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Development Team Member
Posts: 36
Hi ... wondering whether people here could help me interpreting SmO2/Thb data from a cycling fitness test? 

It's the Sufferfest 4DP "Full Frontal" fitness test which packs two 5 sec, a 5 min, a 20 min and a 1 min interval into a test of about one hour.

I know that that topic is an aggressively debated one on some of the fora because of what some felt to be an overly aggressive advertisement etc ... and I definitively don't want to have that kind of debate happen here. 

What I am wondering and would like to ask for your help is what people here would think the SmO2/Thb data tells about each of the intervals ...
- whether I went to the max of my capabilities or whether there is room for improvement?
- what the limiter might be?
- what I could have technically done better (e.g. higher cadence, etc)?
- what the best pacing strategy would be? (Feeling? MMP? HR? SmO2?)

It feels as if I can read something in the data but I might be seeing ghosts knowing my subjective RPE. (I will post my subjective RPE afterwards.)

Concerning the question whether packing so much into one test makes sense: My personal surprise was that with sufficient (1 week) rest I was pretty much able to meet what I thought were my current MMP values in all of the intervals.

Concerning whether it makes sense to "optimize" performance in a fitness test, I don't necessarily believe in optimizing to get "exact" results - that's, like, BSX kind of thinking and also easily influenced by the amount of rest. But I think this might be interesting enough as an though exercise and I might learn something of it ... and also, if I was a coach (which I am not) I would actually be interested in using SmO2 to judge whether a fitness test was done well and is trustable.

Sensors were placed on right VL and Deltoid. (The csv also contains left VL.) Note that Thb has been scaled to 10xThb in the graphs to improve readability.

2ndFFFT overall.jpg 

2ndFFFT intervals.jpg 

Attached Files
csv 2nd.csv (178.05 KB, 7 views)


Development Team Member
Posts: 36
PS: It might be better to think of this as a (TT) race pacing problem and less as a fitness test.

Development Team Member
Posts: 227

Hi Takura,


Ramp tests or 20min TT are very good at creating and showing delivery issues, they always show the same situation: delivery issue. It is clearly visible in your first 5min interval, you increased the power in last 1.5-2min and that was way too much, both VL and systemic SmO2 dropped like a rock creating O2 deficit.

In 20min attempt your Deltoid Smo2 stays stable despite the fact you increased the power half way through, we can see blood redirection from that point on, and deltoid tHb goes down. Your body is desperately trying to provide O2 to your legs. From that point hhb at systemic level is increasing.


Your right VL again shows O2 deficit from that point on. Your HR is increasing, tHb is increasing as well, SmO2 drops. This is most likely not sustainable situation for very long.

In first attempt you hit 180bpm in second only 177bmp.


You could pace this a bit differently and your 20min average could be slightly higher, I think you started slightly too easy, 5W-10W on the low side.


If your 20min TT was RPE 9-10 quad utilization seems like potential limiter, connecting HR to this picture we might see small aerobic tank. If your RPE was 10 in 20min attempt, I’m curious why HR didn’t hit above 180bmp could it be because of cardiac limiter?


I was researching Aerobic vs Anaerobic energy production and it seems many people, including myself are totally neglecting aerobic workouts, we desaturate quite well with our “after burner” anaerobic engines, producing massive CO2 amounts, but power is relatively not there, it is there if your weight is 100-120lb.

I also think your 5min warmup effort was a bit too hard to have max power at 20min.


First I would not test 5s, 1min 5min and 20min all in one test. You could slightly improve 20min average but changing warmup strategy, and going a bit easier in 5min interval, then start your 20min 5-10w higher and see how you feel after 5min if good add 2-3w if it feels very hard go easy 5w, after 5min reassess again. I would also skip 5s all out tests during 20min test. To get best results for 5s all outs, you would need warmup with more than two 5s efforts, but again not all out but slightly below, some people need 4 some 6.


I watched this cool movie about some great marathon runners, top in the world, and athlete said: I never test my max in training, ever, I leave my max efforts for the race day, or otherwise my max might stay unnoticed, it would be shame. So simple, but some true and I never thought about it.

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