The Serratus anterior aka the "Boxer's Muscle!" has a large role in stabilizing your scapula, (refer back to episode 220 and 304 for more info) when this muscle has poor function it often manifest in poor scapulo-humeral rhythm or winging.
When perform an uppercut, often times one will overcompensate with the Pectorial muscles! If your intent of this exercise is to target the Serratus Anterior here is a quick tip: Externally rotate your shoulder as you elevate your arm. Your Pectoralis Major is an Internal rotator at the shoulder; external rotation will be reciprocally INHIBITING these larger pectoralis musculature!
Make sure to keep the elbow medial to your wrist during this exercise, this will ensure external rotation at the shoulder, a secondary benefit of this variation is increase demand of the external rotators such as teres minor and infraspinatus.
Tag a friend that needs a stronger punch!