Our Second Heart and More

 
In a recent class, I mentioned that the calf muscles are sometimes referred to as the second heart.

Some of you wanted to know a bit more about this idea, so I have linked two very short articles that explain it:

ARTICLE 1
ARTICLE 2 

I am not one to have a muscle hierarchy or ascribe to the idea that there are magic muscles.

That is, muscles that are significantly more important or create more problems, than others. But it is interesting to look at the differences in our muscles' shape, design and location and the different roles this enables them to carry out. This diversity in muscle behavior is one of the many things that makes our bodies so amazing and adaptable.

Muscles located at the proximal and distil ends aren't specialized to carry out the same role(s). 

Let's look at the lower leg. For instance, the gastrocnemius and soleus that are the muscles mentioned in the articles I have linked to and sometimes referred to as the second heart. They are short fiber pennate muscles. Here is a definition of a pennate muscle.  Definition: A pennate muscle (also called a penniform muscle) is a muscle with fascicles that attach obliquely (in a slanting position) to its tendon. 

These types of muscles generally allow better stabilization and force production but less flexibility.

 The muscle fibers insert into the central tendon at an angle that does not align with the main axis of force transmission. This arrangement gives them greater capacity to function isometrically and to both manage and generate forces through energy storage and return via their interaction with the long Achilles tendon. Compare this arrangement to the fiber arrangement of glute max for instance, which has long parallel fibers that run along the length of the muscles and in the direction of force transmission. This means the glutes have a greater capacity to generate force (those heavy kettle bells swings, or big jumps or leaps, for instance) and over a wider range of motion via eccentric and concentric behaviors.
  
The articles I have linked to describe how the muscle contractions in our lower legs act like a pump to help move our blood back toward the heart, hence the term "the second heart." 

This is just another small thing that illustrates how this biological system of ours is multifaceted, complex, functional, and fascinating in its evolution and design. Many tissues, many roles, all moving together, sharing workloads in different circumstances and under different environmental and task constraints, and somehow manifesting one harmonious symphony.

This is one of the many reasons to keep moving. So that we give the many instruments that make up this symphony of a body a chance to play their role in a whole that is somehow greater than the sum of its parts.