The change in the horizontal velocity during the braking, propulsive and stance phase are calculated. In the results the changes are summarized and the variables are presented in relation to the body weight of the individual rather than in Newtons. The discussion includes the explanation of the general pattern of the Fz- and Fy- time traces an dthe change in magnitude of the Ground Reaction Force (GRF) variables between each running speed.
The paper aims to investigate the effect of increasing running speed on ground reaction force (GRF) related variables. According to the Newton’s Law of Gravitation, any two objects with masses attract each other and the magnitude of this attracting force is proportional to the product of the masses and inversely proportional to the square of the distance. The gravitational force acted upon an object by the earth is called gravity or weight of the object. Since we always have contact with the ground due to this gravity there is always an interaction between our bodies and the ground. The reaction from the ground is called the Ground Reaction Force (GRF). The GRF is important external force acting upon the human body in motion. This force is used as propulsion to initiate and control the movement.
A single male weighing 74kg uninjured participant was subjected to an exercise to determine the ground reaction force. Following habituation, GRF was recorded while he was running across the Kistler Force Plate five times at 3, 4 and 5 m-s-1 10% . Following each trial during the laboratory session, a MS-Excel spreadsheet containing Fz (i.e the vertical component of GRF) and the Fy (i.e. the anterior-posterior component of GRF) versus time data and the braking and propulsive impulse were produced. From this raw data, we will need to obtain the magnitude of the following GRF related variables (shown in fig. 1) for each trial. Calculation of the changes in horizontal velocity during the braking