Muscle Contraction Types

Question 1

Isometric contractions

Answer 1

Isometric contractions:

• Operator’s force = Patient’s force
  
  • A fixed tension develops in the muscle
  • Distance between the origin and the insertion of the muscle is maintained at a constant length.
    
    • preventing shortening of the muscle from the origin to the insertion.

i.e.: with the patient’s elbow flexed, the operator holds the distal forearm and shoulder. The patient is instructed to bring the wrist to the shoulder while the operator holds the wrist and shoulder in the same relative position. The force inserted by the patient’s contracting biceps has an equal counterforce applied by the operator. This results in of the biceps brachii muscle. .

Question 2

Concentric Isotonic contractions

Answer 2

Concentric Isotonic contractions:

• Operator’s force < Patient’s force
  
  • muscle tension causes the origin and insertion to approximate.

i.e.: a concentric isotonic contraction occurs during the process of holding a weight in the hand and bringing it to the shoulder by increasing the flexion at the elbow. The concentric isotonic contraction of the biceps brachii increases muscle tone, and the origin and insertion are approximated.

Question 3

Eccentric Isotonic contractions

Answer 3

Eccentric Isotonic contractions:

• lengthening of muscle during contraction due to an external force
  i. e.: An interesting example of this would be the pelvic diaphragm musculature elongating due to the contraction of the abdominal diaphragm during respiratory inspiration.

Another example: when the weight brought to the shoulder is now returned to the starting position by increasing the amount of elbow extension. There is tone within the biceps brachii allowing the origin and insertion to separate in a smooth and easy fashion as the elbow extends and the weight is taken away from the shoulder.

Question 4

“Isolytic” contractions

Answer 4

“Isolytic” contractions:

• Operator’s force > Patient’s force
  
  • a non-physiologic event
  • the patient attempts to concentrically contract a muscle with approximation of the origin and insertion
    
    • but an external force applied by the operator occurs in the opposite direction.

i.e. isolytic contraction occurs when the elbow is flexed at 90 degrees and the patient attempts to increase the flexion of the elbow while the operator holding the shoulder and wrist forcefully extends the elbow against the effort of the patient to concentrically contract the biceps brachii. An isolytic procedure must be used cautiously to lengthen a severely contractured or hypertonic muscle because rupture of the musculotendinous junction and insertion of tendon into bone or muscle fibers themselves can occur