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Bat compression test results describe the amount of pressure required to compress the barrel of a bat. A higher compression result (usually stated in terms of pounds per area) means a barrel’s walls are more rigid. A bat with a lower compression means the barrel walls are more flexible or elastic.
Some believe that a more elastic barrel wall can produce faster exit speeds. In no small measure, according to every manufacturer and bat engineer we spoke to, the belief is not valid. We discussed the topic with every major manufacturer and compiled their sentiment, as we understood it, below.
Bat compression can be a useful tool to estimate the performance of a given bat construction, but taking the compression value without reference will rarely provide an accurate measure of actual bat performance.
~Kyle Hodge, Product Engineer, Axe Bats
Historically, accurate compression testing has been a slightly useful indicator of ball exit speeds. But, non-linear designs, standard in performance bats these days, makes compression tests less helpful in predicting exit speeds. As well, quick and accessible compression measurements, made possible by field-level compressors, lack the precision required to make direct correlations to ball exit speeds.
Measuring only how loose the springs are in your trampoline tells you virtually nothing about how high you can jump.
~Brian Duryea, Bat Digest
We asked several industry experts from a major manufacturer to comment on the usefulness of bat compression. Read below what they had to say about bat compression tests predictive power of ball exit speeds.
Here is a sampling of compression tests we took on bats at Bat Digest. As we say in this article, making full-on determinations about ball exit speeds based on these numbers doesn’t mean very much. You can see this list on our ball exit speed spreadsheet too.
One useful way to visualize how easier compression is not always better is to consider the trampoline in your backyard.
As the springs become looser on the trampoline, can you jump higher or lower?
The answer, of course, depends. Specifically, how much does the person jumping weigh? And, how much elasticity is retained in the springs as they become loose? We could imagine an equation that optimizes the trampoline’s effectiveness. That equation, based on factors like the jumper’s weight and leg strength, as well as the quality of the spring’s recoil, would set the optimal amount of taut in the tramp’s springs.
Much like the perfectly dialed in trampoline, a bat’s effectiveness is not always maximized by merely making the barrel walls more flexible. Or, as we might say, loosening the springs of the bat. Instead, the right elasticity in the barrel simply depends. Factors like pitch speed, bat and ball weight as well as the quality of the barrel’s material all play significant factors in the optimal compression. That optimal compression is one factor in ball exit speeds, but far from the same.
Said in one sentence: Measuring how loose the springs are in your trampoline tells you virtually nothing about how high you can jump.
When measuring within the same class of bat (BBCOR, USSSA, USA), our bat compression test results provided little predictive power for exit speed.
One general theme we gathered from the experts was that bat compression test results are useful in monitoring the life of a bat. As a composite bat is worked in more, its compression will become easier.
We also had a good back and forth with some engineers at DeMarini who felt, without putting words in their mouth, much like everyone else we spoke to. They add how bat compression is done at a field level (with devices like the one you see in the video above) aren’t reliable. Most bats in a particular classification sit real close to each other on a compression test scale. Small changes from one bat to another are not predictive enough, nor is the device accurate enough to make determinations about ball exit speeds.
Compression doesn’t matter to me; I’m hitting bombs either way. Hitters should focus less on barrel compression and more on swing mechanics, timing, and approach at the plate. Blaming your bat for a bad AB is counter-productive.
~Former Oregon Duck, Hailey Decker
Here are some notes we took from our conversation. We paraphrased, as far as we understood it.
A well respected Easton engineer had similar things to say. Simply, the difference between compression and exit speeds are uncorrelated enough to put little stock into compression tests alone.
“In the current landscape of many associations/leagues, there seems to be a misconception that bat compression is the end-all, be-all of performance. Compression is the easiest / outer-most layer than can easily be peeled back, but there are many different factors beneath that compression figure that impact the performance of the bat…”
Henry Fitzpatrick, Bat Engineer
Those factors include, among other things, both the quality and durability of the material.
Rawlings said, without surprise at this point, very similar things. Compression made more sense as a stand-alone performance test a long time ago. Now, construction is “non-linear.” Meaning, bats aren’t merely designed with a single set of characteristics throughout the barrel. As such, measuring pressures at a point of the bat and calling it a performance comparison is not accurate.
Compression numbers matter in a few specific instances.