It is well known the importance of hip muscles, especially gluteal muscles and external rotators. They play an important role in not only stabilizing the hips but also the knees and lower legs. Every baseball pitcher has to be on one foot during stride phase of the pitching motion. If he is not able to maintain the stability of his lower leg, hip, and trunk, he will not be able to effectively transmit a ground reaction force through trunk, upper body, and to his arm and to the ball. Doing hip exercise on a table is a good way to start but he will need to train the muscles in standing as well. Here is one easy way to work on his hip muscle strength.
This is an isometric hip muscle (gluteal) strengthening exercise. He is pushing the physio ball into the wall with his left knee while trying to maintain his upright posture with his right leg. With this exercise, he should be able to maintain the upright posture without moving any part of the body. This works on his bilateral hip muscles, especially gluteus medius. If he brings his left knee up to the level of his hips, he now is working on his external rotators of his left hip as well as his right gluteus medius. Also he needs to use his core muscles to stabilize his pelvis.
