take a 30" draw bow for example, with a 6" brace height there is a 24" power stroke (the arrow is on the string for 24"

but with a 7 1/2" brace height the arrow is only on the string for 22 1/2". that is why a shorter brace bow has more speed because it has a greater power stroke but is more critical to shoot because the arrow is on the string longer giving the archer more time to screw things up like we do.....