| Purpose: Short-distance track cycling has the characteristics of static starting in situ and short riding distance.The technical action of starting in situ has a direct impact on the athletes' starting speed,and it is of great significance to improve the initial speed as soon as possible to win the race.Therefore,the purpose of this study is to analyze the kinematic parameters of the national team's short-distance field cyclist's in-situ starting technique,analyze the changes of kinematic data of the cyclist himself and the bicycle in this stage when using bicycles with different transmission ratios,analyze the influence of transmission ratios on the performance of the cyclist,and provide theoretical basis for coaches to improve the in-situ starting technique of short-distance field cyclists.Methods: The subjects were 9 national team cyclists,including 4 males and 5 females.Using the Z Camera,place it on the left side of the athlete to photograph the athlete's performance when starting in situ,with a shooting range of 10 m and a shooting frequency of 30 Hz.Each athlete chooses two transmission ratios to test according to his own situation.Two tests were conducted for each transmission ratio,and four data were obtained for each subject.The video analysis was carried out using video analysis system 4.0 developed by the Department of Sports Biomechanics of Beijing Sports University,and the subjects were identified as the center of the shoulder joint,elbow joint,hip joint,knee joint,ankle joint,toe point and crank center by using a planar two-dimensional fixed-point multi-point model,with a total of 7 analysis points.This paper analyzes the kinematic differences between the bicycle and itself when the athlete starts in situ with different transmission ratios.The data results are expressed in the form of Mean±SD.The two-factor variance analysis was used to analyze the changes of bicycle and its own kinematics data of male and female athletes under two different transmission ratios.Results: In the whole riding process,when using bicycles with large and small transmission ratios,the end speed is 6.78±0.52 m /s and 7.44±0.64 m/s respectively,with significant difference(p = 0.002);The average vehicle speed is 3.83±0.44 m/s and 4.06±0.40 m/s respectively,with no statistical difference(P=0.109).The lateral distance between hip and crank midpoint changes regularly,and there is no statistical difference between the two transmission ratios.For the index of hip-crank mid-point longitudinal distance,the small transmission ratio is always greater than the large transmission ratio.Shoulder joint angle,trunk angle,hip joint angle,knee joint angle and ankle joint angle are not statistically different among different transmission ratios.Conclusions: 1.When using bicycles with large or small transmission ratios,when the crank turns around 450 degrees at the same time,the speed of bicycles with small transmission ratios is greater than that of bicycles with large transmission ratios.2.In the start-up stage of bicycle in short distance,when bicycle rides with large transmission ratio,the pelvic movement distance is less than that of bicycle with small transmission ratio,which is more conducive to the strength of hip muscles.3.In the start-up stage of bicycles in short distance,the range of upper limb movement is similar when bicycles with different transmission ratios are used.4.As athletes gradually sit on their seats,the range of motion of each joint will be similar regardless of the transmission ratio of the bicycle used. |
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