Can capsular stretching change the scapulo-humeral coordination in baseball pitchers?

Abstract

Main topics:Analysis of clinicalmovement data; Outcome after clinical intervention Introduction: Injury in the throwing shoulder of baseball pitchers andoverhead throwingathletes is common. Previous studies assessed scapular kinematics using electromagnetic tracking devices, demonstrating that patients with impingement have a reproducible pattern of shoulder dyskinesia [1]. In addition, they showeda correlationbetweenposterior shoulder tightness and forward scapular posture and confirmed that baseball players have more forward scapular posture of the dominant arm [2]. Possibly, capsular stretching programs might help restoring a normal scapulo-humeral coordinate. The aim of this study was to test this hypothesis by studying the scapular kinematics before and after a four weeks posterior stretching protocol in asymptomatic baseball pitchers. Patients/materials and methods: Eleven asymptomatic collegiate baseball pitchers were involved in the study. Pitchers were randomly separated in two groups: groupA (6 pitchers) underwent four weeks of a regimented therapy protocol; group B (5 pitchers) didnot received any treatment. Eachpitcherwas testedon two separate days: at the first day of the study (S1) and after four weeks (S2). The ISEO protocol was used to collect the kinematics of trunk, scapula and humerus [3] of both the throwing side (TS) and the contralateral (CS). The scapulo-humeral coordination (SHC) during humerus elevation in the sagittal (FlexExtension – FE) and scapular (AbAdduction – AA) plane was collected and then analyzed by means of coordinationplots, considering a commonhumeral Range of Motion (ROM) from 10◦ to 110◦, divided in steps of 5◦. SHC’s patterns of each subject were compared to age stratified reference bands (RB) computed from healthy subjects [4]. In order to verify if biologicalmodifications occurred, for each subject, firstly, the SHC’s pattern of TS and CS were compared to the age stratified reference bands (RB); secondly, the scapula ROM variations of TS between S1 and S2 were computed and compared to the Smallest Detectable Difference (SDD) of ISEO [5]. Results: The comparison of the SHC patterns with RBs showed that both TS (in S1 and S2) and CS of all subjects are within the correspondent reference bands, except one subject from group B, that presented alterations at TS only in S1. From the comparison of scapula ROM variations (S1–S2) with SDD values, group B showed that significant variations occurred only for one subject in MELA ROM during FE and AA and PA during AA. On the contrary 4 out of 6 pitchers that received the therapy showed clear signed of SHC alterations. Specifically, 4 subjects (67%) had variations in MELA during FE and 3 (50%) inMELAduringAA, and 1 subject in PAduring both FE and AA. These changes were towards the RB mean patterns, proving an improvement of the SHCs of TSs after the physical therapy. It is important to notice that variations in the subjects of group A occurred for both movements (FE and AA), strengthening the conclusion that the variation was real. Discussion and conclusions: This study highlights how posterior capsular stretching protocol can favour the maintenance of the SHC in asymptomatic baseball pitchers. Being a randomly and blinded study all pitchers of group A underwent the physical therapy protocol even if in S1 they had not presented an altered SHC compared to reference bands. The preliminary result of the study can indicate that, in order to prevent the pathologic cascade linked to these sports activities, this physical training protocol might become integral part of thenormal daily exercises of baseball pitchers and over-head athletes.