Root Mean Square Slope Research Articles

The legged asteroid probe: Touchdown on locally refined rocky terrains and landing safety assessment

Studying the landing of a legged probe on asteroids with widely distributed rocks is of great significance. However, the landing safety of legged probes with flexible appendages (solar panels and touchdown legs) on the rocky terrain of asteroids is still unclear. In this study, we establish a complete rigid-flexible coupling touchdown dynamics model for an asteroid probe, and propose a new method for constructing locally refined rocky terrain. Moreover, two criteria for safe touchdown of the probe are established. Monte Carlo simulations are performed to analyze the landing success probability of the probe on different locally refined rocky terrains. The validity of the rock generation method and safety assessment is confirmed through repeated landing simulations. The simulation results show that the effect of the flexible appendages on the probe landing process cannot be ignored. With the same propulsion force of the probe, the landing success probability first increases and then decreases with increasing probe mass. Based on the original terrain, increases in rock size, quantity and power- index lead to the increase of the root-mean-square (RMS) height and RMS slope of rocky terrain, and then cause a decrease in the landing success probability of the legged probe. The results are expected to provide guidance for asteroid touchdown missions.

Effect of roughness small scales on the adhesion of randomly rough surfaces with high fractal dimension

Surface roughness affects several tribological phenomena like adhesion. In this work, JKR-like experimental tests were performed between Polydimethylsiloxane (PDMS) spherical samples and flat glass substrates with different surface roughness properties. Data were interpreted in the light of classical JKR theory. We find that adhesion is destroyed by roughness in agreement with the most common and well-known results in the literature. However, from the analysis of the Power Spectral Density (PSD) of the surfaces, it emerges that the smaller scales of roughness have a greater influence on the surface adhesion energy in the range of the high fractal dimensions (D > 2.5). In this range, for surfaces with the same root mean square (RMS) roughness amplitude hrms , which is mainly affected by large scale roughness, the pull-off force (i.e., the maximum tensile force reached during the retracting phase) is observed reducing by increasing the RMS slope of the surface roughness , that is by changing the roughness content at the small scales. This result agrees with recent theoretical findings and has never been shown experimentally in the literature to the best of our knowledge.

On the nature and propagation of errors in roughness parameters obtained from spectral analysis of atomic force microscopy topographic images

Scale-dependent surface roughness strongly affects critical surface properties of materials, including adhesion, wettability, and optical/thermal properties. As a particular example, tuning the ratio of the true to nominal area—a parameter that depends on the root mean square (RMS) local slope of the finest scales of topography—is an effective approach to tailor the wetting characteristics of solid surfaces. While power spectral density (PSD) analysis of atomic force microscopy (AFM) topographic images allows for directly assessing the scale-dependence of surface roughness, this approach to analyze AFM height maps requires power-law modeling and extrapolation of a PSD with inherently non-normal error distributions. Here, we use a Monte Carlo approach based on synthetic AFM images of known input power-law parameters to (1) evaluate the accuracy of fitting techniques based on the expected distribution of the PSD; (2) evaluate the error propagation from the standard errors of the fitted power-law parameters to the computed RMS slope and area ratio; and (3) evaluate the statistical power of various PSD regression techniques when differentiating surfaces. The results indicated that standard error for ordinary least squares on a log-log PSD (log OLS) underpredicts the observed variance by ∼50%. This underprediction can be eliminated by implementing a log-link gamma regression. Moreover, when propagating the standard error to derived parameters (e.g., the RMS slope), the propagated error is generally conservative relative to the observed variance and closely predicts the observed variance when extrapolating to the finest scale. This result demonstrates the possibility of accurately estimating roughness parameters that are critical for evaluating surface phenomena on the basis of fitting and extrapolating AFM data using self-affine models. Finally, our results provided evidence for the possibility of statistically differentiating surfaces with similar power-law parameters when using weighted gamma regression with a mean of 10 images, as opposed to unweighted log-OLS that requires as many as 10 000 images to differentiate images.

A Fully Coupled Normal and Tangential Contact Model to Investigate the Effect of Surface Roughness on the Partial Slip of Dissimilar Elastic Materials

By adopting a global search method for all shear tractions in the contacting area and using an alternative convergence criterion regarding load balance in the lateral direction, the newly developed algorithm provides stable solutions to partial-slip problems of elastically dissimilar materials. The model is validated via the comparison between the simulation and literature results for a sphere-on-flat problem under fully coupled conditions. It is then employed to investigate the influence of surface roughness parameters including the root mean square (RMS) roughness and RMS slope on partial-slip solutions under coupled conditions. Since the gross sliding condition is modified under coupling effects, the relationship between the ratio of the stick area to the contacting area (stick ratio) and tangential load in the coupled case, unlike that in the uncoupled one, becomes non-linear for all tested rough surfaces. Under low or medium tangential loads, the surface with a higher RMS gradient or a lower RMS roughness experiences more stick regions within the contacting area. This trend then becomes irregular at higher tangential loads.

Elastic Rough Surface Contact and the Root Mean Square Slope of Measured Surfaces over Multiple Scales

This study investigates the predictions of the real contact area for perfectly elastic rough surfaces using a boundary element method (BEM). Sample surface measurements were used in the BEM to predict the real contact area as a function of load. The surfaces were normalized by the root-mean-square (RMS) slope to evaluate if contact area measurements would collapse onto one master curve. If so, this would confirm that the contact areas of manufactured, real measured surfaces are directly proportional to the root mean square slope and the applied load, which is predicted by fractal diffusion-based rough surface contact theory. The data predicts a complex response that deviates from this behavior. The variation in the RMS slope and the spectrum of the system related to the features in contact are further evaluated to illuminate why this property is seen in some types of surfaces and not others.

Lower limb muscle fatigability is not associated with changes in movement strategies for balance control in the upright stance.

Fatigue is a distressing symptom inversely related to postural stability in adults with neuromuscular and systemic diseases. However, there is no information about the effects of lower limb muscles fatigability on the movement strategies for balance control in the upright standing. This study enrolled 41 healthy subjects (female/male: 22/19; age 23±3years; body mass index 25.4±3.7kg/m2). Participants underwent posturography and surface electromyography of the gastrocnemius medialis muscle during a sustained, fatiguing voluntary contraction of the gastrocnemius preceded and followed by quiet standing (120s). Amplitude of electromyograms and fatigability were evaluated using the root mean square (RMS) value and both the RMS and spectral median frequency (fmed) slopes. Balance control was evaluated using the center-of-pressure elliptic area (Area) and average velocity (Vavg). Movement strategies for balance control were evaluated using the number of high-density regions (nHDR) and spatial patterns of the three-dimensional statokinesigram. Mean time to muscle fatigability was 258±190s. Area and Vavg but not nHDR increased after the fatiguing task. Single-centered spatial patterns were predominant in both tasks (pre-fatigue: n=22/41; post-fatigue: n=19/41), with no evidence of an association between the spatial patterns and tasks (γ=0.237, 95%CI=[-0.338; 0.542]). Lower limb muscle fatigability increases postural instability, but it is not associated with changes in movement strategies for balance control in the upright stance.

Assessment of Topography Parameters During Running-In and Subsequent Rolling Contact Fatigue Tests

Rolling contact fatigue (RCF) is one of the major problems observed in gear mechanisms, which leads to high friction, ultimately resulting in high energy consumption. This paper demonstrates the evolution of surface topography during running-in and subsequent RCF tests under boundary or mixed-elastohydrodynamic lubrication regimes. The case-hardened disks of equal surface finish and hardness are used in the experiments, and the evolution of surface topography is investigated using a white light interferometer. Surface topography at different load stages is measured at three distinct points, on the disks and average roughness and topography parameters are reported. Semi-quantitative techniques are used to determine the asperity-level parameters at different load stages. From the running-in experiment, it is found that running-in is a fast process where substantial change in surface topography occurs due to plastic deformation of most prominent asperity. From the RCF test, it is concluded that within range of the fatigue cycles, the root-mean-square (RMS) roughness (Sq) is negatively correlated with the summit radius (R) and the autocorrelation length (Sal) and positively correlated with the summit density (Sds) and the RMS slope (Sdq). Scanning electron microscope (SEM) analysis reveals the disappearance of grinding ridges, the formation of micropits at a very small scale, and pit growth in the sliding direction.

Investigation of EM Backscattering from Slick-Free and Slick-Covered Sea Surfaces Using the SSA-2 and SAR Images

This paper is devoted to investigating the electromagnetic (EM) backscattering from slick-free and slick-covered sea surfaces at various bands (L-band, C-band, X-band, and Ku-band) by using the second-order small slope approximation (SSA-2) and the measured synthetic aperture radar (SAR) data. It is known that the impact of slick on sea surface is mainly caused by two factors: the Marangoni damping effect and the reduction of friction velocity. In this work, the influences induced by these two factors on the sea curvature spectrum, the root mean square (RMS) height, the RMS slope, and the autocorrelation function of sea surfaces are studied in detail. Then, the slick-free and slick-covered sea surface profiles are simulated using the Elfouhaily spectrum and the Monte-Carlo model. The SSA-2 with the tapered incident wave is employed to simulate the normalized radar cross-sections (NRCSs) of sea surfaces. Furthermore, for slick-free sea surfaces, the NRCSs simulated with the SSA-2 at various bands are compared with those obtained by the first-order small slope approximation (SSA-1), the classic two-scale model (TSM), and the geophysical model functions (GMFs) at various bands, respectively. For slick-covered sea surfaces, the SSA-2-simulated NRCSs are compared with those obtained from C-band Radarsat-2 images and L-band uninhabited aerial vehicle synthetic aperture radar (UAVSAR) images, respectively. The numerical simulations illustrate that the SSA-2 can be used to study the EM backscattering from slick-free and slick-covered sea surfaces, and it has more advantages than the SSA-1 and the TSM. The works presented in this paper are helpful for understanding the EM scattering from the sea surface covered with slick, in theory.

Combining TEM, AFM, and Profilometry for Quantitative Topography Characterization Across All Scales.

Surface roughness affects the functional properties of surfaces, including adhesion, friction, hydrophobicity, biological response, and electrical and thermal transport properties. However, experimental investigations to quantify these links are often inconclusive because surfaces are fractal-like, and the values of measured roughness parameters depend on measurement size. Here, we demonstrate the characterization of topography of an ultrananocrystalline diamond (UNCD) surface at the angstrom scale using transmission electron microscopy (TEM), as well as its combination with conventional techniques to achieve a comprehensive surface description spanning 8 orders of magnitude in size. We performed more than 100 individual measurements of the nanodiamond film using both TEM and conventional techniques (stylus profilometry and atomic force microscopy). While individual measurements of root-mean-square (RMS) height, RMS slope, and RMS curvature vary by orders of magnitude, we combine the various techniques using the power spectral density and use this to compute scale-independent parameters. This analysis reveals that "smooth" UNCD surfaces have an RMS slope greater than 1, even larger than the slope of the Austrian Alps when measured on the scale of a human step. This approach of comprehensive multiscale roughness characterization, measured with angstrom-scale detail, will enable the systematic evaluation and optimization of other technologically relevant surfaces, as well as systematic testing of the many analytical and numerical models for the behavior of rough surfaces.

L-Arginine supplementation does not improve muscle function during recovery from resistance exercise

The purpose of this study was to investigate the effects of l-arginine supplementation on muscle recovery after a single session of high-intensity resistance exercise (RE). Twenty healthy young adult participants (22.8 ± 3.4 years old) were assigned to 1 of 2 groups (N = 10 per group): a placebo-supplement group or an l-arginine-supplement group. The groups completed a session of high-intensity RE (0 h) and 3 subsequent fatigue test sessions (at 24, 48, and 72 h postexercise) to assess the time course of muscle recovery. During the test sessions, we assessed the following dependent variables: number of maximum repetitions, electromyographic signal (i.e., root mean square (RMS) and median frequency (MF) slope), muscle soreness, perceived exertion, blood levels of creatine kinase (CK) and lactate, and testosterone:cortisol ratio. Number of maximum repetitions increased at 48 and 72 h postexercise in both groups (time, P < 0.05). CK levels and muscle soreness increased at 24 h postexercise and then progressively returned to baseline at 72 h post exercise in both groups (time, P < 0.05). Lactate levels increased immediately postexercise but were reduced at 24 h postexercise in both groups (time, P < 0.05). Testosterone:cortisol ratio, RMS, and MF slope remained unchanged during the recovery period in both groups (time, P > 0.05). No significant (P > 0.05) group × time interaction was found for all dependent variables during the recovery period. In conclusion, our data indicate that l-arginine supplementation does not improve muscle recovery following a high-intensity RE session in young adults.

Breast masses in mammography classification with local contour features

BackgroundMammography is one of the most popular tools for early detection of breast cancer. Contour of breast mass in mammography is very important information to distinguish benign and malignant mass. Contour of benign mass is smooth and round or oval, while malignant mass has irregular shape and spiculated contour. Several studies have shown that 1D signature translated from 2D contour can describe the contour features well.MethodsIn this paper, we propose a new method to translate 2D contour of breast mass in mammography into 1D signature. The method can describe not only the contour features but also the regularity of breast mass. Then we segment the whole 1D signature into different subsections. We extract four local features including a new contour descriptor from the subsections. The new contour descriptor is root mean square (RMS) slope. It can describe the roughness of the contour. KNN, SVM and ANN classifier are used to classify benign breast mass and malignant mass.ResultsThe proposed method is tested on a set with 323 contours including 143 benign masses and 180 malignant ones from digital database of screening mammography (DDSM). The best accuracy of classification is 99.66% using the feature of root mean square slope with SVM classifier.ConclusionThe performance of the proposed method is better than traditional method. In addition, RMS slope is an effective feature comparable to most of the existing features.

Surface roughness impact on the heat loss of solar vacuum heat collector elements (HCE)

Heat losses from line focus solar collectors, such as parabolic troughs and Linear Fresnel Reflectors (LFR), are reduced by using selectively coated vacuum heat collector elements (HCE). The main parameters governing convective and radiative heat losses are the metal tube's outer surface radiative emittance and the vacuum level between tube and glass envelope. We investigate the effect of surface roughness on tube emittance as function of substrate roughness. Through a series of experiments, using several surface polishing techniques, such as grinding processes and electro polishing, a good correlation between tube surface roughness and heat loss was obtained. We show the limitations of representing the surface roughness by only using the roughness average (Ra) or the root mean square (RMS) roughness (Rq), especially when an electro polishing process is involved. A better metric is the roughness slope (1/Er) or RMS slope (RΔq) in addition to the roughness height (Rz) for which a good correlation to heat loss is demonstrated. While the electro polishing process is shown to reduce emittance and therefore heat losses, less costly and simpler changes in the grinding process can lead to a similar result. Recommendations for metal tube roughness yielding minimum heat loss are presented.

Planetary landing-zone reconnaissance using ice-penetrating radar data: Concept validation in Antarctica

The potential for a nadir-looking radar sounder to retrieve significant surface roughness/permittivity information valuable for planetary landing site selection is demonstrated using data from an airborne survey of the Thwaites Glacier Catchment, West Antarctica using the High Capability Airborne Radar Sounder (HiCARS). The statistical method introduced by Grima et al. (2012. Icarus 220, 84–99. http://dx.doi.org/10.1007/s11214-012-9916-y) for surface characterization is applied systematically along the survey flights. The coherent and incoherent components of the surface signal, along with an internally generated confidence factor, are extracted and mapped in order to show how a radar sounder can be used as both a reflectometer and a scatterometer to identify regions of low surface roughness compatible with a planetary lander. These signal components are used with a backscattering model to produce a landing risk assessment map by considering the following surface properties: Root mean square (RMS) heights, RMS slopes, roughness homogeneity/stationarity over the landing ellipse, and soil porosity. Comparing these radar-derived surface properties with simultaneously acquired nadir-looking imagery and laser-altimetry validates this method. The ability to assess all of these parameters with an ice penetrating radar expands the demonstrated capability of a principle instrument in icy planet satellite science to include statistical reconnaissance of the surface roughness to identify suitable sites for a follow-on lander mission.

Simulation and control of aggregate surface morphology in a two-stage thin film deposition process for improved light trapping

This work focuses on the development of a model predictive control algorithm to simultaneously regulate the aggregate surface slope and roughness of a thin film growth process to optimize thin film light reflectance and transmittance. Specifically, a two-stage thin film deposition process, which involves two microscopic processes: an adsorption process and a migration process, is modeled based on a one-dimensional solid-on-solid square lattice. The first stage of this process utilizes a uniform deposition rate profile to control the thickness of the thin film and the second stage of the process utilizes a spatially distributed deposition rate profile to control the surface morphology of the thin film. Kinetic Monte Carlo (kMC) methods are used to simulate this two-stage thin film deposition process. To characterize the surface morphology and to evaluate the light trapping efficiency of the thin film, aggregate surface roughness and slope corresponding to length scale of visible light are introduced as the root-mean squares of the aggregate surface height profile and aggregate surface slope profile. An Edwards–Wilkinson (EW)-type equation with appropriately computed parameters is used to describe the dynamics of the surface height profile and predict the evolution of the aggregate root-mean-square (RMS) roughness and aggregate RMS slope. A model predictive control algorithm is then developed on the basis of the EW equation model to regulate the aggregate RMS slope and the aggregate RMS roughness at desired levels. Closed-loop simulation results demonstrate the effectiveness of the proposed model predictive control algorithm in successfully regulating the aggregate RMS slope and the aggregate RMS roughness at desired levels that optimize thin film light reflectance and transmittance.

Predictive control of surface mean slope and roughness in a thin film deposition process

This work focuses on the development of a model predictive control algorithm to simultaneously regulate the surface slope and roughness of a thin film growth process to optimize thin film light reflectance and transmittance. Specifically, a thin film deposition process modeled on a one-dimensional triangular lattice that involves two microscopic processes: an adsorption process and a migration process, is considered. Kinetic Monte Carlo (kMC) methods are used to simulate the thin film deposition process. To characterize the surface morphology and to evaluate the light trapping efficiency of the thin film, surface roughness and surface slope are introduced as the root mean squares of the surface height profile and surface slope profile. An Edwards–Wilkinson (EW)-type equation is used to describe the dynamics of the surface height profile and predict the evolution of the root-mean-square (RMS) roughness and RMS slope. A model predictive control algorithm is then developed on the basis of the EW equation model to regulate the RMS slope and the RMS roughness at desired levels by optimizing the substrate temperature at each sampling time. The model parameters of the EW equation are estimated from simulation data through least-square methods. Closed-loop simulation results demonstrate the effectiveness of the proposed model predictive control algorithm in successfully regulating the RMS slope and the RMS roughness at desired levels that optimize thin film light reflectance and transmittance.

Non-sequential optimization technique for a computer controlled optical surfacing process using multiple tool influence functions

Optical surfaces can be accurately figured by computer controlled optical surfacing (CCOS) that uses well characterized sub-diameter polishing tools driven by numerically controlled (NC) machines. The motion of the polishing tool is optimized to vary the dwell time of the polisher on the workpiece according to the desired removal and the calibrated tool influence function (TIF). Operating CCOS with small and very well characterized TIF achieves excellent performance, but it takes a long time. This overall polishing time can be reduced by performing sequential polishing runs that start with large tools and finish with smaller tools. In this paper we present a variation of this technique that uses a set of different size TIFs, but the optimization is performed globally - i.e. simultaneously optimizing the dwell times and tool shapes for the entire set of polishing runs. So the actual polishing runs will be sequential, but the optimization is comprehensive. As the optimization is modified from the classical method to the comprehensive non-sequential algorithm, the performance improvement is significant. For representative polishing runs we show figuring efficiency improvement from approximately 88% to approximately 98% in terms of residual RMS (root-mean-square) surface error and from approximately 47% to approximately 89% in terms of residual RMS slope error.

Lumbar muscles recruitment during resistance exercise for upper limbs

The aim of this study was to evaluate the EMG activity of lumbar multifidus (MU), longissimus thoracis (LT) and iliocostalis (IC) muscles during an upper limb resistance exercise (biceps curl). Ten healthy males performed maximal voluntary isometric contraction (MVC) of the trunk extensors, after this, the biceps curl exercise was executed at 25%, 30%, 35% and 40% one repetition maximum during 1 min, with 10 min rest between them. EMG root mean square (RMS) and median frequency (MFreq) were calculated for each lifting and lowering of the bar during the exercise bouts, to calculate slopes and intercepts. The results showed increases in the RMS and decreases in the MFreq slopes. RMS slopes were no different between muscles, indicating similar fatigue process along the exercise irrespective of the load level. MU and LT presented higher RMS irrespective of the load level, which can be related to the specific function during the standing position. On the other hand, IC and MU presented higher MFreq intercepts compared to LT, demonstrating possible differences in the muscle fiber conduction velocity of these muscles. These findings suggest that trunk muscles are differently activate during upper limb exercises, and the fatigue process affects the lumbar muscles similarly.

The role of the slope of oxygen consumption and EMG activity on freely chosen pedal rate selection

The objective of this study was to verify the following hypothesis: the pedal rate that minimizes root mean square (RMS) slope and the slow component amplitude of oxygen consumption could be close to the freely chosen pedal rate (FCPR) used by well-trained cyclists. Nine male competitive cyclists performed a 21 min submaximal exercise on a cycle ergometer at a workload of 65% of their respective peak aerobic power. For each session, the subject's pedal rate was freely chosen or assigned to 60, 75, 90 or 105 rev min(-1). When pedal rates were imposed, the electromyographic root mean square slope, the oxygen uptake during the third minute and the 20th min, and the slow component amplitude of oxygen consumption were used in the analysis. In order to determine the optimal pedal rate (OPR), a quadratic function was fitted to the data by regression, for each variable measured. The mean values of OPR relative to oxygen uptake during the third min (71+/-9 rev min(-1)) were lower than the mean values of the OPR relative to the slow component amplitude of oxygen consumption (82+/-8 rev min(-1)), the electromyographic root mean square slope (80+/-7 rev min(-1)) and freely chosen pedal rate (86+/-13 rev min(-1)). Freely chosen pedal rate was not significantly different from the OPR in reference to the amplitude of the slow component of oxygen consumption, electromyographic root mean square slope, and oxygen uptake during the 20th min. OPR for RMS slope was correlated (R=0.72) to FCPR. Expert cyclists were likely to use a spontaneous pedal rate that minimizes neuromuscular fatigue.

Comparison of an Accelerometer and a Condenser Microphone for Mechanomyographic Signals during Measurement of Agonist and Antagonist Muscles in Sustained Isometric Muscle Contractions

The purpose of this study was to investigate the influence of the force tremor (FT) on mechanomyographic (MMG) signals recorded by a condenser microphone (MIC) and an accelerometer (ACC) during measurement of agonist and antagonist muscles in sustained isometric contractions. Surface electromyographic (EMG) signals and MMG signals by MIC (MMG-MIC) and ACC (MMG-ACC) were recorded simultaneously on biceps brachii (BB) and triceps brachii (TB). Following determination of the isometric maximum voluntary contraction (MVC), 10 male subjects were asked to perform sustained elbow flexion and extension contractions at 30% MVC until exhaustion. We analyzed the root mean square (RMS) for all signals and compared the sum of the power spectrum (SPA) for 3-6 Hz and 8-12 Hz and the ratio of the sum of SPA for 3-6 Hz and 8-12 Hz in SPA for 3-100 Hz (SPA-FT/SPA-(3-100 Hz)) between MMG-MIC and MMG-ACC. During all sustained muscle contractions, the RMS of EMG and MMG-(MIC) was significantly (p<0.05) increased in antagonistic muscle pairs, while the increase was more noticeable for the agonist than for the antagonist. In addition, the antagonist had a significantly (p<0.05) smaller amplitude than the agonist muscle. The RMS of MMG-ACC, however, showed no significant (p>0.05) difference in RMS amplitude and slope between agonist and antagonist muscles during flexion. In extension, the MMG-ACC-RMS amplitude showed a tendency to be higher in the antagonist than in the agonist, while their slopes showed no significant (p>0.05) difference. The SPA for 3-6 Hz and 8-12 Hz in MMG-(MIC) showed a tendency to be higher in the agonist than the antagonist, and the slopes of the agonist were significantly (p<0.05) higher than those of the antagonist in all contractions. In MMG-ACC, SPA and slopes for 3-6 Hz and 8-12 Hz tended not to differ between agonist and antagonist. The SPA-FT/SPA-(3-100 Hz) in MMG-ACC showed that the antagonist was higher than that of the agonist in all contractions. The MMG-(MIC), however, showed a tendency toward no difference between the agonist and antagonist. In the assessment of muscle activity during simultaneous measurement of the agonist and antagonist during sustained muscle contractions, the MMG signal detected by MIC appeared to be less affected by FT than by ACC due to the different inherent characteristics of the two transducers.

A proposta biomecânica para a avaliação de sobrecarga na coluna lombar: efeito de diferentes variáveis demográficas na fadiga muscular

OBJETIVOS: Analisar a fadiga de músculos lombares e determinar as variáveis demográficas relacionadas com a fadiga destes músculos. MÉTODOS: A atividade eletromiográfica (EMG) dos músculos iliocostal direito (IL-D), iliocostal esquerdo (IL-E), multífido direito (MU-D) e multífido esquerdo (MU-E) de 18 voluntários foi captada durante contrações isométricas sub-máximas. Valores de root mean square (RMS) e freqüência mediana (FM) foram correlacionados com o tempo de resistência isométrica (TRI). Slopes de RMS positivos e de FM negativos indicaram a ocorrência da fadiga muscular. Procedimentos de regressão múltipla foram realizados para verificar as variáveis demográficas relacionadas com a fadiga muscular. RESULTADOS: A fadiga foi identificada em todos os músculos e intensidades de contração (p&lt;0.01), exceto no MU-E em 5% na análise do slope de RMS. Diferenças significantes foram encontradas entre o TRI de 5% e 15% (p=0.01), 5% e 20% (p=0.0002). Níveis de fadiga mais elevados estiveram bilateralmente presentes nos músculos multífidos na análise do slopes de FM. A associação do TRI, da idade e da massa corporal dos voluntários foi identificada como fator determinante para a ocorrência da fadiga nos músculos avaliados. CONCLUSÕES: Intervenções destinadas ao tratamento de problemas na coluna lombar devem considerar os vários fatores responsáveis pela fadiga dos músculos desta região.