We all should know by now that long distance running is bad for pitchers (read 2009 article called Just Say NO to Long Distance Running) but now everyone needs to know how bad it really is. Yes, the study below proves that long distance running reduces the bodies ability to absorb and use the power of elastic energy.
If you have spent anytime on this site, you have learned the importance of elastic energy to pitching velocity. If you need a refresher or a basic understanding here are some of the key components that use elastic properties to generate high pitching velocity.

Elastic Pitching Velocity Components

1. The "Load" Position - This position as defined in the 3X Pitching Velocity program is the first moment in the power pitching mechanics or 3X mechanics where elastic energy is absorbed to enhance force production in the following component. When the pitcher moves from lift to load, as he aligns his force vector into a linear position for launch, he is stretching his quads and calves through knee flexion and dorsiflexion. This stretching of the quads and calf muscles builds elastic energy in the muscles to enhance force production as the muscles contract to fire the drive leg into triple extension which is the next component in the 3X Pitching Velocity program.
2. Front Leg Stabilization - This is the final component listed in the 3X mechanics. Elastic energy occurs during this component just after front foot strike when the flexed knee stabilizes, stretching the quads of the front leg before contracting into extension before pitch release.
3. Hip to Shoulder Separation - This is one of the key components in the 3X mechanics where elastic energy is most important and has been proven by the National Pitching Association (NPA) to have the potential to produce 80% of a pitchers velocity. This is when the front foot lands and stabilizes as the hips completely open separating from the shoulders. This is allowing the muscles of the core to absorb a good amount of elastic energy before they contract and fire the shoulders towards the target.
4. External Rotation of the Throwing Arm - This is not a component of the lower limbs, so I will not talk about this elastic component because the study below only proves the reduction of elastic energy in the lower limbs but I believe that there is a link to pattern overload and this reduction of elastic energy as well. I will leave this subject for another article once I find some research to support it.

This information of these elastic pitching velocity components should help you understand how significant elastic energy is to pitching velocity. Elastic energy is absorbed and transferred into force production in almost all of the pitching components of power pitchers, therefore a small reduction in the bodies ability to absorb elastic energy would have a chain reaction on the energy moving through these components which would have a major impact on pitching velocity. Now for the study!

Elastic Properties of Muscle-Tendon Complex in Long-Distance Runners

This study was performed at the Department of Life Science (Sports Sciences), University of Tokyo, Japan. Here is the link to the study. Here is a summary of the final results of the study.

Long distance runners showed significantly less elastic energy absorption than in untrained individuals. Not only jump heights but also the differences between the heights in squat jumps and counter-movement jumps.

This study does not go into the physiology of the final conclusion but proves, without a doubt, the final result that long distance runners do not absorb as much elastic energy as untrained athletes.
In my world, long distance running does not fit the mold of the power pitcher because it is not even close to being sport specific. Pitchers are never performing in a game at a low intensity for a long period of time. In today's game where pitching velocity still is king, these pitchers must perform at a high intensity as long as possible but for very short periods of performance time; mainly under 2 seconds. Not only this but if you know anything about the importance of muscle fiber types, you will learn that power pitchers need more fast twitch muscle fibers than slow twitch to produce power and long distance running remodels an athlete into more slow twitch muscle fibers than fast twitch muscle fibers.
With all of this knowledge on long distance running and power pitchers, you should have no qualms with removing the "old school" approach of long distance running to train the pitcher from your program but if you are playing for a coach who has not made this leap then you need to find the best most professional way to educate him without insulting him. Just remember though, you can loss velocity a lot faster than you can gain it, so you need to take this information very seriously.