How do I improve my ability to hold position in the basketball key?

Holding your position in the paint requires stability as well as lower-body and core strength.  Before resistance training, incorporate 2-3 core exercises as a warm-up.  During your resistance training program, make time for stability and strength training of your lower body.  You can superset strength and stability exercises by following a stable strength exercise with a balance exercise. For example, perform a back squat and followed by a single-leg deadlift.

To improve your ability to maintain position in the paint, you must train your core and glutes for stability and strength.  Core exercises focusing on changing planes of motion are best.  These are exercises such as cable chops and lifts.  Exercises such as these challenge you to remain stable while rotating or turning.  This simulates your ablity to hold position in the post against an opponent who is fighting to gain an advantage from different angles.  Glute strength is another huge key to post-position strength.  Therefore, be sure to pair glute strength and stability exercises in your lifts.  This often means a heavy-weighted 2-legged exercise such as a dumbbell squat (for 6 to 8 reps) followed by a single-legged exercise such as a single leg squat (for 10 to 12 reps).  Lifts like these allow you to train for both strength and stability at the same time, and can be quite beneficial to building low post-position strength for both offense and defense.