Effects of Different Phases of Static Stretch Training on Ankle Dynamics and Lower Limb Cushioning Properties in Male Volleyball Athletes

Objective: To investigate the effects and mechanisms of static stretch training on ankle dynamics and lower limb cushioning properties by measuring the biomechanical parameters of ankle and lower limb during flex-dorsiflexing and cushioning phase after landing before and after static stretch training in male volleyball athletes. Methods: 22 male health young elite volleyball athletes were randomly divided into training and control group. Lower limb static stretch training was conducted in training group for 36 sessions, and the ankle flex-dorsiflexion dynamics, calf muscle imaging, lower limb and its joints kinematics and dynamics during cushioning phase were measured at before training, after 12, 24 and 36 training sessions and after 4 weeks recovery,respectively. Results: The flex-dorsiflex range of motion was increased from 12 training sessions to recovery period(P<0.01), and the calf muscle's passive stiffness was significantly decreased(P<0.05). Both of the changes of increase/decrease rate were significant after 36 sessions(P<0.05), and a positive correlation was observed between their change rate(P<0.05). After training,the hysteresis was significantly decreased(P<0.05), but the tendon elastic recoil rate was significantly increased(P<0.05), a negative correlation was observed between them(P<0.05). In addition, the leg stiffness were significantly decreased after training(P<0.05), but the joints work of hip, knee, ankle were all increased(P<0.05). The contribution of ankle work was greatest in all training periods(P<0.05). Conclusion: In the early phase of static stretch training, the ankle range of motion was significantly enlarged through decreasing the passive stiffness, and tendon elastic recoil rate was significantly promoted through decreasing hysteresis, which sustained to retention period. It was suggested that the stretch-shortening cycle performance can be elevated through increasing flexibility of muscle-tendon complex and increasing elastic energy utilization of tendon. The lower limb stiffness was decreased and joints' energy absorption were increased, and at the same time the ankle energy absorption was the greatest during different phases after training, which suggesting that the static stretching can impair the lower limb injury risk through modulating lower limb cushioning pattern, promoting joint energy absorption, reinforcing ankle function in volleyball athletes.