Two parameters determine how far a batter will hit a ball. The first, and most important, is the speed at which the bat travels through the hitting zone. The second is the weight of their bat. As a player physically matures, a batter can increase their bat weight while maintaining the bat speed. On the other hand, player's physically maturity does not have any impact on their bat speed. Bat speed is a function of the development of fast twitch muscle memory. Lets work our way through the biology of muscle fiber, overload and underload batting practice, and a couple of drills that help players develop a quick bat through the hitting zone.
Muscle fibers
The human body consists of two types of muscle fibers: Type I (slow twitch) and Type II (fast twitch).
- Type I (slow twitch): The slow muscles are more efficient at using oxygen for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can be used for a long time before they fatigue. Type I muscles are commonly used for aerobic (oxygen consuming) exercise involving long, low levels of exertion where the muscles are used at well below their maximal contraction strength for long periods of time.
- Type II (fast twitch): The fast twitch muscles are much better at generating short bursts of speed than slow muscles. Type II fibers use anaerobic (oxygen free, glycogen) metabolism to create fuel and fatigue more quickly, but typically produce the same amount of force per contraction as slow muscles for very short bursts.
Each person has a genetically determined mixture of both slow and fast fiber types. On average, individuals have about 50 percent slow twitch and 50 percent fast twitch fibers in most of the muscles used for movement. Our muscle fiber type may influence what sports we naturally gravitate towards with sprinters having a higher percentage of fast twitch fiber and marathoners having a higher percentage of slow twitch fibers.
Baseball and softball player need to develop their muscles in the same speed and motion as they do in there games (sometimes referred to as ballistic training). Batting is a quick explosive movement, so players need to emphasize the training of their Type II (fast twitch) muscle fiber. Training with their personal bat and regulation ball will only develop their muscles to get as strong as the weight of the bat and ball. To get stronger, one needs to use a heavier bat. To get quicker, one uses a lighter bat.
Heavy bat (Overload)
The use of a bat should develop a quicker, faster, and stronger swing with proper mechanics. For overloading to be effective, the fundamental swing must be exactly the same as in the competitive situation - same speed and motion as during competition. This requires the bat weights to be located on the handle or just above the hands, not at the end of the barrel (like a variable bat weight). Placing the weight near the hands increases the bat weight while reinforcing the proper fundamental swing that stimulates the hitter's fast twitch muscles while providing resistance to increase strength.
Issues with bat donuts and barrel weighted devices
Bat donuts are a popular item to use, both with professional and youth batters, but are often used incorrectly. Many youth batters will use a donut to strengthen their core and produce a stronger swing. Actually, donuts and barrel weighted devises slow down a hitters swing by as much as 10% and retards the hitters performance. First, these devices stimulates the hitters slow twitch muscles making them stronger through the whole swing, which is why after using them their regular bat feels lighter. The problem is the fast twitch muscles were not stimulated like in game situation so the hitter is not quicker. The second problem is that donuts put the extra weight at the end of the bat that leads to a hitting flaw called "casting". Casting occurs when a batter's first forward movement is to take their hands away from their body, instead of directly towards the ball. When the end of the bat has the weight and the bat starts moving forward, the natural forces of the weighted bat pull the hands away from the body and the hitter has to exert an opposite or pulling force to keep the hands near the body. As the hitter brings their hands forward the bat pulls away from their body and the hands naturally follow. This creates hitter muscle memory to take the bat in a looping path. What happens when the donut is taken off? The hands follow the muscle memory and bring the bat in this same looping fashion toward the point of contact. The swing slows down and diverts some of the bats energy away from the point of contact producing a slower, less powerful swing. Throw the donut away! Better yet, give it to your fiercest rival :=)
Light bat (Underload)
Similar to the overload practice, for underloading to be effective the player needs to use the proper swing mechanics. The heavy bat develops the strength of the fast twitch muscle fiber. Conversely, the underload bat increases the speed of muscle memory. The light weight bat allows the hitter to swing faster during practice than a regular bat, quickening the fast twitch muscle fibers, and take hundreds of quality swings quickly without developing muscle fatigue. Most underloaded bats have a smaller diameter, when used with a small wiffle ball, helps the hitter focus on the point-of-contact and fine tunes the hand-eye coordination. By swinging faster, the batter has more time to see the ball and make a good swing that the muscles will automatically remember when they are at the plate.
Drills for Overload and Underload
Over the past couple of years, I have heard of all types of drills to use with an overload and underload bats. I have also heard some pretty extravagant claims about bat speed improvement. What I can confirm is that the teams I have coached have noticeably improved our players bat speed with the following simple drills when used consistently during hitting practice. Please note the word "consistently" in the previous sentence because it takes about ten practices using these drills before a player and/or coach will notice the difference.
Drill 1: Take ten swings with the overload bat. Immediately following, take ten swings with the underload bat. Repeat the previous two steps three times. This gives a player 60 perfect swings to develop muscle memory.
Drill 2: Using the underload bat, have a coach soft toss ten wiffle balls on the inside portion of the plate, then toss ten balls down the middle, and finally toss ten balls on the outside corner. Repeat three times. The batter should pull the inside pitches and hit the outside pitches to the opposite direction, which also helps develop players recognition of pitch location and timing. This gives the player 90 perfect swings to develop muscle memory.
Using these two drills in practice puts an emphasis on the underloaded bat. A variation that another successful local coach uses keeps the swing repetitions more towards half overload and half underload by including a overloaded soft toss drill. I have adjusted the overload to underload swing ratio on my teams but found that too much of an emphasis on using the overload bat created fast twitch muscle fatigue in the players and they were having a hard time maintaining their swing mechanics. I would encourage you to start with the two drills above. If you choose as the season progresses, you may want to add a third drill that includes ten or twenty soft toss swings with overloaded bat. The key here is to make sure the swing mechanics are correct.
Practice does not make perfect. Perfect practice makes perfect play. Using a heavy bat combined with a light bat will increase the hitter's bat speed but if the swing mechanics are incorrect the player will not realize the benefits of a quicker bat. By focusing first on the swing mechanics and then on the bat speed, your team will develop the reputation of being good hitters that pitchers fear.
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