Training exclusively with Moxy / SmO2

Hey folks,

Long story short, I might be without a power meter for an extended period of time. I’d be interested in how I might train using SmO2 exclusively. My framework from previous conversations is something like this:

  1. LT1 is at highest intensity one can maintain peak levels of SmO2 after an extended warm-up
  2. Tempo would correspond to 78-82% max HR and should see stable to rising SmO2
  3. Critical Power may correspond to the highest intensity at which one can maintain stable SmO2

I think this is at least in the ballpark. I’ve read less on using SmO2 for VO2 Max and anaerobic work. As I understand it, one should allow SmO2 to come back to baseline between intervals, but I’m less clear on if it’s possible to us SmO2 data to determine the duration of these hard efforts.

@steveneal do you have any advice?


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@fazel1010 yes I can add to this for sure.

Just at a race and will be busy tomorrow can respond Sunday.

In the meantime down my new Garmin connect app search moxy and Steve neal

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Think about FatMax being the last step that smo2 is still rising, LT1 would be the first step that smo2 is stable.

For this I would agree to use those heart rate numbers, but also keep in mind that smo2 should be stable, so you can modify this zone each day, making sure to gradually warm-up.

We all use different terms here but yes the final step where smo2 is stable would be considered threshold.

all above relating to a 4-5m step test, with 1m static rest between.


A real life example below. Athlete in mtb race this past weekend, first elite race, at altitude.

Day before the race hill repeats at gradually increasing pace to define pacing strategy.

You can see that there is a point at 310 watts, and heart rate of 176 where smo2 stable, last repeat a little harder smo2 starts to drop during the interval.

Race file below.

Main climb in the race each lap below. Was really proud of his pacing for his first elite race especially at altitude.

Let me know if you have any questions, if you want to do a 4-1-4 test with gradual heart rate increase, you could post it on here and we could have a look.

Also, remember when using your rollers, keep the tire pressure exactly the same everytime, this will really help with consistency of the data when looking at different tests.


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Also @fazel1010 my garmin app that compares current smo2 to lap average is finally available.


Here’s my top-of-the-head advice, for what it’s worth.
edit: woops, I wrote a 1000 word essay :upside_down_face:

In our 5-1 dataset with trained female & male cyclists, SmO2peak tended to occur lower than LT1. And in subjects with a ‘monotonic’ response profile - meaning SmO2 declines at each progressive workload (mostly males with low skinfold thickness) - there was really no association, since SmO2peak occurred almost exclusively in the first work stage, by definition.

That being said, I would still agree that maintaining SmO2 ‘as high as reasonably possible’ is a good way to remain in moderate intensity domain. but this still means we have to pay attention to the sensations for what constitutes ‘reasonable’. For monotonic responders, trying to keep SmO2 ‘as high as possible’ will basically mean walking… which is maybe not a bad idea for low-intensity training? :wink:

The absolute SmO2 value of course will be individual. A bit of trial & error here will help very quickly.

Some more details on response profiles here:

Here are visualisations of LT1 (actually LTmin) association with SmO2peak in the curvilinear and monotonic response profiles

SmO2 should indeed be stable over a long duration in heavy domain. You may see a rise over the first ~10 min if starting from ‘cold’ related to cutaneous thermoregulatory blood flow. And again for monotonic responders, the SmO2 value can still be very low, even approaching your individual minimum as you get closer to FTP / CP / critical oxygenation, or fatigue accumulates over longer durations. This is something Andri Feldmann, Brett Kirby, and I are trying to understand better right now (shameless name-dropping :yum: @steveneal I should get your insight :+1:)

So once again, respecting the sensations and a bit of trial and error triangulating between sensations & SmO2 (and HR) will help you dial in an appropriate range.

Yes in theory, probably yes in a multi-stage test, maybe no? in real-world training… And I assume we’re talking about VL here.

Coming up at CP from below will probably allow you to remain at a more-or-less stable critical oxygenation, but any intermittency above and below CP will likely lead to lower stable SmO2 values related to disrupted metabolic milieu, even if you are then able to sustain a metabolic steady-state (ie. under CP).

Basically, athletes can be riding “at threshold” (which 50/50 might mean they’re above or below on any given day at any given moment) and still see SmO2 reach near their individual minimum, where SmO2 is stable or even increasing, since there’s no further room to decrease.

I don’t have a great visual for this precisely, but here’s an example of an athlete working at 105 or 110% CP (can’t recall) as determined from a 3-min all-out test the previous week. So he’s in severe domain.

Pay attention to the blue line is VL SmO2. :point_down:

The point here is that he’s basically already at minimum after the initial ~90-sec deoxygenation onset kinetics, so SmO2 cannot continue to decline, and in fact rises in the second half (the paraspinals in orange is a different story, for another discussion :wink:)

You will see ‘exercise hyperemia’ which is a transient increase in blood flow & SmO2 after HVY or SVR exercise, so it’s not just about SmO2 returning to maximum/baseline, but actually reaching the supramaximal peak and declining back to baseline which may take ~3-5 min, depending of course on work & rest intensity & duration. See the image above for a reasonable example (although I realise he stops pedalling briefly which will exaggerate and shorten the appearance of the hyperemic peak)

I’m not sure how best to use NIRS to modulate work duration either. For the very reason given above for the athlete working at 105/110% CP. I can’t predict TTE from a flat line.

But maybe I can say “I see a flat SmO2 line near minimum, so I’m in the right intensity domain… Can I back-off and go longer? Oh, SmO2 rose a bit too much, I’ll go harder. Ok, now I can probably hold this 10-min max, so I’m gonna go 4x6-min with 3-4 min rest intervals… 2 intervals later and I don’t think I can keep the effort up… oh look, now when I back-off the power a bit the SmO2 remains low, so I’m gonna do that and hedge for a bit longer duration”… Or “oh, I can’t actually keep the effort up to keep SmO2 low. I think that’s me done for the day!” etc. etc.

Conclusion: I’m probably overcomplicating things, and you’ll probably figure out what works for you straight away!

Honestly, I found the more I used NIRS during training, the more it just allowed me to associate the sensations to the effort or recovery readiness. So it’s a good confirmation process. But I found for myself and other athletes, the actual NIRS device became redundant after a few weeks. Which is a great outcome!!


Posting here because I don’t want to start a new thread. I’ll keep it short…can extended warm ups (20-30 min) from like 35%-60% of threshold affect heart rate response? That is, if you take the time to build SmO2, will heart rate response be different than if you do a relatively short warm up and don’t really see SmO2 raise above baseline?

I just did a 35 min warm up like this on the rower, and had a super hard time getting my heart rate up doing tempo/sweet spot. I assumed it was fatigue, but just checking. Thanks!

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Hi @fazel1010 I hope you are doing well. I don’t really have an answer here, but a suggestion.

If you are doing a workout where you are trying to get the heart rate up, did you try some shorter intensity at the end of this long warm-up?

Were you just doing a gradual warmup to get to an endurance pace? Tempo pace?

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Hi @steveneal. I hope you are well too! To be honest, I’m trying to train intuitively. I basically do a gradual warm up from like 35-50% of threshold over 20’ while monitoring SmO2 and HR, then decide if I’m going to do intensity or just easy. I have general goals for each week in terms of time-in-zone, but I don’t map anything out other than strength work (lifting through the end of March). That said, if I get towards the end of the week and am short, I do what you suggest - shorter easy build before something like 2’ building to threshold then some 30/30’s.

I found myself in the same situation last night and just rowed easy instead of pushing it. It’s almost certainly fatigue. I was just thinking that really good SmO2 response (relatively high amounts of oxygenation in the muscles) might result in the heart being slow to respond due to not needing to supply as much oxygenated blood, at least initially.

I am not so sure about that.

I do a ramp from 50w to 25w above current fatmax as a warmup almost daily.

The RPE and moxy are almost identical, if I have a high smo2 response in the ramp, I feel much more ready…

I do agree with using some sort of daily check-in to decide what to do that day…if you are patient and have the time to decide on the fly, it can work very well.

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Hi, can you make it compatible with the FR965 please?

@ogni I can ask Moxy as they built under my guidance