Yeah that’s actually technically correct. The kinetics (rate of change ΔVO2/ΔPower) might not change per se (although it might actually get slower with increasing intensity, see below) at least within the severe intensity domain. The speed of the VO2 response will be faster for a hard-start because the higher power (↑ ΔPower) target stimulates a greater amplitude (↑ ΔVO2) of response, eg. trying to reach >100% VO2max, so it reaches the “real” amplitude of eg. 90% VO2max faster.
That being said, functionally if we were to evaluate ‘apparent’ VO2 kinetics of a hard-start interval, the kinetics would be modeled as being faster, since the real VO2 response will of course be clamped at 100% VO2max. This might be a limitation of monoexponential modeling of VO2 kinetics (one more fascinating paper down below).
It doesn’t change the intent of the protocol, but I’ve probably been saying the wrong thing that “VO2 kinetics get faster” when I should have been saying “the speed of the VO2 response increases”.
The ‘priming’ effect does increase the rate of VO2 kinetics, so that also plays a role, but more during subsequent intervals after the first, or after a warm-up.
I find the workouts I’ve created to be easier than Kaiser specifically in the last two intervals. They are harder in the initial intervals.
But it’s the last two intervals in the likes of Kaiser or Spencer that can cause me to “fail” the workout.
Hence why I created declining power targets in successive intervals. You can see in some of the workouts I’ve posted that my HR continues to rise with successive intervals, but I don’t get to the point in the last two intervals like I did with Kaiser where my heart is maxed out and can’t keep up.
The tau ‘speed of change’ shouldn’t change regardless of amplitude, even with the hard start. Though yes following intervals will be primed alright .
Actually did undergraduate research very similar to this. Was looking at the VO2 kinetics effects of priming in older and diabetic individuals vs healthy. The protocol was 2 min warm-up, 6min @80%Vt, followed by 6min @50%Δ, 10 min break (ideally would have been 6 but with diabetics and older more recovery needed and protocol needed to be kept consistent), and then repeat.
It was absolutely brutal. Only a couple made it through the full 6min of heavy intensity, think we need 3-4 mins data for analysis. Tau increased for ‘primed’ bout but RPE went through the roof .
Stats as follows for the flat 3.5 minutes in each interval:
Interval 1: HR 91% of max
2: 94%
3: 96%
4: 97%
Despite a lower IF for this workout vs. the 6x3.5 I did a couple of weeks back (0.91 vs. 0.94), this workout felt harder. But could also be I wasn’t as strong today vs. a couple of weeks ago.
I’ll add this workout to the team page when I get a chance.
Given its early season I should probably stick to base miles, so might be a while before I do another VO2max.
This isn’t a solid truth though, especially because even if your power degrades you might still be getting vo2max adaptations (won’t improve MAP but i don’t think that’s the point of this session, unless I missed that above somewhere).
Also, athletes learning to go as hard as they can go, even when the watts aren’t there, and still fighting through, is a great mental skill. I wouldn’t have them pull the plug based on that %…even low vo2max has benefit, esp if it’s cause you just smashed two or three hard ones previously.
Not challenging you, just another viewpoint on that chart.
VO2max is a weak point of mine (well one of them!) so @DaveWh’s workouts are very useful. I attempted the 6x3 yesterday and got to the third interval before my wife complained that the furniture in the house was shaking My legs were also a bit sore, probably DOMS from shifting a few tonnes of stone three days earlier.
Going over the data, I only had 3m30s above 90%MHR and the ramp rate (kintetics) of my HR response was probably part of that. I didn’t hit 90% until 2m30s in the first interval and 1m30 in the next two. I kept to the power for those three intervals pretty well - I’m on a dumb, wheel-on, trainer so no ERG mode. Cadence at the start of the intervals was 100-103rpm
My plan is to repeat this workout weekly over the next few weeks (I’ve added this as an extra workout to the Sustained Power Build plan) with the idea both to complete it* and improve my execution of it.
So tips? I’m significantly aerobically inclined - very much at the “light the blue touch paper … shall we go and have a cup of tea while we wait?” end of the spectrum. A bit of “man up” should see me doing more intervals but how do I improve the HR ramp rate?
*I’ll be doing it when my wife isn’t in the house!
I think it’s very hard to get it “right”, and there will always be a lag with HR!
Have you tried longer intervals?
Personally I find it much easier RPE & psychologically to execute 4x8min. The power is lower, the HR lag time is similar, so end up with a good amount of time at HR > 90% of MHR.
No, that was my first hard start workout but done a few of the “standard” stomp start workouts that drop back to just below FTP or even SS. Quite hard to hold power exactly so not a big difference between 110% and 106%, about 11W in my case.
Intervals.icu gives my HR lag as 55s. Also I’ve estimated my LHTR from various threshold intervals and my 90% MHR is within 1bpm of that value. Not sure if that is usual or I’ve got my figures wrong.
In the workouts I posted, I “designed” them to work for me - get my heart rate up quickly then hold it there for the remainder of the interval. - The workouts likely need to be tailored to better suit your physiology.
A few thoughts:
Increase the 110% (flat section of each interval) to a higher number.
And/or
Increase the interval duration.
I think both of these would allow you to get more time at high heart rate.
@SpareCycles also wrote some tips in the following post:
Ta. I’ve read the blog post but this is confusing:
A more ‘aerobic/slower-typology’ athlete can probably program the hard-start at a lower power target above their Threshold and/or for a shorter hard-start duration . Because they likely have faster VO2 onset kinetics and their Threshold is already at a higher percentage of their VO2max. Meaning they need less of a stimulus to get near VO2max.
I’m not sure if 55-90 seconds HR lag qualifies as “fast VO2 onset kinetics”
Maybe begin with 140% hard start dropping to 115% over 90 seconds then whatever length of hold. Star with workouts with 6x3, 5x4 and 4x5 sets. Sound about right?
I realised last night after posting that I’d confused/conflated HR lag with VO2 kinetics. But then further thought that HR lag could well be an indicator of the latter since HR would need to increase to supply the extra oxygen to the muscles.
Another point about my attempt was that my cadence during the recovery intervals was pretty low. A bit of a habit I’ve got into . I’ll raise that by 15rpm or so and keep the effort aimed at the cardio-vascular system.
What about adding a third segment below FTP after the tapered power?
For example: 90sec. hard start (135% FTP) / 3min Tapered Power (110% FTP) / 90sec (95% FTP).
I tried this and for me, during the 90sec. @ 95% FTP, my HR only falls slowly which leads to high durations above 90% HR max. At the same time it´s something like a “VO2 max over/under” that may potentially help with lactate processing. Just a thought…
Your second part here - the self-experimentation - is more important than the first part, IMO. Fast or slow is vague on purpose. It’s more about finding the balance of pacing for the interval that works best for you, given your goals for doing the workout and your physiological response.
Good question. I went down a brief rabbit hole to try and learn how HR kinetics correspond to VO2 kinetics. They are certainly related, but it seems to be that HR kinetics are more variable than VO2 kinetics. So the value of HR time response (say 55-90 sec) would not be a good predictor for VO2 time response. However a change in the former probably directionally indicates a change in the latter.
Good thought. Would definitely slow the recovery and maintain a higher VO2, HR, lactate, etc. metabolic flux for longer. Although taken to a logical end-point I think you’ve just re-invented continuous threshold training instead of interval training?
Ta. I’ve been going through most of the other posts on your blog
I think that the “long” recovery after the initial warm-up anaerobic bursts/efforts and before the first main interval is too long for me, my HR is way down so there’s more work to get things going. If we assume that 90%MHR is enough for 90%VO2max then I’m a couple of bpm down at the end of the descending power portion of the interval for all the intervals. So I need more work prior to that without too much stress.
I’ve had a play with Workout Creator and made a version of the 6x3 of my own: the initial peak isn’t quite so high but I stay there for 30 seconds before dropping. Hopefully this will get my HR to rise quicker without overstressing my muscles. I’ll see next week when I do it!
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But then further thought that HR lag could well be an indicator of the latter since HR would need to increase to supply the extra oxygen to the muscles.