Assessing the magnitude and direction of asymmetry in physical tests and morphological measurements in professional female soccer athletes

Objectives: To analyze the magnitude and direction of inter-limb asymmetries in vertical jump, T-test, isokinetic peak torque, and muscle volume in professional female soccer players. Methods: Sixteen female soccer players participated in the study (22.7 +/- 3.5 years, 60.4 +/- 12.7 kg, 164.2 +/- 8.7 cm). The following tests were applied; the unilateral countermovement jump (CMJ), T-test (agility), peak torque of concentric knee extensor (PT_Con_Q), concentric and eccentric knee flexor (PT_Con_H; PT_Ecc_H), and muscle volume of quadriceps (MV_Q) and gastrocnemius (MV_G). The interlimb asymmetry magnitude was calculated as the percentage difference between the stronger and weaker limbs. For the direction of asymmetry, a negative sign (-) was assigned when the non-dominant lower limb was the stronger one, and a positive sign (+) when the dominant lower limb was the stronger one. Results: The asymmetry (%) values varied from 0.7 to 11.9%, with the highest values of asymmetry found in the CMJ, PT_Con_Q, PT_Con_H, and PT_Ecc_H tests. Moderate levels of agreement were observed for CMJ - Vol_G (K = 0.53; 75% agreement); PT_Con_Q - PT_Con_H (K = 0.48; 75% agreement); T-test - PT_Ecc_H (K = 0.43; 68.7% agreement). Fair levels of agreement were found between the T-test - Vol_Q (K = 0.21; 62.1% agreement); PT_Con_Q - PT_Ecc_H (K = 0.36; 68.8% agreement); and PT_Con_H - PT_Ecc_H (K = 0.31; 68.8% agreement). Conclusions: We concluded that of greater asymmetries in the vertical jump and isokinetic torque tests. The direction of the asymmetry seems highly variable, however, the isokinetic tests showed greater agreements with the other tests.