THE PHYSIOLOGY OF BASEBALL PITCHING
In a previous post discussing the aerobic vs. anaerobic debate of baseball pitching, I concluded that baseball pitching is primarily an anaerobic event.
However, there are many pitchers, according to Szymanksi, who use long-slow distance running (LSD) as a part of their training program. This modality of training is indeed an aerobic event.
Should we say that this LSD is so bad for pitchers and should never, ever perform it? No, we shouldn’t. But, we could say that it’s something to be done in moderation.
In this article, we will have a better understanding on the physiology of baseball pitching, and showing why LSD (or aerobic training) may be necessary in some cases.
Baseball is surely the game of tradition. There is a plethora of research coming out all the time, yet some coaches stick to the old-school style of training.
LSD is mainly used to decrease body fat % for optimal body composition. While this is a great adaptation from aerobic training, it certainly won’t help you throw harder!
In a study comparing the effects of aerobic and weight/sprint training, pitchers could improve their throwing velocity and anaerobic power by 3.0% and 4.2%, respectively. 
Taking it one step further, another study investigated the differences in the type of conditioning program that was used in a resistance training program.
The speed/speed endurance training group saw a significant improvement in their lower body power (vertical jump) by 15.3%! The aerobic training group saw a decrease in their lower body power! These results are in concurrence with extensive physiology research: the aerobic energy system interferes with anaerobic development.
Baseball is an anaerobic sport, so it makes sense to develop the anaerobic energy pathway!
Therefore, we can say that yes, aerobic training does have some benefits, but is it something that should be done on a regular basis? NO!
STIFFNESS AND SORENESS
In his article, Szymanski brings up an excellent point in the difference between pain and soreness: Pain is to long-term as soreness is to short-term.
With that being said, Szymanski states that “LSD running is not going to relieve chronic arm pain” (pg. 42).
Short-term soreness comes from the body’s inflammatory response to stress. With this, muscles are damaged and metabolites decrease the pH levels within surrounding tissues, resulting in that aching feeling the day after!
The aerobic pathway is very important for clearing the buildup of metabolites and increasing muscle temperature. This process produces a relaxing feeling to the body, which is why pitchers feel good after running as soon as they are done throwing.
However, pitchers are using aerobic conditioning after they throw for the wrong reasons: “flushing out” lactic acid.
THE LACTIC ACID MYTH UNCOVERED
Previous research has looked at the lactic acid myth on baseball pitching. According to some research, high levels of lactic acid accumulation will return to baseline within 40-60 minutes after high-intensity exercise, even if the individual does not do any exercise for recovery. There are no differences in blood lactate levels before and after baseball pitching. 
Now, time for some logic:
Lactic acid is produced in the body under highly intense conditions for a prolonged period. If lactic acid was the REAL problem for soreness and stiffness, then the pitcher would have to throw an absurd amount of pitches with very little rest between each pitch. For example, throwing 35 pitches in one inning with 3 seconds of rest between each pitch. 
Obviously, this will never happen in the game of baseball. By the time the catcher receives the ball, throws it back to the pitcher, and goes through his windup, 3 seconds will already have passed.
Also, think about what the pitcher is doing when he completes an inning…sitting his butt on the bench and recovering!
Therefore, lactic acid is NOT the reason why pitchers are sore after they throw!
So…what IS the reason then?
THE REAL REASONS FOR SORENESS
With the throwing motion being the fastest motion in all of sport, one must consider the speed of these muscular contractions.
Since we know that the eccentric component (muscle lengthening) causes the most amount of muscle damage, it would make sense that the arm becomes very stiff and sore after throwing.
Soreness is the body’s protective mechanism, so it’s a good thing!
This mechanism involves the protection of disrupted muscle fibers. When our muscles undergo a certain stress that they are not accustomed to, they create an inflammatory response so that they are ready to endure the next event, just like the previous one. Therefore, this becomes an adaptation as well!
The scientific name for this after-game soreness is delayed-onset muscle soreness (DOMS).
This unaccustomed activity involves possible changes in throwing mechanics, throwing with greater intensity than usual, or throwing more frequently than usual (pitches or days in the week).
This is why recovery methods are highly valuable for the baseball pitcher, and something that cannot be ignored (especially in-season).
After every time you throw, I highly recommend to ice and perform very light aerobic activity to bring blood to the area. It’s important to deliver blood to any affected area because it contains many essential molecules that aid in tissue repair.
Increasing your protein after you throw won’t hurt either!
Jarad Vollkommer, CSCS
Szymanski, D.J. (2009). Physiology of baseball pitching dictates specific exercise intensity for conditioning. Journal of Strength and Conditioning 31(2), 41-47.