Analysis of range of motion and isokinetic strength of internal and external rotation according to humeral retroversion of the dominant shoulder in youth baseball players: A pilot study

Background: we aimed to analyze the range of motion (rom) and internal rotation (ir) and external rotation (er) isokinetic strength according to humeral retroversion of the dominant shoulder. methods: we included 40 elite baseball players in korea (obp group: n=20 players with careers spanning >10 years,age: 19.37±2.21 years,height: 181.00±5.41 cm,weight: 84.58±7.85 kg; bbp group: n=20 players with careers spanning <10 years,age: 16.55±1.36 years,height: 177.27±7.57 cm,weight: 77.27±8.14 kg). radiography was performed to examine humeral retroversion,a goniometer was used to measure irom and erom,and a dynamometer was used to measure ir and er isokinetic strength (speed set at 180°/s or 300°/s). results: the bbp and obp groups had significantly different ir and er isokinetic strength (180°/s and 300°/s) (p<0.001) and dominant shoulder retroversion (p=0.009). in the bbp group,retroversion had no correlation with rom and with ir or er isokinetic strength (180°/s and 300°/s). in the obp group,retroversion had no correlation with rom and with er isokinetic strength at 180°/s,but had significant correlation with ir isokinetic strength at both 180°/s (r=0.483,p=0.007) and 300°/s (r=0.373,p=0.043) and er isokinetic strength at 300°/s (r=0.366,p=0.046). conclusion: thus,youth players with careers spanning >10 years had significantly higher humeral retroversion,irom,erom,and ir and er isokinetic strength of the dominant shoulder than youth players with careers spanning <10 years. furthermore,humeral retroversion and rom were not significantly related,but ir and er isokinetic strength were significantly positively related with retroversion in both groups.