quote:
is there any way to strengthen my pitching arm
you didn't say how old you are or at what level you pitch? Your question is a one that you should be asking. One can't deny that building your legs and core will help you be a better conditioned athlete and contribute SOME to throwing harder, longer. I always find it humorous that pitchers spend so much time running for conditioning, but yet Managers become stressed if they have to "run the bases." Like running from home to second will "gas them."
However, to throw a baseball 85mph or 90mph the arm has to generate that delivery speed and endure the associated stresses. You don't throw the ball with your legs so you best condition your arm. My ways are controversial to some but;
If you want to throw hard you must THROW hard more! Long periods of rest are your enemy! I've employed Marshall's 120day Training program with my son with great results (iron ball throws, wrist weight exercises, and throwing hard .... DAILY).
He conditions in all the conventional ways as well, weight training, stretching, speed and agility, etc. Why take a chance, leave no rock unturned.
Keep researching and asking and listening ... then get to work!