Fixators (Muscle)

Fixators: Fixators are muscles that act to reduce or prevent movement of joints proximal to the joint in motion. For example, the muscles of the core (rectus abdominis , external obliques , internal obliques , quadratus lumborum , erector spinae ) are important fixators, reducing trunk motion during motion of the arms or legs.

• Note: For analysis purposes, it is important to differentiate "fixators" from "stabilizers." A stabilizer improves arthrokinematics by maintaining optimal alignment of joint surfaces during joint actions. For more information, check out stabilizer .

For additional information, including a video lecture:

• Lesson 21: Functional Roles of Muscles

Functional Roles of Muscles Glossary Terms:

• Prime Mover
• Agonist
• Synergist
• Antagonist
• Neutralizer
• Fixator
• Stabilizer

Articles listing all of the muscles by functional role for each joint action:

• Kinesiology of the Shoulder and Scapula
• Kinesiology of the Elbow
• Kinesiology of the Trunk
• Kinesiology of the Hip
• Kinesiology of the Knee
• Kinesiology of the Ankle

Examples of Hip Extension Kinesiology Analysis, including Fixators:

Hip Extension

• Prime Mover: Gluteus maximus
• Synergists: Biceps femoris (long head) , semitendinosus, semimembranosus , posterior head of adductor magnus
• Antagonists: Psoas , iliacus , tensor fascia latae  (TFL), rectus femoris , anterior adductors (especially pectineus) , sartorius
• Neutralizers: Gluteus minimus and anterior fibers of gluteus medius neutralize external rotation force of gluteus maximus
• Stabilizers: Deep rotators of hip
• Fixators: Intrinsic stabilization subsystem , rectus abdominis , internal and external obliques , quadratus lumborum , erector spinae