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Posts: 266
Presented by Dr. Laurel Wentz and Justin Simmons of East Carolina University.


Posts: 266
Here are the questions that we did not have time for at the end of the webinar.  I will invite Dr. Wentz and Justin to reply to them here.

  1. Just to clarify, you used the ISAK front thigh skinfold site for landmarking where to place the monitor, correct? So this would be a bit more over the rectus femoris, rather than vastus lateralis...did you do some experimenting to see if there was a difference in data depending on the muscle in quad focused on?
  2. Was doing the intervals right after the VO2 max test a possible limiter in seeing lower smO2 levels in the interval efforts?
  3. Was there any relation between the VO2 amplitudes and for the people and the amplitude for the SmO2 drops? 
    • So for example higher VO2 amplitudes also showed higher amplitudes for SmO2 (or not of course)
    • So scatterplots between VO2 and SmO2 (either with a lag or not since there is a lag between the two)
  4. Most studies are using NIRS on the vastus lateralis in cycling, why choosing the ISAK skinfold site?

Posts: 266
I'll add some additional comments on the question of the Moxy data dropouts on the left leg and the differences between the left leg and right leg.

There can be several causes of the reading dropouts.
1) The sensor does not remain in contact with the skin.  This shows up as missing data when the exercise turns more vigorous.  In this case, we also usually see wildly varying readings which we didn't see in the data here.  Here's a video that shows a very robust was to attach the sensor with the CoverRoll Stetch tape.  
2) The ambient light interferes with the readings.  This usually isn't a problem indoors, but it can be if you have incandescent lights or are near a window.  This shows up as missing data and may or may not be accompanied by wildly varying readings.  This can also be motion sensitive.  The ambient light rejection algorithm can reject a lot of ambient light if it's steady, but if it varies rapidly as can happen with motion, it stops the sensor from trying to take a reading.  If you are seeing this issue indoors, a pair of shorts or fabric over the sensor usually takes care of it.  If you are in direct sunlight, fabrics are often not opaque enough and you should use the Moxy light shield or something like it.
3) The ANT+ signal might be interrupted.  In this case, the data will be missing in the PeriPedal or PerfPro data file, but it will be present in the data downloaded from the sensor.  Sometimes the ANT+ dongle has problems when it is plugged directly into the PC.  Often a USB extension cable to get the dongle close to the sensors and away from the noise sources of the PC completely eliminates this problem.
4) We sometimes see missing data when it's downloaded from the sensor.  This is less common.  This will show up as 1 or 2 missing blocks of data in the .csv file and if you download the data a second time without clearing, the missing data will be there.  If you collect the data with PeriPedal, PerfPro, or some other software, then this is not relevant.
5) Sensor placement.  Sometimes if the sensor is not placed over a homogenous muscle, we will see dropouts.  If there's not enough muscle or if the sensor loses contact with the skin due tot he movement of the athlete, it can cause problems.  This typically isn't an issue on quads or calves, but can be if you get close to the knee or if you are trying to get on a small muscle in the arm or back.  This is not a common problem and it's resolved by getting the sensor centered on the belly of the muscle.

Let me know if you are having problems with data dropouts like this and I can work with your to get them solved.  We can generally take readings continuously with 0 dropouts even during the most vigorous exercise.

On the left vs right difference issue, we have done many tests on this where we test and swap sensors and test again and it's always been a real physiologic difference rather than a sensor difference.  When we've done sensor to sensor comparisons, they read the same within less than 1 %SmO2.  Of course, I never want to discourage validating this on your own and if you find something different, I'd want to know about it.

Development Team Member
Posts: 1,501
Super great  info and I will use it for my  high school student to  show a lot of  interesting  questions.
 Key words.
 Lactic acid , Resting  lactate, Use lactate as a  sign of a  " successful  intensity in a VO2  max  test ?
Placement  of  MOXY in cycling in top versus okay  athletes  VL  versus rectus. Statement  that  Lactate VO2  HR  and SmO2  "peak " at teh same time.
 For the latter I need if possible  the CSV  files   from  No  96  if that is possible. If  you do not like to  sent it on here  can you email  me  that  csv  file and if you used  Peripedal  better would be that  section as we have HR on that one much better.
.And if possible  do we have the VO2  data  with  RF , TV  and CO2  at the moment of the   end of the full load  and the post load  reaction of the CO2  and  TV  and RF. ?

 Interesting study and lot's of great questions , when we look established ideas on VO2 and lactate  and than  give it a closer  thought.
 Thanks so much for sharing this  with all of us. I can get some feedback from our small discussions on here  or I  can keep it just on a mail for the research group or I can  just use it for us.
 What ever   you  think  may be fun.

 Here  just for  fun. Can you see   that 2  of the  6  where already   above " LT "  of 4 mmol  so they  where already anaerobic  before they started   out ? I assume   you  did  2  - 3 readings in the cases where you had this high  resting lactate  to confirm ?
 Cheers Juerg

Development Team Member
Posts: 1,501
I will be back  with one big point  and some explanation. The conclusion that the  NADIR  of SmO2  and lactate and HR  and VO2  are  at the same point   throws everything I did over the last 30 years over board. 
 What is possible and would  force me to rethink and reevaluate  many many  tests  and  case studies,  which by he way has happen many times already.
 .  The reason  why we actually  love NIRS  is, that   during my  education we where able to assess  metabolic reactions  +-30 seconds accurate  and  therefor  we learned the interesting idea of ATP  first  followed by CP  and so on. Today where we have tools  and one of them is NIRS, we  can go  on much smaller time intervals  and see, that what we thought is happening  does not happen at all.
 Test  one .
 1. Lactate and low SmO2. What is the lag time of the full lactate reading we can read  it  after an all out 30 second load. What where the lactate readings after the  30 s seconds at the end of the load  by  30 seconds  after the load, 1 min after load and so on. We id a  steady  flow  lactate  testing over  20 years back  with Dr. W  Sanders  and Dr. Gavin Smart in  Quesnel  and had  very seldom  a  peak lactate after the 30 second  all out load. In fact in many cases the peak showed up much later. It could  be as well  not  high at all as  30 seconds is  a  critical time depending on the  athlete.
 Will show  some big studies where  post all out  lactate was tested  after 300 m  and 600 m all out. This  asks the  question. Is lactate  peak  where we  have the lowest  SmO2.
 And is lactate actually available  in any case, where we have a  very low  SmO2.  Result. If your study is true  than we have tho rethink to use  lactate  or SmO2  as a   load  feedback  for saturation of load   and recovery of  load.
I would argue  and i hope  we  have some people on here  who can test lactate. Smile most  point of care  analyzer actually only test  lactate  have to find a analyzer  who can test lactic acid. )
 Next  up.
 HR. What was the HR  really  after the  30 seconds  and  if the HR reacted is it relevant  to he  CO  alone.

 When we looked  at HIIT  many years back and  as well combined  NIRS  ( Portamon)  with VO2  and HR  and physio flow we had in some cases a higher HR before the  lowest  SmO2   at the lowest SmO2  and after the  lowest SmO2 ??( depending on what all out meant).
When we look than we knwo HR is a  small window  to the cardiac hemodynamic.
 So  HR  may  not show  what happens  and depending n the athletes  hemodynamic reaction we have all three options.
 It depends on EF %  LVET, SVR  depending n BP  control and so on.
 So  again. Conclusion HR is at the top when  SmO2  is on the lowest level  has to be  carefully  reviewed  and again let's  look at your datas  you for sure collected  before you made this conclusion on  CO  Ef %  and so on. 

Next  up  SmO2  lowest, when VO2  highest ?  First   if we can look closer  at the  Time VO2  information e   will sees whether there is not a delay of  VO2 information from SmO2 information due to the technology  and the way  you assess VO2  at a  mouth level and SmO2  at a muscular level.
Depending n the VO2  equipment  ( Mouth breathing of  nose  mouth breathing you  have a  different peak situation different VO2  peak  results ) Looking at your  96 athlete  just in the overall view  it seems to me  VO2 peak i   delayed and different.?
Need  to look at one load at the time. 

This leads us to the last  Nadir  Load  is highest when SmO2 is lowest. I have to dig back  but we showed on the forum some case studies  done with Mary Ann in palm Springs, where the load was long over  and SmO2  kept  dropping.
 Why  would we see that.?
So in your datas with VO2  we  have a great chance to see this in all 6  cases. What we need is the raw  CO2 datas and the  timing together with  SmO2.
 This will lead us into the respiratory  question  and  finally to the O  diss  curve  reaction. Depending in the athlete ability to get rid  of CO2  as a part of the H +  buffering or not  we have  an ongoing drop in SmO2 after the load till we have a balanced    O2  disscurve. Or in other words  if the athlete    got hypercapnic,  SmO2  will drop after the load  so lowest SmO2 is  NOT  where we have the  highest  load but after.  In some cases  we can even create the opposite  and    SmO2 will stop dropping  and    even  goes up  despite  a higher load  so by peak load  we may  have a  higher  SmO2   level. than by a lower load.
 Summary . I may be  very wrong  than I have to  go back,  but  I  would first like to see the  raw  datas  whether this is really the case. SmO2  lowest  or  Nadir  when HR . Lactate VO  and   work load is highest.
 If that is the case  NIRS  looses   the  benefit we  like to have ( live feedback with  no time delay ).
 Thanks  again and yes  would be fun to have a closer look at least the No 96  athlete  .  Will be back  with  questions in cycling as a good idea as well as  VO2  max  and lactate  as a  good combination  for  info on all out ?


Development Team Member
Posts: 1,501
Here the summary , why  I would love to see  the raw  data.
 Why. Because I  would have to change the  ideas  and explanations we use  for many of  our  seminars  and presentations.  Here the very  simple  explanation on NIRS>

MOXY  webinar  on e.jpg

And here the counter  argument  from our  webinar. SmO2  lowest  when lactate highest  workload  highest  HR  highest  and VO2 highest

MOXY webinar  2 comnclsuioo0n.jpg 


Development Team Member
Posts: 18
I am surprised that the SmO2 levels were not lower @ max effort for the cyclist.  

Chris Balser
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