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Development Team Member
Posts: 59
I've been going through old forum posts and
a notion of muscle coordination comes
up fairly frequently.

My understanding is that in order to perform some
movement we have to engage one or more muscles
and coordinate between them.

If there's many muscles involved we have intermuscular
coordination where we may manipulate how much each muscle
to perform the same movement. Is that correct?

1. What is intramuscular coordination then? Is there a simple
example of it in running, for example?

2. What is the main physiological benefit of muscle coordination?
Thinking naively, I would think that you always want to use your
strongest muscles to perform some movement as opposed to
engaging other, possibly weaker, muscles.


Development Team Member
Posts: 369
Hi Runner

I am no expert, but my understanding is that intra-muscular co-ordination refers to the co-ordination within the muscle i.e. the co-ordination of the different muscle fibers within a muscle. Where everything within the muscle is co-ordinated, the muscle will be more efficient and produce a better output than what it could without co-ordination. So in your running stride you might want your VL muscle to be co-ordinated as possible.

Inter-muscular co-ordination refers to the co-ordination across different muscles. Again better co-ordination allows a higher overall result, but also prevents one muscle from tiring unnecessarily. So in your running stride you want all the leg muscles to be co-ordinated, and the muscles used in landing would be different to the muscles used in the jump part of the stride.

If i could use an analogy of a corporate company. Intramuscular co-ordination would be like all the workers within a department. Different workers have different skills and some may be better than others but you want them to work together to maximise output for the department.

Intermuscular co-ordination is like the co-ordination across the departments. You want the departments to be well co-ordinated to maximise the efficiency of the company. As one silly example you would want co-ordination between your product development and sales/marketing departments so that they executed their sales strategy to align to the timing of when a new product is available. The point that your product development department might be strong and your sales/marketing department is weak or vice versa, still does not avoid that the optimal outcome would be for them to be co-ordinated).

Sure that others will be able to add with more detailed physiological explanations.


Development Team Member
Posts: 227

Ryan explanation is great, I suffer from similar inter-muscular coordination, in my case I think it is caused by my lower back issues, and nerves not firing properly to my left leg. My fairly static position on the bike is not helping. I’m working on it with quite good results, but it is very hard mental work contiguously reminding myself to introduce slight variety to my position. 

I think in many "healthy cases" where increase in training hours doesn’t translate in increase in power, intra and inter muscle coordination could be low hanging fruit, and I believe off the bike exercises are probably way more efficient at list in first stage of the issue resolution.


Development Team Member
Posts: 59
How do inter-muscular and intra-muscular coordination limitations
show up in SmO2/Thb?

What's a good test to determine if this is an issue?

Development Team Member
Posts: 1,501

It is less   that  you can  "test"   this  limitation  with NIRS  , but rather NIRS is  used  to correct them as  tHb and SmO2  can  be a great  live bio feedback , whether you  improve inter or  intra muscular coordination. We use this feedback  nearly daily  when we  show   workouts on clients  and how  they can see whether  they increase intramuscular  recruitment   and or  change  the intermuscular coordination. Key  words  for Physio  I talk with is  patella tracking ( check  with sky line  x Ray.
 So  for example an intramuscular  strength  for   vastus  medialis. or  an intermuscular coordination between VM  and VL  for proper  patellar tracking.

Now remember in the intermuscular  coordination  2  main options.
 a) muscular  dysbalance  more  used  for  injury  or overload prevention  and
b )  muscular  dysharmonie. more  to improve efficiency  and yes as well  try to avoid compensation.
  Key word  for  example in track intervals. Gluteaus  maximus  and  hamstring  versus  gluteaus  medius and  hamstrings. Look at  end  sprints in a 400 m  track event.
Add the discussion we had  much earlier  on the fact forum already
. Metabolic  acidosis  versus respiratory acidosis  and stress fractures.


Development Team Member
Posts: 36
In relation with inter-muscular coordination: My calves sometimes cramp on very long rides and I wasn't able to correct that by nutrition - which after some doing some research in this topic seems to have been an unfounded approach anyway. Interestingly my calf muscles also had the lowest Muscle Quality score of all muscles when measured with the Skulpt. Though the scientific basis for that score isn't totally clear as well, my analysis now is that I am simply using my calf muscles beyond their capacity, so I have decided to attempt a two way approach with strength training (the result of which should be measurable by that MQ score) and finding a pedaling style that uses less calves - which I am planning to measure by SmO2/tHb on calves vs VL. Wondering what others might think of this reasoning and plan?

Development Team Member
Posts: 217
Yes Takura I agree with your idea, I think it is always worth focusing on each muscles section that is engaged in the action of your main activity.

It's a bit like Bodybuilding, in the sense that you subdivide your body and each day you train a different part of the body, in a sequence where each training routine will not interfere with the next so to yield best recovery response. 

For example(cycling):  but don't take it as a real example because it all depends on the subject time, goals and philosophy to MOXY :
Day 1: CO
Day 2: calf, hamstring, lower back
Day 3: Respiratory
Day4: core exercises
Day5: CO (maybe)


Development Team Member
Posts: 1,501
Takura  and Bobby  good points.
Remember that  the  functional motions in any  body  runs  through a muscle  sling or some would name it chain ,based on a spiral motion ( DNA)   so  when we look at  a calf  muscle than look who is in that  sling pattern  and  who  is not ,  but may be  still engaged. ( Muscular dysbalance)
 Remember the  2  function from the gastrocnemius and look how  that may interfere  with recovery   in the different stages  of a pedal stroke.
  Look how  you can  change  the  force  of  the  calf  before  you  try to change a years  of  same   motion pattern, which is very hard  to  do, where as  the force  engagement change is a question of a  few seconds  and  than reassess the effect  with looking  at  the  NIRS  and if possible SEMG  activity . When you us e NIRS look carefully on the tHb  reactions  and   add the   dysharmony  and dysbalance questions  to the equation.

Here  an example  we just  discuss in a rehab  group  on how to use  NIRS  ( if possible  add SEMG )  in  specific  rehab of ACL  and  patellar  tracking problems )

In this specif  cases  it depends   in the ACL on the  operation technique .
 a) semitendinosus  graft versus  1/3 patellar graft
Graft in this case means, that they take either a part of the semitendino0usus    or a part of the patella tendon   to replace  the  ruptured  ACL.
 So in the case  of  semitendinous  we  have a a  time  restriction of   working well  with  knee flexor  /hipextensor    sling. in the case of  the patellar tendon  we  have a time  restriction  of  working  with  knee extensor  hipflexion  sling.

Now  when we sue  this   for the  3  options.
1. intramuscular  coordination. We  would  try to fire  as individual as possible  either the  quadriceps  or the  hamstrings muscles.( Keep in mind the time restriction fo the  needed  "healing process )  So  during that time we  have a limitation of   contraction intensity  and may use  BFR  to  try to maint8ne  the fiber  ratio of  STF  FTF we  may need  if it is a  top athlete , If  it is a  persons like you and me  we  not   are too much  worried  in the start phase of  this  risk but  we than later have to rebuild  the  ration depending on the profession and or daily activity   this  person we  have to  engage  again.
Go  back and   see the  SCL  NIRS  example I showed  a while back from a  report  to an insurance company  to  show them  why we have an ongoing   problem   in this client. ( lack of  proper  rehab on the fiber  ratio he needs  for his job as only performance  was assessed  and not functionality.
 Or the  world  class downhill skier  with ongoing  knee  discomfort  due to  the  lack  of  specific   fiber constellation   rehab after  ACL.

So intramuscular in this case  would be  to learn to  fire more  motor units in   for example the vastus  medialis  in case of a  semitendinous  graft. For  the  many physios  now  on the forum.
 Think   what  the function of the semitendinosus is beside  hip extension and knee  flexion. This    in knee flexion position.  Now  what is the  problem   when  this occurs ?
Now  tHb  will guide  the  intramuscular coordination progress as well in what knee angel is it most effective  for the VM.
 2.1 Intermuscular coordination.
 Now depends on the activity . If we look in sports it is a difference  for this  section, whether you are a runner  or a  cyclist. ( therefor some  problem  for a  triathlete. ) So  the sling if we  have a patellar tendon  graft  and we work  on the hamstrings  ( knee flexion  section)  the sling for a runner   woudl be a  partnership  between  hipextensor  and knee flexor  for the  extension phase. where in a  cyclists  we would have a sling  with hipflexor  and  knee flexor.
 So  runner  gluteal (9 max )  and hamstrings  for  agonistique   hipextension.
 Cyclist    iliopsoas( rectus )  and hamstrings  for knee  flexion activity in the upstroke  6 - 12 o  clocks  section.
This  would  be to work   against  dysharmony  or  for harmony  in the motion.

2.2  intramuscular   but  against  dysbalance  example.
The  dysbalance  can be  either in a  antagonistic  way  so  for example  too strong hamstrings  and too week  quadriceps  which often happens in a   patellar  tendon graft rehab.   Why ?

Or   in a  more  simpler  options a  dysbalance  between  VL  and  VM  which than leads  to a mal tracking of the  patella in the  femur  trochlea.
 For  the physios  (  functional  sky line  x ray.

Now  in  the  discussed  case here look  at  dysharmony  versus  dysbalance  when assessing  your  calf  muscle activities  and gain think   how hard it may be  to  re learn a new  movement pattern  after  hundred thousands  of  pedal strokes , versus  change  in force  application.

An add on just for  fun.
 In  any case if  you change  the   calf muscle  integration  in your pedal stroke  you will change the  SmO2  pattern  or  trend.
 So  as a BSX user  you will change  your  LT  . (  does  that makes  sense   that the calf  alone  would  severely change  your  LT   ???


Development Team Member
Posts: 227

Great discussion.

Takura I suspect when your calves cramp they actually compensate for some other muscles that got tired. Working on calves will surly get you going a bit further, but will not resolve initial issue, and it might actually introduce new problems.

I read somewhere that calves muscles are not used that much during cycling, they stabilize your leg. Calves could be failing when your hamstrings are very tired, (long rides) or old hip injury. Try to analyze when this happens the most, during hilly or flat rides, are you getting off the saddle a lot or seating in one place for extended period of time. Is your saddle moved forward or back (in the case when saddle is slammed forward your hamstrings are less utilized)

Also check your saddle height and foot angle, too big foot angle you might be getting more power, but you will fatigue easier and calves might hurt.

I use Skulpt as well, just to give you perspective, few months back my VL, Glues and lower back were 99% of muscles quality, my hamstrings, RF,VM  were about 50%-55% of muscle quality, at 50% it is literally untrained, almost…

First thing I did, I started very hard working on my Hamstrings, 3 weeks later I had lower back issues and my respiratory system could not keep up…

Right now, none of my muscles are 99%, but my overall strength increased quite a lot. Funny to say; I train my sprints at 1/3 of power I used to train in the past.

I’m still work in progress, but I’m very happy with where I’m now, if not moxy I would never realize I pedal squares, and I would not be able to workout at the correct level. With my 60min power above 300W, initially I could only work on hamstrings at very low power 80-90W. Without Moxy I would probably dial to 250W and kill myself during first two sessions :0


Development Team Member
Posts: 1,501
Takura's  great  part of  his  calf  muscle  reaction triggered an interesting set  of emails  from cross country coaches.
I had  this winter 4  cases  fom cross county skiers  with the opposite  problem in cross country skiing. Tibialis  anterior  overload .
 Now  we talked  about  intermuscular coordination  and  had  2  sub categories.
1. Muscular  dysharmony
2. Muscular dysbalance

Now  that's  what we look  first  is it  1  or  2.
 Now   we used  NIRS in cross country skiing as it is   super easy to show  coaches  where the problem is  if  you can documented  live  and they can see it. 
 So in skate skiing in   all  cases we  had we solved the problem in a  few  minutes, as it  was a  muscular dysbalance. The  key was  to take load of  the tib anterior  and move it  back into a proper   muscular  harmonies ( sling )  now  the same  can be done in many cases in other sports  where  we  use  additional equipment besides  the body  so  in Takuras  case   the same  can be  done in cycling  just  from a  calf  muscle point of view.
 Takuras   information  creates some additional interesting  questions.
 NIRS on   the gastrocnemius  :
 Which muscle belly, medial or  lateral  and  what  function do they have.
 In other words   a NIRS on each Belly  will show  2  different NIRS reactions  and can show you  some additional feedback.
Which   trend is  LT  smile )
But we leave this  to the cycling community , as they work on this possibly daily in  bike fitting  and  other  assessments . 


Development Team Member
Posts: 227
I'm, in the process of correcting my TT fit with Moxy,  or rather fine tuning.
(unexpectedly my TT position is limited by relatively untrained upper body back muscles.... not inability to breath deep enough due to small hip angle)

Here is gastrocnemius muscle assessment while standing right after I woke up and brushed my teeth, so inactive rest state:

First picture shows composition myography method using Skulpt, and their "kinda unscientific" scale from 1-100 (they have corrected that just now)

Second was performed with Moxy, I hold Moxy in exactly the same place as I had skulpt on, and wrote down the results.

As you can see medial is much stronger than lateral, confirmed by 2 devices, I stopped using skulpt as Moxy is much easier to use, I was just trying to confirm if Moxy numbers could be validate some how with different method.

I find this fascinating, there is no other tool out there that can do this quickly and still combine all data on my Garmin computer.

I'm looking at those numbers as trend not absolute numbers, you got to admit they are impressively close between devices, and demonstrate more than sufficiently where work needs to be done.

Left        Right
77 - 88   91-78
57 - 44   41-55



Development Team Member
Posts: 66
What do you read out of those numbers?

Development Team Member
Posts: 227

Hi Gunnar,

I discovered my left leg was a bit weaker from my right leg. I was very curios where this weakness is coming from, goal was to test all major leg muscles and see what muscles are slightly less developed.


I look at those numbers as relative strength ratios illustrating overall muscle development, less fat more mitochondria etc.


They show my lateral gastrocnemius heads being better developed from medial heads, especially right side.

This group helps with planar flexion and ankle movement that would be bottom of the pedal stroke.

Interesting fact: when I get cramps during long race, it is always medial head never lateral… Again confirming data integrity.


Development Team Member
Posts: 66
Does that mean that when moxy is showing lower values (measured as in your case), the muscle is stronger?

Development Team Member
Posts: 227
I'm not looking at absolute values but ratios, in this case (same recovery, right after sleep etc),  Having said that eg value 45 in 2 different people could mean totally different things. In this particular example lower SmO2 value indicates better trained muscle.
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