To cross the line of painful resistance;
this is as they call ENDORPHINS.
To cross this line ten fold is to rip the muscles beyond were people would normally give up.
Which also allows you to prolong strenuous activity for hours:
"As too called STAMINA".

: Pain is weakness leaving the body- Marine Corps

: Pain is the sensation that lets you know your alive- Navy Seals

Pain is pleasure- A Masochistic Mind

To go beyond your natural ability,
to enhance what you know,
feel, and to gain that extra push in strength,
speed, and reaction.
This is the chemical within the body called ADRENALINE.
To control this sensation and manipulate this impulse is to harness this chemical and make it stronger;
to make it succumb and bend to your will;
This is the power accelerator that lyes within all of us.
For there is a select few that Convolute this impulses of the brain
( mind) , and Body.

: Stop imprisoning your soul, let it flow free.

: To fight with your mind in a cage, you just convolute the natural impulses of the body.

PUSH YOURSELF BEYOND THE LIMITS OF YOUR POWER/ABILITY;
YOU NEVER KNOW YOU MIGHT LIKE IT