Stride-Phase Kinematic Parameters That Predict Peak Elbow Varus Torque

Hiroshi Tanaka; Toyohiko Hayashi; Hiroaki Inui; Tomoyuki Muto; Kohnan Tsuchiyama; Hiroki Ninomiya; Yasuo Nakamura; Syoji Kobashi; Katsuya Nobuhara

doi:10.1177/2325967120968068

Stride-Phase Kinematic Parameters That Predict Peak Elbow Varus Torque

Orthop J Sports Med. 2020 Dec 15;8(12):2325967120968068. doi: 10.1177/2325967120968068. eCollection 2020 Dec.

Authors

Hiroshi Tanaka¹, Toyohiko Hayashi², Hiroaki Inui¹, Tomoyuki Muto¹, Kohnan Tsuchiyama³, Hiroki Ninomiya¹, Yasuo Nakamura⁴, Syoji Kobashi⁵, Katsuya Nobuhara¹

Affiliations

¹ Nobuhara Hospital and Institute of Biomechanics, Tatsuno, Japan.
² Graduate School of Science and Technology, Niigata University, Niigata, Japan.
³ Department of Orthopaedic Surgery, Hyogo College of Medicine, Nishinomiya, Japan.
⁴ Faculty of Health and Sports Science, Doshisha University, Kyotanabe, Japan.
⁵ University of Hyogo, Himeji, Japan.

Abstract

Background: During baseball pitching, a high amount of elbow varus torque in the arm cocking-to-acceleration phase is thought to be a biomechanical risk factor for medial elbow pain and injury. The biomechanics of the stride phase may provide preparation for the arm cocking-to-acceleration phase that follows it.

Purpose: To determine the kinematic parameters that predict peak elbow varus torque during the stride phase of pitching.

Study design: Descriptive laboratory study.

Methods: Participants were 107 high school baseball pitchers (age range, 15-18 years) without shoulder or elbow problems. Whole-body kinematics and kinetics during fastball pitching were analyzed using 3-dimensional measurements from 36 retroreflective markers. A total of 26 kinematic parameters of the upper and lower limbs during the stride phase leading up to the stride foot contact were extracted for multiple regression analysis to assess their combined effect on the magnitude of peak elbow varus torque.

Results: Increased wrist extension, elbow pronation, knee flexion on the leading leg, knee extension on the trailing leg at stride foot contact, and upward displacement of the body's center of mass in the stride phase were significantly correlated with decreased peak elbow varus torque (all P < .05). Moreover, 38% of the variance in peak elbow varus torque was explained by a combination of these 5 significant kinematic variables (P < .001).

Conclusion: We found that 5 kinematic parameters during the stride phase and the combination of these parameters were associated with peak elbow varus torque. The stride phase provides biomechanical preparation for pitching and plays a key role in peak elbow varus torque in subsequent pitching phases.

Clinical relevance: The present data can be used to screen pitching mechanics with motion capture assessment to reduce peak elbow varus torque. Decreased peak elbow varus torque is expected to reduce the risk of elbow medial pain and injury.

Keywords: baseball; elbow; fastball; injury; pain; pitcher; torque; valgus; varus.