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Slugest 2019 - Hi Res Slides

Presentation · November 2019

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Slugfest 2019 Hi Res Slides “Current and Future Concepts

• f The Kinetjc Chain”

Ben Hansen VP Biomechanics & Innovatjon Motus Global, Inc.

B A C K E L B O W F L E X

Mining the Motus MLB database showed that batters with a more ex- tended elbow at contact had greater bat speeds (R = 0.523), whereas batters who make contact in a more flexed position had poorer bat

• speeds. Assuming high bat speed can produce high exit velocity under

ideal impact conditions, it’s desirable to achieve a more extended posi- tion. However, there is likely more complex muscle mechanics at play. Given the Torque-Angle relationship of a muscle, being at either extreme of joint flexion/extension will produce low torques. Similarly, following a Torque-Omega plot, higher torques will be produced during slower contraction velocities.

0 Nm 0% 100 deg 20 Nm 20% 40 Nm 40% 75 deg 60 Nm 60% 80 Nm 80^ 100 Nm 100% 50 deg

E X I T V E L O C I T Y

Two battering datasets from Motus’ MLB database were mined and

• compared. Batter A had exit velocity of 108 mph during testing. Batter

B had 79 mph exit velocity (both from same team). Batter A (108 mph) made contact with the back elbow flexed to 68 degrees, while achieving peak back elbow extension torque. Batter B (79 mph) made contact with the back elbow flexed 18 degrees more than batter A (84 degrees). Batter A’s triceps were at optimal length during peak force develop-

• ment. Batter B’s triceps were not.

Exit Velocity = 79 mph Exit Velocity = 108 mph

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Contact Contact

0 Nm 0% 100 deg 20 Nm 20% 40 Nm 40% 75 deg 60 Nm 60% 80 Nm 80^ 100 Nm 100% 50 deg

Exit Velocity = 79 mph Exit Velocity = 108 mph

P E L V I S R O T A T I O N A T C O N T A C T

Mining 325 MLB batters in the Motus Database, a strong correlation exists between Pelvis Rotation at Ball Contact and Peak Hip Rotation Velocity. Batters who are able to rotate their pelvis to face the pitcher (90 de- grees) tend to have higher hip speeds than those who cannot rotate their pelvis as much. Utilizing the entire range-of-motion of the pelvis from load through contact gives the hip’s external rotators more time to generate rota- tional velocity. `Lack of pelvis rotation at contact is most often due to lack of mobility in the lead hip.

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R E L A T I V E C H A I N

To truly measure the contribution of the upper trunk segment, the angular velocity relative to the pelvis must be calculated. This can be done by subtracting the pelvis rotation velocity from the upper trunk global rotation velocity for every sample of data in the pitch. When inspecting relative rotation velocites of the trunk, the average MLB pitcher has much more separation in timing than the global ve-

• locity. MLB pitchers have over 75 ms of separtion in this method of the

kinetic chain timing.

G L O B A L C H A I N

When comparing pelvis speed to GLOBAL trunk rotational velocity, the two curves remain in phase for the majority of the pitch. This occurs simply because the trunk sits on top of the pelvis. If the pelvis speeds up, the trunk does as well. Only after the pelvis begins to slow down and the trunk rotators con- centrically contract, does the upper trunk rotate independently of the

• pelvis. In pitching, this summation is quite large and occurs 60.4 ms

after the pelvis peaks.

M O T U S B I O M C H L A B

The Motus MLB Pitching database was mined to compile average time-series curves of pelvis and trunk rotational velociites. The global (relative to ground) angular velocity of the pelvis (red) and upper trunk (blue) are plotted above. Key-frames of foot-contact, ball-release, and max-internal rotation are plotted for context. The average MLB pitcher reaches max pelvis rotation velocity 110.4 ms before ball relase, and reaches max trunk rotation velocity 50.0 ms before ball release, leaving a separation of 60.4 ms between peaks.

M O T U S B I O M C H L A B

The Motus MLB Batting database was mined to compile average time-series curves of pelvis and trunk rotational velociites. The global (relative to ground) angular velocity of the pelvis (red) and upper trunk (blue) are plotted above. Key-frames of load, foot contact, ball contact, and follow through are plotted for context. The average MLB batter reaches max pelvis rotation velocity 77.1 ms before ball relase, and reaches max trunk rotation velocity 66.7 ms before ball release, leaving a separation of 10.4 ms between peaks.

B A T T I N G R E L .

Batting mechanics do not allow for maximal exploration of the body’s

• ROM. The batter is dis-advantaged by needing to react to a pitch,

requiring a short and compact, yet powerful swing to gain success. As such, there is little separation between pelvis and trunk rotation

• velocities. Generally, the pelvis is the main producer of rotational

energy, while the trunk adds small portions of energy. The ammount of energy the trunk contributes is variable and may depend on the bat- ter’s choice to execute max effort swings based on pitch type and loca- tion that they identify early in the swing.

P I T C H I N G R E L .

Similar to golf mechanics, pitching mechanics allow maximal explora- tion of the body’s range of motion to generate ball velocity. A key part

• f the kinetic chain in pitching is the ability to separate the trunk from

the pelvis. Pitchers build successive velocity in body segments by first accelerating their pelvis rotationally. As the timing of the pelvis leads to a de-acceleration, the trunk acclereates in rotation, delayed as much as 75 ms. The relative trunk velocity also increases in magnitude compared to the pelvis.

R E L A T I V E C H A I N

The relative trunk rotation velocity of batters has a completely distinct movement batter than that of a pitch. In fact, the relative trunk veloci- ty (on average), peaks AFTER ball contact. There is also a local maxi- mum slightly before ball contact that is very low in magnitude. Timing separation between global pelvis velocity and the small local maximum before contact of the trunk is 54.2 ms, with very little contri- bution of the trunk (compared to pitching).

G L O B A L C H A I N

Similar to pitching, when comparing pelvis speed to GLOBAL trunk rotational velocity, the two curves remain in phase for the majority of the swing. Even in the global plot of trunk rotation velocity, it’s apparent that there is less separation of timing between the pelvis and trunk. In fact, there is only 10.4 ms of time between both peaks (compared to 60 ms in pitching). In this case, the pelvis and trunk move together a lot more in batters than pitchers.

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