Menstrual Cycle Knee Muscle Strength In Adolescent Female Middle-Distance Runners

STUDY OBJECTIVE: To investigate whether and what effect the menstrual cycle has on the muscle strength of female athletes.SUBJECTS: Twenty-three athletes in the middle and long-distance running program at Jilin Sports School,aged 18.30±1.11,none with a history of clinically confirmed knee injury,none on oral contraceptives,and all with normal ovulatory menstrual cycles.Experimental methods and design: Using the ISOMED2000 isometric muscle strength testing system,isometric contraction,60°/s isometric contraction（centripetal,centrifugal）,and 180°/s isometric contraction（centripetal）of bilateral knee flexor and extensor muscle groups were performed during the bleeding phase（BP,0-3 days after menstruation）,FP（FP,1-5 days after the end of bleeding）,and LP（LP,7-10 days after ovulation was determined）of the subjects.muscle strength,and the test results were statistically analyzed to observe any fluctuations in the subject’s knee muscle strength between menstrual cycles.RESULTS: The difference of peak torque in menstrual cycle: there is no significant difference in peak torque of isometric contraction.When the velocity was 60°/s,the peak concentric torque of the left knee flexor and extensor was the highest in the LP;the concentric and eccentric peak torque of the right knee extensor was the highest in the FP.When the velocity was 180°/s,the peak concentric moment of left knee flexor and extensor were the highest during the LP,and the peak moment of right knee flexor was the lowest during menstruation.2.The mean difference of the muscle strength of the bilateral muscle with the same name in the menstrual cycle: the eccentric contraction of60°/s and the peak concentric moment of 180°/s of the extensor group in the menstrual phase are left > right;the extensor group in the FP is at 60° The right side of the peak moment of concentric contraction per s is greater than the left side;the LP extensor group is at the left side of the isometric force of 10° > the right side.3.The difference in the ratio of bilateral muscles with the same name in the menstrual cycle: the difference in isometric strength of bilateral flexors at 10° is the highest during the FP;The difference of 60°/s of the lateral extensor muscle strength was the highest in the BP,and the 180°/s of the bilateral extensor group was the highest in the FP.4.The ratio difference of knee joint H/Q value in menstrual cycle: 60°/s left knee joint Hcon/Qece,right knee joint Hcon/Qcon,right knee joint Hece/Qcon,right knee joint Hcon/Qece are all in the BP The highest,180°/s right knee joint Hcon/Qcon was highest in the FP.CONCLUSIONS: 1.The menstrual cycle has an effect on muscle strength in adolescent female middle-distance runners.2.Peak muscle strength in adolescent female middle-distance runners generally occurs during the follicular and LPs.3.The changes in muscle strength of the same muscle group in both lower limbs of female athletes during the menstrual cycle are not significant.4.The slow H/Q ratio in the menstrual cycle is highest during the BP and the fast H/Q ratio is highest during the FP.