Age-related Changes in Motor Function (I). Mechanical and Neuromuscular Factors

AbstractThis two-part narrative review aims to provide an insight into the age-related mechanical and neuromuscular factors contributing to: (1) decreased maximal muscle strength and power; (2) decreased force control; and (3) increased fatigability. Structural and functional changes from the macro-level of the muscle-tendon unit to the micro-level of the single muscle fibre have been reviewed and are described. At the muscle-tendon unit level, muscle volume, thickness and cross-sectional area, as well as pennation angle and fascicle length all decrease as part of the natural ageing process. These changes negatively affect muscle quality, muscle and tendon stiffness and Young’s modulus and account for impairment in motor performance. A progressive age-related alteration in neuromuscular function is also well-established, with reduction in number and firing rate of the motor unit, contractile velocity and specific tension of muscle fibres, and stability of neuromuscular junction. These could be the result of structural alterations in the: (i) motor neuron, with number reduced, size and collateral sprouting increased; (ii) neuromuscular junction, with decreased post-synaptic junctional fold and density of active zones and increased pre-synaptic branching and post-synaptic area; and (iii) muscle fibre, with decreased number and size and increased type I and co-expression of myosin heavy chain.

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THE CAPILLARY PATTERN IN HUMAN MASSETER MUSCLE DURING AGEING

Image Analysis & Stereology ◽

10.5566/ias.v32.p135-144 ◽

2013 ◽

Vol 32 (3) ◽

pp. 135 ◽

Cited By ~ 1

Author(s):

Erika Cvetko ◽

Jiří Janáček ◽

Lucie Kubínová ◽

Ida Eržen

Keyword(s):

Muscle Fibre ◽

Masseter Muscle ◽

3D Visualization ◽

Fibre Length ◽

Fibre Surface ◽

Fibre Volume ◽

Immunohistochemical Method ◽

Muscle Fibres ◽

Age Related ◽

Novel Approach

The effect of ageing on the capillary network in skeletal muscles has produced conflicting results in both, human and animals studies. Some of the inconsistencies are due to non-comparable and biased methods that were applied on thin transversal sections, especially in muscles with complicated morphological structures, such as in human masseter muscle. We present a new immunohistochemical method for staining capillaries and muscle fibres in 100 µm thick sections as well as novel approach to 3D visualization of capillaries and muscle fibres. Applying confocal microscopy and virtual 3D stereological grids, or tracing capillaries in virtual reality, length of capillaries within a muscle volume or length of capillaries adjacent to muscle fibre per fibre length, fibre surface or fibre volume were evaluated in masseter muscle of young and old subjects by an unbiased approach. Our findings show that anatomic capillarity is well maintained in masseter muscle in old subjects; however, vascular remodelling occurs with age, which could be a response to changed muscle function and age-related muscle fibre type transformations.

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Effects of aging and Parkinson’s disease on motor unit remodeling: influence of resistance exercise training

Journal of Applied Physiology ◽

10.1152/japplphysiol.00563.2017 ◽

2018 ◽

Vol 124 (4) ◽

pp. 888-898 ◽

Cited By ~ 8

Author(s):

Neil A. Kelly ◽

Kelley G. Hammond ◽

C. Scott Bickel ◽

Samuel T. Windham ◽

S. Craig Tuggle ◽

...

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Exercise Training ◽

Neuromuscular Junction ◽

Resistance Exercise ◽

Motor Unit ◽

Type I ◽

Resistance Exercise Training ◽

Age Related ◽

Myofiber Type

Aging muscle atrophy is in part a neurodegenerative process revealed by denervation/reinnervation events leading to motor unit remodeling (i.e., myofiber type grouping). However, this process and its physiological relevance are poorly understood, as is the wide-ranging heterogeneity among aging humans. Here, we attempted to address 1) the relation between myofiber type grouping and molecular regulators of neuromuscular junction (NMJ) stability; 2) the impact of motor unit remodeling on recruitment during submaximal contractions; 3) the prevalence and impact of motor unit remodeling in Parkinson’s disease (PD), an age-related neurodegenerative disease; and 4) the influence of resistance exercise training (RT) on regulators of motor unit remodeling. We compared type I myofiber grouping, molecular regulators of NMJ stability, and the relative motor unit activation (MUA) requirement during a submaximal sit-to-stand task among untrained but otherwise healthy young (YA; 26 yr, n = 27) and older (OA; 66 yr, n = 91) adults and OA with PD (PD; 67 yr, n = 19). We tested the effects of RT on these outcomes in OA and PD. PD displayed more motor unit remodeling, alterations in NMJ stability regulation, and a higher relative MUA requirement than OA, suggesting PD-specific effects. The molecular and physiological outcomes tracked with the severity of type I myofiber grouping. Together these findings suggest that age-related motor unit remodeling, manifested by type I myofiber grouping, 1) reduces MUA efficiency to meet submaximal contraction demand, 2) is associated with disruptions in NMJ stability, 3) is further impacted by PD, and 4) may be improved by RT in severe cases. NEW & NOTEWORTHY Because the physiological consequences of varying amounts of myofiber type grouping are unknown, the current study aims to characterize the molecular and physiological correlates of motor unit remodeling. Furthermore, because exercise training has demonstrated neuromuscular benefits in aged humans and improved innervation status and neuromuscular junction integrity in animals, we provide an exploratory analysis of the effects of high-intensity resistance training on markers of neuromuscular degeneration in both Parkinson’s disease (PD) and age-matched older adults.

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Effect of a Diet Supplemented with Nettle (Urtica dioica L.) or Fenugreek (Trigonella foenum-graecum L.) on the Post-Slaughter Traits and Meat Quality Parameters of Termond White Rabbits

Animals ◽

10.3390/ani11061566 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1566

Author(s):

Sylwia Ewa Pałka ◽

Agnieszka Otwinowska-Mindur ◽

Łukasz Migdał ◽

Michał Kmiecik ◽

Dorota Wojtysiak

Keyword(s):

Muscle Fibre ◽

Fibre Diameter ◽

Quality Parameters ◽

Urtica Dioica ◽

Control Group ◽

Muscle Fibres ◽

Type I ◽

Feeding Regime ◽

Trigonella Foenum Graecum ◽

Trigonella Foenum Graecum L

The purpose of the study was to analyse the effect of nettle (Urtica dioica L.) leaves and fenugreek (Trigonella foenum-graecum L.) seeds as additives to fodder in order to improve post-slaughter traits and quality parameters of Termond White rabbit meat (n = 60; 30 , 30 ). Three experimental groups were created. The control group (n = 20; 10 and 10 ) was fed ad libitum feed containing corn, bran, wheat, dried alfalfa, soybean meal, sunflower meal, dicalcium phosphate, calcium carbonate and vitamin-mineral premix. The animals from the first experimental group (n = 20; 10 and 10 ) were fed a complete mixture added with 1% of nettle (Urtica dioica L.) leaves. Rabbits from the second group (n = 20; 10 and 10 ) were fed with a complete mixture added with 1% of fenugreek (Trigonella foenum-graecum L.) seeds. Rabbits fed with pellets with the addition of nettle were characterized by a higher slaughter weight, higher weight of hot and cold carcasses, lungs, kidneys and head as well as a higher weight of the fore, middle and hind part of the carcass compared to the other two groups. The carcasses of animals fed with fenugreek and nettle had a higher percentage of the fore and hind parts compared to the carcasses of the animals from the control group. The female carcasses were characterized by a significantly higher percentage of the middle part compared to the male carcasses. For most colour measurement traits, the differences depending on the feeding regime were significant. The effect of gender on meat colour was non significant. The effect of feeding regime and of gender on texture traits such as shear force, hardness, springiness, cohesiveness and chewiness were non significant. Feeding had no effect on muscle fibre diameter, but it affected the muscle fibre type I percentage. Thus, the group fed with pellets containing nettle leaves had higher percentage of type I muscle fibres than the control group. The effect of gender on muscle fibre traits was non significant.

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Effect of housing system and genotype on rabbit meat quality

Czech Journal of Animal Science ◽

10.17221/7343-cjas ◽

2014 ◽

Vol 59 (No. 4) ◽

pp. 190-199 ◽

Cited By ~ 7

Author(s):

D. Chodová ◽

E. Tůmová ◽

M. Martinec ◽

Z. Bízková ◽

V. Skřivanová ◽

...

Keyword(s):

Fatty Acids ◽

Muscle Fibre ◽

Meat Quality ◽

Housing System ◽

Muscle Fibres ◽

Physical Parameters ◽

Type I ◽

Guard Hair ◽

Lower Weight ◽

Fibre Characteristics

The effect of the housing system on the carcass characteristics, physical parameters of meat quality, fatty acid composition, and muscle fibre characteristics was studied in some Czech breeds. Ninety-six rabbits from seven different breeds of Czech genetic resources (Moravian Blue, Czech White, Czech Solver, Czech Spotted, Moravian White of Brown Eye, Czech Gold, and Czech Black Guard Hair) and one rabbit commercial hybrid (Hyplus), kept in two housing systems: intensive system (wire-net cages) or alternative (straw-bedded pen), were slaughtered at the age of 91 days. Alternatively housed rabbits had lower weight at slaughter, lower weight of loin, of hind legs meat, and of renal fat than rabbits from cages. The interactions between housing system and genotype were reflected significantly in pH value, and lightness and yellowness of biceps femoris. The highest (P ≤ 0.047) pH was observed in Hyplus (6.68) from cages, while the lowest value was noted in Moravian White of Brown Eye (6.26). The significantly (P ≤ 0.010) lightest meat was detected in Czech Solver (60.93) and the darkest in Czech Gold (47.81). Alternatively reared rabbits showed significantly (P ≤ 0.001) lower monounsaturated fatty acids (MUFA) (26.63%) and higher (P ≤ 0.001) polyunsaturated fatty acids (PUFA) (36.73%) contents than rabbits from cages (36.94% MUFA and 26.23% PUFA). The alternatively housed group had also higher n-3 and n-6 PUFA contents and higher PUFA : SFA ratio than the intensively housed one. Significant interactions (P ≤ 0.001) were observed in cross sectional area (CSA), diameter, and perimeter of muscle fibres of type I. The largest (P ≤ 0.001) CSA of type I muscle fibre had Czech Black Guard Hair from cages (2573.1 μm<sup>2</sup>), while in pens this breed exhibited the smallest CSA (1219.6 μm<sup>2</sup>), diameter (38.68 μm), and perimeter (130.2 μm). Fibre type distribution was not affected by any of the monitored parameters. The effect of interactions of the housing system and genotype was manifested mainly in physical and muscle fibre characteristics.  

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Distribution of acetylcholine receptors in the vicinity of nerve terminals on skeletal muscle of the frog

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1972.0060 ◽

1972 ◽

Vol 181 (1065) ◽

pp. 431-440 ◽

Cited By ~ 29

Keyword(s):

Skeletal Muscle ◽

Connective Tissue ◽

Neuromuscular Junction ◽

Muscle Fibre ◽

Nerve Terminal ◽

Acetylcholine Receptors ◽

Postsynaptic Membrane ◽

Muscle Membrane ◽

Muscle Fibres ◽

Nerve Terminals

1. The acetylcholine (ACh) sensitivity of muscle fibres at the neuromuscular junction of the frog was investigated in preparations in which the nerve terminals could be clearly seen. 2. ACh released iontophoretically from a micropipette that was precisely positioned at various points along the muscle fibre in the vicinity of the synapse showed that the peak chemosensitivity (up to 1900 mV/nC) is confined to an area of postsynaptic membrane within a few micra of the nerve terminal; a tenfold decline in sensitivity was obtained when the ACh was released only 5 to 10 μm from the terminal’s edge. It is estimated that most of the response obtained when ACh is released within 40 μm from the terminal (the area covered in this study) is due to diffusion to the immediate postsynaptic area. The extrasynaptic chemosensitivity of the muscle membrane was too low to be measured with the present methods. 3. The accuracy with which micropipettes could be positioned in synaptic areas and the clarity of viewing nerve terminals were improved by bathing the tissue in collagenase, which reduced the amount of connective tissue. The distribution of chemosensitivity remained unchanged by such treatment. The ACh response was not detectably altered when nerve terminals were lifted off the muscle, exposing the subsynaptic muscle surface.

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Composition and cross-sectional area of muscle fibre types in relation to daily gain and lean and fat content of carcass in Landrace and Yorkshire pigs

Agricultural and Food Science ◽

10.23986/afsci.72772 ◽

1996 ◽

Vol 5 (6) ◽

pp. 593-600 ◽

Cited By ~ 4

Author(s):

Marita Ruusunen ◽

Marja-Liisa Sevon-Aimonen ◽

Eero Puolanne

Keyword(s):

Muscle Fibre ◽

Live Weight ◽

Carcass Composition ◽

Cross Sectional Area ◽

Muscle Fibre Types ◽

Muscle Fibres ◽

Type I ◽

Sectional Area ◽

Cross Sectional ◽

Yorkshire Pigs

The muscle fibre-type properties of longissimus were compared between Landrace and Yorkshire breeds and between the sexes in an attempt to shed light on the relationship of these histochemical parameters to animal growth and carcass composition. Muscle fibres were classified into three groups, type I, type lIA and type 11B, using the myosin ATPase method. At a given live weight, the cross-sectional area of type I fibres (CSA1) was smaller (p

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PL-016 Endurance training, muscle fibre type composition and the maximal capacity for fat oxidation

Exercise Biochemistry Review ◽

10.14428/ebr.v1i1.8193 ◽

2018 ◽

Vol 1 (1) ◽

Author(s):

Chris Shaw ◽

Courtney Swinton ◽

Maria Gabriela Morales Scholz ◽

Tasman Erftemeyer ◽

Andrew Aldous ◽

...

Keyword(s):

Muscle Fibre ◽

Fibre Type ◽

Fat Oxidation ◽

Muscle Fibre Type ◽

Muscle Fibres ◽

Type I ◽

Maximal Rate ◽

Fibre Type Composition ◽

Type Composition ◽

Whole Muscle

Objective A greater capacity for fat oxidation in endurance trained athletes is linked to greater utilisation of intramuscular lipid (IMCL). IMCL breakdown occurs only in type I muscle fibres yet little is known about the fibre type specific abundance of lipid regulatory proteins. We explored the impact of endurance training on the maximal rate fat oxidation, muscle fibre type and muscle fibre type specific abundance of proteins regulating IMCL metabolism. Methods Endurance trained (n=7, 28 ± 3 years, VO2max62.6 ± 1.6 ml·min-1·kg-1) and untrained (n=8, 25 ± 1 years, VO2max44.9 ± 1.9 ml·min-1·kg-1) males performed an incremental exercise test to determine maximal fat oxidation rate. Muscle fibre type composition and fibre type-specific IMCL content was assessed with immunofluorescence microscopy and protein abundance was analysed with immunoblotting on pooled single muscle fibres and whole muscle. Results Endurance trained individuals displayed a higher peak fat oxidation rate (0.49 ± 0.05 vs. 0.20 ± 0.03 g·min-1, P<0.05), which correlated with type I fibre percentage (R = 0.83, P < 0.01) and VO2max (R = 0.78, P < 0.01). Type I muscle fibres from endurance trained individuals had a greater abundance of ATGL. In whole muscle, the endurance trained group had greater abundance of PLIN2, PLIN5 and ATGL compared to the untrained group (P < 0.05). Furthermore, autophagy flux measured as LC3-II/I ratio was higher in type I muscle fibres and LC3-II/I, lysosomal markers (LAMP2) and chaperone-mediated autophagy markers (LAMP2A) were all higher in whole muscle of endurance trained individuals (P < 0.05). Conclusions These results demonstrate that the maximal rate of fat oxidation is related to the proportion of type I muscle fibres. Furthermore, IMCL storage and the abundance of key proteins regulating lipid metabolism is fibre type specific and greater in endurance trained individuals. Muscle fibre type composition should be considered when investigating the regulation of IMCL utilisation and markers of autophagy.

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Tension responses to increased hydrostatic pressure in glycerinated rabbit psoas muscle fibres

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1987.0070 ◽

1987 ◽

Vol 232 (1267) ◽

pp. 217-226 ◽

Cited By ~ 9

Keyword(s):

Hydrostatic Pressure ◽

Muscle Fibre ◽

Room Temperature ◽

Psoas Muscle ◽

Isometric Tension ◽

Muscle Fibres ◽

Single Muscle Fibre ◽

Rabbit Psoas ◽

Rigor Tension ◽

Tension Transducer

A method developed to study the effect of increased hydrostatic pressure on the isometric tension of a single muscle fibre is described and experiments done at room temperature (18–22°C) on glycerinated rabbit psoas muscle fibres are presented. Increase of pressure (range 1–10 MPa) caused little change in tension transducer response when a muscle fibre was relaxed. However, there was a reversible depression of isometric tension with an increase of pressure when a fibre was maximally calcium-activated or in rigor; the depression was around 15% for active tension and 30% for rigor tension, for an increase of pressure of 10 MPa ( ca . 100 atm).

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Relaxation Rate of Constituent Muscle-Fibre Types in Human Quadriceps

Clinical Science ◽

10.1042/cs0560047 ◽

1979 ◽

Vol 56 (1) ◽

pp. 47-52 ◽

Cited By ~ 31

Author(s):

C. M. Wiles ◽

A. Young ◽

D. A. Jones ◽

R. H. T. Edwards

Keyword(s):

Relaxation Rate ◽

Muscle Fibre ◽

Human Subjects ◽

Muscle Fibre Types ◽

Muscle Fibres ◽

Isometric Contractions ◽

Type I ◽

Type Ii ◽

Fibre Type Composition

1. Muscle fibres may be subdivided into type I (with slow-twitch contractile properties) and type II (fast-twitch) depending on their myosin adenosine triphosphatase activity. In voluntary isometric contractions type I fibres are utilized at low forces (<20% of maximum) whereas type II fibres are recruited in addition at high forces. This physiological recruitment order has enabled us to measure the relaxation rate of type I and II fibres in vivo in normal human subjects. 2. Relaxation rate was measured in 16 subjects from low (10% of maximum) and maximum isometric quadriceps contractions and the muscle-fibre type composition determined from needle-biopsy specimens in 10 subjects. The relaxation rate of type II fibres was calculated to be twice as fast as that of type I. 3. It was not possible to estimate, from studies in 33 quadriceps muscles (25 normal subjects), the contribution of type II fibres to overall fibre area from the relaxation rate as determined from electrically stimulated isometric contractions.

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