So here is what I do.
45° bent over rows.
Single arm Dbl rows.
I have tried pull ups but they didnt seem to help much either.
I workout at home so do not have access to pull downs but am trying to think of a way to make that happen.
When I did pull ups would use a neutral grip and get in 50 reps...
Back in the day when I was a middle distance runner a few obscure peeps said that Dessicated Beef Liver helped endurance substantially.
Vince Gironda had all of his athletes use it daily as per this below.
Here's one of Vince's secrets that very few people have ever heard about...
Vince...