Becoming a data driven program- Part 2: Blast Bat Sensors

Jonathan Gelnar

Link to audio version-

Blast Motion Sensors

Concentrate on what will produce results rather than on the results, the process rather than the prize.

— Bill Walsh

Blast sensors (or any form of bat sensors) are probably the most cost effective tool when trying to build a program that uses data to influence outcomes. At around $120 they’re affordable enough that you can have multiple being used at a time, or even an entire team set, which a few teams do. We are seeing them used more and more in the minor leagues during games, and you already know that I believe that in game data is king. Here is our plan for collecting blast data and how we used it.


  • 3 blast sensors
  • 3 iPads

Blast offers a plan for each individual to have an online profile for every swing they take with each sensor at about $10 a player. Having over 50 players in the program, this was way too expensive for us. So the next step would be to do some of the process by hand. I spoke in my last article about the importance simplifying and understanding what you are looking for, and using blast was a big reason why I came to that realization. There are 10 metrics, so trying to track all of these, especially by hand, can seem extremely daunting. We purchased the sensors last February and trying to learn and understand each of these took a large chunk of time. Understand that going in, if you don’t have a system for collection and have an idea of what you are looking for, your head will be spinning. Here’s a few ideas and tips to get you through it.

Test/Retest model

This fall we are performing a pretest, starting the first week of practice and once a month we will do a retest. I’d love to be able to test every 2 weeks, but with only having three sensors and 52 players, we will have to settle for once a month.

We want to see is their data off of stressful velo or the machine. We did not use blast at all on a tee. I could be wrong, but for me, it doesn’t matter. So every time they swung a bat with blast, it would be against a ball thrown overhand.

There were a few things that were interesting with the process. I loved to see how their swing pattern was challenged and changed when they went from BP to the machine. We had some that dropped 10 MPH of bat speed! Or we would have a positive attack angle, and as soon as they saw 88, went back to negative. So there is some value in that model as well. Although seeing the velocity they’re going to see in games will give us the most realistic look, another option to this would be mixed BP.

So now you see what they will be getting tested on, here’s how we set it up.

Instead of paying for the profile, we titled each session as the players name and that player would only use their bat during this time with the sensor. I spoke in this article about how we use weighted bats, but for the sake of getting a larger sample size, we have them skip the overload and underload training for test day. After you do this once, the players should easily be able to connect the next time and take this out of your hands. There are a few things to remember when setting it up this way. *Full disclosure, this is the best way we found to do it, so if you have a better way I’d love to hear suggestions.

  • I’ll be fairly obvious and say that it is best when you have the sensor connected to the iPad with their name in before practice starts. This can be time consuming and you don’t want to take this time away during practice.
  • With our model of testing, each player is responsible for their own iPad and they take it with them through rotations.
  • Make sure to put their name in before the end of the session, or you will have a hard time tracking whose swings are whose.
  • Have a few metrics you are looking for and load them into the dashboard so the players can see them (more on this later).
  • Screenshot the metrics if you don’t plan on putting them in a spreadsheet right away. I went into “collection” mode this spring, we went to spring break, came back and they were gone. You can also pull the CSV file from the blast website.

How we are communicating data

For the initial test, I just want them to swing. I want it to be the closest to their game swing as possible so we can get an accurate read on what we need to work on and where to start. After they get done with their training session, we go over the metrics we want to start with. We then help the player to fully understand the meaning and the why behind it. It’s integral to simplify this as much as possible for the player, because the metrics are coactive and each metric affects the others. For players, it can get extremely confusing and that’s the last thing we want. From there, we develop a plan of attack for what we deem as their biggest area of improvement and we retest in a month to see if our plan is working. Here’s an easy way to track progress.

Shoutout to Chase Glaum creating and sharing the Excel Sheet

Another model would be more 1–1 with a coach and every swing (or every few swings) you track progress. This would be effective with a small group, if you are wanting them to feel through some changes at a slower pace, or if you have one metric they are trying to work on and feel/see the difference between swings. Let me give you an example.

Johnny has a negative attack angle of -5. We know that one metric affects the others but we have decided this is his biggest area of improvement. This is obviously after our initial test, and we have gone over this with him and what this means. He now understands that his barrel is working at a downward angle at contact, so with this model, we would have him take a swing, see what the number is and then try and improve it. Once he gets close, we have him repeat it as close as he can. This model can be somewhat slow, but for initial learning it can be a great way to help them feel the movements we’re trying to get them into. After they fully understand the metric, then you can take this same model to the team setting because they can now coach themselves. If they can feel it, they can fix it. This is why understanding the players feel and language is so important in the player development process.

It’s also important to video as much as we can, because we can use it with blast to help the player to understand the movement even better. They can explain what they feel, and we can watch it and see how it matches up with the metric.

What’s important to us?

Tier 1

Bat speed

Obviously bat speed isn’t something that can change overnight, but it is something we want to track over time. Keeping a simple spreadsheet of average bat speed is a great way to notice trends. Are we ticking up? Down? This can be extremely beneficial in season to monitor workload.

Another benefit would be to see how well their bat speed holds up during stressful velo. We want them to at least stay within 8% of their normal front toss bat speed. So if their average on front toss is 65, they should easily be around 60. Obviously we would would love them to be as close as possible to their peak with adjustability, but this can give coaches a range to look at.

Attack angle

Attack Angle is the angle of the bat’s path, at impact, relative to horizontal. A positive value indicates swinging up, and a negative value indicates swinging down, where zero is perfectly level. Per blast

We would want this range to be between 0–15 for our hitters. A lot of this can depend on pitch location, so giving a range to stay between is a great idea. I would love it if we were able to implement a strike zone with it. Being able to track pitch type and location with each swing and keep the average metrics based on location in the zone would be phenomenal. But at this point, there’s not a way to do it within the app.

Tier 2

The following are what we are looking at if the Tier 1 metrics are within normal ranges. It’s not that these aren’t important, but when each metric affects the other metrics, having a tier system to look at has helped us simplify the data for ourselves and the players. For instance, if our attack angle is negative, its going to affect our on plane percentage. So the hope is that if we work on the root cause, it will help clean up the latter.

Time to contact

Time from the start of your swing to contact. Normal range would be between .14-.18. This is great for guys that we consider to have “long swings” as it can give an objective look and provide immediate feedback to the player. A few things to pay attention to, the players can try and cheat the drill and start chopping down at the ball out front trying to create a “shorter” path. This is obviously frowned upon if we want them to be in the zone for a long period of time. They can also get a lower time if they get beat with the pitch and make contact right before it gets into the catchers mitt. It may be a smaller number, but in no way is this what we want. We also need to let them try a lighter bat. This could be the quickest fix, especially for teenagers who don’t have any idea of what size bat to get.

This is one of our younger players, and one thing he/we decided to work on this fall was being quicker to contact. His bat speed is in the mid 60’s and his attack angle today was 6*. If you’ll notice, when he starts his swing his hands get disconnected from his rotation causing him to be late. And this swing was with a softball bat (cheap underload bat with the ability to teach barrel accuracy). Another part of the problem is that he reaches with his front foot which causes him to reach back with his hands to stay balanced. Let me give you a picture of what I’m talking about.

Notice the large spacing between his hands and shoulder during the launch of the swing.
Again, this player works really hard on his swing and is very coachable. So any swing comments, direct them toward me, not him.

So what are we doing to work on this? One of my favorite constraints is the connection ball. The goal with this is to keep the ball between the forearm and bicep tight, and shouldn’t fall out behind you. This will help give the player a clearer picture of what it feels like to “stay connected” during their swing to contact. Here’s his video with it.

Notice the ball is wiggling a little bit during his load, he still needs to keep his hands a little tighter and get them inside the rotation of his swing, not behind it. He said multiple times during training that he could feel the difference. And if he can feel the difference, he can fix it.

On plane percentage

Per blast- There is a high correlation between the hitter’s setup posture and the On Plane percentage metric. A good functional swing will have an average On Plane percentage starting at 60% or higher. A typical dynamic range for On Plane percentage will be 55%-65% or higher.

This is another one that I wish we had a strike zone in the app for. Our “score” in this is going to have variability based on pitch location and timing, so having a zone and a percentage within that zone would be very helpful. Since we don’t, give them a range to stay above. We want the players to be on plane as long as possible and this is one thing in the hitting community that most would agree on. Here’s a drill we like to use because several of our players cut off their swings and don’t stay “through” the zone very well.

Top hand through


So, with all of that information and with only three metrics covered, where do we start? Here’s the best advice I can give you. Blast provides an opportunity to give objective feedback on what the bat and body are doing throughout the swing. Remember that each metric effects each other, so pick one to focus on at a time. Blast can provide a ton of information and metrics for players, but at the same time it can be overwhelming if you and especially the player don’t know what they are looking at.

Have a great week!


Jonathan Gelnar

Written by

†follower. Husband. Influencer of our nation’s youth through the national past time. @union_baseball. Host of @aotc_podcast

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