Push Up, Biceps or Triceps?

Maybe it is stupid question.

which should be activated? tricpes or biceps?

I know it is triceps but yesterday when I did push up,

very upper part of biceps which meets with very front of deltoids engaged so much that 

it was hard to do RC/PE1 right after that. 

I guess that is because I push diagonally.

To be precise, lets put vertical direction your north, your head as west, feet as east.

If I push strictly north, my triceps are on, no biceps.

but if I push north-east, my end tip of biceps are activated seriously. 

Both are okay? or I should use more triceps in PE2?

I'm curious because I am supposed to depress my shoulders in PE3, engaging lats,

but as I tried to depress my shoulders in PE2, this biceps activation happened.

depressing biceps made north east diagonally movement.

Hanlim Lee said:

 

which should be activated? tricpes or biceps?

 

I know it is triceps but yesterday when I did push up? 

 

very upper part of biceps which meets with very front of deltoids 

It basic Anatomy. Once you learn it, it easy to understand

The main muscle working in the elbow is tricep because the movement of the elbow is extension( elbow flexion= biceps[2 heads: Long and short head], brachialis and brachioradialis )

"very upper part of biceps which meets with very front of deltoids" - There's shoulder flexion in push-up(elbows in) (Prime mover is Anterior Deltoid ; Short Head of The Biceps just helps to perform flexion in the shoulder so you might feel it)

Even when you push diagonally, aka Incline Push-Up , the bicep(short head) will help/work because there's shoulder flexion.

Its also possible that you are getting a stretch you aren't used to in the pec minor area.

HB_Ron said:

It basic Anatomy. Once you learn it, it easy to understand

The main muscle working in the elbow is tricep because the movement of the elbow is extension( elbow flexion= biceps[2 heads: Long and short head], brachialis and brachioradialis )

 

"very upper part of biceps which meets with very front of deltoids" - There's shoulder flexion in push-up(elbows in) (Prime mover is Anterior Deltoid ; Short Head of The Biceps just helps to perform flexion in the shoulder so you might feel it)

 

Even when you push diagonally, aka Incline Push-Up , the bicep(short head) will help/work because there's shoulder flexion.

Oh, so biceps are always engaged in push up. 

but could you explain why the activation was much more intense than usual?

It was really different as if I did several sets of arm curl. I never felt like this from push up.

Have you ever gone through something like this?

I'm guessing I didn't send my elbows to the back enough.

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I found out why. 

If I roll my shoulders forward enough at the bottom, there is no strange biceps activation.