Lower extremity kinematic and temporal changes in adolescent baseball pitchers during a simulated game : a thesis presented in partial fulfilment of the requirements for the degree of Master of Health Science in Sport and Exercise at Massey University, Wellington, New Zealand
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Date
2015
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Massey University
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Abstract
Aim: To investigate whether adolescent baseball pitchers change lower extremity kinematic
and temporal parameters during a simulated game, which may affect performance outcomes.
Method: Twelve male adolescent pitchers (14 – 16 years) threw 90 pitches (6 sets of 15
pitches) from an artificial mound towards a pitching net. Angular displacements, angular
velocities and temporal parameters at the hip, knee and ankle of the trailing and leading legs
were collected throughout the pitching cycle. Dependent variables were analysed from the
balance position through to maximal internal rotation of the shoulder. Performance outcomes
of ball velocity and pitching accuracy were also recorded. The last five pitches of the second
and final sets were compared to determine whether changes in the pitching mechanics and
performance outcomes had occurred by the end of the simulated game. Results: Pitchers
assumed a less upright posture and the leading leg was not raised as high at the balance
position in the final set. Throughout stride phase, pitchers decreased maximal hip extension
and ankle plantarflexion displacements in the trailing leg. Additional decreases in the maximal
angular velocities for hip abduction and knee extension were seen throughout the stride phase
in the final set. Foot contact occurred earlier in the final set, resulting in decreased hip flexion
and increased hip abduction in the leading leg. No kinematic differences were observed
between sets at ball release. Ball velocity and pitching accuracy decreased in the final set.
Conclusion: Kinematic differences in the lower extremities suggest that lower extremity
musculature may have been affected by fatigue by the end of the simulated game.
Consequently, pitchers may have produced less forward momentum during the final set of
pitches, which could have contributed to the decreased ball velocity. The altered balance
position seems to be the underlying factor for the subsequent changes in the lower extremity
pitching mechanics. Therefore, the leading leg hip flexors and the trailing leg hip and knee
extensors may require strengthening to maintain the balance position. Additional
strengthening of the ankle plantarflexors would assist the hip and knee in producing consistent
propulsive forces during the stride phase throughout a game.
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Keywords
Baseball pitchers, Baseball player physiology, Human mechanics, Kinematics, Lower extremity kinematics, Teenage baseball players, Adolescent baseball players