By reviewing the literature, we wanted to determine which parameters of isokinetic measurements of the strength of shoulder rotators are the most suitable for finding a connection between their results and sports performance and the possibility of developing shoulder problems. The search was 12.04. 2021. By searching for volleyball + shoulder + strength we got 68 articles, according to the selected criteria we included 16 articles in the analysis, published by 13 researchers from 10 countries. We included studies that reported at least concentric strength or at least a relationship between the concentric strengths of external and internal rotation of the dominant side at 60°/s. A total of 585 players were included in these 16 articles, of which 403 were male (of which 323 were adults) and 182 were female (of which 144 were adults). According to the report, the youngest group of players included were the U-12 selection, including at least one 10-year-old, the upper limit is not reported. We can conclude, because active athletes are included, that there were no people older than 40 (or just some exception). The mean age in adults, comprising 434 of 467 individuals, was 23 years. In the dominant shoulder in men there is asymmetry, the ratio of external rotation (ZR) and internal rotation (NR) (ZR/NR) is significantly higher in the non-dominant shoulder, partly due to the higher strength of the internal rotators of the dominant side. The highest NR torque of the dominant arm in 483 (out of 585) subjects averaged 0.7 Nm/kg; NR non-dominant at 367 was 0.65 Nm/kg; ZR dominant in 486 subjects was 0.41 Nm/kg, ZR non-dominant in 353 was 0.44 Nm/kg; the ZR/NR ratio of the dominant arm was on average 0.64 for all 568 subjects, and the ZR/NR of the non-dominant arm was 0.7 for 379. From the available data, we calculated that men are stronger than women, but women have a higher ZR/NR ratio on the dominant side. We calculated that adults are stronger than adolescents, the ZR/NR ratio was comparable between the groups. We also calculated that those who have been injured before have a lower ZR / NR ratio of the dominant side than the uninjured, as well as that professional athletes have a lower ZR/NR ratio than amateur players and non-athletes, the latter mainly due to higher strength in the direction of NR in athletes. In men, the ZR/NR ratio was higher on the non-dominant side in injured (13) and uninjured (205 players), the difference was comparable in both groups. There is no such difference in women, the probable cause is a small sample of injured. According to the playing positions, they report a reduced ZR/NR ratio of the dominant side, especially for hitters and blockers, mostly at the expense of higher strength in the direction of NR. The study, which included 49 players, found a reduced ZR/NR ratio in all playing positions except libero, while the study, which included 183 players, to the author's surprise, did not find such differences.
It is recommended that isokinetic measurements as screening should be performed in sitting position, with upper limb in 90/90 position, at an angular velocity of 60◦/s in concentric mode in total range of at least 60°(90-30°ZR). 90°range would be desirable (90 - 0°ZR), so the ZR/NR ratio could be obtained. Eccentric measurements are recommended for those players who already have pain or shoulder injury and for those who do not yet have such problems, but we found abnormal values by screening. In studis where we have measurements from both genders, we recommend that the results be given for each separately.
|
