Lesson 21: Functional Roles of Muscles

This course describes the functional role of muscles as it applies to kinesiology and human movement science. This includes definitions for prime mover (agonist), synergist, antagonist, neutralizer, stabilizer, and fixator. Further, the terms are applied to several joint actions for the major joints of the human body (shoulder, scapula, spine, hip, knee, and ankle joints), and examples of altered recruitment and dysfunction are discussed throughout.

Definitions:

• Agonist: Muscles that perform a joint action, including the prime mover and synergists
• Prime Mover: The muscle contributing the most force to a joint action when resisted by an external load.
• Synergist: Muscles that assist the prime mover in performing a joint action.
• Antagonist: Muscles that oppose the prime mover and synergist(s) for a joint action.
• Neutralizers: Muscles that oppose unwanted joint motions created by the prime mover and/or synergists, and/or muscles that prevent unwanted ancillary motion.
• Stabilizers: Muscles whose primary role is to improve arthrokinematics by maintaining optimal alignment of joint surfaces.
• Fixators: Muscles that act to reduce or prevent movement at proximal joints to improve force transmission.

Example:

• Hip extension:
  • Prime Mover: gluteus maximus
  • Synergists: bicep femoris, semitendinosus, semimembranosus, and posterior head of adductor magnus
  • Antagonist: psoas, iliacus, tensor fascia latae, rectus femoris, anterior adductors, and sartorius
  • Neutralizers: gluteus minimus, tensor fascia latae, and anterior adductors neutralize the external rotation force generated by the gluteus maximus
  • Stabilizers: deep rotators of the hip (gemellus superior, gemellus inferior, obturator internus, obturator externus, and the quadratus femoris)
  • Fixators: intrinsic stabilization subsystem, rectus abdominis, obliques, quadratus lumborum, and erector spinae

Sports medicine professionals (personal trainers, fitness instructors, physical therapists, massage therapists, chiropractors, occupational therapists, athletic trainers, etc.) must understand the functional roles of muscles for analysis of biomechanics and human kinetics, which is necessary for developing optimal exercise programs and therapeutic (rehabilitation) interventions. Further, this course is essential knowledge for future courses discussing motor neuron function (e.g., agonist activity and reciprocal inhibition of functional antagonists), altered motor function (e.g., synergistic dominance, prime mover inhibition, instability), pain and injury (e.g., muscle fiber dysfunction, trigger point development, acute muscle weakness) and sports performance (e.g,. skeletal muscle hypertrophy, maximal recruitment and muscle contraction, and strength and power development).

Pre-approved Credits for:

• Certified Personal Trainer (CPT) Certification

Pre-approved for Continuing Education Credits for:

• Athletic Trainers
• Chiropractors
• Group Exercise Instructors
• Massage Therapists
• Occupational Therapists - Introductory
• Personal Trainers
• Physical Therapists
• Physical Therapy Assistants
• Yoga Instructors

This Course Includes:

• AI Tutor
• Video Lecture
• Study Guide
• Text of Material
• Functional Role of Muscles Activity
• Kinesiology by Joint Action
• Practice Exam
• Pre-approved Final Exam

Bibliography

1. Donald A. Neumann, “Kinesiology of the Musculoskeletal System: Foundations of Rehabilitation – 2nd Edition” © 2012 Mosby, Inc.
2. Tom Myers, Anatomy Trains: Second Edition. © Elsevier Limited 2009
3. David G. Simons, Janet Travell, Lois S. Simons, Travell & Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition,© 1999 Williams and Wilkens
4. Cynthia C. Norkin, D. Joyce White, Measurement of Joint Motion: A Guide to Goniometry – Third Edition. © 2003 by F.A. Davis Company
5. Cynthia C. Norkin, Pamela K. Levangie, Joint Structure and Function: A Comprehensive Analysis: Fifth Edition © 2011 F.A. Davis Company
6. Carolyn Richardson, Paul Hodges, Julie Hides. Therapeutic Exercise for Lumbo Pelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back Pain: 2nd Edition (c) Elsevier Limited, 2004
7. Andrew Biel, Trail Guide to the Human Body: 4th Edition, © 2010
8. David B. Jenkins, Hollinshead’s Functional Anatomy of the Limbs and Back: Eighth Edition © 2002 Saunders
9. John V. Basmajian, Carlo J. De Luca. Muscles Alive: Their Function Revealed by ElectroMyography. 1985