Main points of this article are: - Ground forces and the velocities created (horizontal velocity, vertical velocity, relationship of horizontal and vertical velocities) - Path of the center of mass (a) The path describes a sinusoidal curve when viewing the saggital plane (from the side) (b) The amplitude of the sinusoidal curve provides indications as to the quality and efficiency of the sprinter - Stride length and stride frequency factors (anthropometric factors, strength and power, elasticity, neuromuscular integration, mechanical efficiency, dynamic mobility, training age, genetics) - Relationship between stride length and stride frequency