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Roger

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 #1 
I decided to start a new thread on response times at the onset of load.  I've been working on this topic for a Moxy tutorial and I've run into some aspects that I would like to test my thinking on.

The following graphs are from some data that Daniele posted earlier today.

http://forum.moxymonitor.com/post/show_single_post?pid=1291111468&postcount=37

The first graph shows the SmO2 for the biceps and VL for the entire 4/1 test.  The second graph shows a zoom in on just one load segment.

Note that the Heart Rate, VL SmO2, and Biceps SmO2 all have very different response times to the onset of the load.

Here is my thinking on this.  This load is quite a bit sub-maximal so likely using mostly oxygen dependent metabolism.  The oxygen used by the muscle to produce energy is the combination of the oxygen extracted from the flowing blood and the oxygen extracted from what's stored in the muscle myoglobin (or hemoglobin that's already in the muscle).

The oxygen extracted from the blood is the blood flow rate times the arterial-venous oxygen difference (Fick principle).  At the onset of the load, the blood flow rate is too low because the HR is too low and the arterial-venous difference is too small because the SmO2 is too high.

So right after the onset of load, a lot of the needed oxygen comes from oxygen stored in the muscle.  On the VL, this occurs for the first 43 seconds on the zoomed in load step.  After that point, the combination of blood flow rate and oxygen extraction is sufficient to meet the needs of the muscle without using any more stored oxygen so SmO2 stops dropping.

However, at 43 seconds, the HR is still increasing.  It increases until about 90 seconds.  This probably increases blood flow to the muscle and we do see a slight rise in the VL SmO2 as HR rises from 43 to 90 seconds.

On the biceps, it takes 158 seconds for the SmO2 to reach a steady value.  My hypothesis here is that the oxygen usage in the biceps is much smaller than the VL because it is a minimally involved muscle.  This means it takes longer to use up the stored oxygen.  That's why it takes 158 seconds for the biceps to reach a stead value.

I would appreciate any feedback on this thinking of the response times.

VL Biceps HR.jpg  Response Times.jpg

juergfeldmann

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 #2 
Roger  do the  same  with  tHb ???
bobbyjobling

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 #3 
I think smO2 comparison can be misleading without O2ht. Would comparing O2ht drop delay be better?
Roger

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 #4 
Here are the THb graphs.

The response time indicators are just copied from the SMO2 graph for reference.


Response Times THb.jpg  Response Times THb Step.jpg 

Ruud_G

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 #5 
There is time / intensity depency though) look at time till overshoot peak versus duration (ie intensity). And also the speed at which deoxygenation in non-involved starts
juergfeldmann

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 #6 
fun isn't  it .  There   are  some great additional points  once we look the reactions but as well the    offset. I will show  some pictures  from the same  workout  on graphs   from big  to very close views.
 Here  what you  have to think  and look   when we look time  reactions. Is the  circulation  in the top  are  the same time as in the legs  so  subclavial  and  femoral ideas  as well as    what  happens  with  BP  corrections . Lot's  to think  from a physiological point  and I am looking forward  to see how  math  and physiology  will clash in some cases.   Here  an additional point. What was the bike position  . Was it upright  top handle bar  grip in  forearm pronation,  or on   break  lever in  forearm  neutral zero position of in  elbow  aero position. All three  cases  will how a different  biceps  reaction.  This is  fun as    hen we look the biceps reaction in higher intensity  they could be  some interesting  tHb  reactions showing  up  when you look carefully.  Here my  speculation  and  it  could be  wrong but   he  may have been  at least during he load in  aero   elbow  position ?  Last  question. What  would you  use this timing in the way of practical application ?


Ruud_G

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 #7 
Well from a practical point of view I would say (but that is also dependent on the position (if standing on pedals on steep hill......) try to relax the upper body (as in also including arms of course) as much as possible. The more relaxed it is the more you save for the muscles doing all the hard work [wink]
DanieleM

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 #8 
Hi Roger,

my feedback below:
Quote:
So right after the onset of load, a lot of the needed oxygen comes from oxygen stored in the muscle.  On the VL, this occurs for the first 43 seconds on the zoomed in load step.  After that point, the combination of blood flow rate and oxygen extraction is sufficient to meet the needs of the muscle without using any more stored oxygen so SmO2 stops dropping.
However, at 43 seconds, the HR is still increasing.  It increases until about 90 seconds.  This probably increases blood flow to the muscle and we do see a slight rise in the VL SmO2 as HR rises from 43 to 90 seconds.


I think we can say that during the first 43 seconds utilization/consumption is more than what is delivered.
After that, as you said delivery is still increasing and probably a bit more than what is consumed (perhaps to partially restore myoglobin) until it reaches  homeostasis at 90s where consumption and delivery seems in good balance.

responsetime.jpg 
Below a graph with estimated VO2 based on HR, SmO2 (data)+ SV (estimated).
vo2_hr_smo2.png 
No much correlation with the SmO2 values from the biceps.

DanieleM

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 #9 
And this is the detail on a first interval from Rest to an easy intensity (120W)

Even without a mask for VO2 measurement the graph with HR and SmO2/tHB is telling a lot:
moxy-vo2-graph.png 
Quite a different picture when moving to an higher intensity (240W) during the workout.
moxy-interval-240w.png 
SmO2 start dropping almost immediately (Consumption higher than Delivery) and no HR/VO2 overshoot is seen.

Finally an heavy intensity with VO2 slow component (HR/tHB) even if flat SmO2 (Delivery and consumption are kept at balance but both increasing)

moxy-interval-290w.png 


juergfeldmann

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 #10 
Question.
 
a)  HR increase   can mean  higher  CO    as HR  up  SV stable
 can mean  same CO  as HR  up  SV  drop.
 Can mean Co  down  as HR up but SV  more  drop  so HR  x SDV  =  lower  CO  than before  . And so on.
 So  tHb  up  can mean a  higher CO  so overrule  of  muscle compression. CO  up  can mean higher dilatation  due  to higher CO2   use due to respiratory  limitation?  Now  same  SmO2  %  by the  a higher tHb ?
 What does  that mean ? Can we look at   biased  O2 Hb  and  HHb  at that  specific  stage ?  Remember the weakness of  NIRS  as it is  one single muscle only  and the option intermuscular  to  change the way  we  can supply   performance.

DanieleM

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 #11 
Here we are talking about transitions from rest (or recovery) to activity.
I have only HR as part of the systemic delivery but I can assume that the Q (or CO) is following approximately the same kinetic and until at least moderate intensity we can easily assume that SV is also increasing.

With the appropriate limitations (missing VO2 data), it shows very nicely some relationships between local delivery/consumption and systemic delivery/consumption.

PS: the graphs are from Vastus Lateralis which until moderate intensity can well be considered very involved in cycling (for this reason it has been used in all the scientific studies related to VO2 ON/OFF kinetics)




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