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Sports Engineering

, Volume 19, Issue 4, pp 219–227 | Cite as

Augmented inertial measurements for analysis of javelin throwing mechanics

  • Olli SärkkäEmail author
  • Tuukka Nieminen
  • Saku Suuriniemi
  • Lauri Kettunen
Original Article

Abstract

This paper examines the exploitation of inertial measurements to analyze javelin throwing mechanics. The main objective was to demonstrate that consumer-grade inertial navigation systems, augmented with some position and attitude data obtained from a video sequence, yield detailed information of the mechanics of javelin throwing. Especially, such a system makes it possible to analyze the momentary force and power exerted on the javelin during the acceleration phase. Although the presented system is a pilot, leaving space for further improvements, it already reveals the potential of inertial navigation systems to sports. In practise, an inertial measurement unit was embedded inside the tip of the javelin to determine the javelin’s momentary attitude, position, and velocity. Graphs on the speed and angular velocity about the longitudinal axis of the javelin during the whole performance are presented. The maximum estimated release speed and release angular speed were 28.02 m/s and 215.9 rad/s, respectively. The acceleration phase trajectory of the javelin and its deviation from a straight line path are demonstrated. Additionally, the momentary forces and powers are shown and the effect of aerodynamic forces on the projectile is specified. The magnitude of the maximum tangential forces and accelerating powers were 364 N and 9.76 kW. The duration and length of the acceleration phase trajectory varied between 223 and 231 ms, and 2.48 and 2.75 m. To estimate the accuracy of the inertial measurements, the acceleration phase results were compared to measurements made with high-speed cameras.

Keywords

Time-parametrized trajectory Force Work Power Inertial navigation 

Notes

Acknowledgments

The authors thank the Research Institute for Olympic Sports, Riku Valleala, Simo Ihalainen, and Sami Kuitunen who shot and made the acceleration phase image sequence analysis, and Antti Nikkola who modelled the javelin with CAD system and calculated the principal moments of inertia of the javelin. There are no conflicts of interest to disclose. The Javelin bodies for this study were given by Nordic Sport, Sweden. Two elite javelin throwers volunteered to take part in this study. Both gave their written informed consent to participate in this study, and the experimental study protocol was approved by the chair of the Ethics Committee of Tampere University of Technology, Tampere, Finland.

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Copyright information

© International Sports Engineering Association 2016

Authors and Affiliations

  • Olli Särkkä
    • 1
    Email author
  • Tuukka Nieminen
    • 1
  • Saku Suuriniemi
    • 1
  • Lauri Kettunen
    • 1
  1. 1.Department of Electrical EngineeringTampere University of TechnologyTampereFinland

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