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Posts: 1,501
I like to  give some feedback on this topic on here  to avoid ( if  I can ) a messy  situation.
 The  direction to this feedback is  from some discussion we  had on RPM  and  NIRS feedback.
 Example. The question was, whether a  lower  RPM  may  due to the fact , that we may push harder down  change the reactions on blood  flow  and  we  can or may be able to see this in the tHb respond.  So  we have the  ongoing unanswered  question.What is better a high or  a low  RPM.
My  few  cents  answer is>
 I  do not know, that's  why we look individually  and see  how   the body reacts in the different   RMP situations  as well  as. It may be that  during the process of  improving your biking ability   you may as well change the reaction  you may have in a low RPM.
 My  first  question always  is the same.
 We need energy  and   what is the bets   option  for energy  ability in the activity I  choose.
  Extreme example  here.

 I  do a  squatting exercise  with the goal  to  be able to lift heavier  and heavier weights    in squatting.
 That  means I  more or less for sure will create a delivery  problem,  so  delivery systems  like cardiac system  and  respiratory system  have a minimal impact on my energy  situation. ( read minimal  as respiration may   have some additional   help available prior  and after load.
Same in this case we  will have  most likely  an occlusion   resp arterial occlusion.
 So  tHb is  of some importance  to see  contraction quality   and  SmO2  will  drop  for sure no matter what  muscle fiber systems  we  may or may not activate.
 Any occlusion will create a stimulation of   deoxygenation in one or the other way.
That is  great to know  as in a  workout if your goal is to stimulate  deoxygenation ability   you  simply try to reduce delivery.

The other    side is  your goal  to have  optimal delivery  like in a  long distance event  where you hope your O2  delivery  is  heavily  supported  by an optimal delivery   situation. So optimal economic  cardiac  hemodynamic as well as optimal  respiratory  balance  for  a great  balanced  CO2  level.   Now  lets'  try to keep this in  mind when we look some case studies  of RPM reactions by stable wattage.
So  I like to show  some  studies  we did  and some  form  outside   sources  with  lot's of NIRS experiences. Below is a very nice  paper  on actual pedal stroke  and  NIRS reaction.

I will show later some of our assessments  we did in the same way.
The above  picture  and explanations  shows you the need we started   to create a common NIRS terminology  as well as  color  coding  as it will make  discussions  and  communications so much easier. Just short as a recap   or new  for new readers.
 a) we use the word  compression  when we  have an initial or any muscle contraction, which  " squeezes  "  the diameter of  blood vessels together  so we have a  lower blood flow  but still blood flow.
b)  if we increase the pressure than  we may reach a intensity of pressure  so that the venous  blood vessels  may be  more squeezed than the arterial system as the  venous system is a kind of a " cheaper" easier to compress blood vessel.
 Now we  talk  about outflow restriction  ( some talk about  venous occlusion trend.
 What it means is, that we have more blood moving in than  can  go out  and in this case we will have a pooling of blood   in the area  so tHb  will actually go up, but not because we have more blood flow  but more blood volume  due to the pooling.. If we release   contraction force  we will see thB  dropping as a pooling outflow.
 If we increase  contraction we  can reach   complete  occlusion  or   we stop  inflow and outflow  so tHb  will be flat  and it looks like we have free  blood flow.
. Difference.
 If we let go an occlusion  tHb  will drop (   some exceptions (  and  the other way  you  may have  distinction between free  flow and    complete occlusion. is SmO2  i under activity    and  art occlusion caused by activity we will sue  still a lot of  O2  so SmO2  will drop rapidly  versus free flow  so flat tHb  but  less  SmO2    drop or no drop or even sometimes increase.
 Now keep this in mind to start out  here  and look the explanation above  and it make  somewhat more sense  in the way we discuss  NIRS on here. Next  up  we will look some options.


Development Team Member
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Development Team Member
Posts: 1,501
Okay here the next fun step.
 We were super interested  to see how  a  close up pedal stroke  reaction or in fact any reaction would look like. It could be a rowing motion, a  stride impact  when running, a tennis hit  and so on. A Fore arm reaction during a  motocross  race or a  MTB downhill action. Reactions during a  downhill ski race  and so on.
 Here a very  small example of a  pedal stroke reaction in a 5 1 5   form a  world  class cyclist. This is  an old  case study and we use  a great  equipment  for this   Portamon  from Artinis.

super close look geoff at start after 1 min break.JPG   Short
 Yellow  on here is tHb  reaction  Now  we have  thick and a  thin yellow. The thick one is  more   likely blood flow in the actual muscle . (  same as we  would see with MOXY ). The thin yellow is the blood flow   more on the surface  so more skin   situation..
 The  section you see is  after a 1 min rest in a 5 1 5 assessment.
 So you see the compression outflow  due to  start  of  contractions. Interstice is that in the rest as you can see from the thin trend  the blood flow  was as  expected more in the skin ( co0oling done  effect )  than in the muscle    and than it shifts    as you can see  from the skin  more to the deeper  layers.
Red is  O2Hb  and blue is  HHb and as well thin  and thick is   from the depth.
 You can actually  figure out the RPM  when you take the  time  below  and  each pedal stroke.  Now  the interesting point is :
  Is the drop in the wave  of tHb  due to compression   and the increase  due  to decompression 
 Is eh increase  due tom venous out flow  restriction and the  drop due  to  occlusion outflow reactions.
 I hope you see  where we  go with this.  and the  challenge  for use w as than  to  figure  out    what is what  and if we  may have both  in the same athlete in an  increase in load situation and how  this would create a  Challenger  for   energy delivery.
 Than  if we  change RPM  do we improve   eh situation or do  we  make the challenge of energy supply  even bigger.
 Let's think that through.

 here to end the idea.
 a closer look on the above  pic  and a comparison of two  equal  good world  class cyclists.
gk at start pahse super close.JPG

yama gk rpm tHb.JPG


Development Team Member
Posts: 1,501
I like to add some  additional thoughts  to this  ongoing discussion.
 Reality is the most  decently  trained  cyclist  will choose a higher RPM  than  what  is suggested  form   scientists. This is as well mentioned  in the article  sent o us  by Ruud.

A significant mystery still remains to be solved by science, he says. “Cyclists do not, in practice, choose to pedal at the cadences that scientists find to be the most economical in terms of oxygen cost. Instead they choose to pedal notably faster than this,” says Professor Passfield.

One of the interesting questions is  whether this  question  could be closer to an answer, when we  look  above and beyond a  idea like VO2  peak of max. Regular readers her e my  remember , that we   think VO2 peak is a great tool  to assess overall team performance. . But what we  argue is, that a  high VO2  max  may be a great indication  of a great  endurance   athlete but it as well could be a great indication for a very inefficient  activity .  I did many  really many years back in the high-altitude  center in St, Moritz  Switzerland some fun assessment. We ha rowers  and  cross country skiers  and cyclist.  and we  would  test them in  the least used activity.  So the rower  would  bike , the   cross-country skier would  row    and so ion.
 They improved in a very short time their performance  but what was fun  was, that by the same wattage  they would push the first  day  compared  to after 2  or three weeks  they had a  much lower VO2   as a sign of a much improved  coordination  and therefore  would get rid  of  muscle groups needed  at the beginning to keep  for example balance instead of using that  for performance.

 Now  110  RPM is a very high RPM  even for  top cyclist  and if  we  would look the range  and we would ask Froome  to bike 120  + he may show a  similar  or the same picture  as a non pro cyclists  by  100 or 110 . Coordination problem  so not enough time  to  contract relax.  Now  this could be nicely observed  with NIRS  to see how tHb  reacts  and whether we see a  compression relaxation    or a  occlusion  and a outflow reaction.

Now   here   another point to this.

In the article we have  an interesting section.

Physiologists know that muscle efficiency all comes down to the speed at which your muscles can contract. If you choose a gear and cadence that allows your muscles to contract at one third of their maximum velocity, you’ll maximize your power output.

Allow me to argue  against the statement.
 I believe that muscle efficiency  is  at leads as  dependent on not on the speed  you contract but much   more  rather on the speed  and therefore  time    how you relax.
  Contraction needs  energy  and using energy is  not really  efficient.  loading  and adding  fats and effective O2  back to the   working area  is  a  question  which is  at least as  important to ask  for efficiency in sports, where we  depend  on an ongoing energy supply.
 Contraction  creates a delivery  limitation relaxation ads a  supply  possibility.
Now you add this  to  an intra  and intermuscular coordination  and you see what I mean.
 I need  an optimal relaxation between intermuscular  involved   muscles  as well an optimal relaxation of motor  unit recruitment to  be sure I can supply  enough O2  for the  ongoing  demand .  Here a  fun game I do regular.
 I mount one moxy on the VL  one  on the calf  and one on biceps  femoris  and this on both legs.
 Now  I  look for a  technique   where I see  mainly  calf  muscle deoxygenation  and free flow in the other once. As  soon I feel  bad in the calf, I change technique  and try  to find a  way to use  hamstrings mainly  and desaturate  there  and so on. So I  keep  same wattage  and  just use  different  contributor  to the pedal stroke stroke  and switch them around.  Now this is not  new  as I did  that when I bought my first  SEMG  30 years back. The difference.
 the SEMG    did   give me the feedback , that I really switch  but now  I  have not only the  feedback , that I switch  but as well how long  I can stay there,  before I have to change.
 Main feedback comes  from both SmO2  and tHb.

 In my case    : Calf  muscle I  can create a  complete occlusion  so tHb  can help there  and I  can drop SmO2  really  far  down  when concentrating on this muscle. In  actual  riding  my  calf  is very minimal involved  so barely  any change I n SmO2  and always  good flow  so not  a lot of  ankle  involvement in my  stroke as well not a great  up  pull    with knee flexion. VL   shows  for my technique  in normal riding the best trend  but I have a problem to really drop  further even if  I try to concentrate on this one.
 Hamstrings  is for me easy to  change  by  changing  position on the saddle so I can imagine a leg press option.

Now  next up  some additional thoughts  on the limitation of  using just VO2  max  as   traditionally is done.
 The first step  they now start  and it is  interesting to see, as  other sports  since a long time  added  additional ideas  to efficiency  testing. Here now at least they recognize  RPM as a potential  factor  to look at it closer.

“We conclude that pedaling rate is an important determinant of human VO2 during cycling exercise and it should be considered when predicting oxygen consumption,” says Dr Formenti.



Development Team Member
Posts: 1,501
Now  I like to back this up  as   other sports  may be a little bit ahead of cycling.
 Here a great picture  from the   incredible work   from ostersund  sweden  and Holmberg.

limitation in DP.jpg

 You see what I mean. VO2  and the ability  to  actually use O2 if  you can deliver  depends   not just on physiological  systems  but as well on  equipment  and  technique.

 So in  cycling the discussion  on crank arm  length   when using just VO2  may be not o optimal  but when we add  NIRS  we may get more feedback. Seat  height aero position  and so on., Blood  flow  and therefore   delivery in an endurance  sport may be a very important  factor  to look at.  So  when we go back to RPM we  may have to look the influence  of RPM  on blood flow   but as well on the reaction we may create  toward other  physiological systems.
 Here  one  area  we often forget.

 Okay here a  easy experiment.
 Stand up    jog on the spot. Now  double the arm movement  but keep the same leg  motion. So create a coordination challenge.
 Not easy to do  if not used.
 Now   check   your respiration, when you do normal  on spot jogging  and when you double  arm motion. What  do you observe.?
  Why  ?
  Now  here   the next   section   and why VO2  may be not  optimal as we do not know   from just VO2  max  who   asked  for  how much O2  at the time.
BF and RPM.jpg 
VE and RPM.jpg

VO2 and RPM.jpg 

Now  you add the  answer  you gave on why  respiration reacts  in our  small experiment that  way. Than you add the information  what happens  with Blood  flow  or volume  in this case  and you  have.

respiratroy  muscel blood flow.jpg


Development Team Member
Posts: 1,501
Now  here some additional  ideas   and some unpublished  studies  to give some thoughts on how we look at RPM  or cadence  in different sports.
 The  key word  was  blood flow  or  delivery  situation  to maintain  O2  delivery to maintain  activity  .  First  an old  case study  and keep in mind, that this result  is  for this case only  and may or may not  fit to another persons  situation  and physiological limitations  and compensations.

This is a portamon study  from far back and  red is O2Hb  blue  is HHb  and  green here is tHb Penetration depth  is T2

RPM workout NIRS controlled.jpg

Below is a workout  from a world  class cyclist  world  cup winner.
 Yellow  here is tHb  Blue is HHb  and red is O2 Hb. We  where looking at  different penetration depth to see, whether  RPM  changes  may change  the  blood  flow in the different depth of  a  muscle.
 So thick is muscle  thin more likely surface    so skin  ..

 We repeated  many of the  test  and cases later with Portamon  and MOXY  on the same muscle to see possible differences  but as well confirmations. We use this in  compressor clothing assessments  to  how to fixated  NIRS on a muscle  to  temperature  changes    and so on.

rpm level 2.jpg 

So what you see is a biased  graph  with the same wattage load all they  way but every marker we  increased  RPM  from a baseline RPM we found  as  possibly optimal in a 5/1/5  and in a  specific  bike fitting position of this athlete.

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