| Run with a drag is one of the training methods of running anti horizontal resistance. Because of its technique is closer to specialized training of sports. There are many advantages such as the requirement of the venue is not complicated, load standard is easy to control and it is not easy to be injured when athletics are in practice. So it has long been considered as a good specific strength training tool for sprint. In order to explore what different effects that the different dragging loads will influence a athlete's physically kinematic parameters (such as the extension of the speed and scope of hip, etc.) and how this influence change the gradient force which is the core technology of sprint, therefore improving the dragging loads in sprint and in-depth understanding of different influence that different loads will affect sprint issues and so on, this paper will compare the kinematics parameters with nine first or second class athletics after they respectively run with a loads of 0kg,12.5kg,15kg,17kg.through literature, sports biomechanics test analysis and grey correlation analysis.The results show that:(1) Comparing to ordinary running, the kinematics trend of the run with a drag is: the horizontal velocity of center of gravity, stride length and scope of forward stepping are significantly reduced, while supporting time is obviously extended; the speed of the stretching the hip of supporting leg, the speed of bending the hip of swing leg and the shearing speed of the two legs are significantly less than ordinary running. The range of stretching the hip of supporting leg is obviously expanded. When supporting leg reaches the ground, the angle of knee (the angle of ankle) and their buffer rate are both obviously reduced. the angle of knee of swing leg when the supporting leg reach the ground and take off the ground, the angle of knee of the supporting leg when it take off the ground, the range of stretching the knee and the average angular velocity of the knee of supporting leg are obviously increased.(2) The run with dragging loads will input backward and downward comprehensive resistance to body. It's a similar action to sprint, so it is not only having less possibility to be injured but also more'specific'than the traditional strength methods with a vertical force. It is a better sprinter's specific strength training methods.(3) The value of this sprint special forces training methods is: first, it can develop the core strength of the sprint more effective and more substantial (contraction forces of hip muscle), and secondly, it will have effective influence on the development of the extensor's strength of knee and ankle in reasonable range. Third, it will have effective influence on the development of the concession contract strength of knee and ankle muscles.(4) We can conclude that run with a drag of 12.5kg is the most'specific'for sprint strength training through comparing ordinary running and drag running. As athlete will bear greater additional load when run with a load of 15kg or 17kg. It will have a greater impact on the muscular strength, and thus have unique characteristics. Which loads should athletes choose for strength training depends on their own level of capability and technology. (5) Any special training methods have its limitations; there is no exception to drag running. We know that the zone of exerting forces emphasis on latter supporting stage and there is inadequate training on former supporting stage through comparing run with a drag and run without drag. In addition, if an athlete only uses this single training may cause his rapid of neuromuscular system flu subside, and the muscle may get rigid. Therefore, we should combine all kinds of anti vertical resistance running exercises (such as: run with a sand vest and run in sand, etc.), with anti horizontal resistance running and ordinary running and all kinds of dragging loads running exercises.
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