Introduction: Soccer are held in various fields (such as natural and artificial grass) and in different weather conditions. It has frequently been demonstrated that surface conditions may affect biomechanical parameters of lower extremities during running, jumping and landing. Single leg landing in this sport is common and a major cause of non-impact ACL injuries are considered. It is reported during single leg landing on unstable surface, lower limb muscle activity decreases and subsequent declining balance with it. Given the key role of the knee joint angles in injuries, the purpose of current study was to investigate knee joint kinematics during single leg landing on different surfaces in Martyr Bahonar University of Kerman Soccer team.
Methodology: In this study, 18 football players of Martyr Bahonar University of Kerman Soccer team participated with an average age of 21.1 years and the history of playing football at least five years. The participant stand on the platform with 60 cm height while your hands were on the pelvic, and then with dominant leg performed the single leg drop landing on stable (solid ground) and unstable surfaces (compact foam with dimensions of 6x41x50 cm with medium degree of stiffness). The processes of the landings were recording by use of optoelectronic 3D motion analysis with 6 cameras, and then the recording data were analyzed by cortex software. The parameters of knee angle in the sagittal and frontal planes at the moment of the landing, the maximum knee angle in the sagittal and frontal planes after landing and maximum tibial linear acceleration, were measured. Statistical analysis of the data was performed by SPSS v23 software and using paired sample t-test at the level of 0.05 significance.
Results: Results of independent sample t-test showed that the performance of drop jumps under unstable compared to stable conditions produced a decrease in maximum knee flexion (14%, P˂0.001), an increase in peak knee valgus (38%, P˂0.001) and also reduce the duration of eccentric phase (17%, P˂0.001).
Discussion: The purpose of this study was to investigate the knee joint kinematics during single leg landing on stable and unstable surfaces in amateur soccer players. The results showed that unstable surface, negatively, affect the landing performance. Hence, to prevent joint injuries in various fields and in different weather conditions, purposive training plan to improve landing performance and use of equipment appropriate to the different surfaces is recommended.