Electromyographic analysis of rotator cuff muscles in patients with rotator cuff tendinopathy: A systematic review

The shoulder is inherently an unstable joint which heavily relies on the neuromuscular activation of the rotator cuff (RC) complex for stability during movement. Currently, there is no consensus regarding how the activity of RC muscles is affected among individuals with a RC tendinopathy (RCTe). This study reviewed the evidence of studies comparing the electromyographic (EMG) activity of any RC muscle of shoulders with a symptomatic RCTe to asymptomatic shoulders. Eight databases were searched. Data from 343 participants (201 symptomatic and 209 asymptomatic shoulders) were analyzed from 10 out of 402 included studies. Strong evidence for the infraspinatus and supraspinatus during isometric contractions and limited evidence for the supraspinatus and infraspinatus during isokinetic contractions suggest that the muscular activity is not altered among individuals with a RCTe during these types of contraction. Very limited evidence indicates reduced muscle activity for the infraspinatus and subscapularis in the presence of a RCTe during isotonic contractions, and no alterations for the supraspinatus or teres minor were identified. Lastly, conflicting to moderate evidence suggests alterations in RC muscle activity during unrestrained movements and swimming. These findings indicate that EMG deficits associated with a RCTe can best be appreciated during unrestrained movements.     

A theoretical analysis of preferred pedaling rate selection in endurance cycling

One objective of this study was to investigate whether neuromuscular quantities were associated with preferred pedaling rate selection during submaximal steady-state cycling from a theoretical perspective using a musculoskeletal model with an optimal control analysis. Specific neuromuscular quantities of interest were the individual muscle activation, force, stress and endurance. To achieve this objective, a forward dynamic model of cycling and optimization framework were used to simulate pedaling at three different rates of 75, 90 and 105 rpm at 265 W. The pedaling simulations were produced by optimizing the individual muscle excitation timing and magnitude to reproduce experimentally collected data. The results from these pedaling simulations indicated that all neuromuscular quantities were minimized at 90 rpm when summed across muscles. In the context of endurance cycling, these results suggest that minimizing neuromuscular fatigue is an important mechanism in pedaling rate selection. A second objective was to determine whether any of these quantities could be used to predict the preferred pedaling rate. By using the quantities with the strongest quadratic trends as the performance criterion to be minimized in an optimal control analysis, these quantities were analyzed to assess whether they could be further minimized at 90 rpm and produce normal pedaling mechanics. The results showed that both the integrated muscle activation and average endurance summed across all muscles could be further minimized at 90 rpm indicating that these quantities cannot be used individually to predict preferred pedaling rates.     

Electromyographic analysis of relaxed postures

Six male volunteers assumed either relaxed or unrelaxed postures, as defined by a Behavioral Relaxation Scale, in seven areas of the body. Electromyographic (EMG) levels in the muscle groups associated with each area were determined for both categories of postures. In all instances, the relaxed postures produced significantly lower EMG levels than the unrelaxed postures. This indicates that the Behavioral Relaxation Scale is a valid behavioral measure of relaxation. Also, it supports other studies which have shown that direct training in emitting relaxed postures is an effective means of achieving relaxation.This study was conducted in partial fulfillment of the M.A. degree by Jerry P. Maurer. Appreciation is expressed to Tz-Yi Jiang, Dr. Robert Lehr, and Jim Rice for their assistance.     

A theoretical analysis of an optimal chainring shape to maximize crank power during isokinetic pedaling

Previous studies have sought to improve cycling performance by altering various aspects of the pedaling motion using novel crank–pedal mechanisms and non-circular chainrings. However, most designs have been based on empirical data and very few have provided significant improvements in cycling performance. The purpose of this study was to use a theoretical framework that included a detailed musculoskeletal model driven by individual muscle actuators, forward dynamic simulations and design optimization to determine if cycling performance (i.e., maximal power output) could be improved by optimizing the chainring shape to maximize average crank power during isokinetic pedaling conditions. The optimization identified a consistent non-circular chainring shape at pedaling rates of 60, 90 and 120 rpm with an average eccentricity of 1.29 that increased crank power by an average of 2.9% compared to a conventional circular chainring. The increase in average crank power was the result of the optimal chainrings slowing down the crank velocity during the downstroke (power phase) to allow muscles to generate power longer and produce more external work. The data also showed that chainrings with higher eccentricity increased negative muscle work following the power phase due to muscle activation–deactivation dynamics. Thus, the chainring shape that maximized average crank power balanced these competing demands by providing enough eccentricity to increase the external work generated by muscles during the power phase while minimizing negative work during the subsequent recovery phase.     

Simulation analysis of muscle activity changes with altered body orientations during pedaling

Testing hypotheses related to the effect of gravitational orientation on neural control mechanisms is difficult for most locomotor tasks, like walking, because body orientation with respect to gravity affects both sensorimotor control and task mechanics. To examine the mechanical effect of body orientation independently from changes in workload and posture, Brown et al. (J. Biomech. 29 p. 1349, 1996) studied pedaling at altered body orientations. They found that subjects pedaling at different orientations changed needlessly their muscle excitations, putatively to preserve body-upright pedaling kinematics. We tested the feasibility of this hypothesis using simulations based on a three biomechanical-function pair organization for control of lower limb muscles (limb extension/flexion pair, extension/flexion transition pair, and foot plantarflexion/dorsiflexion pair), where each pair consists of alternating agonistic/antagonistic muscles. Adjustment of only three parameters, one to scale the muscle excitations of each pair, was sufficient to preserve pedaling kinematics to altered body orientation. Because these adjustments produced changes in muscle excitation and net joint moments similar to those observed in pedaling subjects, the hypothesis is supported. Moreover, the effectiveness of a decoupled gain adjustment procedure where each parameter was adjusted by error in only one aspect of the pedaling trajectory during each iteration (i.e., cadence adjusted the Ext/Flex parameter; peak-to-peak variation in crank velocity over the cycle adjusted the transition parameter; average ankle angle over the cycle adjusted the foot parameter) further supports the distinct function of each muscle pair.     

Electromyographic analysis of muscle activation during pull-up variations

This study sought to identify any differences in peak muscle activation (EMGPEAK) or average rectified variable muscle activation (EMGARV) during supinated grip, pronated grip, neutral grip and rope pull-up exercises. Nineteen strength trained males (24.9 ± 5 y; 1.78 ± 0.74 m; 81.3 ± 11.3 kg; 22.7 ± 2.5 kg m⁻²) volunteered to participate in the study. Surface electromyography (EMG) was collected from eight shoulder-arm-forearm complex muscles. All muscle activation was expressed as a percentage of maximum voluntary isometric contraction (%MVIC). Over a full repetition, the pronated grip resulted in significantly greater EMGPEAK (60.1 ± 22.5 vs. 37.1 ± 13.1%MVIC; P = 0.004; Effect Size [ES; Cohen’s d] = 1.19) and EMGARV (48.0 ± 21.2 vs. 27.4 ± 10.7%MVIC; P = 0.001; ES = 1.29) of the middle trapezius when compared to the neutral grip pull-up. The concentric phases of each pull-up variation resulted in significantly greater EMGARV of the brachioradialis, biceps brachii, and pectoralis major in comparison to the eccentric phases (P = <0.01). Results indicate that EMGPEAK and EMGARV of the shoulder-arm-forearm complex during complete repetitions of pull-up variants are similar despite varying hand orientations; however, differences exist between concentric and eccentric phases of each pull-up.     

Vulvodynia: A Psychophysiological Profile Based on Electromyographic Assessment

The objective of this study was to explore the relationship between psychological and physiological processes and how these interact in the case of vulvodynia. The study design consisted of a retrospective review of predominantly premenopausal women presenting with vulvodynia via analyses of questionnaires, psychometric tests, sexual history, surface electromyographic (sEMG) assessments, and clinical notes. Five hundred and twenty-nine patients with vulvodynia (mean age 27.7 years) were studied. The average age of symptom onset was 22.8 years and the average duration of symptoms was 5.0 years. Patients scored higher than the comparison group on global dimensions of the Symptom Checklist—90 Revised (SCL-90R), with anxiety and depression scores showing a significant but modest correlation with severity of pain. sEMG data confirmed an association with pelvic muscle dysfunction but there was no correlation with severity of vulvar pain. A negative correlation between sEMG readings and duration of pain was noted and may be due to progressive time-related quieting of electrical activity in muscle tissues, which is commonly associated with the development of a functional muscle contracture. In conclusion, it is important to view chronic pain syndromes like vulvodynia from a psychophysiological perspective which recognizes the potential contribution of psychological and physiological variables in the aetiology of chronic vulvar pain.     

Electromyographic analysis of walking in water in healthy humans

This study was designed to describe and clarify muscle activities which occur while walking in water. Surface electromyography (EMG) was used to evaluate muscle activities in six healthy subjects (mean age, 23.3 +/- 1.4 years) while they walked on a treadmill in water (with or without a water current) immersed to the level of the xiphoid process, and while they walked on a treadmill on dry land. The trials in water utilized the Flowmill which has a treadmill at the base of a water flume. Integrated EMG analysis was conducted for the quantification of muscle activities. In order to calculate the %MVC, the measurement of maximal voluntary contraction (MVC) of each muscle was made before the gait analysis, thus facilitating a comparison of muscle activities while walking in water with those on dry land. The %MVCs obtained from each of the tested muscles while walking in water, both with and without a water current, were all found to be lower than those obtained while walking on dry land at a level of heart rate response similar to that used when walking on dry land. Furthermore, the %MVCs while walking in water with a water current tended to be greater when compared to those while walking in water without a water current. In conclusion, the present study demonstrated that muscle activities while walking in water were significantly decreased when compared to muscle activities while walking on dry land, that muscle activities while walking in water tended to be greater with a water current than without, and that the magnitude of the muscle activity in water was relatively small in healthy humans. This information is important to design water-based exercise programs that can be safely applied for rehabilitative and recreational purposes.     

Laboratory versus outdoor cycling conditions: differences in pedaling biomechanics

The aim of our study was to compare crank torque profile and perceived exertion between the Monark ergometer (818 E) and two outdoor cycling conditions: level ground and uphill road cycling. Seven male cyclists performed seven tests in seated position at different pedaling cadences: (a) in the laboratory at 60, 80, and 100 rpm; (b) on level terrain at 80 and 100 rpm; and (c) on uphill terrain (9.25% grade) at 60 and 80 rpm. The cyclists exercised for 1 min at their maximal aerobic power. The Monark ergometer and the bicycle were equipped with the SRM Training System (Schoberer, Germany) for the measurement of power output (W), torque (Nxm), pedaling cadence (rpm), and cycling velocity (kmxh-1). The most important findings of this study indicate that at maximal aerobic power the crank torque profiles in the Monark ergometer (818 E) were significantly different (especially on dead points of the crank cycle) and generate a higher perceived exertion compared with road cycling conditions.     

Method agreement analysis: A review of correct methodology

The correct approach to analyzing method agreement is discussed. Whether we are considering agreement between two measurements on the same samples (repeatability) or two individuals using identical methodology on identical samples (reproducibility) or comparing two methods, appropriate procedures are described, and worked examples are shown. The correct approaches for both categorical and numerical variables are explained. More complex analyses involving a comparison of more than two pairs of data are mentioned and guidance for these analyses given. Simple formulae for calculating the approximate sample size needed for agreement analysis are also given. Examples of good practice from the reproduction literature are cited, and common errors of methodology are indicated.     

Electromyographic analysis of motor perturbations linked with gastrointestinal strongyloidiasis]

The effects of experimental infection of lambs with third stage Trichostrongylus larvae are described. Preceding diarrhea, disturbances in the motility of the reticulum, abomasum and jejunum were observed by electromyography. Disappearance of the migrating myoelectric complexes occurred about 24 h before diarrhea and was accompanied by a decrease in both the frequency of reticular contractions and of contractions propagated through the antro-duodenal junction. The significance of these findings is discussed and compared with natural infestation in the field.     

Chemical probes for analysis of carbonylated proteins: A review

Protein carbonylation is a major form of protein oxidation and is widely used as an indicator of oxidative stress. Carbonyl groups do not have distinguishing UV or visible, spectrophotometric absorbance/fluorescence characteristics and thus their detection and quantification can only be achieved using specific chemical probes. In this paper, we review the advantages and disadvantages of several chemical probes that have been and are still being used for protein carbonyl analysis. These probes include 2,4-dinitrophenylhydazine (DNPH), tritiated sodium borohydride ([³H]NaBH₄), biotin-containing probes, and fluorescence probes. As our discussions lean toward gel-based approaches, utilizations of these probes in 2D gel-based proteomic analysis of carbonylated proteins are illustrated where applicable. Analysis of carbonylated proteins by ELISA, immunofluorescent imaging, near infrared fluorescence detection, and gel-free proteomic approaches are also discussed where appropriate. Additionally, potential applications of blue native gel electrophoresis as a tool for first dimensional separation in 2D gel-based analysis of carbonylated proteins are discussed as well.     

Real-time PCR: A review of approaches to data analysis

The registration of the accumulation of polymerase chain reaction (PCR) products in the course of amplification (real-time PCR) requires specific equipment, i.e., detecting amplifiers capable of recording the level of fluorescence in the reaction tube during amplicon formation. When the time of the reaction is complete, researchers are able to obtain DNA accumulation graphs. This review discusses the most promising algorithms of the analysis of real-time PCR curves and possible errors, caused by the software used or by operators’ mistakes. The data included will assist researchers in understanding the features of a method to obtain more reliable results.     

The role of anticipatory postural adjustments in compensatory control of posture: 1. Electromyographic analysis

Anticipatory (APAs) and compensatory (CPAs) postural adjustments are the two principal mechanisms that the central nervous system uses to maintain equilibrium while standing. We studied the role of APAs in compensatory postural adjustments. Eight subjects were exposed to external predictable and unpredictable perturbations induced at the shoulder level, while standing with eyes open and closed. Electrical activity of leg and trunk muscles was recorded and analyzed during four epochs representing the time duration typical for anticipatory and compensatory postural control. No anticipatory activity of the trunk and leg muscles was seen in the case of unpredictable perturbations; instead, significant compensatory activation of muscles was observed. When the perturbations were predictable, strong anticipatory activation was seen in all the muscles: such APAs were associated with significantly smaller compensatory activity of muscles and COP displacements after the perturbations.The outcome of the study highlights the importance of APAs in control of posture and points out the existence of a relationship between the anticipatory and the compensatory components of postural control. It also suggests a possibility to enhance balance control by improving the APAs responses during external perturbations.     

A comparison of visual and mathematical detection of the electromyographic threshold during incremental pedaling exercise: a pilot study

During exhaustive incremental pedaling exercises, root mean square or amplitude of integrated electromyographic values exhibits a nonlinear increase, i.e., the so-called electromyographic threshold (EMG(Th)). As proposed by various authors, this EMG(Th) could be used as a complementary indicator of the aerobic-anaerobic transition in physiological evaluations. However, most of these studies used visual detection for the EMG(Th) and to date no previous study has shown the reliability of this type of EMG(Th) detection. We aimed to compare a visual and a mathematical method for EMG(Th) detection in each of 8 lower limb muscles during incremental cycling exercise. Our results showed an overestimation in the number of cases in which EMG(Th) was detected when using visual inspection (n = 45) compared with the mathematical method (n = 32). However, no significant differences were observed between the 2 methods concerning the power output at which EMG(Th) occurred. These results suggest that EMG(Th) should be mathematically detected. In this context, coaches can easily perform such measurements in order to evaluate the impact of their training programs on the neuromuscular adaptations of their athletes. For example, an automatic mathematical detection of EMG(Th) could be performed during a pedaling exercise in order to detect neuromuscular fatigue. Furthermore, this index could be used during test or training sessions performed either in a lab or in ecological situations. Moreover, the use of EMG(Th) to predict ventilatory threshold occurrence could be an interesting tool for trainers who cannot use the very expensive devices needed to analyze respiratory gas exchanges.     

Feral goat social organization: A review and comparative analysis

Measurements indexing the mating system, home range, peri-parturient behaviour, and group size and composition of feral goats were used to compare studied populations. Geographically diverse populations were similar in most behavioural characteristics and their social systems had similar structures. However, post-partum behaviour and mating systems showed both quantitative and qualitative differences between populations. These similarities and differences are discussed in relation to the diverse selection history of feral goats. It is postulated that selective changes occurring during domestication may contribute to the variability observed in post-partum behaviour and mating systems.     

Immunoaffinity column clean-up techniques in food analysis: A review

This review provides a critical assessment of the applications of immunoaffinity columns for sample clean-up in the field of food safety. The performance of immunoaffinity columns are compared in terms of specificity, binding capacity and recovery, and commercial disposable columns are contrasted with home-made columns. Areas covered include multiple-use of columns, multiple-analyte columns, use with automated systems and validation of IAC methods. Publications illustrating the many varied applications of IAC for sample clean-up in the areas of mycotoxins, veterinary drug residues, pesticide residues, environmental contaminants and vitamins have been compiled, comparing extraction methods, achievable recovery, and illustrating the variety of end-detection methods that have been employed.     

Leishmanial infection: analysis of its first steps. A review

The first steps in leishmaniasis are critical in determining the evolution of the disease. Major advances have recently been done in understanding this crucial moment. Fundamental research in parasite-vector interaction, parasite biology, insect saliva, and vertebrate host response have shed new light and uncovered a most fascinating and complex moment in leishmaniasis. We review here some of these aspects and we try to connect them in a logical framework.