Lecture Notes: Muscle Insufficiency

Types of Muscle Insufficiency

Active Muscle Insufficiency

• Occurs when a muscle crosses multiple joints and cannot generate sufficient force when performing multiple actions simultaneously.
• Example: Hamstrings
  • Hamstrings help extend the hip and flex the knee.
  • When attempting to extend the hip and flex the knee at the same time, the hamstrings cannot achieve the full range of motion for both movements.
• Mechanism
  • Myosin and actin filaments in the muscle are too close together, preventing additional cross-bridge formation, which limits tension production.

Passive Muscle Insufficiency

• Occurs when a muscle is stretched and cannot generate sufficient force.
• Example: Hamstrings (Antagonist Role)
  • During a toe touch, the individual tries to extend the knee and bend the hip.
  • Hamstrings are stretched, making it difficult to touch the toes compared to when the knees are slightly bent.
• Mechanism
  • Myosin and actin filaments are too far apart, hindering cross-bridge formation.
  • Acts as a protective mechanism to prevent muscle damage.

Clinical Relevance

Spinal Injury

• Example: C6 Spinal Injury
  • Client has wrist extension but limited wrist flexion and finger movement.
  • By relaxing the wrist to allow gravity to flex it, the finger extensors stretch due to passive insufficiency.
  • This stretching helps to open the hand.
  • Conversely, wrist extension causes the fingers to close, aiding in grasping.
• Term: Tenodesis
  • Refers to the use of passive insufficiency of finger extensors in spinal cord injury patients.

Posture Correction

• Poor posture results in stretched back muscles and shortened chest (pectoral) muscles.
• Interventions
  • Strengthen stretched back muscles to improve posture.
  • Stretch shortened pectoral muscles to regain proper muscle tension.