Power and energy expenditure are investigated to determine training intensity in running. Most methods are based on force measurement and speed or segmental energy analysis, limiting these calculations to laboratory conditions. In this study, mechanical power is measured using wearable accelerometers. Methods: Six male students between 21 and 23 years old walked and ran at 5 different speeds (4, 6, 8, 10 and 12 km/h). 3D kinematic data was measured using a two camera Krypton system (Nikon Metrology Instruments, Belgium) sampled at 100 Hz. 3D acceleration data from the ankles of the subjects was measured at 125 Hz using 2 Zephyr BioHarness BT accelerometers (Zephyr Technology, Annapolis, USA). 3D ground reaction forces (GRF) were measured using an instrumented, split-belt motorised treadmill (Forcelink, The Netherlands) at 1000 Hz. From the kinematics and GRF mechanical power was calculated. Individual strides were identified by detecting the heel-strike in the GRF data and GRF, acceleration and power were time normalised per stride to 0-100%. For each stride the minimum and maximum values of GRF, power and acceleration were calculated in each direction. Results: The relation between acceleration data and power was analysed for each subject. Pearson correlation coefficients are calculated for minimum and maximum values in each direction, resulting in R2=0.197 and R2=0.737 for forward; R2=0.004 and R2=0.118 for upward; R2=0.177 and R2=0.235 for medio-lateral; and R2=0.083 and R2=0.793 for the resulting acceleration and power. Discussion: A clear disruption in the relation can be seen between the walking speeds (4 and 6 km/h) and the running speeds (8, 10 and 12 km/h). Because only a small number of different velocities were tested, only a very limited number of data points per test subject were available. Therefore statistically sound individual analysis is not possible, where this could be very beneficial to study individually different running characteristics. Looking at the relation between acceleration and power, a moderate relation in maximum forward direction (R2=0.737) is observed, where in the total power a strong linear relation (R2=0.793) between the maximum total power and the maximum total acceleration is seen. Looking at the relation between power and acceleration for the individual subjects, a similar strong relation is present in each of the individual test subjects. Conclusion: Triaxial accelerometers were used to measure mechanical power for different speeds. A strong linear relation was established between the total acceleration and total mechanical power, even for individual test subjects. This relation confirms the possible use of accelerometers as a portable technology to evaluate power expenditure during running.
© Copyright 2012 17th Annual Congress of the European College of Sport Science (ECSS), Bruges, 4. -7. July 2012. Veröffentlicht von Vrije Universiteit Brussel. Alle Rechte vorbehalten. / Übersetzt mit https://www.DeepL.com/Translator