Voted Best Answer
Apr 10, 2012 - 09:33 AM
This can be confusing sometimes because of the definition of reciprocal inhibition is confused with altered reciprocal inhibition. Think of these two as different things. Reciprocal inhibition is normal and needed for movement to take place. Altered reciprocal is not something that should happen.
When as muscle contracts it is being activated by the nervous system and the opposing muscle is being sent a single to become less activated to allow the movement to take place and this is reciprocal inhibition.
Altered reciprocal inhibition is when a muscle is activated (the agonist) when it should not be and it is decreasing the signal strength to the opposing muscle (the antagonist). Think of the agonist as a muscle being activated even if it is not contracting. The antagonist is the muscle that is opposite of the muscle that is activated.
In the example in the book if a person is standing the hip flexors should not be overactive or tight (activated) if they are then the hip flexor will cause inhibition of the glutes. Inhibition of the glutes should only occur if the person was lifting the leg up using the hip flexor muscles. So when muscles are inhibited due to tightness it is termed altered reciprocal inhibition.