4x4 min Workout - Proper Pacing

Despite my not being a fan of steady efforts, I had a great time joining @ryan & @trevor on their 4x4 workout today. All three of us will post our files here to show 2 examples of where we were really recovered & ready for the workout, and 1 example where we were clearly not recovered.

Really valuable doing these NOT on Erg mode and freestyling, The Zwift Beach Front loop is ideal because of minimal elevation changes, or else just set your trainer to a 2% grade resistance.

My workout was super successful. Here are some observations:

  • All 4 efforts perfectly paced and even, both within an effort and across all 4. I averaged 265-268W for them.
  • Last was actually the best one at 268W average, though I did slump over the bars at the end.
  • HR was super responsive, rising quickly. My HRmax is about 158-160, and I hit 147, 147, 150, 150 on the 4.
  • Note how easy the 3 min recovery wattages were. Averaged about 70-80 W. A big mistake is going too hard during these recoveries.

It was great incorporating the systematic warmup to wake the legs up.

Have fun with this workout. Thanks for getting me out of my comfort zone!

Stephen Cheung


Thanks for posting @ThermalDoc! It was great having you join us today!

Here’s my file:

Couple take-aways from this one:

  1. I had a similar HR ramp, suggesting that I was good and ready for a hard session overall. Legs could have felt a little better, but everything else was pointing to being prepared.
  2. Pacing was solid (317w, 324w, 317w, 321w). The second one where I suggested we start only by feel you can see where I went a bit too hard and it took a few seconds to dial into the effort. This is a good reminder that this is something to continuously work on because of how easily we can go out too hard.
  3. HR max is 181. During these intervals I hit 161, 164, 163, 166 on average (89-92% of maximum) and peak HRs during each interval were 168, 172, 176, and 176 indicating that pacing was appropriately hard.
  4. Breathing was in tune with the rest of the metrics. If I attempted to chat, I had to ease up slightly, which would make it hard to hit that maximal sustainable intensity. In order to push adequately hard for this one, I needed to shut up and just breath.

This is one of my favorite sessions to build in this time of year. I have a hard time with sustained intervals and just don’t look forward to them, so this is manageable and actually enjoyable. With regard to the leg comment on #1, this also reinforces why it’s important to give yourself a range of intensity to work at, while considering other metrics. If it was just the feeling of the legs, I might have gone into this one not feeling super confident about hitting high targets. But, knowing that HR was very responsive inspired the confidence of knowing I could still go out and smash myself :grinning:

Thanks for the ride today!


Thanks for sharing the files guys! Obviously I missed the workout, but I wonder if you can discuss the thought process behind the structured warmup that you did. Looks like there were some sprint efforts in there. Would you characterize these as all-out sprints, or more like high cadence short bursts? Very apropo for me as I have 4x3 min on my calendar tomorrow, so basically this workout :sweat_smile:

The other question is about the rest between intervals. Are you doing those by feel, or a set prescription?

Hi @SteveHerman, great questions, and very timely for your workout tomorrow!

So yes, the rationale behind the structured warmup:

  1. Give the body a longer time on the bike to mentally prepare for the main set. Part of this was that @trevor and I were up kind of early for this one, so we just needed to wake up some more.
  2. Use the sprint efforts to prepare from a neuromuscular standpoint. The peak torque during the intervals was only about half of what was produced in the seated sprints (~60Nm vs ~110-120Nm, respectively), but I like to get the “feel” for what the body is doing / can do as another way to gauge preparedness for the workout. If the legs are junky, the power will be lower, the force will feel harder, and the legs will be sluggish overall. Another indicator that it might be better to save this for another day.

With regard to the rest intervals, those were selected based primarily on some of the research that included those intervals and rest periods. I wanted a workout where the intervals were maximal sustainable, and knowing that we were going to be pushing very hard, the 3 minutes felt about right. Plus, the rest periods always seem to go by faster near the last couple intervals! Would you be ok with less? Probably, as Dr. Seiler reported in his video on Short Stacks. So the 3 minute was just a preferred recovery length for me during this workout.

I hope that helps for your session tomorrow!
Good luck!
Coach Ryan

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Here’s my workout. While Ryan and Dr Cheung had excellent workouts, I’m the clear example of someone who shouldn’t have been doing this. I was fatigued and not ready. Full disclosure, I knew that even in the warm-up and had I been training by myself, I would have pulled the plug. I continued for the sake of giving our membership a good workout, but there was only so much my legs were willing to do. So look at my workout as an example of what to never do.

The key thing to notice in my file is that I WAS able to hit the power. In fact, considering my legs were noticeably tired, I was quite surprised and happy with my wattage. What told me I wasn’t ready for intensity was RPE and heart rate. When we did the warm-up, my heart rate was surprisingly low and I was even finding a one minute effort at threshold surprising hard. That’s a good indicator right there.

However, I’ve had times where I’m a little sluggish on the warm-up, but find my legs later. So, I continued with the workouts keeping my fingers crossed. The intervals quickly confirmed that I shouldn’t be going hard. On the first interval, it took me a minute to get up to speed - I was fighting the fatigue in my legs. Likewise, my heart rate was shockingly low. The dotted red line is my threshold heart rate (at 172 BPM.) On intervals like these I should get above threshold in short order. By the end of the first interval, I had only touched 157 BPM and the second interval I maxed out at 165 BPM. By contrast, here’s my 4x8 minute intervals the previous week which did go well:

Notice how much more responsive my heart rate was.

Getting back to my failed 4x4s, I continued with the remaining two intervals at lower intensity, but I was doing myself NO favors. That hurt me more than it helped me. My choice was not based on smart training - it was based on giving Ryan continued support. Selfishly, the smart thing would have been to pull the plug shortly into the first interval.

Oh and that final hard one minute… @ryan looked like he was about to loose his breakfast and, as any good friend would, I wanted to help him get there.


@trevor thanks for suffering for us :slight_smile:

My question about this is that the heat map for your “Good Test” is “cleaner” looking like you stayed pretty consistent - constant yellow and not spikes of yellow, orange, and red. The bad one looks to be all over the place. Is there a reason that doesn’t have to do with the workout on why it looks cleaner or is it that when you are “ready” you tend to produce workouts that look cleaner?

@ryan I like the visual. Is that something I have not discovered in WKO (so much there, even by default, can miss some that are right in front of you) or do you use something different. I like the ability to annotate each interval with numbers and seeing the visual as well.

Nice job with the test and making Trevor suffer :wink:

@bgkeen, thanks for the question. There’s two reasons for the difference. One is definitely the fact that I was struggling in the workout with Ryan and having a hard time maintaining my power. The other, and probably the bigger reason, is that I had my trainer in erg mode for the 4x8s. I do agree with Ryan that there’s a lot of value in self-pacing and I try to do that regularly, but sometimes I like to just get on the trainer, find the right wattage for the day and let the trainer run the show.

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@bgkeen thanks! I always enjoy the days I can make Trevor suffer a bit, because they are so few and far between! :slight_smile:

So that view is actually an app that I was introduced to recently and have been enjoying alongside WKO5 and Xert. This is intervals.icu and connects with your social accounts (Strava, etc.) to pull in workouts. They’ve been doing a great job developing it!


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Thanks! One more tool for me to play with data…I’m sure my wife will appreciate :roll_eyes:


@trevor that explains it. It would be impressive in your “feel” to be so precise. I think the use of ERG mode would be a good topic - when to use or when do you prefer to use. I know for me, I will use if I am truly going easy and just want to focus on being on the bike with a low HR and practice other things like breathing. I when I do my 1-2 hours <50% of 5 min max, my HR can be 10-20 bpm lower than being in slope mode or more if just riding with the terrain changes of zwift.

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Here is my 4x3 min from today (I adjusted the plan because I bruised my knee chasing my kid and it was bugging me on Wed AM).

My target HR was 175 bpm which is 95% of my max. I modulated my power by feel but had 280 watts in mind (110% FTP). On the first interval I went out close to 280 but felt like it was too hard. Ended up with the following average powers: 266, 259, 258, 261.

While my peak HR was quite a bit higher than my target (178-179 each time) I didn’t feel horrible. I’ve noticed recently that my indoor HR has been a bit higher relative to my RPE than I am used to.

Could I have held on to each interval for another minute? Maybe. I wonder whether it would be better to keep the 3 minute duration and work the intensity vs adding another minute to each.

The last time I shared a file, @trevor commented that my HR was a bit slow to respond. It looks like I did not reach a steady state in the 3 min efforts here. Is steady state the goal of these types of efforts? Meaning, maximize the time spent at 95% of HR max? If so wouldn’t a “hard start” protocol be better?


@SteveHerman, nice job modulating those efforts. The HR to me looks pretty responsive. Your first interval of course looks to be a bit slower, but on 2, 3, and 4 it was a faster response. The first 60-90 seconds will be a time where your HR works to achieve the level necessary to meet the metabolic demand, so in a 3 minute interval you won’t have a ton of time where it will stabilize. You can see in @ThermalDoc’s original post how his HR creeps to a peak HR throughout every interval with a fairly small steady portion in each one. I think about these more as the total time spent at ~90% or greater max HR.

So in terms of that, I’m always working to achieve the intended time at that intensity and would normally go first for the appropriate intensity and then build time there to progress. So in my example above I was holding around 315-320w for those 4 min intervals. The next step would be to extend to 5x4, 6x4, and then look at 5x5 and 6x5 intervals. I know around 310-315 is sustainable and extending another minute would give me the same HR response, but more time there, so that’s the rationale for moving into 5x5 and 6x5. This is something I normally work into in the spring to prepare for early MTB races. Right now, I will likely stick with 4x4 or 5x4 for a few weeks just to maintain intensity, but not sharpen the end of that blade too soon. You can see in the video from this week that I haven’t been doing that type of intensity for a while, so physically it was very challenging and that’s another reason for hanging onto something similar for a couple weeks just to get the head back in the game for this type of intensity.

Coach Ryan

Awesome, that makes total sense. I’ve never really had a good idea of how hard to go for intervals like these. Total time above 90% HRmax is a very reasonable goal for this time of the year. Given that I didn’t lose my breakfast, next time I’ll add a minute targeting 265 W, and progress from there.

@ryan, @SteveHerman @bgkeen @trevor Concerning progressing from 4 min to 5 min intervals, this reminds me of the philosophy of Canadian coach & scientist Guy Thibault, which I think makes a lot of sense. With his approach, if the goal is to reach a target power of 300 W for 10 min (as an example), the common approach might be to aim for 280 W for 10 min, then work up to 290 and then 300.

Thibault’s approach is different in hitting that 300 W target first for short durations, and then building up the duration. So start off with (example) 3 sets of 15x45 s at 300 W, 1:30 recovery. Aim is to have lots of volume at that target power, but each one is doable because they’re relatively short. But the aim is to ride at 300 W for them to train yourself to ride at that intensity.

Then, once those short 45 s (again, example) reps are comfortable/easy, move to 1 min reps, then 1:30, 2 min, etc. So overall the intensity/wattage is the same throughout, but the difficulty progresses through extending duration. I’ve tried this approach several times and think it has good merit. I did these a lot especially around 2007-2010, when I was using the ErgVideo system (one of the first to actually have Erg control of trainers, notably the CompuTrainer) and they have a workout specifically with this progression. One thing I like about this approach is that it gives you a great feel for what that wattage actually feels like, but does it in doses that won’t swamp you.

Stephen Cheung


Amazing how we are all so different while being similar in other areas.

I don’t think I’ve ever had even one workout in which my HR shoots up as quickly as Trevor’s. The ramp up is always slower.

I guess if I just mashed the pedals harder, then perhaps the response would be different, the the power wouldn’t be sustainable.

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Great conversation!

I wanted to respond to everything, but there’s just been too many interesting points. So, I’ll just respond to some the thoughts about the shape of the heart rate graph. I think this conversation and the graphs everyone has provided is an amazing example of why heart rate is an important metric. If all we had was power, the workouts would all look pretty similar and most of this conversation wouldn’t have happened.

When we have the heart rate coupled with power, we can see so much more. I’m a pure aerobic time-trial style rider - to an extreme. So, when you look at my workout, you can see how quickly my heart rate responds and levels off. On some of the other graphs here, you can see that heart rate is either slow to respond or never levels off. When I see that it generally means one of two things - the workout was too hard (if it was designed to be a threshold workout) or the athlete has an under-developed aerobic system and its an area of real opportunity for them.

Having that data and seeing that heart rate response then leads to some of these subtleties that all of you are bringing up - such as should you go hard for the first minute to bring heart rate up to threshold. I don’t personally prescribe that, but my old coach Houshang Amiri, was a big believer in that approach. As I remember, he felt time at the target heart rate, not the target power was what was most important in this type of work.

The other thing I love about this conversation is that we’re talking about very simple intervals - 5x4 minutes and 4x8 minutes. But there’s so many nuances in such simple intervals. I personally think you lose those wonderful nuances when intervals get too complex.

But just my opinion. Love the conversation!

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The engineer in me loves the almost mathematical precision in the approach you describe. It actually seems analogous to what is done in strength training in terms of calculating reps vs intensity. It must be important to ensure that the recovery intervals be fairly short in duration, to ensure that we are truly only stimulating aerobic pathways. Is that true?


@SteveHerman that’s one of the reasons Trevor’s 5x5 (1 min rest) intervals work so well. The rest periods are short so that it puts a very heavy emphasis on the aerobic pathway. If you were to do a “hard-start” approach to his 5x5 session, you would quickly find the last couple intervals are very very difficult at best, possibly even unsustainable near the end. So the profile would look quite different. It would still be a hard session, but the focus on the HR response that Trevor prioritizes with that session would be out the window.

Yes, it does seem to have a lot of similarity to strength training with the calculation of reps * intensity. That’s been my preferred method for ensuring overload because it’s simple and it just works. You can easily progress yourself that way.

Coach Ryan


Is this meant to be a VO2 interval? Is the HR target for a VO2 interval 92-95% of HR max? I recall a podcast in the fall where @trevor didn’t seem to be a big fan of VO2 intervals, but I didn’t quite understand why. Was it because people don’t do them properly, and/or do them them too early in the year? What is the physiologic reason why significant gains in VO2 can be had after 4-6 sessions, but threshold intervals/work take much longer to impact significant change (10-12 sessions)?