Muscle Contractions

[Maes Seren]

Hi, I'm new, I'm a first year physiotherapy student and currently feel a little 'short changed' by one of my lecturers so after a discussion with a friend, I decided I'd go on the hunt for a good forum to help me along the way.

In a group tutorial today, our lecturer was using the biceps/triceps as an example as to muscles working concentrically as the agonist. But if you were to pull with force (say in shoulder flexion you forcefully pulled a chair towards you) then the triceps would be the agonist acting concentrically. However, I'm aware that an individual muscle doesn't work independently, and usually theres an antagonist. In the example given previously, would the biceps be the antagonist?

And finally a seriously dumb question but how do you know which muscles are the antagonist of the movement - would it be (in a generalised term) say hip flexors working as agonists and hip extensors working as antagonists?

Apologies if this is in the wrong place, I couldn't decide where it best suited as its plain anatomy really.

Thank you

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[KiranC]

Hi, I'm new, I'm a first year physiotherapy student and currently feel a little 'short changed' by one of my lecturers so after a discussion with a friend, I decided I'd go on the hunt for a good forum to help me along the way.

In a group tutorial today, our lecturer was using the biceps/triceps as an example as to muscles working concentrically as the agonist. But if you were to pull with force (say in shoulder flexion you forcefully pulled a chair towards you) then the triceps would be the agonist acting concentrically. However, I'm aware that an individual muscle doesn't work independently, and usually theres an antagonist. In the example given previously, would the biceps be the antagonist?

And finally a seriously dumb question but how do you know which muscles are the antagonist of the movement - would it be (in a generalised term) say hip flexors working as agonists and hip extensors working as antagonists?

Apologies if this is in the wrong place, I couldn't decide where it best suited as its plain anatomy really.

Thank you

Sorry I didn't understand your example but I want to give you some information regarding this.

Agonists are the muscles which contract to produce the movement & antagonists are muscles which will oppose the agonists.
Just take the example of any movement, just make the fist, the flexors of the fingers will be agonists & the extensors will be antagonists. In opening the fist, the extensors will be the agonists & flexors will be antagonists. Its just simple.

Also, remember one thing in life, no question is stupid or dumb. It may be possible that by asking a question, you may be dumb for 1 minute but by not asking it, you will remain dumb forever.

[Fyzzio]

I would say that if you pull a chair towards you, then the biceps is the agonist - as it is the biceps who causes the actual movement.

Also, adding to KKiran's comments: about concentric/ eccentric. Those words are used to describe whether a muscle shortens or lengthens during contraction.

Example for quads:
1) sitting on a chair, straightening the knee (function: knee extension): quadriceps agonist, hamstring antagonist; quads work concentric, hamstring eccentric
2) walking downstairs (function: knee flexion): quadriceps agonist (!), hamstring antagonist; quads work eccentric, hamstring concentric

Biceps/ Triceps:
1) pulling up a weight (function: elbow flexion):biceps agonist, triceps antagonist; biceps work concentric, triceps eccentric
2) putting the weight down (function: elbow extension):biceps agonist (!), triceps antagonist; biceps work eccentric, triceps concentric

It's a hugely interesting topic (we were asked to proove why the quadriceps is a knee flexor)and we had so many good debates about it, even after being in the job for a few years - so, don't worry if you are a little confused.

Cheers,
Fyzzio