Same run as yesterday with out a 10# Camelbak but at a similar HR intensity.
Yesterday- 10 miles in 1:35 (9:30 per mile) with an average HR of 151.
Today- 10 miles in 1:19:57 (7:59 per mile). Average HR 153. So a ~15:00 disparity.
This "test" is by no means definitive or scientific. Just an interesting way to actually see (and feel) the added stress of 10 pounds.
Holding my HR in the 150's was pretty hard.