comparison of internal-to-external ratios of strength rotation and rom rotation in injured and healthy professional male handball players

introduction: the shoulder is one of the most vulnerable joints for handball players.  frequent throwing movements can change its muscular strength balance and range of motion. however, the balance of strength and range of motion are important factors in injury prevention. the purpose of this study was to compare the internal-to-external ratios of strength rotation and rom rotation in the dominant and non-dominant hands of injured and healthy handball players. materials and methods: in this study, 68 handball players were selected and subsequently divided into the following two groups based on their answers to a questionnaire: injured players (age: 24.27±4.43, bmi: 23.32±2/08, sports experience 11.27±3/90) and healthy players (age: 23.85±3.82, bmi: 23.19±2/08, sports experience 10.82±3.22). a hand-held dynamometer and a leighton flexometer was respectively used for measuring the strength and rom of the participants. results: the results indicated that the strength and rom ratios of internal and external rotation in the dominant hands of the injured and healthy subjects differed significantly (p≤0.001 and p=0.004, respectively). however, no significant difference was observed in their non-dominant hands regarding these variables (p=0.32 and p=0.9, respectively). it was found that there were significant differences between the dominant and non-dominant hands of injured players regarding strength (p=0.01) and rom ratios (p≤0.007).  similar significant differences between the dominant and non-dominant hands of  the healthy players were evident when they were compare with each other according to the strength (p≤0.001) and rom ratios (p=0.04). conclusion: repeated over-head throwing movements can cause the imbalance of muscle strength and rom in the shoulder in the long–term. designing preventive programs for controlling and limiting this risk factor should be one the main concerns of trainers and medical stuff.