Apr 18th, 2013
Soleus is a knee extensor!
The past 4 years have been an incredible journey and eye opener in the realisation that all I previously learnt about Joint Movement and in particular Muscle Actions could be thrown out! (well nearly all)
Not because it is incorrect but because it applies to an isolated reductionist approach which has little appreciation of true muscle activation, real joint motion in function when the human body is upright and moving against gravity.
Just think about this:
If I asked you where is and what joint does the Soleus muscle cross and act on and what is its concentric joint action?
Simple I hear you say – your answer – it lives posterior to the tibia and fibula, crosses the posterior ankle via the calcaneal (Achilles) tendon and creates planter flexion at the ankle.
And you would be correct if that foot and ankle are hanging off the end of a therapy couch or if the person is floating off the surface of the earth or they exist only in an anatomy text!
So what action would it take if the foot was unable to force through the ground or pavement that you are running/walking on? You may still say a degree of planter flexion at the ankle which contributes to forward motion during gait, and of course this is correct as well, however it also extends the knee.
If the insertion (calcaneus) cannot move closer to the origin (upper Tib and Fib) as the concentric contraction takes place the origin will swop over and become the insertion and move, in this case the tib and fib, resulting in a degree of knee extension as the tibiofemoral (knee joint) is the next joint further up the kinetic chain that is acted upon. Hence Soleus is a knee extensor, easy!
I am aware that I have hung myself by picking out one muscle (a reductionist approach!) and its actions as an example; however I hope you can see this is for explanation purposes and keeps it simple for me to understand and explain.
I have found this obvious but basic process to be profound and it’s made me question the way we have traditionally taught Anatomy over the years and in particular its application to training our clients as PT’s/Therapists and Movement practitioners.
I hope to share with you more thoughts on how little we know – but take heart knowing what you don’t know is often the best place to be!
Till next time….we’ll consider some of the fundamental forces that contribute to movement.
Gary Gray, Dr David Tiberio, Doug Gray Gray Institute