The potential use of spectral electromyographic fatigue as a screening and outcome monitoring tool of sarcopenic back muscle alterations

Background: To examine whether or not median frequency surface electromyographic (MF-EMG) back muscle fatigue monitoring would be able to identify alterations in back muscle function in elderly muscles, if a protocol was used that allowed optimum standardization of the processes underlying electromyographic fatigue, and whether these tests were reliable from day to day. Methods: A total of 42 older (21 females; 67 (±10.5) years old) and 44 younger persons (19 females; 33 (±10) years) performed maximum isometric back extensions which were followed by one 30 s lasting 80% submaximum extension. Participants were seated on a dynamometer with their trunks 30° anteflexed, and they repeated all tests after 1-2 days and 6 weeks. SEMG was recorded bilaterally from the L1 (iliocostalis lumborum), L2 (longissimus), and L5 (multifidus) recording sites. Outcome variables included maximum back extension torque, initial MF-EMG (IMF-EMG), MF-EMG slope declines, and individual MF-EMG muscular imbalance scores. Two-factorial ANOVAs served to examine the age and gender-specific effects, and models from Generalizability Theory (G-Theory) were used for assessing retest-reliability. Results: Maximum back extension moment was non-significantly smaller in elders. IMF-EMG was overall higher in elders, with significant differences at the L5 recordings sites. In the elderly, MF-EMG fatigue declines were significantly smaller in L5, in the recording with the most negative slope, or if the slope of all electrodes was considered. Retest reliability was unanimous in young and older persons. ICC-type measurements from G-Theory of both the IMF and the fatigue slopes ranged from 0.7 to 0.85. Absolute SEM values were found clinically acceptable for the IMF-EMG, but relatively high for the fatigue slope declines. Conclusions: The MF-EMG fatigue method is able to elucidate alterations of aging back muscles. This method, thus, might be suggested as a potential biomarker to objectively identify persons at risk for sarcopenia. Considering the clinical relevance of the IMF-EMG relative to the MF-EMG slope declines, spectral EMG may also be used as an outcome monitoring tool in elderly populations

Age and gender related neuromuscular pattern during trunk flexion-extension in chronic low back pain patients

Background: The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from standing has repeatedly been recommended to objectively assess muscle function in chronic low back pain patients. However, literature addressing older patients is sparse. This cross sectional study sought to examine differences in neuromuscular activation between age groups (>60 versus 40-60 versus <40 years) and sexes during a standardized trunk flexion-extension task. Methods: A total of 216 patients (62 older, 84 middle-aged, 70 younger) performed maximum trunk extensions followed by trunk flexion extension testing thereby holding static positions at standing, half, and full trunk flexion. The lumbar extensor muscle activity and 3d-accelerometric signals intended to monitor hip and trunk position angles were recorded from the L5 (multifidus) and T4 (semispinalis thoracis) levels. Permutation ANOVA with bootstrapped confidence intervals were performed to examine for age and gender related differences. Ridge-regressions investigated the impact of physical-functional and psychological variables to the half flexion relaxation ratio (i.e. muscle activity at the half divided by that in maximum flexion position). Results: Maximum back extension torque was slightly but significantly higher in youngest compared to oldest patients if male and females were pooled. Normalized RMS-SEMG revealed highest lumbar extensor muscle activity at standing in the oldest and the female groups. Patients over 60 years showed lowest activity changes from standing to half (increments) and from half to the maximum flexion position (decrements) leading to a significantly lower half flexion relaxation ratio compared to the youngest patients. These oldest patients demonstrated the highest hip and lowest lumbothoracic changes of position angles. Females had higher regional hip and gross trunk ranges of movement compared to males. Lumbothoracic flexion and the muscle activity at standing had a significant impact on the half flexion relaxation ratio. Conclusions: The neuromuscular activation pattern and the kinematics in this trunk flexion-extension task involving static half flexion position changed according to age and sex. The test has a good potential to discriminate between impaired and unimpaired neuromuscular regulation of back extensors in cLBP patients, thereby allowing the design of more individualized exercise programs. Electronic supplementary material The online version of this article (doi:10.1186/s12984-016-0121-1) contains supplementary material, which is available to authorized users

Aging Lubricant solutions: A clinical comment

While the aging of an ophthalmic solution may be viewed subjectively as a series of departures from original chemical and physical values, it is, of course, a much more complex matter clinically. The ultmate scales of solution aging also must take those factors into account that will affect the patient population and/or the lens in any significant way, e.g. toxicity, contamination, lens despoilation, loss of comfort. Since tissue tolerance and lens vulnerabilities are highly individualized, however, due to personal histories, genetics, sensitization, idiosyncracies), and the vast number of eye, lens, and care systemn combinations, the formulator (and through him, the clinician) must fall back on those chemical and physical departures as practical (first order) indices of risk

Ophthalmic salines and the acidity question

What acidity (minimum pH) will most patients tolerate when using ophthalmic salines? After sone decades of trying to answer that question (and many continue to try), it is becoming increasingly evident that the question rather then the answer may be flawed. It is now evident that both patient and saline are variables within the problem; the patient through inherent (genetically based) differences, and gradual physiological change (i.e. aging and environmental history); and the solutions through physical and chemical shifts over time. It is with those changes asociated with the ophthalmic salines that his study was concerned

Do contact lens solutions stand the test of time? II The aging of salines

The contact lens practitioner has at his disposal an extensive array of solutions to recommend to his patients. these solutions have a range of characteristics which could be thought of as suprisingly broad, but which are necessary to accommodate the different tolerances and needs of our patients. (1-2) Within the various classes of contact lens solutions, salines might be expected to be the least complicated in their physio-chemical characteristics and the least likely to be a source of difficulties. Yet these selections do show a range of charcteristics, and the potential for incompatabilities is high since they can influence the integrity of both the contact lens itself (through their direct interaction with lens polymers) and the ocular tissues (through transfer into the eye with the contact lens). Even if an optimum initial selection of a saline solution is made, can we assume stability of the crucial charcteristics of the solution throughout the life of that solution

Do contact lens solutions stand the test of time? : Part 1: The "aging" of lubricants

For some patients, use of lubricant colutions is essential for achieving successful contact lens wear. Matchiing solution actions to the needs of the patient is most typically achieved through trial and error, although those actions must be intimately related to the inherent chemical and physical properties of the lubricants.(1-2) But assuming an effective choice of lubricant has been made, how certain can we be that those same needed properties will be maintained throughout its use? Can changes in those properties occur, sufficiently marked as to cause a significant reduction in or loss of effectiveness? We have explored this potential for instability using a sample of eight lubricant solutions. Four properties - pH (or acidity), buffering capacity, tonicity and refractive index - were measured at two times, immediately on opening, and then after 24 months of subsequent storage

Coherent acoustic oscillations of nanoscale Au triangles and pyramids : influence of size and substrate

We investigate the impulsively excited acoustic dynamics of nanoscale Au triangles of different sizes and thicknesses on silicon and glass substrates. We employ high-speed asynchronous optical sampling in order to study the damping of the acoustic vibrations with high sensitivity in the time domain. From the observed damping dynamics we deduce the reflection coefficient of acoustic energy from the gold substrate interface. The observed damping times of coherent acoustic vibrations are found to be significantly longer than expected from the acoustic impedance mismatch for an ideal gold substrate interface, hence pointing towards a reduced coupling strength. The strength of the coupling can be determined quantitatively. For Au triangles with large lateral size-to-thickness ratio, i.e. a small aspect ratio, the acoustic dynamics is dominated by a thickness oscillation similar to that of a closed film. For triangles with large aspect ratio the coherent acoustic excitation consists of a superposition of different three-dimensional modes which exhibit different damping times

Formation and stability of dense arrays of Au nanoclusters on hexagonal boron nitride/Rh(111)

We have studied the nucleation and growth of Au clusters at submonolayer and greater coverages on the h-BN nanomesh grown on Rh(111) by means of scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). STM reveals that submonolayer Au deposited at 115 K nucleates within the nanomesh pores and remains confined to the pores even after warming to room temperature. Whereas there is a propensity of monoatomic high islands at low temperature, upon annealing, bi- and multilayer Au clusters emerge. Deposition of higher coverages of Au similarly results in Au clusters primarily confined to the nanomesh pores at room temperature. XPS analysis of core-level electronic states in the deposited Au shows strong final-state effects induced by restricted particle size dominating for low Au coverage, with indications that larger Au clusters are negatively charged by interaction through the h-BN monolayer. DFT calculations suggest that the structure of the Au clusters transitions from monolayer to bilayer at a size between 30 and 37 atoms per cluster, in line with our experiment. Bader charge analysis supports the negative charge state of deposited Au. © 2014 American Physical Society

Age and gender related neuromuscular changes in trunk flexion-extension

Background: The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from a standing position and task specific spine ranges of motion objectively assess muscle function in healthy young and middle age individuals. However, literature on neuromuscular activation and associated spine and hip kinematics in older individuals is sparse. This cross sectional study sought to examine the sex and age (60 years) related differences in the neuromuscular activation profiles of the lumbar extensors and the related spine and hip kinematics from healthy individuals during a standardized trunk flexion-extension task. Methods: Twenty five older (13 females, 60–90 years) and 24 younger (12 females, 18–40 years) healthy individuals performed trunk flexion-extension testing by holding static positions at half-flexion way and full range of motion between standing and maximum trunk flexion. The associated lumbar extensor muscle activity was derived from measurements at standing, half, and maximum flexion positions. The range of motion at the hip and lumbar spine was recorded using 3d accelerometers attached to the skin overlying the multifidus and semispinalis thoracis muscles lateral to the L5 and T4 spinous processes, respectively. Statistical calculations were performed using a permutation ANOVA with bootstrap confidence intervals. Results: The muscle activity in the half related to the maximum flexion position (half flexion relaxation ratio) was significantly smaller in older males when compared with younger males. Moreover, measurements revealed smaller activity changes from standing to the half and from half to the maximum flexion position in older compared to younger individuals. Older males displayed smaller gross trunk range of motion from standing to maximum flexion than any other group. Conclusions: Gender and normal aging significantly affect both the activation patterns of the lumbar extensor muscles and the kinematics of the trunk during a standardized trunk flexion-extension task. Measurement results from healthy young and middle age individuals should not be used for the assessment of individuals older than 60 years of age. Electronic supplementary material The online version of this article (doi:10.1186/1743-0003-12-3) contains supplementary material, which is available to authorized users