text: The use of weighted bats is based on the theory of complex training where sets of heavier and lighter resistances are alternated to increase muscle performance.This theory revolves around the idea that muscle contractions are stronger after reaching near maximal contractions. The postactivation potentiation improves motor neuron pool excitability and increases the number of recruited motor units, both leading to greater power output. The additional weight may also help strengthen the muscles of the forearms and wrist thus increasing bat velocity, though some evidence suggests that the effect is psychological rather than biomechanical. The lineup
  The lineup or batting order is a list of the nine baseball players for a team in the order they will bat during the game. During the game the only way to change the lineup is via substitution, as batting out of turn is not allowed. Once the ninth person in the lineup finishes batting, the first person bats again; this is the top of the order. Lineups are designed to facilitate manufacturing runs. Depending on batters' skills, they might be placed in different parts of the lineup. 