@article{b0f9dd5e444443898681fc190a552d4a,
title = "Lower limb joint angle variability and dimensionality are different in stairmill climbing and treadmill walking",
abstract = "The present study tested if the quadratic relationship which exists between stepping frequency and gait dynamics in walking can be generalized to stairmill climbing. To accomplish this, we investigated the joint angle dynamics and variability during continuous stairmill climbing at stepping frequencies both above and below the preferred stepping frequency (PSF). Nine subjects performed stairmill climbing at 80, 90, 100, 110 and 120% PSF and treadmill walking at preferred walking speed during which sagittal hip, knee and ankle angles were extracted. Joint angle dynamics were quantified by the largest Lyapunov exponent (LyE) and correlation dimension (CoD). Joint angle variability was estimated by the mean ensemble standard deviation (meanSD). MeanSD and CoD for all joints were significantly higher during stairmill climbing but there were no task differences in LyE. Changes in stepping frequency had only limited effect on joint angle variability and did not affect joint angle dynamics. Thus, we concluded that the quadratic relationship between stepping frequency and gait dynamics observed in walking is not present in stairmill climbing based on the investigated parameters.",
keywords = "Biomechanics, Gait, Kinematics, Nonlinear dynamics, Stairs, Variability",
author = "Raffalt, {P. C.} and S. Vallabhajosula and Renz, {J. J.} and M. Mukherjee and N. Stergiou",
note = "Funding Information: Ethics. All participants gave their informed written consent after receiving information on the experimental condition and study purpose. The study was approved by the Institutional Review Board of the University of Nebraska Medical Center and the study was carried out in accordance with the approved guidelines. Data accessibility. The electronic supplementary material including data and Matlab codes for this manuscript is available at: https://www.unomaha.edu/college-of-education/biomechanics-core-facility/research/index.php under Related Resources and Stairmill Project Supplementary Material. Authors{\textquoteright} contributions. S.V., J.J.R., M.M. and N.S. designed and performed the experiment. P.R., S.V., J.J.R., M.M. and N.S. conducted the analyses and interpreted the results. P.R., S.V., M.M. and N.S. drafted the manuscript and all authors approved the final version. All experiments were performed at University of Nebraska at Omaha. Competing interests. We have no competing interests. Funding. This study was supported by the Center for Research in Human Movement Variability (NIH P20GM109090). N.S. was also supported by NIH R15HD08682. S.V. and M.M. were supported by the NASA & EPSCoR grant (NNX11M06A). J.J.R. was supported by the Fund for Undergraduate Scholarly Experiences, University of Nebraska at Omaha, Omaha, NE. Acknowledgements. The authors would also like to thank Nathaniel Hunt and Jung Hung Chien for their help with the data processing. Publisher Copyright: {\textcopyright} 2018 The Author(s) Published by the Royal Society.",
year = "2018",
month = dec,
day = "1",
doi = "10.1098/rsos.180996",
language = "English (US)",
volume = "5",
journal = "Royal Society Open Science",
issn = "2054-5703",
publisher = "The Royal Society",
number = "12",
}