staying closed

lately ive been flying open causing me to lose alot of velocity and have alot of arm pain from trying to throw harder. what are some things i could do to stay closed

Maintain good posture and balance, generate good forward momentum, get the arms to equal and opposite at foot plant, stabilize the glove out front and bring the chest to the glove.

And also make sure that you land on the ball or the flat of your foot with your toes pointing slightly in towards the batter. If you’re a righty, your toes should point towards the right handed batting box and the opposite for if you’re a lefty.

ill try that cause im pretty sure im landing on my heel at the moment.

Being balanced is very important, however landing on your heel is not a bad thing. Ending up on your heel would be though. Your issue seems to me of one with muscle memory. You probably already know that your body needs to act as a rubber band. As your stride foot lands and you become open at the pelvis you should feel some tension in your lead side and back to signify that you are staying closed up top. This helps you by keeping stored energy ready to unwind. If timing is correct then as soon as this tension develops you can unload it into the pitch. When you warm up to throw start at a short distance and have hips already rotated to the target. Then without striding to throw, Rotate your torso away from your target until that tension builds up. Get a good stretch and then throw, not letting your pelvis turn the entire time. You could also try this on one knee with your pelvis facing the target. Now that you can begun to feel the tension, begin to throw channeling that tension and not using all arm and you should see better results as well as get rid of the arm pain.

Transfer momentum good and follow through with whole body