Functional shoulder ratios with high velocities of shoulder internal rotation are most sensitive to determine shoulder rotation torque imbalance: a cross-sectional study with elite handball players and controls

The aim of the present study was to determine which approach to calculating shoulder ratios is the most sensitive for determining shoulder torque imbalance in handball players. Twenty-six participants (handball athletes, n = 13; healthy controls, n = 13) performed isokinetic concentric and eccentric shoulder internal rotation (IR) and external rotation (ER) assessment at 60, 180 and 300 degrees/s. We used eight approaches to calculating shoulder ratios: four concentric (i.e. concentric ER torque divided by concentric IR torque), and four functional (i.e. eccentric ER torque divided by concentric IR torque) at the velocities of 60, 180 and 300 degrees/s for both IR and ER, and combining 60 degrees/s of ER and 300 degrees/s of IR. A three factorial ANOVA (factors: shoulder ratios, upper limb sides, and groups) along with Tukey's post-hoc analysis, and effect sizes were calculated. The findings suggested the functional shoulder ratio combining 60 degrees/s of ER and 300 degrees/s of IR is the most sensitive to detect differences between upper limbs for handball players, and between players and controls for the dominant side. The functional shoulder ratio combining 60 degrees/s of ER with 300 degrees/s of IR seems to present advantages over the other approaches for identifying upper limb asymmetries and differences in shoulder torque balance related to throwing.