Thursday, January 18, 2018

Respiratory muscle O2 - How to....

This post will consist of a "methods" section on how the tracings presented on respiratory muscle O2 were done.  It also will give you some ideas how to implement them yourselves.  Firstly a repeat glance at the original first post on getting set up in general may be worthwhile.  Secondly, I can't say how well this would work with a Moxy or Humon hex sensor.  Size and shape possibly will be factors in getting this working.  

Because of the curved shape of the chest/torso, as well as the "wavy" shape of the rib protrusions, getting a nice tight placement is essential.  Coupled with this is getting extra light blocking material over the sensor covering a wide area.  I have wondered at times if riding in bright light could result in some light transmitting through adjacent rib areas polluting the signal.  I have found that putting the sensor vertically just above the lower boundary of the rib margin, at the anterior axillary line to be most helpful.  Further around toward the back and you will start picking up the lats, too far forward into the mid chest does not capture hypoxia as well.

 
A Skins long or short sleeve top is ideal for keeping the senor steady.  I also put a folded Coban wrap on top of the sensor as a light blocker.



If the O2 sat is above 80%, placement may be poor with ambient light degrading the reading.  


Behavior of costal muscle O2 in ramp cycling vs resistance exercise.
An interesting observation is the difference in O2 tracings depending on the exercise done.
As we have seen before, a typical resistance exercise session will cause O2 desaturation, lower total Hb from external compression then a rebound in both parameters after the interval.  With the above sensor placement, there is certainly good desaturation doing 3 sets of sit-ups, then rebound after, presumably because these muscles are used in the exercise:
  
In contrast to the above, a 60 sec cycling interval at above 500 watt average.  Notice the lack of rebound to the O2.
 

The rebound/hyperemia that occurs in locomotor muscles after an interval is a major reason why I can't see O2 sensor tech being particularly useful in judging when to do another effort, or monitoring recovery.  
The two examples are meant to illustrate sensor placement validation.  Either sit ups (with or without extra resistance) and even better a maximum 60 to 120 second cycling interval should be more than adequate to give one their lowest nadir costal O2 possible.  




In the next series of posts we will take a more detailed look at the costal O2 drop under different circumstances, possible use in determining training zones and in preventing over zealous power usage on the road























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3 comments:

  1. Hi. Thanks for your posts, are very useful to try to understand this kind of tools (I´m a moxy (lost) endurance user (runner and cyclist)). Unfortunately, I can´t see all the pictures (google chrome and mozilla firefox don´t show it). One more time, thanks. Very interesting.
    Greetings from Spain.
    Néstor.

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  2. Thanks for the write up. Have been looking for a better location than the deltoids as an less involved muscle for use with Moxy simultaneously with VL and calves, tried the location you mention too but with less convincing results - could be anything so no criticism there - and so far ended up using the pectoralis major. It seems less influenced by changes between handlebar positions than deltoid and giving me some somewhat linear decrease under high load as a measure for how close I am to a general cardio respiratory limit. Wondering if you have ever tried that location too and had any thoughts about it? Thanks.

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    Replies
    1. The costal area is very tricky to get right and if you are using a Moxy, it may not be possible due to it's size. The BSX is a bit smaller and even that can take much fiddling to read properly. If you have an android device with ant+, Ipbike has an annoying but useful feature. If the light leakage is too high, it displays a warning screen that basically blocks the view of your data. So, if that starts happening, I know my placement is not solid and I pull over and readjust(in the name of science). Sometimes only a mm or two makes a difference.
      For the non locomotor area to be somewhat useful, I think two conditions need to be met. One, there needs to be some muscular activity in the area to compete with the legs. I have put the sensor on the forearm without much change, but the bicep (for me) shows better desat since I am using that muscle to stabilize at high intensity. The second is the ramification of the hypoxia of the non locomotor muscle - the desat of the costal muscles herald impending respiratory muscle decompensation with reduced ability to have efficient work of breathing. This will then impact the leg muscles and cardiac system. If you noted your deltoids or biceps desaturate, those muscles are of little consequence in cycling/running. Of course it still shows that cardiac output redistribution is happening but of less consequence.

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