This study aimed to investigate the relationship between shoulder kinematics at the MER and trunk and pelvis kinematics at the SFC during throwing among QBs.
A total of 11 male American football QB players (age, 25.1±6.3 years; body mass, 81.9±9.3 kg; height, 179.1±5.3 cm; and experience, 10.3±5.7 years) were included. Each participant threw five balls, using an official ball (weight 400–425 g), with maximum effort for a distance of 30 yards. The throwing motion was recorded on an iPad (Apple Inc., USA) at 240 Hz, which was positioned on the participant’s side. The captured data of the throwing motion was analyzed using pitch AITM (3Motion AI Inc., Canada) to calculate the trunk (flexion/extension, non-throwing/throwing side rotation), pelvic (non-throwing/throwing side rotation), and hip-shoulder separation angle at the SFC, as well as the shoulder (horizontal adduction/abduction, abduction/adduction, and external/internal rotation) angle at the MER. The hip-shoulder separation angle is defined as the difference between the pelvic and trunk rotation angles, with a positive hip-shoulder separation angle indicating trunk rotation toward the throwing side relative to the pelvis.Simple linear regression was used to examine the relationship between the trunk and pelvic angles at the SFC and the shoulder angle at the MER. Statistical significance was set at p0.05.
Trunk and pelvic rotation angles at the SFC were negatively associated with the shoulder abduction angle at the MER (p=0.014 and 0.021, respectively). The hip-shoulder separation angle at the SFC was positively associated with shoulder horizontal adduction and external rotation angles at the MER (p=0.007 and 0.036, respectively).
QBs who exhibited greater trunk and pelvic rotation angles toward their non-throwing side at the SFC had reduced shoulder abduction and shoulder horizontal adduction angles at the MER. In baseball pitching, early trunk and pelvic rotations at the SFC lead to a decreased shoulder abduction angle and increased horizontal shoulder abduction at the MER (Lin et al.2022). Moreover, decreased shoulder abduction and shoulder horizontal adduction angles at the MER increases the load on the shoulder (Akeda et al.2018; Mihata et al.2015). Based on these findings, we believe that it is crucial for QBs to control trunk and pelvic rotational motions up to SFC to control shoulder motion and reduce shoulder load during throwing.
The results of this study may assist in the rehabilitation of QBs with shoulder injury symptoms during throwing.
throwing
kinematics
