when you cant feel it, hold it

Since my daily work resembles mobility and strength, it is imperative I actually FEEL the target muscles working. I.e. this is not a 3 rep max squat where I need to move as much weight as far as possible. Im building control, stability, strength, and muscle - in that order. This morning I wanted to bail from two movements i couldn't feel and suspected my legs locking up from the effort before I ran across a great idea. If you cant work it, hold it. 

Isometrics are awesome because you can force contractions at any range of motion. Instead of adding speed and movement when a muscle isn't firing, hold still and force it to fire. This is like laying the foundation for future movement.