How to distract yourself from an aching body part or itch

So lets say you are in the middle of a run and your legs are hurting but you need to keep on going, start tensing up your biceps and concentrate on tensing them up as much as possible

Just keep on squeezing and if this doesn't work start tensing your strongest body part to keep you focused on something completely different to take your mind off of your aching body part

This will also work with an itch