THE INFLUENCE OF EFFECTIVE MASS ON IMPACT FORCE AND ACCELERATION

  • W. Brent Edwards
  • Timothy R. Derrick
Keywords: running, landing, injury

Abstract

Accelerometry is often used as a means to quantify the osteogenic or injury potential of impacts. This paper uses a series of four experiments to demonstrate theoretically, mechanically, and experimentally that increasing the effective mass of an impact can lead to an increase in impact force with a corresponding decrease in acceleration. The four experiments included: 1) mass spring models, 2) shoe impact testing, 3) cadaver impact simulation, and 4) an in vivo study manipulating knee angle during running. Results were consistent with the aim, illustrating a limitation for the use of accelerometers for impact assessment. In order to appropriately interpret the results from accelerometry it is necessary to quantify the effective mass of the impact. Failure to account for the influence of effective mass can lead to erroneous conclusions about impact severity.