Frédéric Dierick, Graziella Laine, Bruno Van Oystaeyen and Olivier White
Knee injuries are common in sport competitions. Risks of injuries can be significantly lowered by warm-up exercise prior to intense activity. This study aimed to determine simultaneously the long-term effect of competitive volleyball training and short-term effect of a warm-up exercise on passive kinematics and musculo-articular impedance of the knee joint. Twelve professional volleyball players (mean age 23.8 ± 3.9 years, weight 71.5 ± 7.1kg and height 1.75 ± 0.07m) and 12 moderately active subjects (mean age 20.2 ± 1.1 years, weight 63.2 ± 9.6 kg and height 1.63 ± 0.05 m) participated in the study. Passive knee joint kinematics (number of oscillations, start and end angles, total duration of oscillations, first four peak flexion angles, first peak extension angle, period of the first three cycles, plateau amplitude, amplitude of first flexion and extension, Flexion and Extension Relaxation Indexes), stiffness and viscosity were investigated using a leg drop pendulum test performed before and after a warm-up exercise consisting of a 10-minute treadmill running. Results showed no effect of competitive volleyball training background on knee joint kinematics, stiffness and viscosity. However, in the moderately active subjects, amplitude of the first flexion and Flexion Relaxation Index were significantly higher after the running exercise than before, reflecting greater musculo-articular compliance of the knee after the warm-up compared to volleyball players. In conclusion, no change in the stiffness of the knee in volleyball players could be beneficial to the practice of volleyball since insufficient lower limb stiffness may destabilize joint motion and increase the incidence of soft tissue injuries.
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