5X5 as diagnostic

As a lifelong runner, I am comfortable with intervals and have based my training on Heart Rate. I’ve never had a problem getting up to Threshold or VO2 HR zones in workouts, and then bringing it back down during recoveries.

As a new-ish but older-ish (57) cyclist, I am now beginning to train with both HR and a powermeter. I’ve done three months of mostly base, used Trainer Road for a month, and have gotten consistent FTP results from two ramp tests. (FTP is also consistent with my Garmin’s estimation.) I’m training for cyclocross season.

I just began to incorporated the magical 5Xs5 as outlined by @trevor and as described in the forum. I used my FTP numbers to create power targets and monitored my HR to make sure that I wasn’t going over. In fact, I wasn’t even close to my LTHR. My LTHR is 165, but I didn’t even broach 150 by the end of the 4th interval. When I hit the fifth interval, I increased my power target by 10, but only got my heart rate up to 154.

I’m pretty sure that my HR numbers are accurate. I am less confident that my FTP/power numbers are. I don’t think this is an issue of being overtrained/under-rested as I just came off a backoff week and my waking HR numbers show that I should be rested.

So here’s my question: Does it make sense to repeat the workout with higher power targets for the work/recovery cycle until I am approaching my LTHR by the third or fourth interval? You recently referenced your former coach as stating that there may be some value in starting intervals harder in order to bring up HR for the duration of the interval. I am wondering if I should use my data prescriptively to backwards engineer what my power targets should be.

Does it make any sense to hypothesize that my “functional” FTP is actually 10 higher and then base a workout off of that? As long as I keep an eye on my HR, I don’t see too much of an issue with the N=1 experimentation.

Your thoughts much appreciated in advance.

I guess it would come down to how you determine your FTP and LTHR. I’ve had the best results with a longer 40-45+ minute test. I’ve been doing the baseline test here:

I’m also around your age. My LTHR is 155bpm but I only hit that number 20 minutes into a long 45 minute FTP test and I’m ending the test at 168bpm.

So, I don’t think I’d be hitting 155bpm doing 5x5s with rest intervals. I might get close by the last interval.

Have you used your LTHR from your running because I would have thought it might be higher than when cycling due to more muscle recruitment?

I have seen threshold heart rates up to 10 beats difference between running and cycling (cycling being lower), so that could be what’s going on here. 154-ish may well be your threshold heart rate for cycling.

That may change over time as you cycling develops, or it may not. Best to test HR now too be sure - not just power

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Thank you for the responses.

I do have different LTHRs for running and for riding. My cycling LTHR is 8 bpm lower than running, so you are both correct on that account, but I AM using my cycling LTHR as a reference point.

Experientially, I also thought that the 5x5s felt pretty easy, so my RPE was also pretty low.

Before I got the power meter, I did do some cycling intervals using HR only. And I was able to get it up to the proper zone and maintain.

Previous LTHR measurements were done using Coach Friel’s 20 minute test. FTP estimates were done using the ramp tests on Trainer Road.

I may just try to lift up my power targets and report back.

Thanks for the thoughtful replies

This is coming from a non coach.

I agree with the idea of upping the power for each interval. Start with a 5-10 watt bump for each successive interval until LTHR is reached. Then use the average of the session as your starting power for the next 5x5 session.

It is highly possible the TR ramp test under represents your FTP. It generally does for me.


If I just raised my FTP by 10 watts by doing nothing more than reading this thread… that makes this the most effective cycling forum ever!

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Shouldn’t a 5x5 workout always feel relatively easy? Assuming your FTP is your 30-60+ minute power, 5 minutes should be a piece of cake. You get a rest, and then you do another. If they are a struggle then you are overly fatigued or the FTP is too high.


I think it was originally a 30 minute test averaging the last 20 minutes, but either way I’d be careful with LTHR coming from this if you saw a lot of HR drift in the overall test. This can be huge, making it questionable whether the average HR actually matches your LTHR. My hypothesis (not sure of evidence) is that the less well trained your aerobic system, the more drift you will see.

And if it was a 20 minute test you are for sure riding above threshold. And if you feel like falling off the bike and really gasping for air at the end of that, you are close to VO2 max at that point (not VO2 max power) with HR above LTHR, potentially significantly / even close to max. Averaging tries to remove this, but who is to say that LTHR is the average given you’ve been above threshold power the whole test…

If you look at LTHR from a lab test they do a 4 or 5 minute step test (say 25w increments), then essentially take the final HR from the step which is your threshold power. That’s for sure below (and potentially significantly) the average HR of a 20 to 30 minute effort above threshold. You can try that test yourself and compare (even without lactate you’ll feel when you are below, at and above threshold and just check the Hr afterwards).

I agree with the comment that 5x5 threshold shouldn’t feel that hard

So the N=1 Study continues. A few thoughts first:

  1. I greatly appreciate the advocacy for multiple measures (e.g. powermeter, HR, and RPE). We have the technology, we can rebuild him. While it is easy to take a ramp test and assume that FTP and the resulting prescriptions are accurate, we do have other ways to test out the functional impact(s) of a particular workout.

  2. My Study is N=1 with a capital “N.” Meaning that I am the universe that I am studying. Certainly I am researching all the studies that include multiple "n"s (lowercase) and using those to guide my reasoning for a particular training plan. My goal is to use what knowledge is out there to find and continuously refine (based on multiple data points) what works best for me.

  3. I have tested my cycling LTHR multiple times over the past three years. It hasn’t changed all that much since I started. I used Coach Friel’s 30 min test, taking the last 20 mins average HR. It is 5-8 bpm below my running LTHR. While I have only been training hard for cycling since December, I have been riding pretty consistently over the past three years. Enough to feel confident in the multiple measures of cycling LTHR.

  4. I appreciate the information presented online and via the podcasts, as well as the responses to this thread. Nerds of a feather and all.

So… my first 5X5 intervals resulted in max HR below my cycling LTHR (163). I only got to the high 140s and REALYY pushed the last interval to get to 155.

Last night I ran the workout again, but instead of using my tested FTP (210), I inserted a projected FTP (225) into the equation. I was prepared to stop once I hit LTHR+1. Instead, I hit LTHR evenly in the last minute of the 5th interval and did not hit the +1. Perfect. As far as RPE, I felt like I could have carried the pacing for a few more intervals, and that I was never near a VO2 or red zone. An examination of the data shows that I maintained Threshold power and HR for the majority of my intervals. I feel great now

(Both workouts indoors on rollers, with low resting HRs at wake-up and good fuel/hydration throughout the day. Done at the same time of the evening)

I’d say that this was almost the exact physiological response I was hoping to achieve.

Back to the question in the title of this thread, I wonder if I should continue to base workouts on the thought that my more “functional” FTP (yes, I know I am repeating the word “functional,” but I am referencing how my FTP exits in a more real-world application and not a ramp test) should be prescriptive on the power targets for my next workouts.

Feedback appreciated


FTP and other training intensities are ranges (not to mention the arguments about definition and the ‘right’ protocol for determining it etc) and it’s not a huge difference, so I’d say why not try and see how it affects RPE in workouts, and then recovery afterwards.

Do you also use a combination of power and HR to guide endurance workouts? If so, your FTP setting doesn’t matter so much for those anyway (just for tracking training load)

You could also try a 30+ minute effort at the new FTP as a check. May be interesting observe RPE and HR in that.

I seem to recall that Trevor’s 5x5s are meant to be as aerobic as possible hence the HR and RPE guidelines. They aren’t meant to be intensive and push the boundaries of FTP. Have I got that right?

When looking at VO2max workouts such as these 5X5, HR is the key metric not power. The point of these workouts is to bring the heart rate up to maximal aerobic threshold for a period of time, 5 minutes in this case. HR, not power, time-in-zone is the target. In order to attain TiZ, it’s imperative to get the heart rate close to, but not cross over to anaerobic dominant, as quickly as possible. Everyones FTP as a percentage of VO2max is different and thus prescribing power as a universal target percentage, say 108% of FTP, should be viewed as a recommended power target, however, the first interval may average 125% and the last 105% to keep HR at aerobic threshold over 5 minutes. A quick look at your HR/time curve to find the time at which your HR is at the target, then go to your power/time curve and see the power at that time. A good starting point for power to get your HR up near target.

Given that I was training 100% on HR alone in the past, that was my understanding as well. And I know that we are talking about ranges that may change from one week to the next.

I had my running zones pretty well dialed in (I could predict HR within 2-3 bpm based on my respiration rate/strides and RPE), but I am really far off on the bike.

Perhaps I have to do more fiddling in order hit the proper HR zone and then check out the power, rather than thinking that it would be a straight extrapolation based on a single metric, such as FTP. I am finding the pwoermeter to be helpful, but not a panacea as far as programming and data monitoring.

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I think that some of the frustrations stem from cycling being such a data rich/tech driven sport. Power meters, SpO2, Moxy, HRM, HRV sensors etc are great tools in a lot of ways, but they are machines and we are not. In the totality of the data chain, we, as athletes, are the weakest most inconsistent link. I’m reminded of a comment a coaching mentor of mine once said, “all we really need is a stop watch”.

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There’s a few different things to unpack here:

  1. Coach Connor puts (not sure if he still does) a HR cap on these of 1 bpm above LTHR.
  2. Coach Connor talks about doing these by RPE/“feel”, and in such a way that the power you sustain on the first interval is the same as the power you sustain on the last interval (or very close), and that you’re achieving the desired HR.

If you accomplish both 1) and 2), the efforts will be very highly aerobic.

The problem we have here is that we’re trying to nail in a power target, and that’s not really the way these should be executed. Instead, you want to dial in the feeling of the power you think you can sustain for each interval over the short rest, and let the rest take care of itself.

In other words, take the trainer off of erg mode and do it in resistance mode (if you’re doing these indoors). If you’re doing them outdoors, don’t aim for a specific power target. It’ll probably take a couple of workouts to get this nailed, but that’s no problem since these are intended (under coach Connor) to be done for months at a time.

The last bit to mention is that power seems to fall above FTP… if that FTP is determined by a long testing method such as Kolie Moore’s protocol or an “hour of power”. Through that lens, you might end up doing these at 105% or 108%… but of a lower FTP than what you might get from a ramp test, 8-min field test, etc.

Exactly this. I think the bottom line is that we need to not worry about setting a specific power target and learn to dial these intervals in by feel so they can be done appropriately every day. Your resultant power will necessarily change with fatigue, and all the other factors that normally affect this. Focus more on the HR and the RPE.

This does nothing to mention the incorporation of a 30s hard start, which is something I like and I think coach Connor does now was well. The goal there being to get your HR up around LTHR as quickly as possible and then stay there.


interesting point. I was wondering if you felt the same about a fairly hard start to hours-long endurance rides, to get the HR up to the zone quickly rather than wait for the HR to match the usual power numbers.

I don’t think so just because it creates an unnecessary complexity to a simple ride. The goal of the hard start is to maximize time at a target HR or in a HR zone. Creating an additional minute or two of TiZ can be a good thing when you’re doing 20-30 minutes of work in zone. One minute of additional time above 90% max HR (as an example) in a 20 total minute session is an increase of 5%.

Getting that additional minute or two at 65-70% max HR in a four hour ride is a far smaller impact, so it’s just not worth it. There’d be no harm in it AFAIK provided the “hard start” was still entirely well below threshold/LT2 (think tempo), but I just don’t think it would be worth the trouble.

It could also send a bad message to an athlete… “Well, I started out at this tempo power, so doing more at that tempo power must be better, right?” Meanwhile, in the harder workout, they’re less likely to be able to sustain the hard start and likely welcome the relief! :grin:

Good insights, thanks!