See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/337547393 Slugest 2019 - Hi Res Slides Presentation · November 2019 DOI: 10.13140/RG.2.2.12250.90566 CITATIONS READS 0 708 1 author: Ben Hansen Motus Global 17 PUBLICATIONS 1 CITATION SEE PROFILE Some of the authors of this publication are also working on these related projects: THE EFFECT OF YOGA ON RANGE OF MOTION, SHOULDER STRENGTH, AND PITCHER RECOVERY FOLLOWING IN-GAME THROWING View project All content following this page was uploaded by Ben Hansen on 26 November 2019. The user has requested enhancement of the downloaded file.
Slugfest 2019 Hi Res Slides “Current and Future Concepts of The Kinetjc Chain” Ben Hansen VP Biomechanics & Innovatjon Motus Global, Inc.
100 Nm 80 Nm 60 Nm 40 Nm 20 Nm 0 Nm 0% 100 deg 20% 40% 75 deg 60% 80^ 100% 50 deg 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.
120 Exit Velocity = 79 mph Exit Velocity = 108 mph 100 Nm Exit Velocity = 108 mph 80 Nm 100 60 Nm 40 Nm 20 Nm Exit Velocity = 79 mph 80 Contact 0 Nm 0% 100 deg 20% 40% 75 deg 60% 60 80^ 100% 50 deg 40 E X I T V E L O C I T Y Contact Two battering datasets from Motus’ MLB database were mined and compared. Batter A had exit velocity of 108 mph during testing. Batter 20 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 0 (79 mph) made contact with the back elbow flexed 18 degrees more 50 55 60 65 70 75 80 85 90 95 than batter A (84 degrees). Batter A’s triceps were at optimal length during peak force develop- ment. Batter B’s triceps were not.
850 800 750 700 650 600 550 500 450 55 60 65 70 75 80 85 90 95 100 105 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.
G L O B A L C H A I N R E L A T I V E C H A I N When comparing pelvis speed to GLOBAL trunk rotational velocity, the To truly measure the contribution of the upper trunk segment, the two curves remain in phase for the majority of the pitch. This occurs angular velocity relative to the pelvis must be calculated. This can be simply because the trunk sits on top of the pelvis. If the pelvis speeds done by subtracting the pelvis rotation velocity from the upper trunk up, the trunk does as well. global rotation velocity for every sample of data in the pitch. Only after the pelvis begins to slow down and the trunk rotators con- When inspecting relative rotation velocites of the trunk, the average centrically contract, does the upper trunk rotate independently of the MLB pitcher has much more separation in timing than the global ve- pelvis. In pitching, this summation is quite large and occurs 60.4 ms locity. MLB pitchers have over 75 ms of separtion in this method of the after the pelvis peaks. kinetic chain timing.
M O T U S B I O M C H L A B M O T U S B I O M C H L A B The Motus MLB Batting database was mined to compile average The Motus MLB Pitching database was mined to compile average time-series curves of pelvis and trunk rotational velociites. The global time-series curves of pelvis and trunk rotational velociites. The global (relative to ground) angular velocity of the pelvis (red) and upper trunk (relative to ground) angular velocity of the pelvis (red) and upper trunk (blue) are plotted above. Key-frames of load, foot contact, ball contact, (blue) are plotted above. Key-frames of foot-contact, ball-release, and and follow through are plotted for context. max-internal rotation are plotted for context. The average MLB batter reaches max pelvis rotation velocity 77.1 ms The average MLB pitcher reaches max pelvis rotation velocity 110.4 ms before ball relase, and reaches max trunk rotation velocity 66.7 ms before ball relase, and reaches max trunk rotation velocity 50.0 ms before ball release, leaving a separation of 10.4 ms between peaks. before ball release, leaving a separation of 60.4 ms between peaks.
P I T C H I N G R E L . B A T T I N G R E L . Similar to golf mechanics, pitching mechanics allow maximal explora- Batting mechanics do not allow for maximal exploration of the body’s tion of the body’s range of motion to generate ball velocity. A key part ROM. The batter is dis-advantaged by needing to react to a pitch, of the kinetic chain in pitching is the ability to separate the trunk from requiring a short and compact, yet powerful swing to gain success. the pelvis. Pitchers build successive velocity in body segments by first accelerating their pelvis rotationally. As such, there is little separation between pelvis and trunk rotation velocities. Generally, the pelvis is the main producer of rotational As the timing of the pelvis leads to a de-acceleration, the trunk energy, while the trunk adds small portions of energy. The ammount of acclereates in rotation, delayed as much as 75 ms. The relative trunk energy the trunk contributes is variable and may depend on the bat- velocity also increases in magnitude compared to the pelvis. ter’s choice to execute max effort swings based on pitch type and loca- tion that they identify early in the swing.
G L O B A L C H A I N R E L A T I V E C H A I N Similar to pitching, when comparing pelvis speed to GLOBAL trunk The relative trunk rotation velocity of batters has a completely distinct rotational velocity, the two curves remain in phase for the majority of movement batter than that of a pitch. In fact, the relative trunk veloci- the swing. ty (on average), peaks AFTER ball contact. There is also a local maxi- mum slightly before ball contact that is very low in magnitude. 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, Timing separation between global pelvis velocity and the small local there is only 10.4 ms of time between both peaks (compared to 60 ms maximum before contact of the trunk is 54.2 ms, with very little contri- in pitching). In this case, the pelvis and trunk move together a lot more bution of the trunk (compared to pitching). in batters than pitchers.
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