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    Biomechanics

    (D-129) Influence of ankle stability and directional ground reaction force in baseball pitching

    Friday, October 13, 2023
    3:30 PM – 4:30 PM PDT
    Location: Exhibit Hall - Row D - Poster # 129

      Presenting Author(s)

    • CG

      Connor Gaudette

      Undergraduate Research Assistant
      Worcester Polytechnic Institute
      Holden, Massachusetts, United States

      • Co-Author(s)

    • GF

      Garrett Fernandez

      Graduate Research Assistant
      Wake Forest University School of Medicine, United States

      • Primary Investigator(s)

    • KN

      Kristen Nicholson

      Assistant Professor, Orthopedic Surgery
      Wake Forest University School of Medicine, United States

    Introduction:: In baseball to pitch effectively the body must go through a complex kinetic chain to produce optimum ball velocity, trajectory, and rotation (Seroyer et al., 2010)1. A large portion of this kinetic chain consists of transferring kinetic energy of the lower extremities into core musculature. This transfer of energy has been shown to not only be important in maximizing ball metrics but also in reducing upper extremity injuries (Fortenbaugh et al., 2009)2. It has been well established that hip strength and stride length has a large influence on ball velocity in pitching (Dowling et al., 2022)3, (Manzi et al., 2023)4. However, other lower extremity metrics such as lead, and back foot ground reaction force (GRF) have not shown as significant association. This would suggest that other lower extremity biomechanics measures contribute a larger role in optimizing pitching ball metrics. The direction of GRF for both legs would give insight as to how much of the pitcher’s energy is being transferred into the ball during the pitch. Factors such as ankle stability and the direction of the GRF for both legs have yet to be investigated. Therefore, the purpose of this study was to evaluate the potential association between ankle stability of the back foot and ball velocity. The secondary objective was to investigate possible associations between ball metrics and the direction of the GRF generated by back and landing legs.

    Materials and Methods:: This study was a retrospective review of pitching biomechanics and ball velocity data. Motion capture data, including full body kinematics, were conducted and the results were used in this study. Each player was outfitted with a full-body retro-reflective marker set and was asked to throw a variety of fastballs, breaking balls (curve or slider), and change ups. Reports of kinematics and kinetics were then generated for each athlete as part of a pitching evaluation along with ball velocity data. In this study ankle stability was measured by taking the center of pressure (COP) for the back foot, then measuring the total displacement of this point until max knee height and by taking the mean speed at which the COP was moving through this same time period. Any frame of force plate data collected during motion capture that was incomplete was discarded. Preliminary data included 95 total pitches with 65 right-handed pitches from 7 different pitchers and 30 left-handed pitches from 4 different pitchers. Multivariable regression was performed with control for handedness using MATLAB 2023a.

    Results, Conclusions, and Discussions:: An unpaired T-test comparing the left-handed and right-handed pitches showed that the left-handed pitches and right-handed pitches needed to be analyzed separately. The regression performed on data from the left-handed pitches, shown in Fig. 1, suggested a statistically significant trend existed between the independent variables and ball velocity, with an r2 value of 0.5256. Similarly, a regression using the mean speed at which the COP to measure the ankle stability had an r2 value of .5363 for the left-handed pitches. Right-handed regressions for both measures of ankle stability had a low correlation with a p-value above the calculated Bonferroni correction. In exploring combinations of independent variables, for the multi-variable regression it was determined that ankle stability, back leg GRF direction, and leading leg GRF direction were the best fit. The low r2 values can be explained in part by the large variability of biomechanics and the lack of diversity in pitchers.
    The difference between the two measures of ankle stability was small suggesting that the two could be used to predict ball velocity with similar accuracy. The mean speed of the COP is established as a method for measuring stationary balance of a human subject (Sarto et al., 2020)5, but total distance traveled by the COP is not a common metric for balance. The r2 value calculated for the left-handed pitches is low because of the many significant factors that are known to contribute to ball velocity in a pitch. Due to the low number of subjects with complete data there was no significant trend found for right-handed pitches. However, it is possible that a trend might still exist between these metrics. Butler et al.6 found that players at a higher level of competition have a better dynamic balance than those at a lower level of competition. This research would support their findings, assuming that high level pitchers have a faster pitch velocity. Further research could be conducted comparing pitchers who perform ankle strengthening techniques and single foot balancing tasks as a part of their regular routine against pitchers who do not routinely train their ankle stability.

     


    Acknowledgements (Optional): : This project was supported in part by the NSF REU Site (Award #1950281) in the Department of Biomedical Engineering at Wake Forest University School of Medicine.

    References (Optional): : 1. Seroyer, S. T., Nho, S. J., Bach, B. R., Bush-Joseph, C. A., Nicholson, G. P., & Romeo, A. A. (2010). The kinetic chain in overhand pitching: Its potential role for performance enhancement and injury prevention. Sports Health: A Multidisciplinary Approach, 2(2), 135–146. https://doi.org/10.1177/1941738110362656
    2. Fortenbaugh, D., Fleisig, G. S., & Andrews, J. R. (2009). Baseball pitching biomechanics in relation to injury risk and performance. Sports Health: A Multidisciplinary Approach, 1(4), 314–320. https://doi.org/10.1177/1941738109338546

    3. Dowling, B., Knapik, D. M., Luera, M. J., Garrigues, G. E., Nicholson, G. P., & Verma, N. N. (2022). Influence of pelvic rotation on lower extremity kinematics, elbow varus torque, and ball velocity in professional baseball pitchers. Orthopaedic Journal of Sports Medicine, 10(11), 232596712211303. https://doi.org/10.1177/23259671221130340

    4. Manzi, J. E., Yu, J. S., Sudah, S. Y., Wishman, M., Quan, T., Koo, A., Kunze, K. N., Kew, M., Carr, J. B., Fu, M., & Dines, J. S. (2023). A systematic review of lower-body kinematic and strength factors associated with pitch velocity in adult baseball pitchers. Journal of Sport Rehabilitation, 32(4), 440–448. https://doi.org/10.1123/jsr.2022-0059

    5. Sarto, F., Cona, G., Chiossi, F., Paoli, A., Bisiacchi, P., Patron, E., & Marcolin, G. (2020) Dual-tasking effects on static and dynamic postural balance performance: A comparison between endurance and team sport athletes. PeerJ, 8, e9765. https://doi.org/10.7717/peerj.9765

    6. Butler, R. J., Bullock, G., Arnold, T., Plisky, P., Queen, R. (2016) Competition-Level Differences on the Lower Quarter Y-Balance Test in Baseball Players. Journal of athletic training, 51(12):997-1002. https://doi.org/10.4085/1062-6050-51.12.09