40/20 Workout Analysis

Thanks to @TKskate for the question on our 40/20 workout from February! This was a workout that @chris and I did as one of our structured sessions.

Near the end I talk about the HR response and being able to hit a high % of maximum HR. My max is 181 beats, and I peaked at 179 beats near the end of this workout. So looking at the graphs below, we can take a few things away that can be useful for planning your interval sessions:

  1. On a workout like this, check on how your HR responds. It can give you clues as to your readiness for the workout and suggest if there is any leftover fatigue, etc. You can see in the graph below how the HR rose relatively quickly and sustained well throughout each interval. This is a good indication that the body was pretty fresh. If HR failed to increase appropriately or took a long time, it would be a good indicator that another rest day is probably best before trying it again.

  2. This session was meant to work at >90% HR max. So that HR response helped to achieve ~20 minutes of good quality work to work on that VO2 max. When planning your sessions, start with something achievable (especially for Zone 5 work like this), maybe 8-12 minutes, and then work up from there. You can build your intervals based on the time you want to achieve and then splitting up as necessary to get the time. Remember that there will be some time for HR to achieve that plateau, which is why in this example below you will see 6 minute sets. This actually achieved ~5:30 of time in Zone 5 in the end.

  1. Erg mode vs. non-erg mode - this one I’m partial to non-erg mode because I like to maintain practice shifting gears to create the power on variable terrain. Chris did a fun test where he performed two sets on erg mode and two sets on non-erg mode. His graph is quite interesting because he was able to maintain his average power (per set) within 5 watts of his erg mode power. This speaks to his ability to pace himself well and know how hard to push. Check out his graph:

  1. The other point that I noticed with Chris’ session is that while his average power per set remained basically the same, he was hitting higher peak powers on the non-erg mode. You can see a different strategy here - on the second set, he started somewhat below the erg power, but then ramped up a bit higher on intervals 3, 4, and part of 5, before settling back in on the last interval. On the final set of the workout, he had an upward ramping power with a big, strong finish at the end.

Is one better than the other? Of course it depends (everyone’s favorite answer!). What I’ll suggest is that if you compare our graphs, you can see that I start out hard and then settle in over the course of the workout with a strong final set. Chris, having the ability to experience even pacing during half of the workout from the computer controlling his power, is able to finish strong. So depending on how well you know your body and can pace during high-intensity efforts, one or the other may be optimal for you.

Do you “peak and fade” typically? Maybe erg mode can help you better sustain an appropriate power to maintain consistently high power, and keep enough in the tank for the end of your event.

Do you tend to finish with a lot in the tank? Non-erg mode can be a great way to push your limits and find the edge. As you explore that, you can improve your pacing and find something deeper that you didn’t know you had.

Let’s hear your thoughts and questions!
Coach Ryan

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Hi @ryan - thanks! Could you clarify please your comment about 5:30 minutes in Z5? How’d you derive that number, and as my finance prof used to ask, does that make you happy or sad? (i.e. is it Z5 for HR and you have z5 defined as x% to y% and what are those %s? or is it Z5 for power that you’re referencing? Just want to make sure I’m interpreting correctly.)

haha! That time does me happy @TKskate!

So the ~5:30 time spent in Zone 5 came from checking my HR distribution and adding up the time spent per set. The initial ~30 seconds is where the HR was increasing to that target, so I didn’t count that time. So overall, that’s where the ~20 minute total comes from for the session.

For Z5 I’ll target 90% of max HR and then take everything above that into my total. When I check the power, it’s more like 16 minutes of time at Z5 or above. But HR is my primary target for accumulating the time.

Hi @ryan. So I did my 4x6 40-20 this morning. I get very little time above 90% HR, but some hints in the data, and would appreciate any comments - from the coaches or other Forum members. Overall, I tallied 3 minutes above 88% HR. I used 120% of 270 FTP = 325w as the target. Here are two pix, one of the whole 4 sets, and one just of the last set. I have drawn lines at target watts (dark yellow color) and at 90% of max HR (red). The 88% of max HR line would more or less lie atop the wattage target line, by coincidence, so I didn’t try to draw it. i did ERG - Not ERG - ERG - Not ERG for the sets.

Context: I haven’t done an FTP test in months. Xert has me a little higher, at 275, on no-decay, training-volume driven. Last week was a recovery week, following vEverest on 3-28 (all < LT1). Did 3 hour tempo-sweetspot on Saturday to end recovery week (~190 TSS). Got first vaccine shot Sunday. Rode an hour easy yesterday. My max HR in the past year is 174, but that was in a Zwift race in May, and I haven’t been back there since. Not sure I’ve hit 170 since. 60 years old. Yes, I have other more modern analysis software, but I’m fond of the old school PowerAgent charts :- :grin:

Hey Tom, thanks for sharing all the data. Curious to get other thoughts on this one, but a few areas that come to mind to start with would include:

  1. Vaccine - interestingly, I just had my vaccine (J&J) on Monday morning, so the one-and-done version. I planned this specifically coming off last week’s overload week/training camp knowing I would be resting most of this week. So vaccine on Monday, felt like :poop: on Tuesday, but had a training ride with my junior team Tuesday afternoon. I was able to ride - lower intensities felt spectacular, could have ridden like that for days. Although when we did our threshold efforts, the perception of the effort was high, and the HR response was abysmal. Normally I’ll get my HR up to around 158-163 for threshold intervals (max of 178-181 beats depending on recovery), but could barely reach 147 beats yesterday. HRV dropped 25%, and then bounced back to normal today. But during that ride, there was just a complete inability to go hard. It sounds like you have the 2-dose vaccine coming, and I’m not sure how the first dose affects performance, but just something to consider.

  2. Max HR - you say your max HR in the past year was 174 back in May, and not sure you hit 170 since then. If we’re using an older max HR of 174 to generate that 90% target, that may be too high now, especially if 170 has been hard to hit in recent months. Usually when I see athletes unable to hit their max HR or achieve a high % of it, I find that there is some fatigue still built in/left over. I’ll normally hit just shy of max (176-179 beats) near the end of a workout like this. The other consideration is that this is a hard session. How much of this type of work have you done in the past? I’ve been doing sessions like this for many years, so jumping into a 40/20 Tabata style session is easy for me these days (it doesn’t hurt any less, it’s just that I’m very accustomed to it!).

Thanks for the added data on this one. Looking forward to getting additional thoughts on it!

Thanks @ryan. The 1st dose of Pfizer - my guess is it causes less disruption than the J&J - so I’m not thinking that was my primary issue. But interesting to hear how much the J&J dose hit your HR, a day later.

I originally calculated my wattage targets based on 6-minute power, following some discussion in the Seiler Short Stacks video series. This conveniently worked out to 120% of FTP, but I got there through my Xert power curve. Seiler states that one can do these at 6-minute power or at 5-minute power, and offers some examples. If I, next week, move it up to 5-minute power, that would be 340 instead of 325, pretty close to 125% of an est 273 FTP. It will be interesting to see if I can complete the 4 sets at 15 watts higher, and what that would mean for the HR response. In the last set, not ERG, I felt like I had some dry powder, but … TBD.

Fatigue is a possible factor. I have an ongoing debate/discussion w my pal Dan about the training mix :grin: (Too long to insert here and complicate this thread.)

Experience with this format. I have some, having done structured winter training since 2007. But, to be fair, most of that has not focused on this type of format. And I’ve never viewed VO2 work as something I was good at; I’m more of a steady state rider. I might have 10 or so of these exact types of workouts in my history. I’ll report back next Tuesday!

Well, reporting back. I upped the wattage, as planned, and aimed at 340+, esp in sets 2-4. Pretty much got there. But HR was not higher. Oh well. Did all the sets not in ERG.

I don’t think it’s fatigue in a general sense, and my Elite HRV ‘readiness’ this morning was 9 out of 10. I think it probably has to do with the length of the efforts.

Couple of images below. Top is watts vs HR - definitely higher HR in sets 2-3 as I pushed higher watts 340-350. HR hitting high 80% (of what I think max is… but maybe max only shows for me in races). Set 4 a little ragged.

2nd chart is Garmin zone distr, where I have HR z4 at 88-95%. 2 1/2 minutes this morning, actually a decrease of 30s from last week. That, despite a large increase in time in Z6 power.

My plan is to move on to longer VO2 work next Tuesday, so I won’t be posting a 3rd example on this thread.

One good takeaway for me is that I found I performed better (higher watts) the 2nd week doing the same format. One expects this of course, as the first session sets a benchmark, and no surprise, but worth remembering, and part of the reason @ryan and @trevor advise to not vary workout formats every session.

Hi Tom, looks like a really solid set of intervals and glad you’re building in some consistency. I have noticed with shorter intervals like this, that heart rate tends to stay lower. When I give athletes 20x10s or 30x30s, it’s rare they will get much over threshold heart rate despite saying that they were ready to throw up by the end of the session.

Great job!

@trevor and @TKskate I’ll chime back in with some more data - not exactly 40/20, but 30/15 - close enough to continue the discussion. Interestingly, I did a metabolic test yesterday and happened to have some 30/15 efforts planned this week too. Now, comparing those 30/15s this week to previous efforts has been interesting. Quick background - I’ve always been more of a carb burning, sprinty-type of athlete that despises long, sustained rides and threshold efforts. However, to help with my N1 Challenge this year I decided to suck it up and really work that aerobic system.

Previous metabolic results from past years indicated that my maximum fat oxidation was around 0.4 g/min at a fairly low intensity, so I had a benchmark for yesterday’s test. It was a nice surprise to see that after a great couple of months working on my base, fat oxidation peaked around 0.8 g/min, suggesting that my aerobic capabilities have really improved. So knowing this going into a set of 30/15 intervals I was able to quickly see the HR response more closely resemble what Trevor has experiences. This is suggesting that those adaptations are taking place. Maybe I’ll actually start enjoying chasing @trevor on some really long, steady rides at some point this year! Here’s the interval session from this morning.

This is the first time I’ve done one of these workouts where the HR response did not go above threshold (dotted line), and the power was high (actually had an Xert breakthrough). So there are some cool things coming together to suggest that this focus on training appropriately and not hitting PRs in January is paying off.

For comparison, here’s a session from earlier this year.

You can see how the HR was very responsive and this is where I was spending most of my time above threshold.

With both of these sessions, I felt like I was pretty spent at the end, but the HR response is vastly different following this improved training structure to get ready for Breck Epic versus my usual approach of hitting it harder earlier in the year.

Very interesting, @ryan. Your first four or so 30:15 reps this morning look, i venture to say, pretty similar to the pattern on my charts: slowly increasing wave shapes. And it sounds like you’re saying now that after working the aerobic system to train for longer events, your HR is not hitting 90% of max (not sure exactly what the ‘threshold’ pink dashed line represents) on these 30:15s? So whether the rider exceeds 90% of max HR on these types of intervals may have to do with how the rider trains in general, as well as those other factors we considered earlier such as fatigue etc.?

@TKskate, so that dashed line (pink or red, I can’t really tell, but we’re talking about the same one) is my HR threshold. Earlier in the season I was hitting threshold and above on these 30/15 intervals pretty readily. HR would respond quickly and get right up there.

Now, having gotten some nice adaptations from the base training, the perceived effort seems appropriate, power is better, yet HR is not getting up there as quickly. If I saw the perception of the effort feeling out of balance for the power I was putting out or the quickness of the HR to respond, I would be more concerned about carrying too much fatigue, and overall training balance. However, the initial rise on that first interval from this week was pretty quick. The shape of the HR response wasn’t all that different from earlier in the season; it’s just that it’s not getting up to that same threshold line.

Here’s the other point though. I haven’t tested my threshold recently (except for the metabolic test I did the other day on the cart, which gave me VT1 and VT2) and I believe what is happening is that my maximum HR has declined somewhat as my aerobic fitness has improved, so that threshold line is probably set a bit on the high side. If I take those HR numbers I was hitting this week as a % of maximum (more like 170s versus 181 earlier in the year), then I’m hitting around 88-92% of maximum. What this is indicating is that it’s not time to hit some intensity, so it will be interesting too see as I lay off on the sub-LT work and do more HIIT, how the HR responds. It will be some of that give and take where one system is trained and the other falls away somewhat. And then finding the balance again. For my race in early May, it’s fairly short (50k), so want to have that top end to push hard and attack pretty regularly.

@ryan @TKskate interesting conversation. Ryan is definitely seeing what I see in athletes who are aerobically well trained. The interesting question for me is whether it is a sign that Ryan’s max and threshold heart rate have dropped (I do see that frequently,) or if his body is just better able to tolerate the aerobic demand of the workout better now.

I do thing the latter is definitely a factor. Notice in his old workout, heart rate barely declined during the 15 second recoveries, while in the newer workout there is a more pronounced decline each time (giving that sin wave.) That means that Ryan’s body is handling oxygen debt much better now and even the 15 second recovery is enough to start bringing heart rate back down.

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@trevor and @TKskate this has been a great discussion so far! To your point, Trevor, my threshold HR has dropped somewhat (still within my threshold range), but my max has not changed. I noticed this on a ride with my junior team the other day. We finished off the ride with a fun all-out ~40 second sprint (it hurt bad! :joy:). When I got to the top of the hill, my HR was right back up to max, which would support the notion of being able to tolerate the aerobic demand of the workout better now. And as a side note, I was really glad to see that I didn’t lose any top end either (not that a slight loss would mean much with HIE/W’ of 21kJ) and was still able to set a new 5s sprint PR that bests even my 2019-2020 sprint power when I was more “sprinty” and less “aerobic” in my training.

We did another team workout this week with 3 sets of 12x30/15s and you can see the same thing. The body is better able to tolerate that aerobic demand.

Heart rate over the 3 sets is more variable than what we might expect, but we were on MTB’s riding on snowy, muddy, highly variable terrain with corners and very short climbs and descents along the way. You’ll notice a relatively stable HR response on the whole, and to give an idea, over the first 2.5 sets I didn’t even get above 160 beats (threshold). Only in the last half of the last set did I push up into the mid 160s.

I’ll support Trevor’s notion of handling of oxygen debt too with the sensations in the legs and general performance - normally there are 3-4 members of the team that can easily out-ride me most of the time (they are 17 year old young bucks that just jam along!). However, the workout progression was very interesting. I saw in them exactly what my physiology was allowing me to do under normal circumstances in previous seasons. They all rode away from me on sets 1 and 2. On set 3, they were starting to fatigue and slow down as I was continuing to press on with the same effort. My legs never felt heavy or slow, and I ended up picking off 3 of them and finishing just behind the fastest junior on the team. So basically more power is being put out utilizing aerobic metabolism, recovery is better between efforts, and you can see that by the lower HR response.

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Great observations… I love how you’re using your workouts with the team to experiment and see what’s going on with your physiological responses.

The really really simple way I think of this is when we’re going hard, one of the few immediate responses our bodies have to maintain homeostasis is blood flow. So it raises heart rate. If our homeostatic and cardiovascular systems are underdeveloped, heart rate will sky rocket because that’s all the body can do to respond.

With aerobic adaptations we improve capillarization to working muscles, we increase blood volume, improve oxygen carrying capacity, increase stroke volume, and improve our muscles’ ability to use oxygen for energy. All this means that the heart can accomplish the same thing at much lower heart rates - particularly if stroke volume has been improved. So, with improved aerobic fitness, I’ve seen that it’s much harder for athletes to hit high heart rates. But as Ryan experienced, because so much more energy is being produced aerobically, the ability to do repeated hard work is improved.


hey so this is not exactly 40/20, but it is close, so i’m taking a crack at interpretation the way the rest of the contributors here have.

So this morning i did a Sufferfest workout video called Revolver. It’s 16x1 minute on, one minute off. Sufferfest presents this as a “Maximum Aerobic Power” workout (their version of Vo2max). Even though the on is a bit short and the off is a bit long, i chose this one as i haven’t really done much intensity yet this year (only a short threshold block), so this is a toe dip.

I based the interval targets off of a recent 4DP test, which was:

957 watts for the 5 second portion (don’t laugh)
376 for the 5 min
307 for the 20 min
558 for the 1 min at the end

I figured this workout would start out feeling easy (as i have decent ability to recharge the anaerobic battery), but that it would get hard halfway through. I used 380 watts for the target because i thought i sandbagged a bit on the 5 min (hence why i went higher than the test value).

In terms of heart rate, i had long operated under teh assumption that my max HR was about 200, so i use 180 as the 90% benchmark.

Execution notes:

  1. RPE felt about right, and with those longer rests, it didn’t get that hard until the last three, and even then, the outcome was never in doubt, it just hurt a bit more.
  2. HR didn’t get above 180 until the last three or four intervals, and maxed out at 186 in the final interval. It’s possible that my max HR is no longer 200 but in fact is more like 196 or 197 (the highest instantaneous heart rate i’ve seen in the past 365 days). If so, then i would have gotten a few more minutes at >90%, but not much.

This was a good workout but im’ not sure it really filled the bill in terms of accumulating those high intensity adaptations. I don’t think i was too fatigued as everything felt pretty okay, but heart rate never really got up that high, even accounting for the fact that my max could be more like 196, 197 or 198 rather than 200+.

My guess is the issue is that i’m kind of punchy; repeated, short high intensity efforts are not that hard but sustained high intensity efforts are. In other words, maybe the workout format was just not hard enough (at least, not hard in the way i need it to be hard) and that i’d be better off doing (i) longer intervals like traditional 5x5; (ii) something more like a 40:20 so the rest is shorter; and/or (iii) longer intervals just above FTP with shorter rests (like a 4x8 at 105% or 110%, my hr will get very close to max by the end).

I think i know how to do the 5x5 at this point, but i’m not sure i know how to execute that well on 40/20s. Often targets based on % FTP end up feeling too easy. Any advice on how to set a target starting point? (Of course we learn by doing, but im curious how best to even begin)

Hi @BikerBocker - great detail in your post. Seiler points out in the Short Stack video series that 1:1 rest isn’t likely to trigger high HRs, and 2:1 is better if that’s the aim. So, you could try a 2:1 format to see. Happy to post a Zwift ZWO for that if you like. But, as you may have read in my posts on this thread, even the 40/20 didn’t give me sustained high HRs, even at my self-perceived limit for the watts I could do them at (~125% FTP [i originally wrote 130% here-mis-remembered that]). That’s not to say they weren’t valuable, of course. OTOH, as you note, the longer efforts, e.g. 8 minutes a bit above FTP, generally do give me more accumulated time at the higher HRs. Yesterday, I did a 2x20 at FTP, with a push above in the last 5 minutes, and that got some sustained HRs during that last bit.

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Thanks for the helpful feedback, it’s much appreciated.

How did you set your target for the 40/20s? Just ballpark it and see what worked?

@BikerBocker - I watched the Seiler Short Stacks series and he talked about 5-minute and 6-minute power as typical targets. So, I started with the 6-minute, which was around 120% of FTP for me, and then after several workouts using that, moved to 125% (not 130%, I mis-remembered that, in my last post). 125% is close to my 5-minute power (according to my Xert power profile). Here’s a screen grab from the Seiler videos: image