Acceleration During the initial acceleration period from a static start, both stride rate and length will increase during the first 15 to 20 m or 9 to 12 strides. Analysis of elite sprinters show that stride length increases more than stride frequency during the first 20m of a 100 m dash (65). However, it appears that stride frequency is the performance discriminant among fast and slow team sports athletes(78). During the preliminary portion of the acceleration period, the body will have a forward lean(545),which will progressively move to a more upright position as the athlete approaches maximum velocity The forward lean position allows the athlete to have the vertical projection of the center of gravity ahead of the supporting legs, a technical position that is favorable to higher acceleration. During the whole acceleration phase, the leg is fully extended and in line with the body's longitudinal axis at push-off. From this position, the recovery of the leg is performed by passing the foot progressively higher at each step, always ending with the thigh perpendicular to the trunk. As the leg enters the support phase, it extends downward and back; at the same time, the elbow angle of the arm simultaneously swinging backward will close a little more with each step, finally staying at 90 for the whole cycle when the athlete is in the upright position typical of the maximum speed phase The arm motion should always originate from the shoulder and move backward and forward.These arm motions offset the axial momentum generated by the contralateral leg and hip. During the support phase, the athlete will transition between an eccentric and con centric subphase with the use of a stretch shortening cycle(SSC) action (87). As the athlete accelerates, greater ground reaction forces must be developed to continue to accelerate (54.77).These data seem to suggest that strength training, especially activities that improvethe rate of force development, is an essential component of a training program designed to enhance sprinting performance. Horizontal ground reaction forces, in particular, seem to be the discriminant between slower and faster sprinters(18, 18b, 53, 71, 77, 82), which suggests that more emphasis should be granted to training means with anteroposterior force vector(kettlebell swing versus Olympic lifts, hip thrust versus squat [221) or requiring more horizontal force application (horizontal jumps versus vertical jumps )than traditionally used