This stretch is meant to loosen up some muscular and neural tension surrounding the Latissimus Dorsi.
Start by taking your opposite hand and with a broad open hand contact, compress your hand into your lat muscle. Your arm should be relaxed and loose. You'll keep pressing your hand firmly into your lat as you take your arm and reach up and across your body. As your arm starts to cross the midline of your body you'll start sliding your hand down the lat while keeping that compression.
Repeat multiple times and on both sides.
