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Journal ArticleDOI

The test-retest reliability of centre of pressure measures in bipedal static task conditions--a systematic review of the literature.

01 Oct 2010-Gait & Posture (Elsevier)-Vol. 32, Iss: 4, pp 436-445
TL;DR: The studies reviewed show that bipedal static COP measures may be used as a reliable tool for investigating general postural stability and balance performance under specific conditions and recommendations for maximizing the reliability of COP data are provided.
About: This article is published in Gait & Posture.The article was published on 2010-10-01 and is currently open access. It has received 500 citations till now. The article focuses on the topics: Reliability (statistics).

Summary (2 min read)

INTRODUCTION

  • Shortly after the Securities Act of 19331 (“1933 Act”) became law, critics from the securities industry charged that the civil liability provisions created by Section 11 of the Act made it excessively draconian.
  • This article is an effort to rethink civil liability in capital-raising transactions by large capitalization issuers.

DIGRESSION: WHO SHOULD SET THE STANDARDS?

  • Before turning to the substance of reform, the authors should consider seriously what many scholars are recommending as a threshold jurisdictional matter: eliminating exclusive federal jurisdiction over capital-raising disclosure standards and enforcement.
  • A threshold issue, of course, is whether the market would rationally “price” competing legal regimes.
  • The resulting pressures on how the exchanges formulate disclosure and enforcement policy would be unpredictable and not necessarily conducive to the public good.

CONTINUOUS DISCLOSURE LIABILITY UNDER THE 1934 ACT

  • Act of 1934 is designed to promote the integrity of stock prices for publicly-traded issuers.
  • 45 Faced with this, issuers may perceive that the risk of detection and sanction in any given case is far less than certain, and somewhat arbitrary, insofar as even good-faith compliance can trigger litigation that has to be settled.
  • Furthermore, as I have argued elsewhere, various individual and organizational biases in risk perception can also lead to disclosure failures.
  • If the authors move toward a model of annual certification of disclosure accuracy, the initial question is whether this should be a wholly new system of certification, as both Fox and Cox recommend, or simply an expansion of the current annual certification required under the 1934.

REVISING SECTION 11: LIABILITY UNDER THE SECURITIES ACT OF 1933

  • The current integrated disclosure structure for 1933.
  • It would not necessarily justify the prevailing system of strict liability for the issuer and due diligence liability for signatory officers and the company’s inside directors.
  • Underwriter liability is maintained, but the definition of what constitutes due diligence is modified in certain kinds of transactions to “take account of” the collapsed timing attendant to short-form offerings.
  • 111. See Donald Langevoort, Information Technology and the Structure of Securities Regulation, 98 HARV.
  • Because Section 12(a)(2) uses a negligence standard, this was thought to impose some sort of due diligence obligations on private offerings, though it was unclear precisely how much diligence was due.

CONCLUSION

  • There can be no successful reform of the system of capital-raising regulation in the United States without rethinking the liability regime.
  • To be sure, this is a difficult task: A strict system of securities fraud liability under the Securities Act has been a signature feature of American securities regulation since the 1930s, and questioning it can easily start the process of unraveling the whole set of assumptions under the 1933 Act.
  • It is similar to insider trading regulation, a core element of the identity of their system of regulation.
  • 122 Notwithstanding my strong commitment to aggressive regulation generally, reform of the sort outlined here is long overdue and can readily be accomplished in a way that does not unnecessarily compromise investor protection.
  • 122. See Donald C. Langevoort, Rereading Cady, Roberts: The Ideology and Practice of Insider Trading Regulation, 99 COLUM.

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Citations
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Journal ArticleDOI
TL;DR: Patients with NSLBP exhibit greater postural instability than healthy controls, signified by greater COP excursions and a higher mean velocity, and the decreased postural stability in NSL BP sufferers seems unrelated to the exact location and pain duration.
Abstract: Over the past 20 years, the center of pressure (COP) has been commonly used as an index of postural stability in standing. While many studies investigated COP excursions in low back pain patients and healthy individuals, no comprehensive analysis of the reported differences in postural sway pattern exists. Six online databases were systematically searched followed by a manual search of the retrieved papers. The selection criteria comprised papers comparing COP measures derived from bipedal static task conditions on a force-plate of non-specific low back pain (NSLBP) sufferers to those of healthy controls. Sixteen papers met the inclusion criteria. Heterogeneity in study designs prevented pooling of the data so only a qualitative data analysis was conducted. The majority of the papers (14/16, 88%) concluded that NSLBP patients have increased COP mean velocity and overall excursion as compared to healthy individuals. This was statistically significant in the majority of studies (11/14, 79%). An increased sway in anteroposterior direction was also observed in NSLBP patients. Patients with NSLBP exhibit greater postural instability than healthy controls, signified by greater COP excursions and a higher mean velocity. While the decreased postural stability in NSLBP sufferers further appears to be associated with the presence of pain, it seems unrelated to the exact location and pain duration. No correlation between the pain intensity and the magnitude of COP excursions could be identified.

281 citations


Cites background or methods from "The test-retest reliability of cent..."

  • ...With few exceptions [2, 20, 23, 31], most of the studies conducted the trials under visual deprivation while only four [24, 28, 32, 38] applied a sampling duration that has shown sufficient reliability [36]....

    [...]

  • ...combination with the appropriate number of recordings (3–5) showed to yield reliable data for most COP parameters such as mean velocity (mVel) or area [32, 36, 37]....

    [...]

  • ...Table 3 gives an overview of how the studies included meet the ideal experimental setup for reliable data [36]....

    [...]

  • ...The reliability of COP measurements is determined by factors such as sampling duration, sampling frequency and number of trials [36]....

    [...]

Journal ArticleDOI
TL;DR: After careful consideration it was decided that the recommendations made in the previous Standardization proposal in 1983 regarding environmental conditions should be maintained.

253 citations

Journal ArticleDOI
TL;DR: Biofeedback-based Wii training led to marked improvements in maximal leg muscle strength (maximal voluntary contraction; rate of force development) and overall functional performance in community-dwelling older adults.
Abstract: Background. Older adults show increased risk of falling and major risk factors include impaired lower extremity muscle strength and postural balance. However, the potential positive effect of biofeedback-based Nintendo Wii training on muscle strength and postural balance in older adults is unknown. Methods. This randomized controlled trial examined postural balance and muscle strength in community-dwelling older adults (75±6 years) pre- and post-10 weeks of biofeedback-based Nintendo Wii training (WII, n = 28) or daily use of ethylene vinyl acetate copolymer insoles (controls [CON], n = 30). Primary end points were maximal muscle strength (maximal voluntary contraction) and center of pressure velocity moment during bilateral static stance. Results. Intention-to-treat analysis with adjustment for age, sex, and baseline level showed that the WII group had higher maximal voluntary contraction strength (18%) than the control group at follow up (between-group difference = 269 N, 95% CI = 122; 416, and p = .001). In contrast, the center of pressure velocity moment did not differ (1%) between WII and CON at follow-up (between-group difference = 0.23mm2/s, 95% CI = −4.1; 4.6, and p = .92). For secondary end points, pre-to-post changes favoring the WII group were evident in the rate of force development (p = .03), Timed Up and Go test (p = .01), short Falls Efficacy Scale-International (p = .03), and 30-second repeated Chair Stand Test (p = .01). Finally, participants rated the Wii training highly motivating at 5 and 10 weeks into the intervention. Conclusions. Biofeedback-based Wii training led to marked improvements in maximal leg muscle strength (maximal voluntary contraction; rate of force development) and overall functional performance in community-dwelling older adults. Unexpectedly, static bilateral postural balance remained unaltered with Wii training. The high level of participant motivation suggests that biofeedback-based Wii exercise may ensure a high degree of compliance to home- and/or community-based training in community-dwelling older adults. Language: en

193 citations


Cites methods from "The test-retest reliability of cent..."

  • ...Postural balance testing comprised two successive 60-second trials (analyzed data collapsed into mean values) separated by a 30-second rest period (36)....

    [...]

Journal ArticleDOI
TL;DR: This work features a comprehensive and consistent overview of the methods for elliptic area approximation contrasting general principles of confidence and prediction regions and recommends the usage of the prediction ellipse, as far as it is demonstrated that confidence ellipses emerge to be inappropriate for posturographic scatter evaluation.

133 citations


Cites methods from "The test-retest reliability of cent..."

  • ...As 10 Hz is assumed to be an adequate cutoff value for a low-pass filter in posturography [27,28], we recommend subsequent to the filtering, a downsampling of 20 Hz prior to the analysis....

    [...]

Journal ArticleDOI
TL;DR: A systematic review of the literature shows that postural deficit may be dependent on experimental conditions in which patients with LBP have been assessed, and that between-group differences did not increase with increased complexity of sensory manipulations.

122 citations


Cites methods from "The test-retest reliability of cent..."

  • ...To enhance reliability, it has been recommended to use a minimum sampling duration of 90 s in combination with 3–5 repetitions [48]....

    [...]

References
More filters
Journal ArticleDOI
TL;DR: In this article, the authors present guidelines for choosing among six different forms of the intraclass correlation for reliability studies in which n target are rated by k judges, and the confidence intervals for each of the forms are reviewed.
Abstract: Reliability coefficients often take the form of intraclass correlation coefficients. In this article, guidelines are given for choosing among six different forms of the intraclass correlation for reliability studies in which n target are rated by k judges. Relevant to the choice of the coefficient are the appropriate statistical model for the reliability and the application to be made of the reliability results. Confidence intervals for each of the forms are reviewed.

21,185 citations


"The test-retest reliability of cent..." refers background or methods in this paper

  • ...For the purpose of this review, we used the definition stated in the classic Shrout and Fleiss [13] paper, regarding an ICC≥0....

    [...]

  • ...The most commonly applied statistical tests were different models of the intra-class correlation coefficient (ICC) [13] and the coefficient of variation (CV)....

    [...]

  • ...Recent studies suggest that the COP time series may represent the dynamics of a nonlinear (chaotic) system [31] that may be characterized using fractal dimension [13,19,30] and Stabilogram Diffusion Analysis (SDA) [30,32]....

    [...]

  • ...While most used models described originally by Shrout and Fleiss [13], others again employed modified versions [14]....

    [...]

Journal ArticleDOI
TL;DR: In this review, the basics of classic reliability theory are addressed in the context of choosing and interpreting an ICC and how the SEM and its variants can be used to construct confidence intervals for individual scores and to determine the minimal difference needed to be exhibited for one to be confident that a true change in performance of an individual has occurred.
Abstract: Reliability, the consistency of a test or measurement, is frequently quantified in the movement sciences literature. A common metric is the intraclass correlation coefficient (ICC). In addition, the SEM, which can be calculated from the ICC, is also frequently reported in reliability studies. However, there are several versions of the ICC, and confusion exists in the movement sciences regarding which ICC to use. Further, the utility of the SEM is not fully appreciated. In this review, the basics of classic reliability theory are addressed in the context of choosing and interpreting an ICC. The primary distinction between ICC equations is argued to be one concerning the inclusion (equations 2,1 and 2,k) or exclusion (equations 3,1 and 3,k) of systematic error in the denominator of the ICC equation. Inferential tests of mean differences, which are performed in the process of deriving the necessary variance components for the calculation of ICC values, are useful to determine if systematic error is present. If so, the measurement schedule should be modified (removing trials where learning and/or fatigue effects are present) to remove systematic error, and ICC equations that only consider random error may be safely used. The use of ICC values is discussed in the context of estimating the effects of measurement error on sample size, statistical power, and correlation attenuation. Finally, calculation and application of the SEM are discussed. It is shown how the SEM and its variants can be used to construct confidence intervals for individual scores and to determine the minimal difference needed to be exhibited for one to be confident that a true change in performance of an individual has occurred.

3,992 citations


"The test-retest reliability of cent..." refers background in this paper

  • ...The issue with the described heterogeneity of the chosen ICC models is that, depending on the data, differentmodels are likely to yield varying results [20]....

    [...]

  • ...application in test–retest reliability studies is often discouraged for its inability to detect systematic error [20]....

    [...]

  • ...Conversely, even in the presence of low inter-participant variability, small test–retest variations may cause low ICC value [20,21]....

    [...]

Journal ArticleDOI
TL;DR: The inverted pendulum model permitted us to understand the separate roles of the two mechanisms during these critical unbalancing and rebalancing periods and confirmed the critical importance of the hip abductors/adductors in balance during all phases of standing and walking.

2,940 citations


"The test-retest reliability of cent..." refers background in this paper

  • ...4 1) Body segment displacement refers to the change in position of body segments such head or trunk during adaptive movements in order to maintain balance [4]....

    [...]

  • ...While COP theoretically completely coincides with COM at low sway frequencies below 1Hz [4], its displacement during sway always exceeds that of the COM [7]....

    [...]

Journal ArticleDOI
TL;DR: It was concluded that mean displacement velocity seems to be the most informative parameter in most situations, and sum of maximal deviation time (SDT) was proposed showing complete discrimination between frail elderly and other old subjects when obtained while visual input was suppressed.

578 citations


"The test-retest reliability of cent..." refers background or methods in this paper

  • ...It has been shown that COP measures and its reliabilities vary depending on both the acquisition and cut-off frequency chosen [30,36]....

    [...]

  • ...1% greater when sampling frequencies of 50 Hz were used compared to 10 Hz [30] as it would be expected with more data points describing the shape of the COP....

    [...]

  • ...SDA assumes that COP can be modeled as a system of correlated, random walks, thereby addressing the dynamic nature of COP motion, its analysis is based on the random selection of two pairs of COP data [30]....

    [...]

  • ...While the evaluation of COP excursions is a commonly used method for measuring postural stability [21–38] no standardization of thismethod exists....

    [...]

  • ...[30–38])....

    [...]

Journal ArticleDOI
TL;DR: Preseason balance measurement (postural sway) served as a predictor of ankle sprain susceptibility in a cohort of high school basketball players to help reduce the risk of these injuries and furthermore save health care costs.
Abstract: ObjectiveThe purpose of this study was to determine if a preseason measurement of balance while in a unilateral stance could predict susceptibility to ankle injury in a cohort of high school basketball players. Predicting risk for ankle injury could be important in helping to reduce the risk of thes

573 citations


"The test-retest reliability of cent..." refers background in this paper

  • ...In sport, problemswith balancemay lead to serious injuries [1]....

    [...]

  • ..., 2 0 0 8 [1 6 ] B P , E C /F , n a rr o w st a n ce M P F, m V e l, R M S , a re a , D FA...

    [...]

  • ...3 3 a re in te rp re te d a s a cc e p ta b le [1 5 ]....

    [...]

Frequently Asked Questions (15)
Q1. What are the contributions mentioned in the paper "The test-retest reliability of centre of pressure measures in bipedal static task conditions a systematic review of the literature" ?

In this paper, the reliability of traditional COP parameters was investigated and the authors concluded that the test-retest reliability depends primarily on factors such as the number of trial recordings and duration rather than the selection of particular COP parameters. 

During balance control, the muscle action appears to be an anticipatory feed-forward mechanism that is determined by an internal model of the inverted pendulum and acts in the long-term. 

it has been stated that averaging two [35], three [24], four [38] or seven [17] trials yields acceptable reliability for the majority of COP parameters. 

The test-retest reliability depends primarily on factors such as the number of trial recordings and duration rather than the selection of particular COP parameters. 

While intra-trial and inter-trial reliability needs to be discussed, inter-rater reliability is unlikely to be of concern due to the simplicity of the apparatus, task and instructions. 

The statisticsAs with the general experimental setups, an equally heterogeneous selection of statistics for describing the reliability was used, including the coefficient of variation (CV), generalizability coefficient (GC) as well as Pearson’s correlation coefficient (PCC). 

In addition, the trend by recent papers to report higher reliability estimates under eyes closed conditions may at least partially be attributed to improved technicalequipment, a more rigorous scientific procedures in conducting the studies or a higher true score variability. 

In the literature, sampling frequencies ranging from 10-200Hz have been reported [9,16,17,22,27,37-41] and it seems that the reported variations in COP reliability across similar experimental setups are at least partially due to the different frequencies chosen. 

While the evaluation of COP excursions is a commonly used method for measuring postural stability [21-38] no standardization of this method exists. 

Of these, one of the most commonly used tools to investigate this complex balance system is the stabilogram, which is a measure of the time behaviour of the COP of a person positioned on top of a force platform consisting of a rigid plate supported by force transducers. 

The complementation of this mechanism by the feed-forward control is necessary as the muscle stiffness itself is not sufficient to stabilize the body if the critical level of displacement is reached [2] 

In addition, papers that were anecdotal, speculative or editorial in nature or studies that employed dynamic task conditions such as one-leg hopping, walking or some form of translation of the force platform were excluded. 

In addition to trial duration, the number of repetitions needed to gain acceptable reliability (r≥0.75) also varies with the COP parameter under investigation and conflicting results have been reported. 

For COP mean velocity for example, just two 120sec trials were required to reach an ICC2,1 >0.90, whereas COP range and RMS needed four 120sec trials to reach similar reliability levels [22]. 

The authors recommend the following methods should be employed: Regarding the data acquisition duration, the results suggest that a minimum of 90sec is required to reach acceptable reliability for all traditional COP parameters in healthy subjects. 

Trending Questions (1)
What are normative values for COP mean velocity, variability, ellipse area and amplitude?

The paper does not provide normative values for COP mean velocity, variability, ellipse area, and amplitude.