| Post-activation potentiation,or PAP,is an acute,high-intensity contraction of skeletal muscle that leaves a "muscle memory-like" trail of contraction,that is,the muscle is "activated," A physiological phenomenon in which muscle capacity increases in the following specific periods of time,also known as post-activation enhancement effect.Through muscle tonic contraction to enhance the short-term performance of muscles,mainly suitable for explosive force dominated sports.However,pulsed current stimulation of skeletal muscle can cause instantaneous and high-intensity muscle contraction,which fully meets the prerequisite of post-activation enhancement effect.Research Objectives: This study tested the characteristics of muscle strength changes of lower limb muscles of jumping athletes at different recovery times after the main leg muscles were stimulated by pulse current.Specifically,the change characteristics of SFJ height,hip,knee and ankle Angle（PFA）,ground vertical reaction force（v GRF）,peak power output（PPO）,peak force development rate（RFD）and peak impulse（PI）at different recovery times after stimulation were compared.In order to determine whether electrical stimulation can be used as a PAP induction mode,and whether it has PAP effect on the main leg of jumping athletes,providing theoretical basis for electrical stimulation to induce PAP.Research methods: In this study,10 jumping athletes（long jump,high jump and triple jump）were selected as experimental subjects.The COMPEX electric stimulation apparatus was used to induce the maximum tolerance intensity in 1 minute.Then,AMTI force measuring table and VICON infrared 3D motion capture high-speed camera were used to synchronously collect the kinematics data of the main leg hopping at 15 s,4min,8min,12 min,16min and 20 min before and after induction,mainly including SFJ height and hip,knee and ankle joint Angle.Kinematic data: Peak reaction force（v GRF）,peak power（PPO）,peak impulse（PI）and peak development rate（RFD）.MR3 was used for quantitative processing of the collected data,and SPSS software was used for one-way repeated measurement an OVA to explore the differences between before and after induction and the differences at each time point after induction.Results: There was a significant difference between the jump height and the reference value in the recovery time of 4-20 min under PAP induction mode stimulated by 1-minute maximum intensity pulse current（P < 0.05）.There were no significant differences in hip,knee and ankle joint angles at peak force（P > 0.05）.There was significant difference between v GRF and PI at 4-16min（P < 0.05）.PPO and RFD were significantly different at 8-16min（P< 0.05）.Conclusion: 1)PAP effect can be successfully induced by electric stimulation.2)The takeoff height reaches the maximum at the recovery time of 12 min.3)Under the induction mode of electrical stimulation,PAP effect was produced in 4-16 min,and the maximum time of PAP appearance was 8min.It was mainly reflected in the increase of peak ground reaction force,peak power,peak impulse and peak development rate,which enhanced the ability of subjects to recruit motor units and improve their explosive power. |
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