Recall with a Whistle

I've been wanting to get a video of Isaac coming when I blow the whistle.  Sometimes it is ridiculously hard to get things on video.  Seems like he never does it then way I want him to when I have the camera available. 

Usually he comes running at full tilt.  This time, he came right away but not running.  Of course, when I didn't have the camera ready, then he ran so fast he practically skidded past me.

Still, we worked hard on his recall with the whistle.  So here it is.