THE RELATIONSHIP BETWEEN MAXIMUM TORQUE OF LOWER EXTREMITY MUSCLES WITH ANTERIOR KNEE SHEARING FORCE DURING SINGLE LEG DROP LANDING

The purpose of the present research was to study the relationship between peak torques of lower extremity muscleswith anterior knee shearing force (AKSF) during single-leg drop landing.22healthy mal e student athletes voluntarily participated in the research. The peak torque of the quadriceps, hamstring and soleus of the subjects was measured using Biodex Isokinetic System. Then the subjects were asked to perform single-legdrop landingfroma box 30 cm in height placed at a 15-cm distance from a force plateand to jump at its center while the data were collected by the force plate during landing. The peaktorques of lower extremity musclesand the peakposterior ground reaction forcewere normalizedto the body weight of the subjects. The peak posterior ground reaction force (GRF) was considered equivalent toAKSF and loading on the ACL.Data were analyzed using Pearson's correlation coefficient and multivariate regression. Results revealed a significant relationship between quadriceps (r = 0.68), hamstring (r = -0.79) and soleus-to-quadriceps peak torque ratio (r = -0.64) with AKSF at P ≤ 0.05 significance level. In the third predictor model, using multivariate regression (R = 0.834, β = 0.50, β = -0.48 and β = -0.26), the variables of hamstring,quadriceps and soleus peak torque 2 Q H S were significant (F =30.90, P = 0.0000). Considering the results of the research, during single-leg drop 3,18 landingthe hamstring acts asthe muscle reinforcing the ACL (agonist tothe ACL) and the quadriceps acts as the muscle generating force on the ACL (antagonist tothe ACL). Moreover, the soleus works in conjunction with the hamstring as an agonist tothe ACL.