Why would any trainer....

allow their dog to hit them so hard during training that they were bruised?

That's a really good question and I'd like to answer it.  Some of you have asked me directly and I'm quite sure that others have been thinking it.

First of all, I do NOT allow my dogs to maul me, and I do NOT think it is necessary to allow out of control behavior in order to train a dog in drive.

I was trying to better understand the relationship between play, barking and training in drive.  Specifically, I have students who have very barky dogs, and I was recreating it in one of my own dogs so that I could learn how to solve the problem.

Whenever possible,  I solve problems "in drive".  That means rather than avoiding issues, I induce them under controlled training circumstances.  Then I try to make the dog conscious of their behavior so they can correct it.  If that is successful, they are rewarded for the new behavior.

None of my personal dogs have a barking problem during work, but I knew that I could create one simply by getting Raika out of control.  Remember, I am a dog trainer.  Better that I practice on my dog (who is retired) than on your dog (who is not).  And anyway, she needs something to learn during her training time,  retired or not.

In her first session, Raika barked for nine minutes straight without a break.  That means for nine minutes I had no opportunity to reward her. Indeed, I ended the lesson without ever sending her for a dumbbell (punishment).

The clip I took a few days ago when Raika bruised me was from her first success - she shut up in her second session.  Unfortunately, by the time she was sent to retrieve she was so worked up that she came back much faster and harder than I expected.  Normally, I "catch" Raika on the return (my dogs are taught to come to my hands), but I did not anticipate her speed.

Here is a video showing the barking (you dont' need to watch nine minutes so I clipped it down to several seconds), and then I added a portion from a later session where she was rewarded for cessation of barking by a send for the dumbbell.  She had several successes in that session.  At this point she wasn't so frantic, so I was able to "catch" her comfortably when she launched at me:

So....I learned!  The first thing I learned is not to let a dog bark for nine minutes straight.  I should have ended the lesson after two minutes of continuous barking.  My thinking was that any second she would stop.  I was wrong.

The second thing I learned is that I can eliminate barking this way, if it is under the control of the dog.  Induce the barking (so you can isolate it), refuse to look at the dog or to send until she takes a breath (cessation of barking), and reward (in this case a dumbbell retrieve).  Next step would be an expectation of dead silence from the dog before sending (no whining).  After that would be to incite barking by pretending to go for the dumbbell myself.  Repeat above steps until she can show control under those circumstances.  And finally, test the behavior in a different context (maybe incite a high level of arousal in heeling and see if I could control the barking).  Odds are you'd have to train it through a few different exercises before the dog would generalize.

So....all of that is to explain how I ended up with my dog so out of control that she's hurting me. I would never suggest that you allow or encourage your dog to behave in that manner, unless you had a specific reason.

I had a reason.