Dena Farajollahi - Qazvin Branch, Islamic Azad University, Qazvin, Iran
Hamidreza Barnamehei - Washington State University, Department of Integrative Physiology and Neuroscience, Pullman, USA.
Ghazaleh Bonyadi - Qazvin Branch, Islamic Azad University, Qazvin, Iran
Rozhina Ghaderyzadeh - Qazvin Branch, Islamic Azad University, Qazvin, Iran
Ghazal Mostafizi - Qazvin Branch, Islamic Azad University, Qazvin, Iran
Saman Dehghan - Qazvin Branch, Islamic Azad University, Qazvin, Iran

Football is one of the popular and high-risk sport. Non-contact anterior cruciate ligament (ACL) injuries often happen during the forward jump-landings in soccer. Two main parts of the forward head jump are jumping and landing. Usually, one leg locates front, and another leg locates back during jumping and landing phases. The ground reaction force, which presents the impact loads, affects the knee joint reaction loads and can grow biomechanical stress on the anterior cruciate ligament. Therefore, the aim of the current study was to compare knee joint reaction loads between the back and front leg during the soccer forward jump. Twenty elite soccer athletes (۶۸.۳±۷.۵ kg, ۱۷۸±۵.۳ cm, ۲۷.۵±۴.۵ years) participated in the current study. Ten Vicon motion captures (Vicon MX, Oxford, UK, ۲۰۰ Hz) were used to measure the kinematics variables. EMG activity in the rectus femoris, vastus lateral, vastus medial, tibialis anterior, gastrocnemius medial, gastrocnemius lateral, soleus, biceps femoris, and semitendinosus was recorded by the Myon wireless EMG system. Raw EMG signals were full-wave rectified and linear enveloped using a dual-pass fourth-order low-pass Butterworth filter at ۴ Hz. A musculoskeletal model with a total of ۱۰ bodies and ۹۲ muscles was used to estimate joint reaction loads in OpenSim. The inverse kinematics, static optimization, and joint reaction analysis were used to estimate angles, muscle loads, and joint loads, respectively. Based on results, the anterior-posterior and media-lateral forces of the knee joint presented the highest forces in the front and back leg, respectively.

Washington State University, Department of Integrative Physiology and Neuroscience, Pullman, USA.