A method to concatenate multiple short time series for evaluating dynamic behaviour during walking

Novel approaches in Extended Principal Component Analysis to compare spatio-temporal patterns among multiple image time series

Inter-rater reliability of shoulder measurements in middle-aged women

Foot anthropometric dimensions may influence moment arm lengths and respective moments of force resisted by skeletal muscles. Depending upon circumstances, absolute or normalized expressions of these measures may have greater utility. PURPOSE: To determine the stability reliability and precision of two absolute and normalized moment arm lengths of the foot. METHODS: Longitudinal foot dimensions were obtained in 27 men and 27 women including the anterior-posterior distance between the posterior calcaneus and: 1) talocrural (TALO) and 2) metatarsophalangeal (META) joints. Bilateral measurements of seated subjects were performed using a digital sliding caliper. Absolute dimensions were normalized to height and lower-limb length (LLL, greater trochanter to lateral malleolus). Measures were obtained twice, separated by either 24 or 48 hours. Stability reliability was determined using intraclass correlation coefficient (ICC), and precision using standard error of measurement (SEM). RESULTS: The scatter of points around the trend lines for all 54 subjects combined appear to be uniform and the separate SEMs for men and women are similar. Assuming homoscedasticity, data are reported for the combined groups. For the 3 bilateral expressions of the 2 foot dimensions (12 measures), the low and high means (standard deviation) are reported for each session as well as the ICC and SEM for the pair of sessions. For TALO, means were 5.1 (0.4) and 5.2 (0.5) cm, ICCs were 0.79 and 0.82, and SEMs were 0.2 and 0.2. When normalized to height, means were 0.030 (0.002) and 0.030 (0.002) cm/cm height, ICCs were 0.65 and 0.75, and SEMs were 0.001 and 0.001. When normalized to LLL, means were 0.062 (0.005) and 0.063 (0.005) cm/cm LLL, ICCs were 0.69 and 0.73, and SEMs were 0.003 and 0.003. For META, means were 17.0 (1.2) and 17.1 (1.1) cm, ICCs were 0.97 and 0.98, and SEMs were 0.2 and 0.2. When normalized to height, means were 0.098 (0.002) and 0.100 (0.002) cm/cm height, ICCs were 0.92 and 0.94, and SEMs were 0.001 and 0.001. When normalized to LLL, means were 0.205 (0.010) and 0.208 (0.011) cm/cm LLL, ICCs were 0.92 and 0.92, and SEMs were 0.003 and 0.003. CONCLUSIONS: Surface landmarks and digital calipers can be used to precisely measure the 2 foot dimensions in question, whether or not they are normalized. Reliability is high for the META dimension, and lower for the TALO dimension. Meticulous data acquisition protocols are required to acquire potentially useful data.

Background: Assessing walking impairment in those with multiple sclerosis (MS) is common, however little is known about the reliability, precision and clinically important change of walking outcomes. Objective: The purpose of this study was to determine the reliability, precision and clinically important change of the Timed 25-Foot Walk (T25FW), Six-Minute Walk (6MW), Multiple Sclerosis Walking Scale-12 (MSWS-12) and accelerometry. Methods: Data were collected from 82 persons with MS at two time points, six months apart. Analyses were undertaken for the whole sample and stratified based on disability level and usage of walking aids. Intraclass correlation coefficient (ICC) analyses established reliability: standard error of measurement (SEM) and coefficient of variation (CV) determined precision; and minimal detectable change (MDC) defined clinically important change. Results: All outcome measures were reliable with precision and MDC varying between measures in the whole sample: T25FW: ICC=0.991; SEM=1 s; CV=6.2%; MDC=2.7 s (36%), 6MW: ICC=0.959; SEM=32 m; CV=6.2%; MDC=88 m (20%), MSWS-12: ICC=0.927; SEM=8; CV=27%; MDC=22 (53%), accelerometry counts/day: ICC=0.883; SEM=28450; CV=17%; MDC=78860 (52%), accelerometry steps/day: ICC=0.907; SEM=726; CV=16%; MDC=2011 (45%). Variation in these estimates was seen based on disability level and walking aid. Conclusion: The reliability of these outcomes is good and falls within acceptable ranges. Precision and clinically important change estimates provide guidelines for interpreting these outcomes in clinical and research settings.

Slowness plays a crucial role in geriatric assessments and is closely linked to frailty. In an attempt to propose alternatives to gait speed, the Moberg picking-up test (MPUT) was proposed for measuring slowness in older adults. Concurrently, we developed the Twelve-ball test (TBT) as a novel and simplified alternative to the MPUT. This study aimed to assess and compare the intra-observer and inter-observer repeatability of the MPUT and TBT in a large sample of community dwelling older adults. This study used data from the population-based Lausanne cohort 65+. In 2020, 596 individuals, aged 81-86 years, completed two sets of MPUT or TBT measurements. Intraclass correlation coefficients (ICCs) and 95% confidence intervals (CI) were used to examine intra-observer (two-way mixed-effects model) and inter-observer (one-way random-effects model) relative repeatability of both measurements for either the MPUT or TBT. Absolute repeatability was determined by the standard error of measurement (SEM). Bland-Altman plots were plotted for visual representation of heteroscedasticity. Subgroup analyses were conducted per gender, education, and speed. For the MPUT, intra-observer repeatability was ICC = 0.77 (95% CI 0.65 to 0.84) and SEM = 1.76, while inter-observer repeatability was ICC = 0.74 (95% CI 0.66 to 0.80) and SEM = 1.23. For the TBT, intra-observer repeatability was ICC = 0.89 (95% CI 0.80 to 0.93) and SEM = 0.91, while inter-observer repeatability was ICC = 0.84 (95% CI 0.78 to 0.89) and SEM = 0.91. In all subgroup analyses, the TBT exhibited higher intra-observer and inter-observer repeatability compared to the MPUT. The MPUT and TBT appear reliable in terms of intra- and inter-observer repeatability. However, the assessments of repeatability, considering both relative and absolute consistency, show stronger results in the TBT compared to the MPUT test. With its simplified application, the TBT proves to be a promising measure of slowness in older adults.

Vaginal birth is a risk factor for weakening of the pelvic floor muscles (PFM) and development of pelvic floor dysfunction (PFD). Perineal tears may decrease PFM function. PFM tone can be assessed with surface EMG (sEMG), but reliability studies of sEMG in women with perineal tears are lacking. The aims of this study were to evaluate test-retest and intrarater reliability of sEMG and compare PFM activation between nulliparous and primiparous. A sEMG test-retest was performed in 21 women (12 nulliparous and 9 primiparous with grade II tears) to assess intra-rater reliability during rest and maximal voluntary contraction (MVC) of the PFM. Intraclass Correlation Coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC) were tested. A comparison between nulliparous'and primiparous'PFM activation during rest and MVC was performed. sEMG demonstrated fair reliability in nulliparous (ICC: 0.239; SEM: 5.2; MDC: 14.5) and moderate reliability in primiparous (ICC: 0.409; SEM: 1.5; MDC: 4.2) during rest. For peak MVC very good intrarater reliability was found in nulliparous (ICC: 0.92; SEM: 8.0; MDC: 22.2) and in primiparous (ICC: 0.823; SEM: 8.0; MDC: 22.2). Statistically significant lower PFM activation was found in primiparous women with perineal tear grade II than in nulliparous at rest (mean difference 9.1 µV, 95% confidence interval[CI] 3.0-19.0, p = 0.001), and during MVCpeak (mean difference 50.0 µV, 95% CI 10.0-120.0 p = 0.021). sEMG is reliable when measuring PFM activation in primiparous women with perineal tears grade II. Women with perineal tears grade II have lower PFM activation both during rest and MVC.

Low skeletal muscle area (SMA) and muscle radiation attenuation (MRA) have been associated with poor prognosis in various patient populations. Both non-contrast and contrast CT scans are used to determine SMA and MRA. The effect of the use of a contrast agent on SMA and MRA is unknown. Therefore, we investigated agreement between these two scan options. SMA and MRA of 41 healthy individuals were analysed on a paired non-contrast and contrast single CT scan, and agreement between paired scan results was assessed with use of Bland-Altman plots, intraclass correlation coefficients (ICCs), standard error of measurements (SEM) and smallest detectable differences at a 95% confidence level (SDD95 ). Analyses were stratified by tube voltage. Difference in SMA between non-contrast and contrast scans made with a different tube voltage was 7·0±7·5cm2 ; for scans made with the same tube voltage this was 2·3±1·7cm2 . Agreement was excellent for both methods: ICC: 0·952, SEM: 7·2cm2 , SDD95 : 19·9cm2 and ICC: 0·997, SEM: 2·0cm2 , SDD95 : 5·6cm2 , respectively. MRA of scans made with a different tube voltage differed 1·3±11·3 HU, and agreement was poor (ICC: 0·207, SEM: 7·9 HU, SDD95 : 21·8 HU). For scans made with the same tube voltage the difference was 6·7±3·2 HU, and agreement was good (ICC: 0·682, SEM: 5·3 HU, SDD95 : 14·6 HU). In conclusion, SMA and MRA can be slightly influenced by the use of contrast agent. To minimise measurement error, image acquisition parameters of the scans should be similar.

Changes to the variability within biomechanical signals may reflect a change in the health of the human system. However, for running gait variability measures calculated from wearable device data, it is unknown whether a between-day difference reflects a shift in system dynamics reflective of a change in human health or is a result of poor between-day reliability of the measurement device or the biomechanical signal. This study investigated the reliability of stride time and sacral acceleration variability measures calculated from inertial measurement units (IMUs). Nineteen runners completed six treadmill running trials on two occasions seven days apart. Stride time and sacral acceleration signals were obtained using IMUs. Stride time variability and complexity were calculated using the coefficient of variation (CV) and detrended fluctuation analysis (DFA), respectively. Sacral acceleration regularity was quantified using sample entropy with a range of input parameters m (vector length) and r (similarity threshold). Between-day reliability was assessed using the intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimum detectable change. Stride time CV displayed moderate relative reliability (ICC = 0.672), but with a large absolute minimum detectable change=0.525%, whilst stride time DFA-α displayed poor relative reliability (ICC = 0.457) and yielded large minimum detectable changes (≥ 0.208). Sample entropy displayed good relative reliability in mediolateral and resultant sacral acceleration signals for certain combinations of the parameters m and r, although again with large minimum detectable changes. Researchers should be cognisant of these reliability metrics when interpreting changes in running gait variability measures in clinical contexts.

There is increasing evidence supporting the additional utility of nonlinear techniques such as chaos analysis of heart rate (HR) time series as indictors of prognosis in cardiac patients. Prolongation of rate-corrected QT interval, QTc, is strongly associated with sudden cardiac death. Recent studies of beat-to-beat QT interval variability (QTV) have shown that an increase in QTV is associated with increased sympathetic activity. QTvi, a QT variability index (QT variance corrected for mean QT divided by HR variance corrected for mean HR), is also a predictor of sudden cardiac death. We studied the utility of a measure of chaos, the Largest Lyapunov Exponent (LLE) of beat-to-beat HR and QT time series at baseline and after treatment in patients with congestive heart failure (CHF). We compared beat-to-beat HR and QT interval data in 23 patients with CHF and 19 age-matched normal controls. The ECG data were acquired in lead II configuration at a sampling rate of 1000 Hz. CHF patients had a significantly lower LLE of HR and a significantly higher LLE of QT time series than did normal controls. Clinical improvement in a subgroup of these patients was associated with a decrease in QT-LLE and a decrease in LLEqthr (LLE-QT/LLE-HR). These results demonstrate a decreased chaos of HR and increased chaos of QT time series in patients with CHF suggesting decreased cardiac vagal and increased sympathetic function in patients with CHF. Nonlinear measures may prove to be of additional utility to linear measures as surrogate end points to evaluate treatment effect in these patients.

To describe a novel method for measuring eccentric hip adductor (EHAD) strength during the Copenhagen adduction exercise (CAE) and investigate the test re-test reliability of this measure. Test re-test reliability study. Twenty male athletes aged 24±6 years participated in two data collection sessions 7±2 days apart. During each data collection session, participants performed three maximal effort repetitions of the CAE with their leg supported by an ankle strap hung from a fixed barbell. We attached a commercially available load cell in-series with the ankle strap to measure peak force in Newtons (N) during the eccentric lowering phase of the CAE. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), SEM as a percentage of the mean (SEM%) and minimal detectable change at a 95% confidence interval (MDC95) were calculated for this measure of EHAD strength. Test re-test reliability was good for EHAD strength measured during the CAE on dominant (ICC=0.84; SEM%=3.6%; MDC95=33N) and non-dominant (ICC=0.87; SEM%=3.3%; MDC95=29N) legs. This study provides proof-of-concept that EHAD strength can be measured during the CAE with good test re-test reliability.

Postural stability control performance assessment is necessary in providing important information for individuals who are at risk of falling or who have balance impairment. Instrumented assessment is suggested as a valid and reliable test, but the cost and the difficulty of setup are significant limitations. The aim of this cross-sectional (test-retest reliability) study was to develop and determine the reliability of a low-cost posturography for assessing postural stability control performance during standing. The low-cost posturography was developed with four load cells and an acrylic platform. The center of pressure (COP) displacement and velocity were analyzed using written software. Test-retest reliability was performed with six different standing postural stability tests in twenty healthy volunteers on two different days. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), coefficient of variation (CV), and Bland–Altman plot and limits of agreements (LOA) were used for analyses. The low-cost posturography was accurate (ICC = 0.99, p < 0.001; SEM = 0.003 cm) when compared to the true with calculated X and Y coordinates, with a moderate to excellent test-retest reliability for both COP displacement (ICCs ranged 0.62–0.91, p < 0.05; SEMs ranged 17.92–25.77%) and COP velocity (ICCs ranged 0.62–0.91, p < 0.05; SEMs ranged 18.09–27.69%) in all standing postural stability tests. Bland–Altman plots and LOAs suggested good agreement of tested parameters from the developed low-cost posturography between different days. In conclusion, the developed low-cost posturography had adequate reliability for assessing COP displacement and velocity during standing postural control stability performance tests.

Head posture (HP) is used as part of the clinical examination of patients with neck pain to inform diagnosis, plan treatment, and monitor progress. For related information to be interpreted correctly, clinicians need to know how much of the variation in HP between measurements can be attributed to a change in the patient condition and how much is due to measurement error and/or biological variation. The aim of this study was to investigate the variability of angular measurements indicative of forward HP, head extension, and side flexion within a session, within a day, and over a 7-day period. Angles were calculated from 27 participants in three sessions over a period of 7 days through digitization of video images. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) showed that forward HP (ICC between 0.82 and 0.91; SEM between 1.42° and 1.70°) and side flexion (ICC between 0.63 and 0.85; SEM between 0.83° and 1.27°) were stable within a session, within a day, and over a 7-day period. Head extension was found to be less stable (ICC between 0.71 and 0.83; SEM between 2.69° and 3.72°). Time of day did not appear to influence forward HP, side flexion, or head extension.

SUMMARY The problem of testing for periodicities in multiple time series is considered. The test statistic proposed is based on the Euclidean norm of the matrix of periodograms. We first obtain the exact distribution of our test statistic under the hypothesis that observations are taken from an n-vector time series consisting of independent series of independent normal variables. We extend the theory to normal linear series with a specified spectral density matrix and then show that a suitable estimate can be used to replace this matrix in our test statistic. These results are asymptotic in nature. Extreme value theorems are stated for the case of normal variates and it is shown that the distributions for nonnormal series can be approximated adequately by those for normal series. An exact test for periodic components in an univariate time series was first proposed by Fisher (1929) who considered the null hypothesis of normal white noise. The test was based upon the maximum of a set of periodogram ordinates each divided by their sum, the division making it unnecessary to know in advance the variance of the components of the series. The use of the rth largest of these ordinates, r > 1, in testing for periodicities was also discussed by Fisher (1940). Whittle (1951, p. 101) showed how one could apply the Fisher tests to normal linear series provided the number of observations was large and one could specify the spectral density for the series. Hannan (1961) proposed a modification to this test that removed the necessity of knowing beforehand the spectral density function. Nicholls (1967) proposed a variation on Hannan's test statistic that improves its power under certain alternatives. Some extreme value results for periodogram ordinates were given by Walker (1965), who also demonstrated that dropping the normality condition has little effect on the large sample distributions, at least in the upper tails. In the sequel we consider the problem of testing for periodicities in multiple time series and pursue a course that parallels the historical development for univariate series as outlined in the paragraph above. Our tests are based on the Euclidean norm of the matrix of periodo- grams. In this connection Nicholls (1969) has discussed a test for discrete mass in a cross- spectrum. We consider real, discrete time parameter, n-vector, time series, Z(t) (t = 0, + 1, + 2, ...), where Z(t) = It+m(t) +X(t), with ,u+m(t) being a mean value function and X( ) being a weakly stationary, zero mean, time series possessing a spectral density matrix fxx(A) with tr{fxx(A)} <1 M < oo (JAI < 7r). We also assume the existence of a moving average representation 00 wo,t) , CO v - )

The ability of the locomotor system to maintain continuous walking despite very small external or internal disturbances is called local dynamic stability (LDS). The importance of the LDS requires constantly working on different aspects of its assessment method which is based on the short-term largest Lyapunov exponent (LLE). A state space structure is a vital aspect of the LDS assessment because the algorithm of the LLE computation for experimental data requires a reconstruction of a state space trajectory. The gait kinematic data are usually one- or three-dimensional, which enables to construct a state space based on a uni- or multivariate time series. Furthermore, two variants of the short-term LLE are present in the literature which differ in length of a time span, over which the short-term LLE is computed. Both a state space structure and the consistency of the observations based on values of both short-term LLE variants were analyzed using time series representing the joint angles at ankle, knee, and hip joints. The short-term LLE was computed for individual joints in three state spaces constructed on the basis of either univariate or multivariate time series. Each state space revealed walkers' locally unstable behavior as well as its attenuation in the current stride. The corresponding conclusions made on the basis of both short-term LLE variants were consistent in ca. 59% of cases determined by a joint and a state space. Moreover, the authors present an algorithm for estimation of the embedding dimension in the case of a multivariate gait time series.

A.GreenExploring Language Assessment and Testing: Language in ActionRoutledge Introductions to Applied Linguistics2013978-0415597241269 pp