Shock absorption and reducing the Rate of Loading (ROL) during daily activities are considered as a reason for reducing the rate of injuries. Since, skeletal muscles utilize as shock absorber during weight bearing tasks, the purpose of this study was to examine the relationship between the maximum torques of lower extremity muscles with the ROL during SINGLE LEG DROP LANDING. 33 men subjects (23±2years and 73±3 Kg) from Tarbiyat Moallem University of Tehran volunteered in this study. Maximum torque of lower extremity muscles and the Ground Reaction Forces (GRF) were measured by the Biodex system and force plate (AMTI), respectively. The Pearson correlation used to analyses the data at the a£0.05 threshold. The mean torque of the quadriceps, hamstring, plantar flexors, dorsi flexors, invertors and evertors muscled were 2.70, 1.75, 0.77, 0.43, 0.43, 0.40 Nm respectively, and the mean ROL was 519/60 N/ms. Significant correlations wasn't seen between maximum torque of lower extremity muscles with ROL. Due to results of this study it seem that quadriceps, hamstring, plantar flexors, dorsiflexors, invertors and evertors muscles have no role in decreasing the ROL in SINGLE LEG DROP LANDING.

Purpose: The purpose of this study was to investigate the kinematic and kinetic variables, which predict anterior tibia shear force during SINGLE-LEG LANDING in female athletes.Methods: Forty-three subjects (mean and standard deviation for age 21.12 ± 2.00 y, height 168.58 ± 7.62 cm, and weight 60.27 ± 7.80 kg) participated in this study. Kinematic and kinetic variables of lower extremity and trunk during SINGLE-LEG LANDING were collected by 5 Vicon cameras and Kistler force plate. Stepwise multiple regression and Pearson correlation were used to identify predictor variables of anterior shear force (P £ 0.05).Results: Peak of extensor moment (P = 0.004, r = -0.394) and maximum knee flexion (P = 0.007, r = -0.370) were the best predictors that explained 30% of the variance of the shear force data. Therefore, rise in maximum extensors moment of knee and knee maximum flexion causes increase and decrease in anterior shear force, respectively. In addition, a significant relationship between trunk flexion (P = 0.039) and knee flexion angular velocity (P = 0.048) at the moment of initial contact with the anterior shear force.Conclusion: On the basis of previous research, and the relationship between clinical findings, the noncontact of anterior cruciate ligament injury during LANDING was confirmed. These results can be used in prospective studies examining modifiable noncontact risk factors of ACL injury.

Purpose: ACL injury is one of the most common non-contact injuries among women athletes. ACL injury prevention is especially important with the purpose of decreasing risk factors. The results indicate that during LANDING, there is a lot of pressure on lower limb joints. The purpose of the present study was to investigate the Effect of 8 weeks of theraband training on ACL injury Risk Factors in SINGLE-LEG DROP and double LEG LANDING. Methods: In this study, 26 female amateur athletes with a mean age (25. 3± 3. 6) years, height (162. 2± 3. 8) cm, weight (59. 9± 5. 9) kg were purposefully and accessibly selected and randomly divided into two experimental group (n=13) and control (n=13). The experimental group performed their exercises for 8 weeks, three sessions per week and 60 minutes per session, and the subjects in the control group continued did not exercise. SINGLE-LEG DROP and double LEG LANDING tests were taken from the two groups of subjects before and after 8 weeks of training. In order to measure the risk factors of ACl injury (knee valgus, range of knee flexion and hip) in SINGLE-LEG DROP and double LEG LANDING, analytical software kinovea (8. 27) was used. In order to analyze the data, Mixed Repeated Measures ANOVA was used at a significance level of p≤ 0. 05 using SPSS software, version 24. Results: The results of study showed that after eight weeks, a significant improvement in decreasing the amount of knee valgus and increasing the range of motion of the hip flexion SINGLE-LEG DROP and double LEG LANDING (p≤ 0. 05) was observed in the experimental group. Also, in the experimental group, a significant improvement was observed in increasing the range of motion of hip flexion in double LEG Drobe LANDING task (p≤ 0. 05), but no significant difference was observed in the range of motion of hip flexion in SINGLE LEG Drob LANDING task (p>0. 05). Conclusions: The results of this study showed that Theraband exercise program during LANDING movements can improve some kinematic variables of the hip and knee joint and reduce the risk factors of ACL injury in women.

The purpose of this study was to compare anterior knee shear force in pronated and supinated foot in SINGLE LEG DROP LANDING. 30 student (15 male and 15 female) from department of Physical Education and Sport Sciences of Tarbiat Moallem University with the mean and standard deviation of age (22 ± 1.73 years), weight (73.32 ± 7.24 kg) and height (175.08 ± 5.34 cm) participated in this study. Subjects divided into 3 groups (normal, pronated and supinated foot) in each one of gender based on navicular DROP test. Subjects land on the center of force plate from a box with the height of 30 cm that placed at the 15 cm from the edge of force plate. Ground reaction forces data normalized by weight of subject and then filtered. Maximum posterior ground reaction force (PGRF) assumed to be equivalent with maximum tibia proximal anterior shear force. One-way ANOVA tests results showed significant difference between female pronated and normal groups for maximum PGRF (p£0.05). Female pronated foot group showed higher maximum PGRF compared to other groups. Due to result of this study, females with pronated foot are at higher risk to have anterior cruciate ligament injury compared to others groups.

Background and Aims: Activity of knee joint muscles can influence the magnitude of ground reaction forces during jump-LANDING tasks. The objective of the present study was to examine the relationship between electromyography activity of the knee joint muscles and ground reaction forces during SINGLE-LEG DROP LANDING task. Materials and Methods: A total of 20 healthy male athletes (mean ± standard deviation, age 25. 4± 4. 45 years) participated in the present correlational study. Activity of knee joint muscles, including quadriceps, hamstrings, and gastrocnemius, at pre and post LANDING phases were analyzed and their relationships with ground reaction forces (vertical, anterior-posterior, and medial-lateral) were assessed during SINGLE LEG vertical DROP LANDING task. Pearson correlation coefficient was used for data analysis. Results: The results demonstrated significant negative correlation between lateral gastrocnemius muscle activity and all components of ground reaction forces (P= 0. 001). Also, there was a significant positive correlation between medial gastrocnemius activity and all components of ground reaction forces at pre LANDING phase and also a significant negative correlation with vertical and anteriorposterior component at post LANDING phase (P=0. 001). Moreover, there was a significant negative correlation between lateral hamstring activity and anterior-posterior ground reaction force at postcontact phase (P=0. 001). Conclusion: It seems that gastrocnemius (medial and lateral) and lateral hamstring muscles play important roles in adjusting ground reaction force components during SINGLE LEG vertical DROP LANDING task. According to the results of the current study, it is suggested that rehabilitation specialists focus especially on activation exercises for gastrocnemius (medial and lateral) and lateral hamstring muscles in order to prevent anterior cruciate ligament injury.

Objective: The purpose of this study was to consider the relationship between maximum torques of lower extremity muscles with anterior knee shearing force during SINGLE LEG DROP LANDING.Methods: 22 male students from department of Physical Education and Sport Sciences with the mean and standard deviation of weight (75.89±3.22 kg), height (177.84±4.52 cm), and age (22±3 years) participated in this study. Maximum torque of quadriceps, hamstring, and soleus muscles calculated using Isokinetic Biodex dynamometer. GRF data during SINGLE LEG DROP LANDING collected with Force Plate system (AMTI). Maximum PGRF assumed equivalent with anterior knee shearing force and ACL loading. Data analysis performed by means of Pearson coefficient method and multi regression at the significant level of p≤0.05.Results: The results showed significant relationship between maximum torque of quadriceps(r=0.68), hamstring (r=-0.79), and soleus to quadriceps maximum torque ratio (r=-0.68) with maximum PGRF at the significant level of a≤0.01. Three predictor models have been extracted using multiple regression analysis. In third and the main predictor model, the significant variables were the maximum torque of hamstring, quadriceps and soleus muscles and the amount of this model was significant at the level of a≤0.01 (R2=0.834, βQ=0.50, βH=-0.48, βS=-0.26), (F2, 18=30.09, P=0.000).Conclusion: Regarding the finding this study, the role of hamstring and quadriceps muscles determined as ACL protective muscle (ACL agonist) and ACL loading muscle (ACL antagonist) respectively. The role of soleus muscle as a synergist muscle with hamstring was also determined as the agonist of ACL.

Background and Aims: Knowing the changes of motor control strategies during LANDING provide well understanding to preventing knee injuries in people with flatfeet. Hence, the purpose of the present study was to compare the motor control strategies using lower limb joints power in different phases of SINGLE LEG DROP LANDING between athletes with flatfeet and normal foot. Materials and Methods: A total of 10 individuals were randomly selected from among athletes with flatfeet and 10 were randomly selected from among athletes with normal foot. Lower limb joints power in three motion plates was recorded according to data from kinematic and kinetic motion analysis and force plate. Data was analyzed using Matlab and SPSS softwares and running independent t-test (p< 0/05). Results: There was a significant difference in knee power in sagital plane (P=0/003 ) in initial contact phase (IC ), knee power in sajital plane (P=0/0001 ), and Thigh power in horizontal plane (P=0/05 ) in pick of knee flexion, Thigh power in sagital plane (P=0/022 ) in pick of ground reaction force between flat foot and a normal foot. However, there was no significant difference in joints in the other phases and plates between the two groups. Conclusion: The results of our study study showed that significant differences were observed in Knee and Hip powers in sagital plane in three phases, which shows the impact transfere to the upper joints from incapability in lower joints in flatfeet people. This could be a major factor for foot injuries in the individuals with flat foot. The results of the current study can help better organizing a rehabilitation program and activities for those with flatfeet.