Claudia,
I finally got out this weekend to try the new harness [our Bjorkis Buggy harness] on my dog Buddy [Springer Spaniel].  …  First we did the ¼ mile track to see how the harness would work and he did so well we moved to the 4 mile track.  I was amazed, no wheezing (no ring to cut into his neck) and more power.  I didn’t realize but when the ring was cutting into him he was backing off – I thought he just didn’t like to pull that much but with this new harness he pulls hard the whole time and didn’t slow down, he was even trying to pull me up the steep hills!  4.5 miles was nothing for him in that harness, not so for me, the last few hills were killers but I plan to go back again this week sometime.  Thanks so much for the harness! 
Maggie