Muscle oxygen saturation rates coincide with lactate-based exercise thresholds
How does it correlate with me?
https://pubmed.ncbi.nlm.nih.gov/37261552/
Philip M. Batterson · Brett S. Kirby · Georg Hasselmann · Andri Feldmann
Okey, NIRS is cool! After listening to Olav Aleksander Bu he said something like: “If you see a study, try reproducing it yourself to understand it better”. Tim Podlogar said something like this himself, so here I am!
Before trying to reproduce the same test there is some questions I would question about the study design.
1: The muscles where the NIRS is measuring.
Right Vastus Lateralis, Left Vastus Lateralis, Left Gastrocnemius and Left Biceps Femoris. Why not measure Rectus Femoris, which many would use for measuring running. (Including me).
2: Why are the intervals 3 minutes?
Normally when doing a lactate profile I would like the lactate to be able to stabilize, using longer working intervals.
3: Why only 30 seconds rest?
Will be hard to do the testing by yourself, taking good samples in such a short time is hard. But then again, the lactate would not fall down as much during the short intervals?
I sent this question to the Philip Batterson @cricitalo2 on instagram, together with requesting access to the article.
And then I got his answers:
“We chose 3 minutes as it’s adequate for reaching muscle oxygen steady state without extending the intervals too long. 30s rest was just to be able to collect lactate values but for the most part oxygenation can recover between 30-90 seconds but we weren’t really looking at that.”
I then had the question if the lactate would have been stabilized with only 3 minutes, since that is what you are comparing it with.
“I think 3-4 minutes is adequate. That’s one of the challenges with lactate is that you never know if it’s truly stabilized because you are only doing one reading at the end of each step”
So then I had to try it myself. I was sceptical as you can read from my questions, some other thoughts was: Why is the steps so big? (1,8km/h). Why is there no warmup?
What I did
So I placed the Moxy sensor on my right Vastus Lateralis:
I had my girlfriend Unn Marit to help me out, because still… 30 sec rest to measure? Still a pretty short time, and if something is wrong its hard to fix it.
Started to run, without any warmup at 9km/h. Which is somewhat normal for me, but with only 3 minutes I did not get the feeling that I was warmed up. First measurement of lactate at 2.0mmol/L.
Next step was 10.8km/h, good feeling. Lactate measured: 2.1mmol/L
Third step: 12.6km/h, big increase, it took some time before I felt comfortable. This is where I have been running my intervals lately, so not that unfamiliar to the speed. Lactate measured: 2.7mmol/L.
Fourth step: 14.4km/h, this is fast! For me not running at this speed at any point other than maybe doing some sprinting at the end of a 10km race I dont run at this speed. Lactate measured: 4.5mmol/L.
Fifth step: 16.2km/h, knowing that some people are running a marathon at these paces are insane! First minute went by okey, second minute I started struggling to focus, and the last minute I was starting to feel burn in my arms! Lactate measured: 7.9mmol/L.
The results
Well, it holds up! At least for me it does. And that is really interesting, seeing as high r value as -0.9850. If you have not heard about r values here is a list:
So the correlation is very strong. The r values from the study:
“Correlation between blood lactate and delayed SmO2 rate Running speed was related to lactate (r=0.999), as well as SmO2 rate (RVL, r=− 0.961; LVL, r=− 0.976; LG, r=− 0.985; LHAM r=− 0.979 (Fig. 2). Muscle O2 saturation rate was correlated with blood lactate concentrations for all muscle sites; RVL, r= − 0.974, p = 0.001; LVL, r=− 0.969, p=0.001; LG, r=− 0.942, p=0.005; LHAM, r=− 0.907, p=0.013 (Fig. 3)”
How will it hold up using a different protocol?
Funny that you asked, so I did dig up my latest lactate profile from 10th of July 2023. Ploting it with the same script:
With the r value at -0.9509 I would say that it still holds up pretty good!
What’s next?
Now that for me atleast the sloperate holds up to measuring lactate that would mean I can measure things instantly, without sticking my fingers and having to stop. And know that what I’m measuring is holding up to lactate. But…. Calculating sloperate?
This is how I do it in a python script:
def slope_utregning(slope_seconds_start, slope_start, seconds, slope_end):
if (slope_end - slope_start != 0):
return (float(slope_end - slope_start) / (seconds - slope_seconds_start))
return NoneSo to explain the code:
slope_seconds_start = The start of the interval, timepoint 60 (because we start 60 seconds into the interval).
slope_start = The value that the NIRS device measured 60 seconds into the interval, timepoint 60.
seconds = How long the interval is measured in seconds.
slope_end = That value the NIRS device measured when the interval ended.
It will give you a value, which in this example is from my 3 minute test:
Sloperate for the whole interval: [-0.09444444444444444, -0.027777777777777776, -0.027777777777777776, -0.09444444444444444, -0.18888888888888888]
Sloperate for one minute into the interval: [0.016666666666666666, 0.025, -0.008333333333333333, -0.025, -0.125]
As you can see it is not something that you would calculate in your head while you are out running or riding your bike. But WHEN we will get to the point where someone has made a Connect IQ app that gives this information in realtime, then we are talking about valuable information! Until then? I will still use my NIRS device, helping me to make choices during intervals. But I understand really good that its not for anyone! ….Yet.
But with some fancy math, you could predict what the lactate is when knowing the slopevalue.
You can find the Python code here: https://github.com/thomasholmesland/moxyprofile
Next up? To see how it correlates with cycling!