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Pink Noise in Rowing Ergometer Performance and the Role of Skill Level

Ruud J. R. Den Hartigh, Ralf F. A. Cox, Christophe Gernigon, Nico W. Van Yperen, and Paul L. C. Van Geert

The aim of this study was to examine (1) the temporal structures of variation in rowers’ (natural) ergometer strokes to make inferences about the underlying motor organization, and (2) the relation between these temporal structures and skill level. Four high-skilled and five lower-skilled rowers completed 550 strokes on a rowing ergometer. Detrended Fluctuation Analysis was used to quantify the temporal structure of the intervals between force peaks. Results showed that the temporal structure differed from random, and revealed prominent patterns of pink noise for each rower. Furthermore, the high-skilled rowers demonstrated more pink noise than the lower-skilled rowers. The presence of pink noise suggests that rowing performance emerges from the coordination among interacting component processes across multiple time scales. The difference in noise pattern between high-skilled and lower-skilled athletes indicates that the complexity of athletes’ motor organization is a potential key characteristic of elite performance.

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Hip Sway in Patients With Hip Osteoarthritis During One-Leg Standing With a Focus on Time Series Data

Takuya Ibara, Makoto Takahashi, Koichi Shinkoda, Mahito Kawashima, and Masaya Anan

) = ∑ i = 1 m ( x i − x ¯ ) . (3) Here, x i and x ¯ indicate the original time series data and the mean value of the time series data, respectively. Figure 2 —The detrended fluctuation analysis protocol for estimating the scaling exponent α. (a) The acceleration time series data in the medial

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Gait Variability Measures Reveal Differences Between Multiple Sclerosis Patients and Healthy Controls

Jeffrey P. Kaipust, Jessie M. Huisinga, Mary Filipi, and Nicholas Stergiou

The purpose of this study was to determine the differences in gait variability between patients with multiple sclerosis (MS) and healthy controls during walking at a self-selected pace. Methods: Kinematics were collected during three minutes of treadmill walking for 10 patients with MS and 10 healthy controls. The Coefficient of Variation (CoV), the Approximate Entropy (ApEn) and the Detrended Fluctuation Analysis (DFA) were used to investigate the fluctuations present in stride length and step width from continuous strides. Results: ApEn revealed that patients with MS had significantly lower values than healthy controls for stride length (p < .001) and step width (p < .001). Conclusions: ApEn results revealed that the natural fluctuations present during gait in the stride length and step width time series are more regular and repeatable in patients with MS. These changes implied that patients with MS may exhibit reduced capacity to adapt and respond to perturbations during gait.

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Rambling and Trembling in Response to Body Loading

Behdad Tahayori, Zachary A. Riley, Armaghan Mahmoudian, David M. Koceja, and Siang Lee Hong

Various studies have suggested that postural sway is controlled by at least two subsystems. Rambling-Trembling analysis is a widely accepted methodology to dissociate the signals generated by these two hypothetical subsystems. The core assumption of this method is based on the equilibrium point hypothesis which suggests that the central nervous system preserves upright standing by transiently shifting the center of pressure (COP) from one equilibrium point to another. The trajectory generated by this shifting is referred to as rambling and its difference from the original COP signal is referred to as trembling. In this study we showed that these two components of COP are differentially affected when standing with external loads. Using Detrended Fluctuation analysis, we compared the pattern of these two signals in different configurations of body loading. Our findings suggest that by applying an external load, the dynamics of the trembling component is altered independently of the area of postural sway and also independently of the rambling component. The dynamics of rambling changed only during the backloading condition in which the postural sway area also substantially increased. It can be suggested that during loaded standing, the trembling mechanism (which is suggested to be activated by peripheral mechanisms and reflexes) is altered without affecting the central influence on the shifts of the equilibrium point.

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Stride Interval Dynamics Are Altered when Two Individuals Walk Side by Side

Jeff A. Nessler, Tomas Gonzales, Eric Rhoden, Matthew Steinbrick, and Charles J. De Leone

The purpose of this study was to examine the effects of interpersonal synchronization of stepping on stride interval dynamics during over-ground walking. Twenty-seven footswitch instrumented subjects walked under three conditions: independent (SOLO), alongside a partner (PAIRED), and side by side with intentional synchronization (FORCED). A subset of subjects also synchronized stepping to a metronome (MET). Stride time power spectral density and detrended fluctuation analysis revealed that the rate of autocorrelation decay in stride time was similar for both the SOLO and PAIRED conditions, but was significantly reduced during the FORCED and MET conditions (p=0.03 & 0.002). Stride time variability was also significantly increased for the FORCED and MET conditions (p<0.001). These data suggest that forced synchronization of stepping results in altered stride interval dynamics, likely through increased active control by the CNS. Passive side by side stepping, where synchronization is subconscious, does not appreciably alter stepping in this manner.

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Restoring Walking Complexity in Older Adults Through Arm-in-Arm Walking: Were Almurad et al.’s (2018) Results an Artifact?

Samar Ezzina, Clément Roume, Simon Pla, Hubert Blain, and Didier Delignières

and/or lag 1, depending of the leader/follower statuses within the dyad ( Roume et al., 2018 ). Note that WDCC correlation coefficients could take values in the interval [−1, 1]. We used the detrended fluctuation analysis (DFA, Peng et al., 1994 ) to estimate the complexity of each data series. For

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Postural Sway and Muscle Activity Dynamics of Upright Standing on Sloped Surfaces

Jacey Baldridge and Adam C. King

analyzed using a detrended fluctuation analysis that indexed the fractal dimension of a time series. To compute the output variable of alpha, the COP time series was centered to a zero mean and integrated and then detrended. Next, the data were divided into a number of time scales having equal number of

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Increased Speed Elicited More Automatized but Less Predictable Control in Cyclical Arm and Leg Movements

Werner A.F. van de Ven, Jurjen Bosga, Wim Hullegie, Wiebe C. Verra, and Ruud G.J. Meulenbroek

(PSD) analysis and detrended fluctuation analysis. Hausdorff et al. ( 1995 ) found long-range correlations in stride interval time series during walking. Both PSD and detrended fluctuation analysis analyses revealed pink noise within the stride interval time series during walking. Pink noise, analyzed

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Bimanual Coordination in a Whole-Body Dynamic Balance Sport, Slacklining: A Comparison of Novice and Expert

Kentaro Kodama, Hideo Yamagiwa, and Kazuhiro Yasuda

et al., 2020 ). In this previous work, researchers acquired a time series of the acceleration of both ankles and conducted a detrended fluctuation analysis to assess the temporal structure. Their results showed a persistent temporal structure of velocity fluctuations in both ankles and revealed