scholarly journals Human motor unit characteristics of the superior trapezius muscle with age-related comparisons

2019 ◽  
Vol 122 (2) ◽  
pp. 823-832
Author(s):  
Eric A. Kirk ◽  
Kevin J. Gilmore ◽  
Daniel W. Stashuk ◽  
Timothy J. Doherty ◽  
Charles L. Rice
Keyword(s):  
Motor Neuron ◽  
Motor Unit ◽  
Compound Muscle Action Potential ◽  
Age Groups ◽  
Stability Parameters ◽  
Discharge Rates ◽  
Age Related ◽  
Lower Amplitude ◽  
Human Motor ◽  
The Impact

Current understanding of human motor unit (MU) control and aging is mostly derived from hand and limb muscles that have spinal motor neuron innervations. The aim here was to characterize and test whether a muscle with a shared innervation supply from brainstem and spinal MU populations would demonstrate similar age-related adaptations as those reported for other muscles. In humans, the superior trapezius (ST) muscle acts to elevate and stabilize the scapula and has primary efferent supply from the spinal accessory nerve (cranial nerve XI) located in the brainstem. We compared electrophysiological properties obtained from intramuscular and surface recordings between 10 young (22–33 yr) and 10 old (77–88 yr) men at a range of voluntary isometric contraction intensities (from 15 to 100% of maximal efforts). The old group was 41% weaker with 43% lower MU discharge frequencies compared with the young (47.2 ± 9.6 Hz young and 26.7 ± 5.8 Hz old, P < 0.05) during maximal efforts. There was no difference in MU number estimation between age groups (228 ± 105 young and 209 ± 89 old, P = 0.33). Furthermore, there were no differences in needle detected near fiber (NF) stability parameters of jitter or jiggle. The old group had lower amplitude and smaller area of the stimulated compound muscle action potential and smaller NF MU potential area with higher NF counts. Thus, despite age-related ST weakness and lower MU discharge rates, there was minimal evidence of MU loss or compensatory reinnervation. NEW & NOTEWORTHY The human superior trapezius (ST) has shared spinal and brainstem motor neuron innervation providing a unique model to explore the impact of aging on motor unit (MU) properties. Although the ST showed higher MU discharge rates compared with most spinally innervated muscles, voluntary strength and mean MU rates were lower in old compared with young at all contraction intensities. There was no age-related difference in MU number estimates with minimal electrophysiological evidence of collateral reinnervation.

scholarly journals Neuromuscular changes of the aged human hamstrings

2018 ◽  
Vol 120 (2) ◽  
pp. 480-488 ◽  
Author(s):  
Eric A. Kirk ◽  
Kevin J. Gilmore ◽  
Charles L. Rice
Keyword(s):  
Motor Unit ◽  
Contractile Function ◽  
Age Groups ◽  
Biceps Femoris ◽  
Surface Emg ◽  
Muscle Group ◽  
Voluntary Activation ◽  
Discharge Rates ◽  
Age Related ◽  
Motor Unit Discharge

Despite the life-long importance for posture and locomotion, neuromuscular properties of the hamstrings muscle have not been explored with adult aging. The purpose of this study was to assess and compare age-related effects on contractile function, spinal motor neuron output expressed as motor unit (MU) discharge rates in the hamstrings of 11 young (26 ± 4 yr) and 10 old (80 ± 5 yr) men. Maximal voluntary isometric contractions (MVC), stimulated contractile properties, and surface and intramuscular electromyography (EMG) from submaximal to MVC were recorded in the biceps femoris (BF) and semimembranosus-semitendinosus (SS) muscles. MVC torque was ~50% less in the old with both age groups attaining ≥93% mean voluntary activation. Evoked twitches in the old were ~50% lower in amplitude and >150% longer in duration compared with those in the young. At successive voluntary contractions of 25, 50, and 100% MVC, MU discharge rates were up to 45% lower in old, with no differences in relative submaximal surface EMG between age groups. Furthermore, the old had significantly lower MU discharge rates in the SS at all contraction intensities compared with the BF muscle. Men in their 8th to 10th decades of life demonstrate substantially lower strength and MU discharge rates in this functionally important large lower limb muscle group, with greater age-related effect on discharge rates in the medial hamstrings. These findings, compared with those in other muscles studied, highlight that the neuromuscular properties of limb muscles, and indeed within functionally similar portions of a muscle group, are not all affected equally by the aging process. NEW & NOTEWORTHY In the hamstrings, we found that both contractile function and motor unit discharge rates across the range of voluntary intensities were lower in the old. The differences in discharge rates due to age were greater in the medial hamstrings muscle group compared with the lateral hamstrings. Compared with previous studies, these results highlight that not all muscles are affected equally by aging and there may be compartmental differences within functionally similar muscles.

scholarly journals Bioengineered model of the human motor unit with physiologically functional neuromuscular junctions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rowan P. Rimington ◽  
Jacob W. Fleming ◽  
Andrew J. Capel ◽  
Patrick C. Wheeler ◽  
Mark P. Lewis
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neuron ◽  
Motor Unit ◽  
Motor Nerve ◽  
Motor Units ◽  
Extracellular Matrices ◽  
Synaptic Membrane ◽  
Type I ◽  
Dependent Manner ◽  
Human Motor

AbstractInvestigations of the human neuromuscular junction (NMJ) have predominately utilised experimental animals, model organisms, or monolayer cell cultures that fail to represent the physiological complexity of the synapse. Consequently, there remains a paucity of data regarding the development of the human NMJ and a lack of systems that enable investigation of the motor unit. This work addresses this need, providing the methodologies to bioengineer 3D models of the human motor unit. Spheroid culture of iPSC derived motor neuron progenitors augmented the transcription of OLIG2, ISLET1 and SMI32 motor neuron mRNAs ~ 400, ~ 150 and ~ 200-fold respectively compared to monolayer equivalents. Axon projections of adhered spheroids exceeded 1000 μm in monolayer, with transcription of SMI32 and VACHT mRNAs further enhanced by addition to 3D extracellular matrices in a type I collagen concentration dependent manner. Bioengineered skeletal muscles produced functional tetanic and twitch profiles, demonstrated increased acetylcholine receptor (AChR) clustering and transcription of MUSK and LRP4 mRNAs, indicating enhanced organisation of the post-synaptic membrane. The number of motor neuron spheroids, or motor pool, required to functionally innervate 3D muscle tissues was then determined, generating functional human NMJs that evidence pre- and post-synaptic membrane and motor nerve axon co-localisation. Spontaneous firing was significantly elevated in 3D motor units, confirmed to be driven by the motor nerve via antagonistic inhibition of the AChR. Functional analysis outlined decreased time to peak twitch and half relaxation times, indicating enhanced physiology of excitation contraction coupling in innervated motor units. Our findings provide the methods to maximise the maturity of both iPSC motor neurons and primary human skeletal muscle, utilising cell type specific extracellular matrices and developmental timelines to bioengineer the human motor unit for the study of neuromuscular junction physiology.

Effects of Aging on Musical Performance in Professional Orchestral Musicians

2018 ◽  
Vol 33 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Dianna T Kenny ◽  
Tim Driscoll ◽  
Bronwen J Ackermann
Keyword(s):  
Psychological Health ◽  
Work Performance ◽  
Perceived Exertion ◽  
Age Groups ◽  
Musical Instrument ◽  
Physical And Mental Health ◽  
Age Related ◽  
Physical And Psychological Health ◽  
Orchestral Musicians ◽  
The Impact

BACKGROUND: The physical and psychological demands of playing a musical instrument are likely to be affected by age-related decline in function, including physical, cognitive, psychological, and organ-related changes. However, the complex neurophysiological demands of playing a musical instrument may delay many normal aging-related changes. AIM: This study compared professional classical musicians of different ages, using a range of physical and psychological measures, to discover how increasing age might affect work performance and to identify possible risk and protective factors for physical and psychological health as the musicians age. SUBJECTS: 377 professional orchestral musicians from eight Australian orchestras (70% response rate), ages 18 to 68 yrs (mean 42.1). Multiple standardized physical and psychological tools were used to evaluate the impact of age on a range of physical and mental health variables. RESULTS: Age was not statistically associated with frequency or severity of performance-related musculoskeletal disorders, ratings of perceived exertion, QuickDASH scores, use of beta-blockers, workplace satisfaction, and most psychological tests. Differences were observed on SPIN (social anxiety) scores, with lowest scores in the oldest age group (10.66 in 55+ yrs vs 17.83 in 18-30 yrs, p=0.016). Older musicians had higher BMIs and fewer practice sessions per day than younger musicians and also were more likely to consume alcohol on 5+ days/wk (44% vs 9%, p=0.003). CONCLUSION: Advancing age does not appear to exert undue negative impacts on physical and psychological health or performance capacity of professional orchestral musicians. However, dwindling numbers in the older age groups may suggest a "survivor" effect, whereby those who develop significant age-related decrements may cease professional performance at earlier ages. Longitudinal studies on the professional trajectories of professional orchestral musicians are needed to explore this question further.

scholarly journals Assessing Rat Forelimb and Hindlimb Motor Unit Connectivity as Objective and Robust Biomarkers of Spinal Motor Neuron Function

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Markus E. Harrigan ◽  
Angela R. Filous ◽  
Andrew P. Tosolini ◽  
Renee Morris ◽  
Jan M. Schwab ◽  
...  
Keyword(s):  
Motor Neuron ◽  
Motor Unit ◽  
Compound Muscle Action Potential ◽  
Motor Units ◽  
Longitudinal Assessment ◽  
Muscle Contractility ◽  
Cross Sectional ◽  
Muscle Action Potential ◽  
Experimental Findings ◽  
Neuron Function

Abstract Sensitive and objective biomarkers of neuronal injury, degeneration, and regeneration can help facilitate translation of experimental findings into clinical testing. Whereas measures of upper motor neuron connectivity have been readily established, functional assessments of lower motor neuron (LMN) innervation of forelimb muscles are lacking. Compound muscle action potential (CMAP) and motor unit (MU) number estimation (MUNE) are well-established methods that allow longitudinal MU integrity monitoring in patients. In analogy we refined CMAP and MUNE methods for assessing spinal MU input in the rat forelimb and hindlimb. Repeated CMAP and MUNE recordings are robust (coefficients of variability: 4.5–11.3%), and MUNE measurements from forelimb wrist flexor muscles (415 ± 8 [SEM]) align with back-traced anatomical LMN counts (336 ± 16 [SEM]). For disease validation, cross-sectional blinded electrophysiological and muscle contractility measurements were obtained in a cohort of G93A SOD1 mutant overexpressing rats and compared with controls. Longitudinal assessment of mutant animals demonstrated progressive motor unit decline in the hindlimb to a greater extent than the forelimb. Hindlimb CMAP and MUNE demonstrated strong correlations with plantarflexion muscle contractility. Cross-species assessment of upper/fore- limb and lower/hind- limb motor units using objective electrophysiological CMAP and MUNE values as biomarkers will guide and improve bi-directional translation.

Age-related efficacy and safety of apalutamide (APA) plus ongoing androgen deprivation therapy (ADT) in subgroups of patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC): Post hoc analysis of SPARTAN.

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. 5024-5024 ◽  
Author(s):  
Julie Nicole Graff ◽  
Matthew Raymond Smith ◽  
Fred Saad ◽  
Boris A. Hadaschik ◽  
Hiroji Uemura ◽  
...  
Keyword(s):  
High Risk ◽  
Safety Profile ◽  
Age Groups ◽  
Progression Free Survival ◽  
Controlled Study ◽  
Castration Resistant Prostate Cancer ◽  
Cox Models ◽  
Free Survival ◽  
Age Related ◽  
The Impact

5024 Background: SPARTAN, a randomized phase 3 placebo (PBO)-controlled study in pts with high-risk nmCRPC and PSA doubling time ≤ 10 mo, showed that, compared with PBO, addition of APA to ongoing ADT treatment (tx) prolonged metastasis-free survival (MFS) by > 2 y, reduced the risk of symptomatic progression by 55%, and increased second progression-free survival (PFS2), which is the time from randomization to disease progression on first subsequent anticancer tx, or death. The impact of APA in terms of benefit and safety profile was evaluated in pts aged < 65, 65-74, and ≥ 75 y. Methods: Pts with nmCRPC were randomized 2:1 to APA (240 mg QD) or PBO; ADT was continuous. APA effect was analyzed by Cox models and Kaplan-Meier methods across age subgroups. Results: Baseline characteristics among age groups were similar, although ECOG PS 1 vs 0 increased with age. MFS benefit with APA was highly significant for all age subgroups (Table). In pts ≥ 75 y, MFS risk with APA vs PBO was reduced by 59%; MFS risk was reduced by 86% and 76% for pts < 65 and 65-74 y, respectively. Risk of PFS2 with APA vs PBO was reduced across all age subgroups. PFS2 in pts < 65, 65-74, and ≥ 75 y: HR, 0.09 (p < 0.0001); HR, 0.56 (p = 0.0343); HR, 0.59 (p = 0.0092), respectively. Risk of symptomatic progression was lessened with APA vs PBO for all age subgroups (Table). There was a similar increase in incidence of tx-emergent adverse events (TEAE) with age in both tx arms that remained higher with APA. Incidence of grade 3/4 TEAE (≥ 75 vs < 65 y): APA, 50% vs 37%; PBO, 37% vs 28%. Conclusions: Pts in all age subgroups with high-risk nmCRPC had significant improvement in MFS with APA + ongoing ADT. The safety profile of APA was similar across age subgroups. Clinical trial information: NCT01946204. [Table: see text]

The Impact of Age on Visual Search Performance

1993 ◽  
Vol 37 (2) ◽  
pp. 172-176 ◽  
Author(s):  
P. Manivannan ◽  
Sara Czaja ◽  
Colin Drury ◽  
Chi Ming Ip
Keyword(s):  
Visual Search ◽  
Reaction Time ◽  
Selective Attention ◽  
Search Task ◽  
Visual Search Task ◽  
Age Groups ◽  
Search Performance ◽  
Performance Effect ◽  
Age Related ◽  
The Impact

Visual search is an important component of many real world tasks such as industrial inspection and driving. Several studies have shown that age has an impact on visual search performance. In general older people demonstrate poorer performance on such tasks as compared to younger people. However, there is controversy regarding the source of the age-performance effect. The objective of this study was to examine the relationship between component abilities and visual search performance, in order to identify the locus of age-related performance differences. Six abilities including reaction time, working memory, selective attention and spatial localization were identified as important components of visual search performance. Thirty-two subjects ranging in age from 18 - 84 years, categorized in three different age groups (young, middle, and older) participated in the study. Their component abilities were measured and they performed a visual search task. The visual search task varied in complexity in terms of type of targets detected. Significant relationships were found between some of the component skills and search performance. Significant age effects were also observed. A model was developed using hierarchical multiple linear regression to explain the variance in search performance. Results indicated that reaction time, selective attention, and age were important predictors of search performance with reaction time and selective attention accounting for most of the variance.

scholarly journals Age-Related Differences in Experiences With Social Distancing at the Onset of the COVID-19 Pandemic: A Computational and Content Analytic Investigation of Natural Language From a Social Media Survey (Preprint)

2020 ◽  
Author(s):  
Ryan C Moore ◽  
Angela Y Lee ◽  
Jeffrey T Hancock ◽  
Meghan C Halley ◽  
Eleni Linos
Keyword(s):  
Public Health ◽  
Age Groups ◽  
Prevention Measures ◽  
Middle Aged ◽  
Social Distancing ◽  
Aged People ◽  
Age Related ◽  
Health Related ◽  
The Impact ◽  
Health Guidance

BACKGROUND As COVID-19 poses different levels of threat to people of different ages, health communication regarding prevention measures such as social distancing and isolation may be strengthened by understanding the unique experiences of various age groups. OBJECTIVE The aim of this study was to examine how people of different ages (1) experienced the impact of the COVID-19 pandemic and (2) their respective rates and reasons for compliance or noncompliance with social distancing and isolation health guidance. METHODS We fielded a survey on social media early in the pandemic to examine the emotional impact of COVID-19 and individuals’ rates and reasons for noncompliance with public health guidance, using computational and content analytic methods of linguistic analysis. RESULTS A total of 17,287 participants were surveyed. The majority (n=13,183, 76.3%) were from the United States. Younger (18-31 years), middle-aged (32-44 years and 45-64 years), and older (≥65 years) individuals significantly varied in how they described the impact of COVID-19 on their lives, including their emotional experience, self-focused attention, and topical concerns. Younger individuals were more emotionally negative and self-focused, while middle-aged people were other-focused and concerned with family. The oldest and most at-risk group was most concerned with health-related terms but were lower in anxiety (use of fewer anxiety-related terms) and higher in the use of emotionally positive terms than the other less at-risk age groups. While all groups discussed topics such as acquiring essential supplies, they differentially experienced the impact of school closures and limited social interactions. We also found relatively high rates of noncompliance with COVID-19 prevention measures, such as social distancing and self-isolation, with younger people being more likely to be noncompliant than older people (<i>P</i>&lt;.001). Among the 43.1% (n=7456) of respondents who did not fully comply with health orders, people differed substantially in the reasons they gave for noncompliance. The most common reason for noncompliance was not being able to afford to miss work (n=4273, 57.3%). While work obligations proved challenging for participants across ages, younger people struggled more to find adequate space to self-isolate and manage their mental and physical health; middle-aged people had more concerns regarding childcare; and older people perceived themselves as being able to take sufficient precautions. CONCLUSIONS Analysis of natural language can provide insight into rapidly developing public health challenges like the COVID-19 pandemic, uncovering individual differences in emotional experiences and health-related behaviors. In this case, our analyses revealed significant differences between different age groups in feelings about and responses to public health orders aimed to mitigate the spread of COVID-19. To improve public compliance with health orders as the pandemic continues, health communication strategies could be made more effective by being tailored to these age-related differences.

scholarly journals Age and Gender Differences in Performance at Cross Triathlon World Championships

2018 ◽  
Vol 25 (3) ◽  
pp. 17-22 ◽  
Author(s):  
Oscar Romero-Ramos ◽  
Emilio Fernández-Rodríguez ◽  
Rafael Merino-Marbán ◽  
Daniel Mayorga-Vega ◽  
Robert Podstawski
Keyword(s):  
Age Groups ◽  
Performance Ratio ◽  
Age Group ◽  
Men And Women ◽  
Race Time ◽  
Age Related ◽  
And Performance ◽  
And Gender ◽  
High Level ◽  
The Impact

Abstract Introduction. Cross triathlon is a sport consisting of three segments: swimming, off-road cycling, and running. Our study analyses the differences in performance between genders and changes in performance in selected age categories at the ITU Cross World Championships held between 2011 and 2016. Material and methods. During this period, a total of 1,933 triathletes were analysed (1,472 men and 461 women). Two-way analyses of variance (ANOVA) were used to examine the impact of sex differences and age-related changes on performance (time, percentage of time, and performance ratio) in swimming, cycling, running, and total race. Results. The age groups with the highest level of participation were persons aged 40-44 and 45-49 years among men and women, respectively. With regards to performance in the different age groups, in men and women, its high level was maintained between 25 and 49 years, and it decreased significantly from the age of 50-54. In men, the best results in cycling and total race time were obtained in the 30-34 age group and in swimming and running in the 40-44 group. Women obtained the best results in running in the 25-29 age group, in cycling in the 30-34 group, and in swimming and total race time in the 35-39 group. Conclusions. The results of the study have confirmed that there is a demand for sports in 40+ age groups. As for performance in the different age groups, it was on a high level between 25 and 49 years and decreased significantly from the age of 50-54 onwards. According to these results, the sports training of these triathletes should be oriented so that they obtain their best results between 30 and 35 years of age.

scholarly journals Differential brain activity in visuo-perceptual regions during landmark-based navigation in young and healthy older adults

2020 ◽  
Author(s):  
Stephen Ramanoël ◽  
Marion Durteste ◽  
Marcia Bécu ◽  
Christophe Habas ◽  
Angelo Arleo
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Spatial Information ◽  
Brain Activity ◽  
Age Groups ◽  
Retrosplenial Cortex ◽  
Central Visual Field ◽  
Cortical Projection ◽  
Age Related ◽  
The Impact

AbstractOlder adults exhibit prominent impairments in their capacity to navigate, reorient in unfamiliar environments or update their path when faced with obstacles. This decline in navigational capabilities has traditionally been ascribed to memory impairments and dysexecutive function whereas the impact of visual aging has often been overlooked. The ability to perceive visuo-spatial information such as salient landmarks is essential to navigate in space efficiently. To date, the functional and neurobiological factors underpinning landmark processing in aging remain insufficiently characterized. To address this issue, this study used functional magnetic resonance imaging (fMRI) to investigate the brain activity associated with landmark-based navigation in young and healthy older participants. Twenty-five young adults (μ=25.4 years, σ=4.7; 7F) and twenty-one older adults (μ=73.0 years, σ=3.9; 10F) performed a virtual navigation task in the scanner in which they could only orient using salient landmarks. The underlying whole-brain patterns of activity as well as the functional roles of scene-selective regions, the parahippocampal place area (PPA), the occipital place area (OPA), and the retrosplenial cortex (RSC) were analyzed. We found that older adults’ navigational abilities were diminished compared to young adults’ and that the two age groups relied on distinct navigational strategies to solve the task. Better performance during landmark-based navigation was found to be associated with increased neural activity in an extended neural network comprising several cortical and cerebellar regions. Direct comparisons between age groups further revealed that young participants had enhanced anterior temporal activity. In addition, young adults only were found to recruit occipital areas corresponding to the cortical projection of the central visual field during landmark-based navigation. The region-of-interest analysis revealed increased OPA activation in older adult participants. There were no significant between-group differences in PPA and RSC activations. These results hint at the possibility that aging diminishes fine-grained information processing in occipital and temporal regions thus hindering the capacity to use landmarks adequately for navigation. This work helps towards a better comprehension of the neural dynamics subtending landmark-based navigation and it provides new insights on the impact of age-related visuo-spatial processing changes on navigation capabilities.

scholarly journals Bioengineered model of the human motor unit with physiologically functional neuromuscular junctions

2020 ◽  
Author(s):  
Rowan P. Rimington ◽  
Jacob W. Fleming ◽  
Andrew J. Capel ◽  
Patrick C. Wheeler ◽  
Mark P. Lewis
Keyword(s):  
Motor Neuron ◽  
Motor Unit ◽  
Neuromuscular Junctions ◽  
Motor Nerve ◽  
Motor Units ◽  
Model Organisms ◽  
Synaptic Membrane ◽  
Type I ◽  
Dependent Manner ◽  
Human Motor

AbstractInvestigations of the human neuromuscular junction (NMJ) have predominately utilised experimental animals and model organisms. Consequently, there remains a paucity of data regarding the development of the human NMJ and a lack of systems that enable temporal investigation of the motor unit. This work addresses this need, providing the methodologies to bioengineer 3D models of the human motor unit. Separate maturation of primary human skeletal muscle and iPSC derived motor neurons seeks to accurately represent neuromuscular development via controlled addition of motor axons following primary myogenesis. Spheroid cultures of motor neuron progenitors augmented the transcription of OLIG2, ISLET1 and SMI32 motor neuron mRNAs ∼400, ∼150 and ∼200-fold respectively. Axon projections of adhered motor neuron spheroids exceeded 1000μm in monolayer, with transcription of SMI32 and VACHT mRNAs further enhanced in a concentration dependent manner within optimised 3D type I collagen extracellular matrices. Bioengineered skeletal muscles produce functional forces, demonstrate increased acetylcholine receptor (AChR) clustering, and transcription of MUSK and LRP4 mRNAs indicating enhanced organisation of the post-synaptic membrane. Dosed integration of motor neuron spheroids outlined the motor pool required to functionally innervate muscle tissues in 3D, generating physiologically functional human NMJs that evidence pre- and post-synaptic membrane and motor nerve terminal co-localisation. Spontaneous firing was significantly elevated in 3D motor units, confirmed to be driven by the motor nerve via antagonistic inhibition of the AChR. Finally, functional analyses outlined decreased time to peak twitch and half relaxation times, indicating enhanced physiology of excitation contraction coupling of NMJs within innervated motor units.

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