Question About Plank Holds

So I am starting my V-Diet and using the beginner workout program.
I am unclear on how many Planks to do.

The instructions say hold for 45 seconds and repeat.
Does that mean 2 x 45 second sets?

The workout sheets have 12 rows like for the lifting exercises.
Does this mean to do 12 sets to failure?
(I can’t do 12 sets of 45 seconds)

Any clarifications appreciated.

Also, is it common to feel some pressure/stabilization effort in my lower back?
I am in a perfect straight line and have never done planks before.

My breathing was slow and steady.

Is this for abs or back or what?


Two sets of plank holds, each held for as long as possible, with 45 seconds rest between them.

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