time as is necessary to recover has been suggested when using a Moxy (or other near infrared spectroscopy) device, which can measure oxygen supply at the muscles. It’s good to see some scientific research backing up this training approach. More recently, we’ve seen the results of this study largely replicated among runners, giving us some extra confidence in this training approach.
Overall, it’s definitely an interesting interval design, based on good physiological theory, and is something we’ll be experimenting with over coming weeks. We’re also considering adding the session to our Complete Workout Library once we’ve done some of our own testing (so watch this space!).
2. How to structure session in practice
It’s interesting to note that the amount of time the participants were able to sustain the intervals before they reached exhaustion was surprisingly low for all protocols (roughly between 10-13 minutes). In practice, you’d probably look to include perhaps 2x blocks of intervals, with a longer period of recovery between, in order to allow more total training time spent close to VO2max overall.
A session we’ll be testing and finessing will look something like:
2x blocks of:
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3M hard 2M easy
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2M hard 1M20S easy
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1M hard 40S easy
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30S hard, 20S easy
Where the hard intervals are done at roughly 110-125% FTP or 5-min max power and the easy intervals are done around 80% FTP.
5-mins gentle recovery between blocks.
We’re proposing to skip the 45-second interval that preceded the 30-second interval in the present study. This is in order to simplify the design, and also slightly shorten each block of efforts so that people hopefully aren’t going completely to the point of exhaustion at the end of each block.
3. Individual Variability
As mentioned in relation to the study limitations, there was considerable variability in terms of how different athletes responded to the three types of session. This highlights the importance of including some variety in your training (although you should avoid including too much variety as this makes it hard to gauge progress and refine your pacing strategy!).
In addition, it’s worth noting that there was also wide variation in the percentage of critical power at which the efforts were paced. The hard intervals were pitched at each participant’s estimated 5-min maximal power. The standard deviation in workloads was 6%, which means that the majority of participants had a workload ranging between 111% to 123% of critical power. This is quite a broad range in and of itself. In addition, a minority (roughly 4-5/12 participants) will have had powers that were above or below this range.
It’s always really important to individualise your interval sessions to suit your own physiology and abilities. We have an article on methods you can use to do this here. A good strategy for this particular session would be to use data from a 5-min max effort to pace your work intervals.