This thesis reviewed variables of baseball mechanics and performance as discussed in current literature. This included investigating factors of biomechanics, the health of players, and comparisons across demographics. At the biomechanical level, components of the kinetic chain were observed as the energy transferred from the lower body to the upper body. Additionally, the upper body appeared to compensate for deficits in the rotation of the trunk. Injuries to the abdominal and low back were correlated with trunk rotation, while arm injuries were traced back to overuse and fatigue. When considering experience level, variation tended to decrease. Youth players demonstrated different patterns of fatigue and different injury correlates compared to adults. At a geographic level, American pitchers may be associated with an increased risk of elbow injuries, with Japanese and Korean pitchers to shoulder injuries; these differences are thought to be due to differences in instruction. Applying this research and findings to current baseball players may help guide training and performance or continue research.