چکیده مقاله
Purpose: This study aimed to evaluate the biomechanical effects of different knee flexion angles on internal joint forces at the knee and lumbosacral L5/S1 joints during squat lifting with a flat back posture There is a lack of integrated studies examining how varying knee angles combined with maintained lumbar lordosis affect load distribution, especially under lifting tasks Understanding these interactions is critical for designing safer resistance training programs and minimizing injury risk, particularly for athletes and individuals with lower back vulnerability Methods: In this semi experimental study, ten healthy young males mean age: 23 5 ± 1 9 years performed squat lifts at three knee flexion angles: full flexion 10° , semi flexion 35° , and low flexion 70° , lifting an 8 4 kg standardized box Kinematic data were captured using a 56 marker setup and a VICON motion capture system, while kinetic data were recorded via AMTI force plates A 3D linked segment model and inverse dynamics approach were applied to calculate shear forces ML and AP , compressive forces, and time to peak TTP for both the knee and L5/S1 joints Results: A significant increase was observed in L5/S1 maximum ML shear force from 2 62 to 4 95 N/kg as knee flexion increased p = 0 001 Time to peak compressive force at L5/S1 decreased significantly from 56% FF to 43% SF p = 0 003 In contrast, maximum ML shear force at the knee decreased from 4 13 to 2 13 N/kg p = 0 003 with increasing flexion Knee compressive force rose from 3 32 to 4 18 N/kg, although not significantly Conclusion: Increased knee flexion with a flat back posture leads to higher lumbar shear forces but reduces knee shear loading while increasing compressive forces at the knee These insights emphasize the importance of adjusting knee angles and trunk posture in resistance training to optimize joint safety and efficiency Keywords: Squat, Knee Flexion Angles, Inverse Dynamics, Joint Forces, Lumbar Spine, Time to Peak TTP Introduction Squat lifting is a key exercise in resistance training that involves significant biomechanical interactions between the knee, hip, and lumbar spine Proper analysis of these forces is crucial to prevent injury and optimize performance Previous studies, such as those by Biscarini et al 2020 2 , have emphasized the importance of joint reaction forces in squat exercises, while others, such as Yavuz et al 2015 10 , have focused on how knee flexion affects muscle activation during squats Additionally, spine posture, particularly the flat back position, plays a major role in distributing forces during lifting tasks, which has been explored by Kim et al 2021 5 in their analysis of joint forces Despite its importance, biomechanical analysis in squat lifting often overlooks the combined effects of knee position and spine posture Most studies isolate knee flexion angles or spine posture, but the interaction between these factors is rarely explored Von Arx et al 2021 8 showed that lumbar spine loading varies across lifting styles, highlighting the need for further research on the interplay between knee flexion and lumbar spine posture Furthermore, research by Whitting and Meir 2016 9 demonstrates how varying squat depths affect lower limb forces, emphasizing the need for a more comprehensive biomechanical approach Although there has been substantial progress in biomechanical modeling and squat analysis, several gaps remain A major gap is the limited exploration of how flat back postures, commonly recommended in resistance training, interact with knee flexion variations during squat lifting Some studies have analyzed the biomechanical impact of squat movements in specific knee flexion angles or lumbar postures, but few have combined these factors comprehensively For instance, Yavuz et al 2015 10 explored the kinematics and muscle activity in different squat variations, but the interaction between knee angles and lumbar posture was not addressed Similarly, Kim et al 2021 5 focused on the muscle activation patterns in
کلیدواژهها
نویسندگان
Sajad Azizi
Department of Biomedical Engineering, Faculty of Medical Sciences and Technologies, Science and Research Branch, Islamic Azad University, Tehran, Iran
شیوه ارجاع
Azizi, Sajad,1404,The Biomechanical Effect of Knee Flexion Angles on Squat Lifting with a Flat Back Position,21st International Conference on Innovation and Research in Engineering Sciences
ارائهشده در
مجموعه مقالات بیست و یکمین کنفرانس بین المللی نوآوری و تحقیق در علوم مهندسی31 تیر 1404