| Objective:The technical movement of stepping is a hot topic in the current biomechanical research of badminton.Previous studies on the performance of stepping have focused more on the entire stepping movement,while the characteristics of the lower limb power of high-level badminton players and their correlation with specific physical fitness indicators are not fully clear.To explore the kinematics,dynamics,and indicative electromyographic characteristics of the forward and backhand forward stepping support legs of male badminton players under different run-up conditions,and to analyze the correlation between the power characteristics of the forward stepping support legs and their maximum strength,isokinetic muscle strength,jumping ability,specific sensitivity,and specific athletic performance,in order to provide a basis for formulating scientific and reasonable special training programs.Method:Recruit 16 high-level badminton players,with a sports level of more than Grade 1,and use the infrared motion capture system,three-dimensional dynamometer and surface electromyography to measure the athletes’kinematics indicators such as the landing time of the left（backhand）,right（forehand）,short distance（1 step）,middle distance（2 steps）and long distance（3 steps）pedaling support leg,lower limb joint angle and joint angular velocity in the front field,Dynamic indexes such as ground reaction force,peak torque and maximum power of lower limb joints,and surface EMG of front and rear leg muscles.At the same time,the athletes’maximum strength of lower limbs,isokinetic muscle strength of knee joint,jumping ability,special sensitivity and sports performance indicators were measured;Two-factor analysis of variance（approach steps×Step direction）to test the difference of the kinematics,dynamics and surface EMG indexes of the support leg under different run-up steps and step directions,and to reflect the correlation between the strength characteristics of the support leg and the physical fitness indexes of each special item by using Person correlation analysis.Result:（1）The hip adduction angle at the landing and maximum buffering time of the support leg in the left and right 2-step and 3-step run-up conditions was significantly lower than that of the 1-step condition（P<0.05）,and the knee flexion angle during the backpedaling period was significantly greater under the 3-step run-up condition than that of the 1-step condition（P<0.05）.From the perspective of the range of motion of the hips,knees,and ankles during the landing phase,during the process of completing the landing action,the range of motion required by the ankle joint accounts for more than 60%of the maximum range of motion of the ankle joint,while the range of motion required by the hips,knees,and ankles during the completion of the action accounts for 40-50%of the maximum range of motion of the joint.During the cushion stage of the support leg,the angular velocity variation of the hip,knee,and ankle joints（°/s）is about twice as fast as the knee joint and about three times as fast as the hip joint.The angular velocity of the ankle during the buffer period（eccentric contraction）is four times that of the back pedal period.The adduction angular velocity of the hip joint during the buffer period of the support leg is about twice that during the back pedal period,and is higher than the flexion and extension velocity of the hip joint.（2）The maximum vertical force of the support leg during the buffer period of the left and right 3-step approach conditions was significantly greater than that of the 1-step and 2-step conditions（P<0.05）,and the RFD 0-50msvalue of the left and right 3-step approach conditions was significantly greater than that of the 1-step condition（P<0.05）.There is a significant difference in the RFD0-50msvalue between various run-up conditions.There was no significant difference in RFD 0-100msbetween various run-up conditions.The greater the number of run-up steps,the greater the 0-50ms reaction force on the ground,and the faster the lower limb muscle group touches the ground during the landing stage of the support leg.（3）The peak moment of hip joint extension during the buffer period,knee joint extension during the back pedaling period,and ankle metatarsal flexion during the left and right three step approach conditions were significantly greater than those under the one step condition（P<0.05）;During the pedal extension period（centripetal）,the output power from the largest to the smallest is the hip,knee,and ankle joints.When the buffer period increases by 3 steps with the number of steps,the output power of the ankle joint is the highest,followed by the knee joint and the hip joint.（4）The RMS standard values of the rectus femoris,lateral femoris,semitendinosus,and medial head of gastrocnemius during the buffer period of the support leg under the left and right three-step approach conditions were significantly greater than those under the one-step condition（P<0.05）,the RMS standard values of the biceps femoris under the two-step and three-step conditions were significantly greater than those under the one-step condition（P<0.05）,and the RMS standard values of the gluteus maximus under the three-step condition were significantly greater than those under the one-step and two-step conditions（P<0.05）.The RMS standard values of the rectus femoris muscle during the left and right 3-step back pedaling conditions were significantly greater than those under the 1-step condition（P<0.05）.Under the same run-up conditions,the RMS standard values of the medial femoris muscle during the landing stage of the right step support leg were significantly smaller than those of the left step（P<0.05）.（5）There was a significant negative correlation between the value of 1RM and maximum power in squatting and the left and right two-step conditional pushback time,respectively（P<0.05）.（6）There was a significant positive correlation between the peak knee flexion torque at 60o/s and 180o/s and the maximum RFD value at the landing stage of the left step,3 step,1 step,2 step,and 3 step stepping support leg in the front field（P<0.05）.There was a significant positive correlation between the peak knee flexion torque at 180o/s and the peak knee extension torque at 60o/s and the maximum RFD value at the right step,2 step,and 3 stepping step（P<0.05）.（7）There was a significant positive correlation between CMJ-P and the vertical maximum force value of the support leg during the buffer period of the right 1-step approach condition,and the maximum RFD value of the right 1-step and 2-step conditions（P<0.05）.There was a significant positive correlation between SJ-H and the right 2-step buffer period hip joint extension,the right 1-step knee joint extension,abduction,and the right 3-step ankle joint plantar flexion peak torque during the backpedaling period（P<0.05）.CMJ-P was also significantly correlated with the right1-step condition buffer period hip joint adduction There was a significant positive correlation between knee flexion and peak moment of plantar flexion of the left ankle joint under 2-step condition（P<0.05）.There was a significant positive correlation between RJ-CT and the buffer time of the left 3-step conditional support leg（P<0.05）,a significant negative correlation between DJ-CT and the vertical maximum force value during the left 3-step conditional buffer period,the peak moment of hip joint extension,the maximum RFD value under the left 1-step approach condition,and the peak moment of ankle joint plantar flexion（P<0.05）,and a significant negative correlation between DJ-RSI and the vertical maximum force value during the left1-step buffer period There was a significant negative correlation between the maximum RFD value and the peak moment of plantar flexion of the ankle joint（P<0.05）,while there was a significant positive correlation between RJ-H and the peak moment of hip joint extension during the right two-step run-up and back pedaling period（P<0.05）.（8）There was a significant positive correlation between the maximum force and maximum RFD values during the left 1-step approach conditioning buffer period and the time used in the four-corner low center of gravity run（P<0.01）,and a significant negative correlation between the right 2-step conditioning buffer period hip extension,knee flexion,and peak ankle plantar flexion torque.There was also a significant negative correlation between the right 1-step hip extension,knee valgus,and peak ankle plantar flexion torque during the back pedal period（P<0.05）.There was a significant negative correlation between the time used for 15m round trip running and the peak moment of hip abduction during the right 3-step buffer period and the peak moment of hip adduction during the back pedal period（P<0.05）.There was a significant negative correlation between the time used for 15m round trip running and the peak moment of hip extension and lateral rotation during the left 1-step condition（P<0.05）.Conclusions:（1）From the perspective of kinematics,the"fast"characteristics of lower limb force generation are mainly reflected in:under different run-up conditions and stride directions,1)from the perspective of action Characteristic velocity,from the perspective of short buffer time,lower limb muscles are required to be eccentric and fast.Short stretching time requires fast centripetal velocity of lower limb muscle groups.2)From the perspective of joint speed,the ankle joint braking（buffering）of the step support leg is four times the starting（rebound）speed,and the ankle joint braking speed is the highest,playing an important role in the completion of step technology.From the perspective of ankle joint movement amplitude,the range of motion accounts for over 80%,and the contribution rate of ankle joint toe flexion and back flexion in stepping movements is much higher than that of knee joint and hip joint.The hip joint adduction angular velocity during the buffering period（centrifugal）of the step support leg is about twice that during the step extension period（centripetal）,and is higher than the hip joint flexion and extension velocity.The centrifugal speed of the hip joint is beneficial for optimizing the completion of step stepping movements.（2）From the perspective of dynamics,the"large"feature of lower limb force is reflected in:as the number of approach steps increases,the impact force on the ground is greater,and the fastest speed becomes 0 in a short period of time.It requires the maximum centrifugal contraction force of lower limb muscles and the maximum centrifugal force of lower limb flexors.As the number of steps increases,during the buffering period（centrifugation）,the output power decreases in descending order from ankle,knee,and hip.During the stretching period（centripetal）,the output power in descending order is the hip,knee,and ankle joints.When buffering and stretching,the hip joint output power is the highest under slow speed conditions at 1 step.RFD0-50ms value is used to evaluate the performance of stepping exercise;The ankle joint output power during the buffering period plays an important role in the completion of step stepping under the 3-step condition,while the hip joint output power during the buffering period and the back stepping period are both the highest under the 1-step condition.（3）From the perspective of dynamics,the characteristic of"stability"in lower limb force is reflected in the balance between the left and right forces of the ankle,which is used to maintain the opposite force of the body and prevent the lower limb from flipping and causing instability of the body’s center of gravity.（4）In terms of surface EMG characteristics,with the increase of run-up distance,the activation degree of gluteus maximus,rectus femoris,lateral femoris,semitendinosus,and the medial head of gastrocnemius muscle in the buffer period of the pedal stride support leg is increasing.（4）Maximum strength indicators such as half squat lift 1RM and maximum power,isokinetic knee flexion and extension strength indicators such as slow,medium,and fast conditions,jumping indicators such as half squat jump height,squat jump output power,standing triple jump distance,rebound jump height and touchdown time,deep jump height,and reaction strength index,as well as hexagonal jump,quadrangular low center of gravity run Special sensitive and athletic performance indicators such as the time required for the 15m round trip and round-trip running around the pole can affect the power characteristics of the lower limbs by influencing the landing time,ground reaction force,and lower limb joint peak torque indicators of the support leg of the front court step,and can be used as effective specific physical fitness indicators to evaluate the front court step technique,and introduced into the special physical fitness training plan. |
