Downhill Workouts

I am reading Dr. Philip Maffetne's The big book of Endurance
training and Racing while my daughter was playing Tennis
tournament(the players did not like us to watch anyway).

In the chapter 6, he talked about the downhill training to help
the training of a quicker leg turnover.  Perhaps that's a good way
to train the "faster steps". I checked my pace for my San Francisco
half marathon race last weekend. For the mile 11, my pace was
7:01, and that was my fastest pace during the race. But I did not
feel tired at all since this was a downhill mile and I noticed
my legs turn over much faster. So I might add two miles running
down the hills every week or every two weeks?