Building an aerobic base

Question first with background info below: If I feel like I still do not have a good aerobic base at then end of the base phase and I have no events picked in the future, should I repeat the base phase before moving to the build phase? My goals are to be faster and enjoy longer efforts. Currently every ride feels like a race, even easy efforts.

Background info:
I have always been a strength sports athlete with great fast twitch strength and virtually no aerobic abilities. About three years ago I shifted from attempting to compete at strongman and powerlifting events after injury sidelined me for a few months and changed my priorities.

Even on an easy ride, I will spend all most all of my time in tempo to threshold heartrate zones.

If I take it extremely easy, I can get my heartrate to stay at a rate low enough to not be super painful. But, suddenly it will spike and never return to a manageable level with no real change in perceived effort.

My training time is very limited. I work between 50-60 hours most weeks and less than a month from the birth of my third child (3 kids under 5).

I know consistency is most important, but will high intensity work continue to make my body think it should default to high energy output even when I’m trying to maintain moderate efforts?


Heart rate spike seems very odd go see a cardiologist.

Did you start riding uphill at that very moment? It seems so from the strava shot.

It would be unlikely to see a 120 to 160bpm change without any trigger.

Did you every so FTPhr testing to set HR training zones? What do you call easy - RPE 2-4?

Looks like the Strava screen grab I picked was a bad example for the spike since it coincides with a hill, but it happens on most training days.

The screen grab from the run is a really obvious example of when it happens.

It could be a result of a small hill or headwind, but once it spikes its not coming back down.

For FTP-HR I seem to be able to hold 165 for an hour. But all my rides are at 165.

Honestly it looks like either a wonky HR monitor or a busted ticker - try someone else’s HR monitor and see if you see the same behavior. If you do - go see a doctor

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That looks like a bad HR strap. I’ve had it happen where my HRM reads really low or really high for portions of my runs. An instantaneous spike in HR like that is probably a monitor issue.

Thanks for the comments… I think the readings are accurate since they are repeatable across different devices and monitors. During a recent physical blood pressure, cholesterols, and all measured health items were in the ideal range. Except weight, I am about 215 lbs on a 5ft 9in frame (not ideal).

I think the high heart rate is a function a base fitness level. My real question is would I benefit more from repeating the base phase or starting a build phase?

Yes, if you’re concerned about aerobic base, you’d be well served to stay in Base training until you’re confident your aerobic capacity can support higher level training. This is pretty common among new endurance athletes, particularly those training for longer events.

Heart rate decoupling from effort is very common, and can be marked if you don’t have an established aerobic base. That said, it does not happen instantaneously. Instead, you’ll see a heart rate that’s maybe 10% higher at the end of a long sustained effort than it was at the start of the steady state effort once it had settled out. For example, after the first mile of a 6 mile run, your HR is 150, and by the end of it running at the same pace you’re up to 165. That’s a decoupled HR indicative of inadequate aerobic base.

I’ve never seen a 20bpm spike like that over the course of a few seconds without it being an issue with the monitor. Even a step increase in effort should see a more gradual build in HR than that. If that’s consistent and not an equipment issue, you might consider getting checked out.


One point you have to make sure: does your heart rate strap works like it should? I know the problem of some straps from running and (maybe) some kind of clothing.

There’s couple of things here to consider:

  1. Make sure your HR monitor is working properly. I have seen that kind of behaviour before, e.g., with optical HR monitors where the reading suddenly become higher and never comes back. Also, I have never seen before anything like what you are showing with a properly functioning HR monitor; or only when doing intervals. You could investigate this issue by trying to get your heart rate back down after that spike. Just follow your HR (e.g., with average HR on 1 mile laps) and after you notice the rise, try to get your HR back down to the initial level. It should take some time to get your HR down – but it always comes down. If it doesn’t get back or with your lower HR you are going absolutely nowhere, there most likely is something wrong with the measuring. You can even try to do the same hill multiple times to be able to compare your speeds.
    It seems like you already tried out several different HR monitors, or that’s something you should definitely do. Also, consider your other devices like the one that is picking up and collecting the HR data.

  2. It’s not always necessary to consider some part of your fitness separated from your overall fitness. My point is, easy rides can feel hard because they actually aren’t easy for you. Trying to make easy rides easy may not be achieved best by building a better base but by building a better fitness overall: from base to high end. What I mean concretely is increasing your FTP. This is why it might not be necessary to build a better base but to go on with your training to the threshold and high end stuff. That will increase rapidly your fitness in hard efforts but in easy efforts as well.
    You can approach it like this: let’s consider that you can put out some level of effort for one hour. That one hour maximal effort is a hard effort and your easy rides are far below that intensity. Let’s say that, at the moment, on your easy rides you have to ride on 70-80% of the effort you can put out for an hour. Now, you can train your body to handle better the 70-80% and enable you to have it a little bit more easy on your easy rides. However, if you train your high end, the effort you can put out for an hour increases. Thus, the easy ride becomes easier, and now you can do it with only 65-75% of your maximal effort for an hour.
    To put it simply, for many new cyclists, easy rides become easier by increasing your high end and overall fitness, not by training more your low end.

  3. Repeating a phase in training is problematic since doing the same things twice will not force your body to adapt as well as it adopts on the first run. You can see this as diminishing returns: at first you improve quickly but after a while you get smaller gains from the same effort. This is why proceeding with your plans, i.e., continuing to your build phase could be a better idea. First of all, the build increases your high end fitness and thus makes your easy rides easier. Second, the build phase provides your body with new kind of stimulus which helps you to maintain the rate of your improvement. In the Ask a Cycling Coach podcast, coach Chad recommends repeating both your base and build phases together if you have excess time; instead of just repeating or continuing the base.

  4. Building a proper base is necessary; but with very limited training time, low end training may not help you enough or at all. If you consider the TrainerRoad plans, the three-rides-a-week base plan has actually quite a lot of higher end training. I’m not sure, what is the training you have been doing on your base phase rides: if you’re doing the TrainerRoad plans with low volume, coach Chad knows what he’s doing and you can really improve by just following the TrainerRoad plans. However, if you have been doing your own rides and the rides have been easy, most likely you would get big gains from upping your intensity.
    The issue with cycling is that the traditional long slow rides have to be very long and you have to train close to ten hours a week to get proper gains from that kind of training. With your limited training time, high end work will help you much more. The book Time-Crunched Cyclists discusses this subject widely and describes how you can use high end work effectively with limited training time.

This statement seems strange.

Another thing: You are not going easy enough on your easy rides. If your HR is the the same for both hard and easy, then you are not going easy enough.

An indicator I was told sometime ago was if you think you are going easy enough, so easier. These are the hardest workouts for me. Your HR should be in zone 1 – very easy conversation. If you are by yourself, try singing a song. If you get out of breath, you are going too hard.

How are your TR workout HR numbers? I find that with sweet spot workouts my HR is in a good spot, Antelope I was at high 140s every interval (max hr is 195ish). Then I go outside and ride at a similar rpe with some harder intervals and my hr is a good 15-20 beats higher.

Could be just a symptom of being outside, training with an incorrect ftp, or going harder outside than you do inside.

Also looks like you’re running outside and riding inside. Not sure that all aerobic fitness is created equal.

Continuing training base is useful if the issue is lack of aerobic base. However, I’m not sure it is in this situation:

First, the training data and the comments indicate that the person in question doesn’t have very high overall fitness. (It might be that I’ve misunderstood this). In other words, the issue may not be that the athlete can push very high watts for 1-3mins while lacking in 3h power; but the fitness should be improved both in 1-3mins and in 3h.

Second, with very limited training time, I would be hesitant to say that continuing base training actually produced proper gains. As the situation is with TrainerRoad’s low volume base plans, traditional easy base training should not be relied upon too much but there should be also threshold and high end work.

Definitely a suspect HR monitor I reckon… After 10 minutes ago you get sweaty enough for the electrodes to start working properly. Do you have a power meter or smart trainer? It would be interesting to see what happens in a controlled environment…

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This is definitely something to look into. I used to run and cycle with the chest strap HRM and I didn’t like them. I found them uncomfortable and prone to errors like you’re seeing (especially early on in an activity when it’s cold and you don’t have a sweat up yet). I switched to the Scosche Rhythm which for me was a huge improvement. I wear it on the upper bicep and it’s much more comfortable and I’ve never had a problem with weird data spikes or dropouts.

So here’s my plan from reading all of the input and trying to piece together how I train and when the weird spikes happen.

  1. the spikes are probably equipment related. After checking more workouts it seems to happen about a third of the time when it’s cooler outside (less sweat for good contact) and doesn’t happen inside on the trainer. I will continue to monitor and maybe even check HR the old fashion way of it seems too low 10 minutes into a run.

  2. when I complete the low volume base I’ll move to the low volume general built. Trying to build my overall fitness to make it so the same efforts are a little easier to maintain.

Thanks for all of the great advice! Endurance training is still quite mysterious to me.

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I usually wet my HR strap with tap water before I put it on.

Regarding repeating base, that came up on the most recent podcast episode. See “Should I follow low volume plans before mid-volume plans?” in:

Not wanting to go on ‘feel’ I wondered something similar recently: is my base good enough to go onto build? I found this article explained it pretty well and even provided a way to asses it:


Thanks, I just finished the episode and it really helped provide a little more clarity.

3 kids under 5… You poor bastard… :frowning: