Abstract
ABSTRACT The pitching motion is an asymmetric action by which coordination of scapular rotation in the dominant arm might be affected in time and in comparison with the non-dominant arm. The study aimed to compare asymmetry and the evolution of scapular upward rotation over a one-year period. Data were collected twice, before and after a one-year period, from 92 participants (age = 15.1 SD 1.4 years, body height = 177.3 SD 10.9 cm, body weight 69.2 SD 14.5 kg). Scapular motion was tracked at different glenohumeral angles of elevation in the scapular plane: anatomical position (0°), 45°, 90° and 135°. Scapular upward rotation was calculated as the angle between the spinae scapula and the spine. Scapular upward rotation of the dominant arm was 5.1° (95% CI: 2.1°−8.1°) more compared to the non-dominant arm. Age group or glenohumeral angles of elevation did not affect this difference. Scapular upward rotation of the dominant arm decreased 1.9° (95% CI: −0.5° to 4.3°) after a one-year period, however, neither this observation, nor the interaction with age group or elevation angle was significant. These findings may indicate that pitchers could be at risk to develop shoulder injuries especially those that have been associated with scapular asymmetry.
Highlights
Overhead throwing athletes solve a complex full body problem in order to generate high throwing velocities
The scapular upward rotation of the dominant arm decreased with 1.9° on average over the one-year period, but this change was non-significant (95% CI: −0.5° to 4.3°, F(1,37) = 2.53, p = 0.120)
The present study demonstrated a non-significant decrease in the scapular upward rotation in youth baseball pitchers of 1.9° over the one-year study period
Summary
Overhead throwing athletes solve a complex full body problem in order to generate high throwing velocities. Baseball (170 km/h), handball (130 km/h) and javelin (113 km/h) are all examples of sports that involve very high throwing velocities. Such high speeds can only be reached with a perfected technique that involves the entire body (Putnam 1993; Matsuo et al 2001). On of the components of this throwing action, the scapula, plays an important role in controlling the shoulder joint. The scapula must move in accordance with the humerus to provide a stable base for the humeral head, and plays an important role in the transfer of energy from torso to arm (Borsa et al 2008; Forthomme et al 2008). Scapular support is essential for stability and mobility during the throwing action in overhead throwing athletes
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