Research On The Performance Characteristics Of Muscle Activity And Running Economy Of Middle- And Long-distance Runners Under Different Exercise Intensitie

Objective: This study discusses the relationship between muscle activity and running economy(RE)of middle and long-distance runners from three intensities: low intensity,moderate intensity and high intensity,and how to show the characteristics and internal relations of muscle exertion with the change of running intensity,so as to optimize middle and long-distance running techniques and improve running performance,and provide theoretical reference for scientific and systematic training.Methods:Fourteen male middle-distance and long-distance runners in Tianjin Institute of Physical Education who specialize in 800 m and 5000 m were selected.Through secondary screening,10 middle-distance and long-distance runners were selected as the experimental subjects.After testing the maximum oxygen uptake of the subjects,according to the recorded maximum oxygen uptake test results and heart rate and other related indicators,three kinds of exercise intensities were determined:low intensity(12km/h),medium intensity(14km/h)and high intensity(16km/h).After that,Noraxon wireless surface electromyography tester and video were used.Simultaneously collect the RE index and EMG data of the exercise muscles of the subjects at different exercise intensities,export and process the collected data,and analyze the characteristics and correlation between the EMG,RMS,MPF and running economy at different intensities by statistical methods.Results:(1)The RE level of 5000 m special subjects showed significant correlation under low intensity(12km/h)and moderate intensity(14km/h)(P<0.05),while that of 800 m special subjects showed significant correlation under medium intensity and high intensity(16km/h)(P<0.01).(2)Under the low intensity of exercise(12km/h),the contribution rate of the medial thigh muscle was positively correlated with the RE value(P<0.01).The degree of deltoid activation was negatively correlated with RE(P < 0.05).The degree of tibialis anterior activation was significantly correlated with RE value(P<0.01).At low intensity,the RMS value of deltoid muscle was significantly higher than that at moderate intensity(P < 0.05).The RMS values of medial femoral muscle,tibialis anterior and lateral gastrocnemius muscle were significantly lower than those of high intensity(P<0.05).(3)Under moderate exercise intensity(14km/h),the contribution rate of gluteus maximus and biceps femoris was significantly correlated with RE(P<0.05),and the MPF value of rectus femoris was significantly higher than that of low intensity and high intensity(P<0.05).(4)Under the high intensity of exercise(16km/h),the contribution rate of the medial thigh muscle of the subjects was highly correlated with RE(P<0.01),and the activation degree of biceps femoris was significantly positively correlated with RE(P<0.05).At high intensity,the IEMG values of deltoid,gluteus maximus,biceps femoris and tibialis anterior were significantly higher than those at low intensity(P <0.05).The IEMG values of biceps femoris and rectus femoris were significantly higher than those of moderate intensity(P<0.05).At high intensity,the MPF values of medial femoral muscle and erector spinae were significantly lower than those at low intensity(P<0.05).Conclusion:(1)The 5000 m special subjects showed high level of RE at low intensity,so the level of RE was also high at medium intensity.However,the 800 m special subjects have low RE value at moderate intensity,less oxygen and energy consumption during running,and low RE value at high intensity,and less oxygen and energy consumption during running.(2)At low intensity,the higher the contribution rate of the subjects’ medial thigh muscles,the worse the RE performance and the uneconomical running;The higher the degree of deltoid activation,the better the running economy performance,the more obvious the balance and coordination function,and the more stable the body.On the contrary,the higher the tibialis anterior activation level,the worse the RE level.(3)Under moderate intensity,the more obvious the work done by gluteus maximus and biceps femoris,the worse the performance of RE level;The stronger the tibialis anterior activation,the higher the RE value and the worse the sports performance.With the increase of exercise intensity,subjects need to mobilize more muscles to participate in activities,and the function of rectus femoris is poor,and the knee joint is not actively stretched.(4)Under high intensity,the more fully the subjects’ medial thigh muscles do work,the higher the RE value,and the uneconomical running performance;The more obvious the activation of biceps femoris,the higher the RE value and the worse the running efficiency.During high-intensity exercise,erector spinae and medial thigh muscles bear more and more loads,so it is necessary to recruit other muscles to participate in coordination and gain greater impetus to keep their speed above a higher level to maintain the stability of the subjects during exercise.