I have been playing a lot more aggressive, especially with my serve. I have been trying the explosive serve by lobbing the ball hight and then jumping up to hit the ball. The serves have been working very well for me, but my upper left abdominal is in a great pain after a while. I am a right hander. The severe pain only occur during the serve and overhead only. Any idea of how to reduce or even prevent this pain? Please help me out as a big match is coming soon. Thank you.