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Mt Airy Exercise

What are your muscles really up to?

In last week’s blog post, we talked about the intentionality of rest in workouts and everyday life. This week we’ll talk about muscle contraction and the reason why we rest! 

Anatomy and Physiology just happened to be my favorite class! 

Let’s start from the beginning. The parts of your muscle that actually do the contracting (or shortening) are buried deep within your muscle. Try to think of the following as nested within one another. 

From largest to smallest:

  1. Muscle 
  2. Fascicle
  3. Fiber
  4. Myofibril (Actin & Myosin: the parts of your muscle that contract)

Actin and myosin are two strands that slide past one another, in order to shorten your muscle. Think about one of the largest muscle groups in your body – your quads. These small fibrils which are embedded in your muscle fibers, which are embedded in your fascicles, which are embedded in your quad muscles, are responsible for your ability to squat, run, and jump – to name a few! 

Muscle contraction is incredible, isn’t it? So why do we rest? We rest, in part, because actin and myosin cannot contract repeatedly on end. We would need an endless supply of calcium and ATP (energy) to make that happen! 

Calcium makes our actin and myosin filaments ready for contraction, and ATP sets it into action! Better yet, this whole process is triggered by our brains! 

Some additional food for thought: We need ATP for both contraction and relaxation.

Want to learn more about ATP? Tune in next week for our blog post on different energy sources for different types of exercise! 


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