Root Mean Square Slope Research Articles

Insights into central and peripheral factors affecting the “oxidative performance” of skeletal muscle in aging

During exercises with relatively small muscle masses, limitations to exercise performance by the cardiovascular system should be significantly reduced, allowing one to fully-test the "oxidative potential" of the investigated muscles. Ten elderly males (E, 77.8 +/- 2.9 years [x +/- SD]) and eight young controls (Y, 26.6 +/- 3.0) underwent incremental exercises to voluntary exhaustion on a dynamic leg-extension (dominant limb) machine (knee-extension, KE) and on a cycloergometer (CYCLO). During KE the load was increased every 3 min to loads corresponding to 20, 40 and 60% of the force of one-repetition maximum (1RM). The following variables were determined (vastus lateralis muscle): concentration changes of deoxygenated haemoglobin and myoglobin (Delta[deoxy(Hb + Mb)]) by near-infrared spectroscopy (NIRS), expressed as percentage of the maximal value obtained during transient limb ischemia, and taken as an index of O2 extraction; root mean square (RMS) and median power frequency (MDF) by electromyography. The total lifted load during KE and peak workload during CYCLO were lower in E versus Y (620.4 +/- 321.9 kg vs. 1347.4 +/- 458.7; 113.5 +/- 23.9 W vs. 224.3 +/- 41.0, respectively). During CYCLO Delta[deoxy(Hb + Mb)] peak (i.e. the value determined at exhaustion) was lower in E (44.5 +/- 17.7%) versus Y (67.1 +/- 22.9), whereas during KE Delta[deoxy(Hb + Mb)] peak was higher in E (56.8 +/- 20.9%) versus Y (38.6 +/- 15.8). "Thresholds", that is abrupt increases in RMS slopes, were detected in Y but not in E, suggesting less recruitment or a preferential atrophy of type 2 fibers in the elderly. These findings, associated with the preserved capacity of O2 extraction, suggest a shift towards oxidative metabolism in skeletal muscles of 78 year-old subjects, which could preserve, at least in part, their capacity to carry out exercise.

Generalized fractal‐based laws for scattering from planetary surfaces: A unifying scale‐explicit paradigm

Fractal‐based scattering laws, when used to fit radar observations, provide an estimate for surface root‐mean‐square (RMS) slope that is explicit in its scale dependence. Furthermore, fractal‐based laws outperform, in a minimum residual sense, the widely used Hagfors' and Gaussian laws, which they subsume as special cases when their Hurst exponent parameter, H, takes the values 1/2 and 1, respectively. The use of a fixed, scale‐independent value for H restricts the modeling capacity of the fractal‐based laws. Allowing H to be a function of the horizontal scale R leads to a generalized scattering law that unifies the fractal‐based laws with fixed H and the conventional Hagfors, Gaussian, and exponential laws. A new procedure employing the generalized fractal‐based laws is applied to Magellan altimetry data for the surface of Venus at 12.6 cm −λ. Near‐nadir Magellan backscatter data are modeled using a linear combination of two conventional scattering laws in order to obtain statistically significant fits. The Hankel transform is used to obtain a scale‐explicit interpretation that gives the surface RMS slope as a function of horizontal scale. An analysis of the scattering integral gives insights into the range of scales which are effective in the scattering process and for which the RMS slope estimate can be considered reliable.

Gender‐specific differences in electromyographic changes and perceived pain induced by experimental muscle pain during sustained contractions of the upper trapezius muscle

The aim of the study was to investigate gender-specific differences in the pain-induced alterations of muscle activity during sustained contractions of the upper trapezius muscle. Surface electromyographic (EMG) signals were recorded bilaterally from the upper trapezius muscles of healthy volunteers (10 men and 9 women). The subjects held the arms at 90 degrees abduction for 5 s (short contraction) and 3 min (sustained contraction). These contractions were performed before, during, and after injection of 0.5 ml of hypertonic saline (5.8%) bilaterally in the upper trapezius muscles. Injection of isotonic saline (0.9%) served as control. The root mean square (RMS) and mean power frequency (MPF) were computed from the EMG signals and normalized to the values obtained during maximal voluntary contractions. In the short contractions, injection of hypertonic saline, but not isotonic saline, induced a less pronounced decrease in RMS in women than men, and a significant decrease in MPF in men but not women. In the sustained contractions, RMS slope increased and MPF slope decreased (less negative) with muscle pain in men but not women. It was concluded that the pain-induced changes in motor control strategies during sustained contractions differ in men and women, which may partly explain gender differences in the incidence of musculoskeletal pain.

The value of electromyography of the lumbar paraspinal muscles in discriminating between chronic-low-back-pain sufferers and normal subjects.

The authors studied the surface electromyographic (EMG) spectrum of the paraspinal muscles of 350 subjects. They were classified by their history as normal (n=175), chronic low back pain (n=145), or past history (n=30). They pulled upwards on a floor-mounted load cell at two-thirds of their maximum voluntary contraction for 30 s, while the EMG was measured from the paraspinal muscles at the L4/L5 level. From the EMG signal the root-mean-square (RMS) was calculated. Power spectrum analysis allowed calculation of the median frequency slope, the initial median frequency (IMF), modal frequency, peak amplitude and spectral width at half peak amplitude (half-width). All of the variables of the chronic group were significantly different from the normal group, except the median frequency slope, RMS slope and mode. Half-width, age and maximum voluntary contraction were shown to be independent predictors of back pain classification. Half-width classified the subjects with a sensitivity of 0.65 and a specificity of 0.75.

RMS slope of exponentially correlated surface roughness for radar applications

In radar signature analysis, the root mean square (RMS) surface slope is utilized to assess the relative contribution of multiple scattering effects. For an exponentially correlated surface, an effective RMS slope can be determined by truncating the high frequency tail of the roughness spectrum. The choice of the cutoff frequency and the effect on surface scattering simulations are discussed.

Evaluation of the root-mean-square slope of 3D surface topography

Based on the application of fractal geometry theory, a quantitative evaluation method of root-mean-square (RMS) slope of 3D homogeneous and stochastic surface topography is proposed, by means of the concept of surface spectral moments. Through the FFT of discrete data from the profiles measured by a Talysurf-5 contact stylus instrument, the power spectrum and the fractal dimensions of the profiles are obtained. Furthermore, the second order spectral moments of the profiles and the surfaces are found. These parameters are used to define the evaluation measure of RMS slope of the surface. By the experiments for ground and fine turned specimen, the results confirm the correctness of this method.

Magellan: Electrical and Physical Properties of Venus' Surface

Magellan probes Venus' surface by 12.6-cm-wavelength vertical and oblique radar scattering and measures microwave thermal emission. Emissivity and root-meansquare slope maps between 330 degrees and 30 degrees E and 90 degrees N and 80 degrees S are dissimilar, although some local features are exceptions. Inferred surface emissivities typically are approximately 0.85, but vary from approximately 0.35 at Maxwell to approximately 0.95 northeast of Gula Mons and other locations. Lowest emissivities appear in topographically high areas; this relation suggests that a phase change or differences in chemical weathering occur at about 6055-kilometer radius. Initial results indicate that there are significant variations in the surface scattering function.