Push Ups are an undervalued exercise and should be a staple in any baseball players strength training program. They're considered easy, but unfortunately people screw them up all the time.
Pictured above is a very common push up mistake. We obviously do not want our elbows flaring out to the sides, but they should not be tight to the body either. A happy medium of about 45 degrees is going to be much more shoulder friendly.
Hugging the elbows too tight to the body leads to anterior humeral glide. In other words, the elbows are dipping way too far past the body, and rounding the shoulders forward.
Most baseball players are going to have excessive external rotation on their throwing side, meaning that they have increased anterior shoulder instability. Cranking our humerus into hyperextension during push ups is going to exacerbate that anterior instabilty and can lead to bicep tendon issues.
Fix this mistake with 3 simple cues:
1.) Hands Should be slightly outside your shoulders
2.) Make sure the scaps protract and retract during the push up motion
3.) Don't let the elbows pass the mid line of the body