Influence of biomechanical models on joint kinematics and kinetics in baseball pitching

ABSTRACT

In baseball pitching, biomechanical parameters have been linked to ball velocity and potential injury risk. However, although the features of a biomechanical model have a significant influence on the kinematics and kinetics of a motion, this influence have not been assessed for pitching. The aim of this study was to evaluate the choice of the trunk and shoulder features, by comparing two models using the same input. The models differed in thoraco-humeral joint definition (moving or fixed with the thorax), joint centre estimation, values of the inertial parameters and computational framework. One professional pitcher participated in the study. We found that the different features of the biomechanical models have a substantial influence on the kinematics and kinetics of the pitchers. With a fixed thoraco-humeral joint the peak average thorax angular velocity was delayed and underestimated by 17% and the shoulder internal rotation velocity was overestimated by 7%. The use of a thoraco-humeral joint fixed to the thorax will lead to an overestimation of the rotational power at the shoulder and will neglect the power produced by the forward and upward translation of the shoulder girdle. These findings have direct implications for the interpretation of shoulder muscle contributions to the pitch.

KEYWORDS:

• Inverse dynamics
• modelling
• overhand throw
• shoulder
• trunk

Acknowledgements

The authors would like to thank for their support Peter Hordijk, the technical team from the Vrije Universiteit Amsterdam (Leon Schutte, Franz-Joseph Halkes, Vincent Tuinder, Siro Otten and Hans Agricola) and Martijn Nijhoff. The authors also thank Dr Fleisig for sharing his PhD thesis.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary Material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Dutch Technology Foundation (STW) under grant number 12893