Claim: "Unit of Time at Z1 = Unit of Time at Z2-3"

Came across the claim from another prominent Sports Physiologist (can provide details for school of thought context).

"…for the vast majority of athletes, in terms of aerobic fitness gain, zone 2 and 3 give no additional benefit per unit of time than zone 1."

It’s basically another Polarised training concept, and seems to support the three zone <LT1 [stuff in the middle] >LT 2. But it did make me wonder, so posting here for thoughts. How low is too low before it’s not helping anymore? Is a 3hr Z1 ride really the same as a 3hr Z2 ride in terms of physiological response?

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My reply has to be taken in terms of heart rate and power.

This is topical for me as i have made myself a recumbent bike setup for my computer, idea to get 20 hour training weeks easily. And recumbent setup doesn’t provide nearly as high HR as cycling would so i was worried about it providing enough stress for me. As a avid cyclist with good aerobic base, able to hold 130 BPM (70% of HRmax) for hours, it seemed that under 110 BPM, 55% of HRmax, in recumbent setup would cause me nearly any stress.

I’ve been mainly on recumbent to test it out for, l only few times to get on bike to test my legs. Basically my legs are very tired from pedaling hours with 55% of HRmax. Yes, the setup is new to me so muscularily my body needs yet to learn economy so this isn’t apples to apples comparsion. But what i’ve gathered from this is that if it causes straining it’s enough to cause response. If my legs wouldn’t be tired enough from 4 hours on recumbent to affect my road bike the stress would be too low.

I don’t have power in recumbent so i can only estimate my power output, but i think i generally pedal around high Z1 low Z2 (z5 model). For my road bike that would be easy riding and i generally don’t do it but like to hover low-high Z2.

I’ve had this setup for 10 days, so i can’t provide long term observations. Only acute ones. But that’s the mental game with which i’ve come to terms with it:

tiredness = response. And from there on i try to estimate tiredness as a measure of sufficient response (=what is too low and what is not). Not because it’s optimal or correct, but that is all i have.

EDIT: I do physical job and do hold 80-90BPM in my work, however that isn’t enough straining for me to effect my training on bike… And it hasn’t baked me into pro level cyclist either. sadly. So i think i know when low is too low.

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Thanks for the thoughts.

Can you expand on this thought? I’ve been riding recumbent 7 years now and disagree that you can’t reach high heart rates. It’s just that it takes time to adapt to the position before you can.

Because recumbent is easier on muscle support, no upper body or core engagement to same degree. Working muscle mass in lower and heart is lower do it has to fight less against gravity. So at same wattage there is no need for such a high heart rate. That’s the theory at least.

I tested this on myself by building recumbent setup for my Tacx neo2. My HR is about 5 BPM lower at given wattage. it seems that it took couple weeks of lots of riding to get acclimated to the position. Thou i still don’t claim to be proficient at it.

I read an study where they compared upright, recumbent and supine at various exertion levels. Don’t recall nearly all details to be more specific than that, but pretty much thru out the board after 70watts resistance upright was “better” when looking at heart rate and wattage. Supine being the worst (=lower) in ability to produce wattage and high heart rates. I think there the difference between upright and recumbent was 5 BPM as well. Supine was then another 5 BPM.

Thou insights based on broader experience are always welcome.

Ah ok, you can push higher wattages at same heart rate as upright is another way of looking at it.

But also power produced drops. Efficiency is better upright with everything past 70 watts, upper body is got behind each pedaling motion.