If you watch any baseball game, even a Major League game, you’ll see a lot of on deck hitters put some sort of weight on their bat and swing it several times before they go to the plate. Why do they do this? Because they have seen lots of people do it over the years while they were growing up. They also think that they are swinging their regular bat faster at the plate because it feels lighter right after swinging it with the weight on it.
But do they actually gain bat speed by doing this? In a word, NO. There is only a perception of swinging faster because of having used the weighted bat. The fact is, they are slowing down their bat speed at the plate by swinging a weighted bat first. There have been several studies I have read over the past few years that demonstrate this. They have all used a good number of test subjects that played baseball. While their results differed a little they were all conclusive in showing that the slowest bat speed at the plate came after swinging a weighted bat. The highest “at plate” speeds came when they swung their regular bat while in the on deck circle. The latest one was printed in the Journal of Strength and Conditioning Research. http://faculty.fullerton.edu/leebrown/KNES%20510%20Research%20Methods/Montoya-Effect_of_Warm_up_With_Different_Weighted_Bats.pdf
While they don’t investigate why it happens, they just show that it does. This is the fact and what people feel is the perception. This happens to us a lot in life. Have you ever been sitting in a parked car and a car in the space next to you starts moving and you think your car is moving? It’s just perception.
Here’s my theory of what is happening. When you swing with a weighted bat just before going to the plate you are programming your body to swing at that slower speed. Think about it. Do you ever see olympic sprinters warm up pulling heavy weights just before a 100 yard dash? No. They do full sprints to get the feel of speed and program their bodies for speed.
Swing with a weighted bat for strenth training at other times. On deck, swing just with your regular bat to program your mind and body for bat speed.