June 5, 2014

Anatomy Lesson: Core


The muscles of the trunk can be divided into “mobilizers” and “stabilizers” 

The Mobilizers of the spine are the more superficial muscles that cross over multiple joints so that when they contract they move many joints at once.  These are the muscles we feel firing with voluntary movement. These muscles are designed for quick, powerful and explosive movements so they fatigue quickly.  Their capacity for endurance or sustained activity is limited due to their muscle fiber type (fast twitch). Therefore, their capacity to provide core stability is limited.

  • Rectus abdominus (Runs from the pubis up to the xiphoid process of the sternum to perform trunk flexion)
  • External Obliques (Runs from ribs 5-12 down to the iliac crest to perform contralateral trunk rotation)
  • Erector Spinae


The Stabilizers of the spine are the deep, core muscles that go from spinal segment to segment. By their fiber type (slow twitch), the core muscles are designed for long term, prolonged use with a high capacity for endurance. They contract for long periods to support us when we sit or stand for a prolonged time. They fire beyond our conscious control, for the most part.

  • Multifidus
  • Transversus abdominus
  • Quadratus Lumborum
  • Internal Obliques
  • Gluteals, psoas, diaphragm, & pelvic floor play a minor stabilizing role


The 2 Main Abdominal Stabilizing Muscles in detail…

1)Transverse Abdominis: Runs from Thoraco-lumbar fascia, anterior 2/3 of iliac crest & ASIS, lateral ½ of inguinal ligament, and lower 6 ribs to the linea alba/pubic crest.

Weakness causes an abdominal protrusion, increasing the weight arm on the Lumbar spine.  Actions are SS Rot, expiration, and abdominal viscera support.

2) Internal Obliques: Runs from anterior iliac crest and thoraco-lumbar fascia to costal cartilage of ribs 8-12.  Actions are rotation and lateral flexion to the same side.


Learned enough? Now let’s get to how to work them. Here are a few links below to some of my favorite Abdominal workouts:

Core Challenges (an entire year of FREE ab exercises!)

6 for 6 (hit the abdominals from all different angles!)

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