Poster

Category:
Obesity Prevention, Physical Activity, Exercise Physiology, Movement
Year:
2018
Title:
Inaccuracies in whole body mass estimates results in error propagation within measures of jump height performance
Presenter:
(School of Public Health (UMD) Kinesiology Doctoral Student)
Authors:
Burnett, Jenna (UMD SPH Kinesiology), Kim, Yong Woon (Kyungnam University), Shim, Jae Kun (UMD SPH Kinesiology)
Abstract:

Background: Human performance is quantified utilizing many variables, with power specifically used to analyze maximal effort in movements such as jumping, which can be a proxy for whole body power. Many jump height calculations use the ground reaction force (GRF) as the basis of calculating the center of mass (CoM) position. However, it is possible that CoM height variables may be influenced by errors in the initial mass estimated from the static portion of the GRF.

Goal: This project investigated how mass errors influenced the CoM position during a countermovement jump.

Objectives: Specifically, this project tested (1) how the static range of the GRF used to calculate the mass changed the CoM position and (2) how incrementing the mass by 0.1 kg up to ±0.5 kg changed the position during a countermovement jump.

Approach: The static portion of 8 GRF trials was divided into 10 static ranges (Tk, k = 1:10), and used to calculate 10 initial masses (Mi, i = 1:10). Each Mi was incremented to simulate 11 masses (Mi,j, j = 1:11) with up to 0.5 kg of error. Using the Mi,j and GRF, the position was calculated as the double integration of acceleration using the cumulative trapezoid method. From the position, the maximum (Hmax) and minimum (Hmin) height, the timing of the maximum (Tmax) and minimum (Tmin), the difference between the initiation (H1) and the landing (H2), the H1 and the final height at the end of the trial (H3), and H3-H2 were calculated.

Results: Preliminary visual results indicate that the Mi,j may significantly influence Hmax, Hmin, H3-H1 and H3-H2, while Tmax and Tmin may not be largely influenced. The Hmax difference between Mi,1 and Mi,11 appeared to be up to ~10 centimeters, a significant change in Hmax. Visual analysis of Tk indicates it may have minimal influence on the variables, assuming the GRF was properly stable.

Importance to public health: These preliminary analyses indicate that researchers may need to proceed with caution if using this method to calculate jump characteristics, as errors may significantly inflate or deflate results, leading to inaccurate conclusions, especially regarding maximal human performance.