Effects of Sampling Rate and Movement Frequency on Entropic Measures of Regularity

Douglas W. Powell, Brian Szekely, Sarah E. Blackmore, Alexis Nelson, Alexandra Schallert, Deranda B. Lester, Nicholas G. Murray, Melissa Puppa

School of Health Studies, University of Memphis, Memphis, TN, USA. Department of Kinesiology, University of Nevada Reno, Reno, NV, USA. Univerity of Tennessee Health Science Center, Memphis, TN, USA.

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Variability is an inherent feature of biological systems and has been measured using a variety of methods.  Sample entropy (SampEn) has been a popular tool to describe the variability of a system, but has been suggested to be sensitive to sampling rate and movement frequency.  This study quantified the effects of movement frequency and sampling rate on SampEn calculations. Continuous ankle joint angles were recorded 10 healthy participants during treadmill walking.  Data were resampled at 50%, 200% and 400% of the original sampling rate and the movement frequency was simulated at 70% and 130% of the original movement frequency.  SampEn was calculated for each data set.  Simulated sampling rates were associated with significant changes in ApEn values.  Faster movement frequencies were associated with significantly greater SampEn values compared to original or slower movement frequency. Current findings demonstrate that sampling rate and movement frequency significantly alter SampEn values.

Journal of Nature and Science (JNSCI), 4(5):e504, 2018

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