There isn’t anything that hurts a young baseball player more than an uppercut swing. No only does this swing make the ball hard to hit, but also the result of making contact is a ball that stays in the infield. The reason its hard to hit a ball when swinging with an uppercut is the fact that the timing of the swing must be perfect in order to hit the ball in the first place.
An uppercut swing cuts through the pitch zone from underneath and follows through above where the ball is pitched. A downward swing through the slot stays in the pitch zone for a much longer period of time and therefore the bat is more likely to strike the ball. The hits of this kinds are also much more solid on the bat and therefore go farther.
An uppercut swing is often caused when the player first starts playing baseball and the coach of father throws baseballs to the child while standing in an upright position. This causes the thrown ball to be pitched in a decending arc toward the batter who then swings upward toward the ball in order to make contact. Then, when the player moves to a situation where other kids are throwing the ball at the same height as the batter, he can no longer make contact with the ball due to this bad swing habit.
This situation can be prevented through the caoch of father throwing to the batter while placing one knee on the ground or using a pitching machne that sends the balls to the batter at the correct height.
However, in order to correct an uppercut swing that has ingrained itself into the players muscle memory, you must change the point of reference in the batters mind. An uppercut swing is caused by swinging at the ball with the dominant arm of the player. For a right-handed batter this would be the rightarm which is the triling arm towards the ball. The upper cut is caused by dropping the right arm topush the bat toward the ball. The way to correct this swing fault is to have the batter swing at the ball with the lead (or left arm) while using the right arm to guide the bat at the ball.
In order to swing at the ball with the lead arm, it is impossible to drop the right arm before the ball is hit. If the player is having trouble grasping this concept, have the player hit balls using the lead arm only until he understands what it feels like to hit the ball with the lead arm. Then he can add the back arm to guide the swing through the pitch.