Study on Counter Movement Jump Performance in a Force Platform – Part 1

Introduction

Vertical jumping ability is an essential motor skill in many sporting, athletic and daily activities. It is common in many sports to perform loaded or unloaded jump series for better performance and explosive strength. This is the reason why many studies have analyzed the vertical jump from a physical point of view to establish the factors that have to be improved to increase jump height and minimize possible injury following higher jumps (Ortega, Rodriguez, & Rosa, 2010). Jumping is usually preceded by a countermovement, which can be described as an initial bend of the hip and knee during which the body’s center of mass drops somewhat before being propelled vertically up off the ground with the extension of hip and knee (Harman, Rosenstein, Frykman, & Resenstein, 1990). According to (Harman et al., 1990), the countermovement jump uses the principle of Stretch-Shortening Cycle, which describes the use of elastic energy produced due to eccentric muscle stretching (during bending movement), is stored which is released or used during the subsequent concentric muscle contraction (during extension and take off).

The aim of this study was to understand and analyze various kinematics and kinetics of vertical jump motion performed on a force platform. Various computer software has been developed that can produce curves of velocity and displacement of the jumper’s center of mass by numerical integration of the force-time record from a force platform. An effective relationship between the forces acting on a body and the resulting acceleration, velocity, and displacement of the body can be achieved and illustrated by the examination of these curves (Linthorne, 2001).

The biomechanical analysis of vertical jump performance has become the essential field of study in many sporting events such as soccer, basketball, tennis etc. for the better performances and to ensure maximum safety during the events. For example, the study of ground reaction forces (GRF) acting on the body especially during landing is of great interest mainly to analyze the cause of injury in different events. The vertical GRF on the body during landing can be a determinant of injury, especially if the jumps are made very often and GRF are high (McNair, Prapavessis, & Callender, 2000). Impact forces may contribute to optimal skeletal health (Fuchs, Bauer, & Snow, 2001). So, these reports focus on the importance of biomechanical analysis of vertical jump in different activities to rule out the impact force that the joints have to withstand and to advise the techniques to reduce the impacts under certain limits so as to reduce the risk of joint injuries involved.

So, in order to understand the fact that why some athletes perform better vertical jump without any injury while many perform relatively lower jump heights and also faces with the injuries, it is necessary to assess and study both their muscle strength capabilities and jump techniques (Vanezis & Lees, 2005). Therefore, the purpose of this study is to assess and understand the factors such as joint angles, moments and powers, muscle performances and ground reaction forces that play a key role in jump performance.

Methods and Procedures