Collar conditioning in drive for retriever training

This is a short clip from last year of Blaze, the puppy from the videos in my puppy program. This is not his first session. I start all e-collar conditioning on a line to guide the desired response if needed.
Here, we are working on collar conditioning. This is "training in drive". The dog is moving to make retrieve happen and to turn off and avoid e-collar pressure.
E-collar conditioning should not be an unpleasant affair for the dog.

[@Mr_Rodgers_neighborhood]

Pat. Can you explain when you're using low stim? My dog drops the bumper once stim starts