Register Latest Topics
 
 
 


Reply
  Author   Comment   Page 2 of 3      Prev   1   2   3   Next
CD

Development Team Member
Registered:
Posts: 6
 #16 
bjrmd nice review, well summarised!

An extra note, from the raw traces the Moxy seems to have less smoothing (lots more movement). Could be as you say that the Portamon is designed for more than muscle use. I'm interested in what is the right amount of averaging for scientific measurement. 
bjrmd

Development Team Member
Registered:
Posts: 29
 #17 
Quote:
I'm interested in what is the right amount of averaging for scientific measurement.


I would guess the effects of "averaging" would depend on what you are trying to prove/understand.  It did not seem like an issue according to the authors of the study.
As far as for personal use, since we are generally interested in major trends and not a percent or two, it probably does not matter.  Garmin connect displays muscle O2 every 4 secs for cycling but every 1 sec for strength training.  The curves look pretty similar anyway.
bobbyjobling

Development Team Member
Registered:
Posts: 208
 #18 
Very interesting paper and it inspires confidence in the Moxy. Well done to Roger.

But not sure why the Thb was not used as this would have added information on how the external pressure effected the blood volume below the sensor. Also I'm not sure if the pressure was adjusted for contact surface area of the NIRS so that it was the same g/mm^2 for both devices.

If the MOXY has a higher dynamic range, then it would be reasonable to assume that it would be able to show a greater pressure effect on SMO2 value.
Stuart percival

Development Team Member
Registered:
Posts: 78
 #19 
@jeffwink

‘Are these measurements noise or real differences?’

Noise in the form of movement artifact or something different ?

If I can add some helpful anecdotal evidence ;
I’ve used the moxy on many athletes
Testing full 5-1-5 in the lab with 3 Moxys
Also played about manipulating my own sessions (modifying respiration or manipulating pedalling for example)
The trends you see are very consistent and repeatable time and time again.

I’ve been doing an informal study on some massage equipment
I sit competly still and record Sm02 / Thb
Use the equipment and reassess the same area of muscle and see a difference - one I was looking for to validate a positive intervention
Next step was to validate early findings
So I measured the other leg but didn’t use the equipment on this leg - the moxy values only changed on the leg I used equipment on-

So I see consistent sensible changes in the moxy data inline with my understanding of what’s potentially happening within the body
I guess the fact we are using arbitrary numbers and changes are small perhaps creates uncertanty?

Lastly I’ve also tested a lot of athletes using V02 and lactate and the historic thresholds we pinpoint / look for in my opinion are good for assessing positive changes in fitness but give little insight into what to do next - that’s not a negative comment as I did it for years but times move on and I’m not one for doing stuff because we always have :)

Andrea

Development Team Member
Registered:
Posts: 7
 #20 
I'm a bit skeptic about the absolute value recorded during a Vo2max test.
%SmO2 value drop a lot ... is normal?

I see some spikes but I think was an error related to stand up/displacement of the MOXY.

Andrea vmax2.jpeg  vmax1.jpeg

Stuart percival

Development Team Member
Registered:
Posts: 78
 #21 
Hi Andrea

I'm a bit skeptic about the absolute value recorded during a Vo2max test.
%SmO2 value drop a lot ... is normal?

I don’t use moxy when doing a V02 peak assessment - it doesn’t tell me a great deal

bobbyjobling

Development Team Member
Registered:
Posts: 208
 #22 
Unfortunately when the Moxy SmO2 reads near 0% that's an indication of to little fat under the sensor and you may lose information. You need to move sensor on area with more fat. For example when I measure in the centre of my VL, SmO2 can go down to 0% but if I move it 15mm towards my RF it will only go down to 5-10%.
Andrea

Development Team Member
Registered:
Posts: 7
 #23 
Hi @bobby, thank you for you answer.
Was quite in the middle of the quads, ok a bit lateral but not so much.
These are pro riders with very low BF% but I guess if is so easy to reach an SMO2% so low just close of the VT1... I can understand on my small engine with a central limiter.
In past with other riders and device I reach an SmO2% of 45-50% at hexaustion that seems quite "normal" if the limiter is more peripheral (muscle) with 75-80ml/kg/min of VO2max.
I did try to do an occlusion "calibration test" to see what level of SMO2% I will reach.
Physiologically seems not possible, any other explanation ?

Andrea
bobbyjobling

Development Team Member
Registered:
Posts: 208
 #24 
I would use a wall sit test and move the Moxy around until the minimum value is not less than 5%.
Andrea

Development Team Member
Registered:
Posts: 7
 #25 
@Stuart Parcivel
there should be a logic information coming from the response of Smo2% value with incremental test, at least to try to describe what happen for example comparing a pro riders with me. Did you have used Moxy to record systematically Smo2%/THB response on a Vp2max test to decide is useless ?
My central limit is reflected in a fast drop in Smo2% than a Pro riders.
Pheripheral adaptation/improvement should be reflected in a different profile kinetics.

Often I read about the positioning of the MOXY on the VL, VM, RF... deltoids.... I think here the error can be to identify a simple spot with the muscle behaviour (like often happen using sEMG). I put-on the belly of the quads (I've a skin reference) for reliability. This is also an area without tendon "interference". What should be the logic to use a wall seat test and choose the point were value not goes down 5% ?

I try to do a "calibration test" with occlusion and this is the results.... (same position than the previous test)

2min rest laying then occlusion till minute ~17 and then released....
We can se that SmO2% drops quite fast at the start and the a bit slow with THB going up...at one point SmO2% drop below 0% and TBH spikes down....
After the release of the cuff we can see a fast return of the basal level.

fig1.png 

fig1a.png 

fig2.png  fig3.png  fig4.png 

Andrea



bobbyjobling

Development Team Member
Registered:
Posts: 208
 #26 
From your graphs it looks like a venous occlusion, irrespective to occlusion type the blood flow is reduced to all cells under the Moxy, so it might be more difficult to find a location which will give a non zero SmO2 during a normal cycling assessment as the blood O2 during the occlusion is gradually consumed by all cells types.

My thoughts with a wall test is that the VL are under high tension, which in itself will effect blood flow and also VL O2 requirements are elevated ( it mimics a very hard cycling test with a low CO) whilst other non muscle cell blood flow is mantained. So by moving the Moxy around the VL you might find a sweet spot. It basically compensate for the the Moxy SmO2 table as when it hits 0% tHb reads incorrect too.

This is just my thoughts and I'm not saying it is 100% correct but just sharing ideas.

Maybe Roger could explain better the limitations of the Moxy SmO2 versus adipose fat.
Andrea

Development Team Member
Registered:
Posts: 7
 #27 
Hi Bobby, thank you for the answer.
Yes, was an occlusion with a cuff with ~300mmHg and so venous flow was probably completely blocked but arterial was still present in part....
During NIRS study normally a test like that (also with higher pressure) is used to "calibrate" and standardise the readings.

The reliability and error of MOXY naturally is lower than a NIRS like Portamon like explained in this paper

https://www.ncbi.nlm.nih.gov/pubmed/29368457

Andrea
sebo2000

Development Team Member
Registered:
Posts: 214
 #28 
I found Moxy very reliable and consistent especially when you follow the same routine while securing the units. I'm afraid slipping it under your bibs might not be enough.

During summer light shield is a great addition if you want consistency. When placing it on the body I use body marks and place it always in the same direction eg. emitter diode always down or up.

Cost of 3 PortaMon devices about 24.000 USD vs 3 Moxy at 2.400 USD is totally out of reach in my case.






Takura

Development Team Member
Registered:
Posts: 30
 #29 
Andrea, not sure I should post this but it’s still an unresolved question for me too ... unluckily I am not a specialist in this and have more questions than answers. I remember that the absolute scale of the SmO2 values were something that I didn’t quite understand when I started using Moxy and even after going so far as to aim at doing some occlusion tests prompted by differences in range compared with BSX. FWIW, in comparison, the BSX usually gave me repeatably higher values between about 40% and 80% (if I remember correctly) at the same location when the Moxy would give 0% to about 80% under similar conditions (though not measurable at the same time). Am therefore using it more as relative values than absolute ones ... and it’s useful even then. Also, there seemed to be differences between individuals in how the two sensors differed and it was reported that the BSX could go down to 0% in occlusion tests too.

PS: has anyone compared with Humon? ;-)
bjrmd

Development Team Member
Registered:
Posts: 29
 #30 
It is probable the different sensor brands have different levels of measurement depth into the muscle.  So even if the algorithms, accuracy, were identical, the results could be vastly different.  There have been many studies looking at muscle O2 and sensor sampling depth issues.  Also, depending on the fat thickness in the area, the different brands may read differently.
Even the same sensor, placed a few mm apart could read differently. 
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

HTML hit counter - Quick-counter.net