When conditioning for any sport, it is important to understand that conditioning doesn't just mean "getting in shape," as most people think. (Check out STACK's conditioning page.) A well-conditioned athlete is fit in relation to his or her sport and position. When planning a baseball conditioning workout for pitchers, think about the nature of the work. A pitcher completes a very explosive movement that lasts about 3 seconds and then rests for 20 seconds. The goals for pitcher conditioning should be to mimic the physical stresses of competition and train the same energy system. (Learn how to condition for your sport.)
If you look at the pitching motion, the push off the back leg and the hips exploding open are two key lower-body movements. With a proper conditioning program, pitchers can learn how to become more efficient in both. Performing plyometric exercises and agility drills will train planting and pushing off explosively, opening the hips, and improving coordination and body control. A pitcher with good body control and awareness will be less likely to have a mechanical issue that could lead to an injury when he or she becomes fatigued during a game.
You have undoubtedly noticed the lack of long distance running. Long-distance running teaches pitchers to be slow. To be fast, you must train fast. Long runs also train the wrong energy system. If you think about it logically, doing the same slow motion continuously for an extended period of time is the exact opposite of pitching. Pitchers, would you rather be built like a sprinter or a marathon runner?
These exercises focus on change of direction, explosiveness, and lateral movement. This workout should not make you feel incredibly tired. Make sure to take the recommended rest breaks. You should feel fast and explosive after these drills.