Inner muscle training used in old school boxing

this is based on some recent reading.

http://fighters-journey.blogspot.com/2012/05/inner-muscle-training-of-boxers-with.html

I understand that you are not suppose to use the dumbells in the way we are normally taught:

Dave suggests: "everyone today assumes that they worked like grip trainers and keeping them closed would work the hands and grip - actually nothing could be further from the truth. I have two pairs and neither is very difficult to close - actually the springs are there to help the trainee feel the various muscles at work and get exactly the right level of tension and relaxation in each movement. This results over time in a huge increase in muscle control."