When a player frequently swings a heavier bat to train, their swings generally become a bit slower because of the extra weight of the bat. Over time, the muscles involved in the swing can get accustomed to this slower movement. This is not a good thing. If muscles get used to moving slower, muscle memory can cause these muscles to remain slower even if the batter switches to a lighter bat. In essence, over time, the player has “taught” his swing to move slower. The now slower muscles are just repeating what they have been trained to do.
Fungo bats don't have to be just for coaches
To account for this, some players occasionally train with a much lighter bat in order to teach their bodies to move faster in the process of swinging. Using a fungo bat or a broom handle can enable a player to do this. The lighter weight allows the hands, wrists, and arms to move faster than they normally would with a regular sized bat. Speeding up the muscles used in the hitting process “teaches” them to move faster. Even when the batter puts a normal bat in his hands, his muscles have been trained to move quickly and will do so even though the bat is heavier. In short, muscle memory works the other way too!This strategy is sometimes used by sprinters. Occasionally they will run on a slight decline to get their muscles accustomed to working faster than normal. This helps them when the race begins even though the race is on a level surface. The running muscles want to keep moving at the speed in which they have been trained. Along those lines, a former manager of mine who played in the major leagues told me that occasionally, towards the end of the MLB season, he would change his on-deck routine. Because the long season wore his body down, he sometimes would not swing the traditional weighted bat in the on-deck circle. He sometimes swung a fungo bat to lighten the strain on his body. He also felt it kept his hands moving quickly even though his body was tired.If you use a heavier bat to train, take some swings with a much lighter bat every now and then. There is benefit to that as well.
