Addressing Swing Deficiencies Using Blast Motion Metrics

By Eddie Lehr (Data Analytics Intern at RPP, Babson BS ‘19), with assistance from Nunzio Signore (BA, CSCS, Co-owner RPP) and Bahram Shirazi (BSEE, MBA, Co-owner RPP)

In my previous internship before RPP, part of my responsibilities included watching Minor League baseball games. After my first few games, I noticed a recurring trend, every player wore a Blast Motion sensor during the game. As I saw more organizations’ Minor League teams, not all had their players wear the sensors; however, the idea behind it was simple, data collection.

At RPP, we use Blast Motion sensors for the same purpose, and this allows us to help identify and develop athletes’ inefficiencies. The only difference is we do not have the ability to collect data from athletes’ in-game at-bats. Therefore, we collect data from batting practice at our facility and are still able to get a good picture of what an athlete does well, and what they struggle with.

When an athlete comes into RPP, they receive a physical assessment of their body, as well as a hitting analysis session. The hitting analysis incorporates three critical pieces of data that we use to assess athletes: a Rapsodo hitting camera, a K-Motion vest, and a Blast Motion sensor.

Blast Motion technology provides sixteen metrics on a player’s swing. We focus on the four that we feel are important to creating the best profile of an athlete and finding what areas they can improve in. The metrics we chose are:

    • Rotational Acceleration
    • Attack Angle
    • Vertical Bat Angle
    • Power

We feel these metrics are important because of the foundation they create for an athlete’s swing, and the fact that they go hand-in-hand. One thing to note, is Blast metrics are directly correlated to the age of the athlete. The ranges below are indicative of most high school athletes. College and professional athletes have a different set of ranges (except for attack angle).

With each metric, it is natural to have athletes be above or below our desired ranges. Whether a player is above or below the range could be caused by how their body is able, or unable, to move. This is where we utilize biomechanics. From a physical assessment done by one of our strength coaches, we can identify inefficiencies in an athlete’s body. This could be either a mobility issue or a strength issue. As a result, here are descriptions, mechanical flaws in the swing, and a few of the biomechanical inefficiencies that we believe cause poor numbers in these four metrics.

Metric 1: Rotational Acceleration

Description—This metric measures how quickly the bat accelerates through the zone from first move to getting on plane. Essentially, it tells how quickly the hitter gets on plane with the pitch once they begin their swing. This helps give the athlete more time for pitch recognition and reduces swing and miss rates. We typically like to have athletes within the 12-15(g) range.

Analysis—In most cases, if not all, cases, poor rotational acceleration is a result of the athlete being under the desired range we are looking for. When an athlete is below this range it is typically a result of a loss of posture, either from the athlete hanging back or being too far forward in their swing. When this occurs, the body loses its axis of rotation, which allows it to quickly and efficiently rotate.

A few biomechanical parameters that could be the cause of this swing issue are limited core control, insufficient lower half strength, limited shoulder mobility/stability, and limited front ankle stability, to name a few. As with the other three metrics we are looking at, addressing these biomechanical flaws in the athlete will give the athlete the best opportunity to improve their swing. With rotational acceleration specifically, fixing these biomechanical issues will allow the athlete to have a more desirable axis of rotation during their swing.

Metric 2: Attack Angle

Description—This metric measures the angle of the bat’s path at impact, relative to the horizontal view from side-to-side. Positive numbers are indicative of an upwards swing, and negative numbers mean a downward swing. We look for hitters to be within 6-12°.

Analysis—If the athlete is outside the desired range of 6-12°, there could be a few contributing factors. It is important to note that different attack angles are necessary for a fastball versus off-speed pitches (Click here for article). Excessive side bend of the torso in either a positive (dominant side), or negative (non-dominant side), creates the athlete to either have an excessive uphill or downhill swing, respectively. An uphill swing and the athlete is hanging back in his swing, a downhill swing and the athlete is using his arms and hands prematurely causing him to push his swing. A loss of posture can also translate to an uphill or downhill heavy swing.

A few of the biomechanical causes of excessive torso side bend are a lack of spinal stability and hip mobility. While causes of a loss of posture can be limited core control, insufficient lower half strength, limited shoulder mobility/stability, and/or limited front ankle mobility, as mentioned above for rotational acceleration. When these factors are improved, the athlete can consistently get themselves within the desired range of attack angle.

Metric 3: Vertical Bat Angle

Description—This metric measures the angle of the bat at contact with respect to the knob. Zero degrees would mean the knob and barrel of the bat are parallel to the ground, and negative numbers result when the barrel is below the knob. This metric varies from pitch location because a lower pitch requires the barrel to be lower to the ground. We look for Vertical Bat Angle to be between (-23) – (-33)°.

Analysis—As a reminder, vertical bat angle is dependent on pitch location. This is important when looking at this metric because an elevated pitch could be around -20°, while a low pitch could be around -35°. With that said, if an athlete is consistently outside of the (-23) – (-33)° range then there are mechanical swing issues that could be the cause. The athlete could be “dumping the barrel”, meaning the barrel falls well below the hands early in the swing, or pushing their hands, both of which cause the athlete to begin their sequence early, or they have excessive torso bend at foot strike and the start of their swing. Torso bend can either be forward (anterior) or backward (posterior).

Biomechanical issues, such as limited pelvis/spine separation, limited wrist/forearm mobility, limited front shoulder mobility, insufficient scapular mobility and/or weak oblique abdominals are a few of the reasons for why a hitter would be dumping the barrel early, or pushing their hands. If the hitter has excessive torso bend in either direction, they have insufficient control in their core and lower back. In fixing this issue, the athlete could consistently make higher levels of contact with pitches in different locations.

Metric 4: Power

Description—This metric measures the power generated from the swing looking at the mass of the bat, bat speed at impact, and acceleration during the downswing phase of the swing. We look for ranges between 3.8-5.1(kW).

Analysis—Similar to rotational acceleration, most, if not all, of the athletes we see have lower levels of power than we would like to see. As mentioned above, power is a combination of the mass of the bat, bat speed at impact, and acceleration during the downswing phase of the swing. When an athlete’s power metric is poor, it could be a cause of drifting during the swing, improper hip/shoulder separation, or of course, a lack of strength.

When an athlete drifts throughout their swing, it is typically caused by poor front hip mobility, insufficient lower half strength, and/or limited ankle mobility. If drifting is their mechanical flaw, fixing this issue will allow their body to generate more acceleration and force in their swing, increasing their power metric. Whereas, if an athlete has poor hip/shoulder separation, this may be caused by insufficient front shoulder mobility, insufficient scapular mobility, limited pelvis/spine separation, limited leg strength, and/or weak oblique abdominals. Increasing this stretch in hip/shoulder separation creates more torque and ability for the athlete to increase their power metric.

Conclusion

Looking at these four metrics in athletes and understanding why they may be out of the desired range is an important step in developing each athlete individually. From this we can give hitters mechanical adjustments to make, as well as mobility and strength exercises to improve their swing.

To conclude, good coaches may be able to identify where issues are in an athlete’s swing using Blast Motion data but understanding why an athlete’s swing is behaving in that specific way is hard. Understanding how biomechanical issues could be causing their body to be unable to behave in a specific way, so that they can get their swing aligned with these ranges, is even more difficult. Being able to identify why something is occurring in an athlete’s swing, gives us the best course of action moving forward in training that athlete.

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