Biomechanical Analysis of Vertical Jump Performance in Well-Trained Young Group before and after Passive Static Stretching of Knee Flexors Muscles

Abstract

The purposes of this study were to explore the biomechanical variations of vertical jump performance in well-trained young group before and after passive static stretching (PSS) of knee flexors muscles and to further discuss how the passive static stretching (PSS) influences vertical jump performance in order to provide a more effective warm-up routine and theoretical basis for physical education (PE) teachers and coaches. 15 male middle school students without any injury histories on lower limbs in the past 3 months were included in this study. Subjects with markers on the lower limbs performed vertical jump performance before and immediately after PSS of knee flexors muscles, respectively. A Vicon motion capture system was used to collect the kinematic data of lower limb and Kistler force platform simultaneously recorded the ground reaction force (GRF) during vertical jump. Significant differences were also found in the kinematics part. In sagittal plane, the hip, knee and ankle highest flexion angles were greater after PSS when take-off (hip: p< 0.05; knee: p< 0.01; ankle: p< 0.05); while the hip and knee highest flexion angles were greater before PSS when landing (hip: p< 0.01; knee: p< 0.05). These results showed that the increased range of motion (ROM) of hip, knee, and ankle because of PSS could boost the explosive extension of lower limb during take-off, which can potentially improve vertical jump performance, although the peak value of GRF after PSS was lower. Therefore, the PSS applied only on knee flexors muscles may have an acute effect on enhancing the vertical jump performance for well-trained young group and should be added to warm-up exercises in middle school sports class and sports training.