Influence of external load during back squats on knee joint arthrokinematics analyzed by vibroarthrography

Abstract

Background This study aimed to use vibroarthrography to evaluate the effect of different external loads on the arthrokinematics of the patellofemoral joint during the back squat motion in vivo. The level of vibroarthrographic signal was expected to increase with the level of applied load; however, the trend of increase was unknown. Methods Participants, who were recruited from team sport athletes, were requested to perform eight trials: four bodyweight squats and four back-loaded barbell squats of 10–70 kg, with 1 min rest between tests. Finally, 38 male volunteers (age: 22.0 ± 1.1 years, body mass: 82.8 ± 10.1 kg, height: 186,7 ± 7.9 cm) were included in the study. All participants described their health condition as “very good.” An average physical activity of moderate-to-vigorous intensity, mostly aerobic, was considered as 12,47 ± 3,37 hours across the week. The arthrokinematic quality of movement of the PFJ was assessed using an accelerometer sensor placed 1 cm above the apex of the patella. Results The experimental results revealed that the vibroarthrographic signal level steadily increased with an increasing knee load during squatting, which could be attributed to higher contact stress and kinetic friction of the joint surfaces. The phenomenon was analyzed throughout the range of loads applied, which followed a linear pattern. Conclusions The proposed method is a promising tool for monitoring the effects of external loads on the knee joint mechanics and adaptive changes that occur during training. Moreover athletes and coaches should take into account that increased loads can result in accelerated joint wear and tear.