This is my absolute favorite stretch.
It helps keep your shoulders and chest open, which can help with your posture. Especially if you’re at a computer all day, it’s common for your shoulders to roll forward; this can help counteract that position.
The picture shows this dude (who I think was passed over for the lead role in the “Take Me On” video) doing it on one side, but you can stretch both shoulders at once. Just place your hands on the door stretch and lean through it – like Rose Dewitt Bukater or whatever her name was in Titanic. Your hands can be lower than this illustration or in one of the positions shown here, whatever feels good.
Start with a very slight lean – if you’re really tight you’ll feel it right away and you don’t want to overdo it. If you do this on a regular basis you’ll open up your shoulders, which can carry over to not just your running posture but improve your breathing, too.
If you feel any pain when doing this stretch – don’t do it. Instead talk to your doctor, because you could have some muscle imbalances or even a tear that needs to be addressed.