scholarly journals Contractile Properties of MHC I and II Fibers From Highly Trained Arm and Leg Muscles of Cross-Country Skiers

2021 ◽  
Vol 12 ◽  
Author(s):  
Kasper Degn Gejl ◽  
Lars G. Hvid ◽  
Erik P. Andersson ◽  
Rasmus Jensen ◽  
Hans-Christer Holmberg ◽  
...  
Keyword(s):  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Contractile Properties ◽  
Specific Force ◽  
Triceps Brachii ◽  
Mhc I ◽  
Mhc Ii ◽  
Leg Muscles ◽  
Generating Capacity ◽  
Cross Country

IntroductionLittle is known about potential differences in contractile properties of muscle fibers of the same type in arms and legs. Accordingly, the present study was designed to compare the force-generating capacity and Ca2+ sensitivity of fibers from arm and leg muscles of highly trained cross-country skiers.MethodSingle muscle fibers of m. vastus lateralis and m. triceps brachii of eight highly trained cross-country skiers were analyzed with respect to maximal Ca2+-activated force, specific force and Ca2+ sensitivity.ResultThe maximal Ca2+-activated force was greater for myosin heavy chain (MHC) II than MHC I fibers in both the arm (+62%, P < 0.001) and leg muscle (+77%, P < 0.001), with no differences between limbs for each MHC isoform. In addition, the specific force of MHC II fibers was higher than that of MHC I fibers in both arms (+41%, P = 0.002) and legs (+95%, P < 0.001). The specific force of MHC II fibers was the same in both limbs, whereas MHC I fibers from the m. triceps brachii were, on average, 39% stronger than fibers of the same type from the m. vastus lateralis (P = 0.003). pCa50 was not different between MHC I and II fibers in neither arms nor legs, but the MHC I fibers of m. triceps brachii demonstrated higher Ca2+ sensitivity than fibers of the same type from m. vastus lateralis (P = 0.007).ConclusionComparison of muscles in limbs equally well trained revealed that MHC I fibers in the arm muscle exhibited a higher specific force-generating capacity and greater Ca2+ sensitivity than the same type of fiber in the leg, with no such difference in the case of MHC II fibers. These distinct differences in the properties of fibers of the same type in equally well-trained muscles open new perspectives in muscle physiology.

Phenotypic adaptations in human muscle fibers 6 and 24 wk after spinal cord injury

2002 ◽  
Vol 92 (1) ◽  
pp. 147-154 ◽  
Author(s):  
R. J. Talmadge ◽  
M. J. Castro ◽  
D. F. Apple ◽  
G. A. Dudley
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Early Time ◽  
Mhc I ◽  
Time Period ◽  
Plasmic Reticulum ◽  
Cord Injury ◽  
Mhc Iia

10.1152/japplphysiol.000247.2001.—The effects of spinal cord injury (SCI) on the profile of sarco(endo) plasmic reticulum calcium-ATPase (SERCA) and myosin heavy chain (MHC) isoforms in individual vastus lateralis (VL) muscle fibers were determined. Biopsies from the VL were obtained from SCI subjects 6 and 24 wk postinjury ( n = 6). Biopsies from nondisabled (ND) subjects were obtained at two time points 18 wk apart ( n = 4). In ND subjects, the proportions of VL fibers containing MHC I, MHC IIa, and MHC IIx were 46 ± 3, 53 ± 3, and 1 ± 1%, respectively. Most MHC I fibers contained SERCA2. Most MHC IIa fibers contained SERCA1. All MHC IIx fibers contained SERCA1 exclusively. SCI resulted in significant increases in fibers with MHC IIx (14 ± 4% at 6 wk and 16 ± 2% at 24 wk). In addition, SCI resulted in high proportions of MHC I and MHC IIa fibers with both SERCA isoforms (29% at 6 wk and 54% at 24 wk for MHC I fibers and 16% at 6 wk and 38% at 24 wk for MHC IIa fibers). Thus high proportions of VL fibers were mismatched for SERCA and MHC isoforms after SCI (19 ± 3% at 6 wk and 36 ± 9% at 24 wk) compared with only ∼5% in ND subjects. These data suggest that, in the early time period following SCI, fast fiber isoforms of both SERCA and MHC are elevated disproportionately, resulting in fibers that are mismatched for SERCA and MHC isoforms. Thus the adaptations in SERCA and MHC isoforms appear to occur independently.

Single muscle fiber contractile properties during a competitive season in male runners

2004 ◽  
Vol 287 (5) ◽  
pp. R1124-R1131 ◽  
Author(s):  
M. P. Harber ◽  
P. M. Gallagher ◽  
A. R. Creer ◽  
K. M. Minchev ◽  
S. W. Trappe
Keyword(s):  
Cell Size ◽  
Peak Power ◽  
Fiber Strength ◽  
Muscle Fibers ◽  
Contractile Properties ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Mhc I ◽  
Intense Training ◽  
Mhc Iia

The purpose of this investigation was to examine the contractile properties of individual myofibers in response to periodized training periods throughout a collegiate cross-country season in male runners. Muscle biopsies of the gastrocnemius were taken after a summer base training phase (T1), an 8-wk intense training period (T2), and a 4-wk taper phase (T3). Five runners ( n = 5; age = 20 ± 1 yr; wt = 65 ± 4 kg; ht = 178 ± 3 cm) completed all three time points. A total of 328 individual muscle fibers [myosin heavy chain (MHC) I = 66%; MHC IIa = 33%; hybrids = 1%] were isolated and studied at 15°C for their contractile properties. Diameter of MHC I fibers was 3% smaller ( P < 0.05) at T2 compared with T1 and an additional 4% smaller ( P < 0.05) after the taper. Cell size was unaltered in the MHC IIa fibers. MHC I and IIa fiber strength increased 18 and 11% ( P < 0.05), respectively, from T1 to T2. MHC I fibers produced 9% less force ( P < 0.05) after the taper, whereas MHC IIa fibers were 9% stronger ( P < 0.05). Specific tension increased 38 and 26% ( P < 0.05) for MHC I and IIa fibers, respectively, from T1 to T2 and was unchanged with the taper. Maximal shortening velocity ( Vo) of the MHC I fibers decreased 23% ( P < 0.05) from T1 to T2 and 17% ( P < 0.05) from T2 to T3, whereas MHC IIa Vo was unchanged. MHC I peak power decreased 20% ( P < 0.05) from T1 to T2 and 25% ( P < 0.05) from T2 to T3, whereas MHC IIa peak power was unchanged. Power corrected for cell size decreased 15% ( P < 0.05) from T2 to T3 and was 24% ( P < 0.05) lower at T3 compared with T1 for the MHC I fibers only. These data suggest that changes in run training alter myocellular physiology via decreases in fiber size, Vo, and power of MHC I fibers and through increases in force per cross-sectional area of slow- and fast-twitch muscle fibers.

scholarly journals Physiological and Biomechanical Responses to Cross-Country Skiing in Varying Terrain: Low- vs. High-Intensity

2021 ◽  
Vol 12 ◽  
Author(s):  
Trine M. Seeberg ◽  
Jan Kocbach ◽  
Jørgen Danielsen ◽  
Dionne A. Noordhof ◽  
Knut Skovereng ◽  
...  
Keyword(s):  
Oxygen Saturation ◽  
Power Distribution ◽  
High Intensity ◽  
Vastus Lateralis ◽  
Time Dependent ◽  
Triceps Brachii ◽  
Cycle Rate ◽  
Muscle Oxygen ◽  
Biomechanical Responses ◽  
Cross Country

The purposes of our study were to investigate the physiological and biomechanical responses to low-intensity (LI) and high-intensity (HI) roller ski skating on varying terrain and compare these responses between training intensities. Nine elite male skiers performed treadmill roller skiing consisting of two 21 min sessions (7 × 3 min laps) at LI and HI with the same set inclines and intensity-dependent speeds (LI/HI: distance: 5.8/7.5 km, average speed: 16.7/21.3 km/h). Physiological and biomechanical variables were measured continuously, and each movement cycle and sub-technique employed were detected and classified with a machine learning model. Both the LI and HI sessions induced large terrain-dependent fluctuations (relative to the maximal levels) in heart rate (HR, 17.7 vs. 12.2%-points), oxygen uptake (V.O2, 33.0 vs. 31.7%-points), and muscle oxygen saturation in the triceps brachii (23.9 vs. 33.4%-points) and vastus lateralis (12.6 vs. 24.3%-points). A sub-technique dependency in relative power contribution from poles and skis exhibited a time-dependent shift from Lap 1 to Lap 7 toward gradually more ski power (6.6 vs. 7.8%-points, both p &lt; 0.01). The terrain-dependent fluctuations did not differ between LI and HI for V.O2 (p = 0.50), whereas HR fluctuated less (p &lt; 0.01) and displayed a time-dependent increase from Lap 2 to Lap 7 (7.8%-points, p &gt; 0.01) during HI. Oxygen saturation shifted 2.4% points more for legs than arms from LI to HI (p &gt; 0.05) and regarding sub-technique, 14.7% points more G3 on behalf of G2 was employed on the steepest uphill during HI (p &lt; 0.05). Within all sub-techniques, cycle length increased two to three times more than cycle rate from LI to HI in the same terrains, while the corresponding poling time decreased more than ski contact time (all p &gt; 0.05). In sum, both LI and HI cross-country (XC) skiing on varying terrain induce large terrain-dependent physiological and biomechanical fluctuations, similar to the patterns found during XC skiing competitions. The primary differences between training intensities were the time-dependent increase in HR, reduced relative oxygen saturation in the legs compared to the arms, and greater use of G3 on steep uphill terrain during HI training, whereas sub-technique selection, cycle rate, and pole vs. ski power distribution were similar across intensities on flat and moderately uphill terrain.

scholarly journals A new method to study in vivo protein synthesis in slow- and fast-twitch muscle fibers and initial measurements in humans

2010 ◽  
Vol 108 (5) ◽  
pp. 1410-1416 ◽  
Author(s):  
J. M. Dickinson ◽  
J. D. Lee ◽  
B. E. Sullivan ◽  
M. P. Harber ◽  
S. W. Trappe ◽  
...  
Keyword(s):  
Fiber Type ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Human Muscle ◽  
Synthesis Rate ◽  
Mhc I ◽  
Fast Twitch ◽  
Mixed Protein ◽  
Mhc Iia

The aim of this study was to develop an approach to directly assess protein fractional synthesis rate (FSR) in isolated human muscle fibers in a fiber type-specific fashion. Individual muscle fibers were isolated from biopsies of the vastus lateralis (VL) and soleus (SOL) obtained from eight young men during a primed, continuous infusion of [5,5,5-2H3]leucine performed under basal conditions. To determine mixed protein FSR, a portion of each fiber was used to identify fiber type, fibers of the same type were pooled, and the [5,5,5-2H3]leucine enrichment was determined via GC-MS. Processing isolated slow-twitch [myosin heavy chain (MHC) I] and fast-twitch (MHC IIa) fibers for mixed protein bound [5,5,5-2H3]leucine enrichment yielded mass ion chromatographic peaks that were similar in shape, abundance, and measurement reliability as tissue homogenates. In the VL, MHC I fibers exhibited a 33% faster ( P < 0.05) mixed protein FSR compared with MHC IIa fibers (0.068 ± 0.006 vs. 0.051 ± 0.003%/h). MHC I fibers from the SOL (0.060 ± 0.005%/h) and MHC I fibers from the VL displayed similar ( P > 0.05) mixed protein FSR. Feasibility of processing isolated human muscle fibers for analysis of myofibrillar protein [5,5,5-2H3]leucine enrichment was also confirmed in non-fiber-typed pooled fibers from the VL. These methods can be applied to the study of fiber type-specific responses in human skeletal muscle. The need for this level of investigation is underscored by the different contributions of each fiber type to whole muscle function and the numerous distinct adaptive functional and metabolic changes in MHC I and MHC II fibers originating from the same muscle.

Effect of resistance training on single muscle fiber contractile function in older men

2000 ◽  
Vol 89 (1) ◽  
pp. 143-152 ◽  
Author(s):  
Scott Trappe ◽  
David Williamson ◽  
Michael Godard ◽  
David Porter ◽  
Greg Rowden ◽  
...  
Keyword(s):  
Resistance Training ◽  
Muscle Fiber ◽  
Contractile Function ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Older Men ◽  
Single Muscle ◽  
Mhc I ◽  
Before And After ◽  
Mhc Iia

The purpose of this study was to examine single cell contractile mechanics of skeletal muscle before and after 12 wk of progressive resistance training (PRT) in older men ( n = 7; age = 74 ± 2 yr and weight = 75 ± 5 kg). Knee extensor PRT was performed 3 days/wk at 80% of one-repetition maximum. Muscle biopsy samples were obtained from the vastus lateralis before and after PRT (pre- and post-PRT, respectively). For analysis, chemically skinned single muscle fibers were studied at 15°C for peak tension [the maximal isometric force (Po)], unloaded shortening velocity ( V o), and force-velocity parameters. In this study, a total of 199 (89 pre- and 110 post-PRT) myosin heavy chain (MHC) I and 99 (55 pre- and 44 post-PRT) MHC IIa fibers were reported. Because of the minimal number of hybrid fibers identified post-PRT, direct comparisons were limited to MHC I and IIa fibers. Muscle fiber diameter increased 20% (83 ± 1 to 100 ± 1 μm) and 13% (86 ± 1 to 97 ± 2 μm) in MHC I and IIa fibers, respectively ( P < 0.05). Po was higher ( P < 0.05) in MHC I (0.58 ± 0.02 to 0.90 ± 0.02 mN) and IIa (0.68 ± 0.02 to 0.85 ± 0.03 mN) fibers. Muscle fiber V o was elevated 75% (MHC I) and 45% (MHC IIa) after PRT ( P < 0.05). MHC I and IIa fiber power increased ( P < 0.05) from 7.7 ± 0.5 to 17.6 ± 0.9 μN · fiber lengths · s−1 and from 25.5 to 41.1 μN · fiber lengths · s−1, respectively. These data indicate that PRT in elderly men increases muscle cell size, strength, contractile velocity, and power in both slow- and fast-twitch muscle fibers. However, it appears that these changes are more pronounced in the MHC I muscle fibers.

Force transmission, compliance, and viscoelasticity are altered in the α7-integrin-null mouse diaphragm

2005 ◽  
Vol 288 (2) ◽  
pp. C282-C289 ◽  
Author(s):  
M. A. Lopez ◽  
U. Mayer ◽  
W. Hwang ◽  
T. Taylor ◽  
M. A. Hashmi ◽  
...  
Keyword(s):  
Transverse Direction ◽  
Muscle Fibers ◽  
Contractile Properties ◽  
Receptor Protein ◽  
Null Mouse ◽  
Force Transmission ◽  
Mechanical Coupling ◽  
Generating Capacity ◽  
Old Mice

α7β1 integrin is a transmembrane structural and receptor protein of skeletal muscles, and the absence of α7-integrin causes muscular dystrophy. We hypothesized that the absence of α7-integrin alters compliance and viscoelasticity and disrupts the mechanical coupling between passive transverse and axial contractile elements in the diaphragm. In vivo the diaphragm is loaded with pressure, and therefore axial and transverse length-tension relationships are important in assessing its function. We determined diaphragm passive length-tension relationships and the viscoelastic properties of its muscle in 1-month-old α7-integrin-null mice and age-matched controls. Furthermore, we measured the isometric contractile properties of the diaphragm from mutant and normal mice in the absence and presence of passive force applied in the transverse direction to fibers in 1-month-old and 5-month-old mutant mice. We found that compared with controls, the diaphragm direction of α7-integrin-null mutants showed 1) a significant decrease in muscle extensibility in 1-year-old mice, whereas muscle extensibility increased in the 1-month-old mice; 2) altered muscle viscoelasticity in the transverse direction of the muscle fibers of 1-month-old mice; 3) a significant increase in force-generating capacity in the diaphragms of 1-month-old mice, whereas in 5-month-old mice muscle contractility was depressed; and 4) significant reductions in mechanical coupling between longitudinal and transverse properties of the muscle fibers of 1-month-old mice. These findings suggest that α7-integrin serves an important mechanical function in the diaphragm by contributing to passive compliance, viscoelasticity, and modulation of its muscle contractile properties.

scholarly journals Comparison of Mitochondrial Respiration in M. triceps brachii and M. vastus lateralis Between Elite Cross-Country Skiers and Physically Active Controls

2019 ◽  
Vol 10 ◽  
Author(s):  
Jonathan Berg ◽  
Vidar Undebakke ◽  
Øystein Rasch-Halvorsen ◽  
Lars Aakerøy ◽  
Øyvind Sandbakk ◽  
...  
Keyword(s):  
Mitochondrial Respiration ◽  
Vastus Lateralis ◽  
Triceps Brachii ◽  
Physically Active ◽  
Cross Country ◽  
Active Controls

scholarly journals Preserved single muscle fiber specific force in facioscapulohumeral muscular dystrophy

Neurology ◽  
2020 ◽  
Vol 94 (11) ◽  
pp. e1157-e1170 ◽  
Author(s):  
Saskia Lassche ◽  
Nicol C. Voermans ◽  
Robbert van der Pijl ◽  
Marloes van den Berg ◽  
Arend Heerschap ◽  
...  
Keyword(s):  
Muscle Fiber ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Fatty Infiltration ◽  
Facioscapulohumeral Muscular Dystrophy ◽  
Single Muscle ◽  
Healthy Controls ◽  
Specific Force ◽  
Single Muscle Fiber ◽  
Muscle Biopsies

ObjectiveTo investigate single muscle fiber contractile performance in muscle biopsies from patients with facioscapulohumeral muscular dystrophy (FSHD), one of the most common hereditary muscle disorders.MethodsWe collected 50 muscle biopsies (26 vastus lateralis, 24 tibialis anterior) from 14 patients with genetically confirmed FSHD and 12 healthy controls. Single muscle fibers (n = 547) were isolated for contractile measurements. Titin content and titin phosphorylation were examined in vastus lateralis muscle biopsies.ResultsSingle muscle fiber specific force was intact at saturating and physiologic calcium concentrations in all FSHD biopsies, with (FSHDFAT) and without (FSHDNORMAL) fatty infiltration, compared to healthy controls. Myofilament calcium sensitivity of force is increased in single muscle fibers obtained from FSHD muscle biopsies with increased fatty infiltration, but not in FSHD muscle biopsies without fatty infiltration (pCa50: 5.77–5.80 in healthy controls, 5.74–5.83 in FSHDNORMAL, and 5.86–5.90 in FSHDFAT single muscle fibers). Cross-bridge cycling kinetics at saturating calcium concentrations and myofilament cooperativity did not differ from healthy controls. Development of single muscle fiber passive tension was changed in all FSHD vastus lateralis and in FSHDFAT tibialis anterior, resulting in increased fiber stiffness. Titin content was increased in FSHD vastus lateralis biopsies; however, titin phosphorylation did not differ from healthy controls.ConclusionMuscle weakness in patients with FSHD is not caused by reduced specific force of individual muscle fibers, even in severely affected tissue with marked fatty infiltration of muscle tissue.

scholarly journals Molecular determinants of force production in human skeletal muscle fibers: effects of myosin isoform expression and cross-sectional area

2015 ◽  
Vol 308 (6) ◽  
pp. C473-C484 ◽  
Author(s):  
Mark S. Miller ◽  
Nicholas G. Bedrin ◽  
Philip A. Ades ◽  
Bradley M. Palmer ◽  
Michael J. Toth
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Muscle Fibers ◽  
Force Production ◽  
Fiber Types ◽  
Specific Force ◽  
Cross Sectional ◽  
Mhc Ii ◽  
Molecular Determinants ◽  
Cross Bridges

Skeletal muscle contractile performance is governed by the properties of its constituent fibers, which are, in turn, determined by the molecular interactions of the myofilament proteins. To define the molecular determinants of contractile function in humans, we measured myofilament mechanics during maximal Ca2+-activated and passive isometric conditions in single muscle fibers with homogenous (I and IIA) and mixed (I/IIA and IIA/X) myosin heavy chain (MHC) isoforms from healthy, young adult male ( n = 5) and female ( n = 7) volunteers. Fibers containing only MHC II isoforms (IIA and IIA/X) produced higher maximal Ca2+-activated forces over the range of cross-sectional areas (CSAs) examined than MHC I fibers, resulting in higher (24–42%) specific forces. The number and/or stiffness of the strongly bound myosin-actin cross bridges increased in the higher force-producing MHC II isoforms and, in all isoforms, better predicted force than CSA. In men and women, cross-bridge kinetics, in terms of myosin attachment time and rate of myosin force production, were independent of CSA, although women had faster (7–15%) kinetics. The relative proportion of cross bridges and/or their stiffness was reduced as fiber size increased, causing a decline in specific force. Results from our examination of molecular mechanisms across the range of physiological CSAs explain the variation in specific force among the different fiber types in human skeletal muscle, which may have relevance to understanding how various physiological and pathophysiological conditions modulate single-fiber and whole muscle contractility.

scholarly journals NetCleave: an open-source algorithm for predicting C-terminal antigen processing for MHC-I and MHC-II

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pep Amengual-Rigo ◽  
Victor Guallar
Keyword(s):  
Open Source ◽  
Antigen Processing ◽  
High Accuracy ◽  
Biological Processes ◽  
Mhc I ◽  
Mhc Ii ◽  
Prediction Tools ◽  
Immunogenic Peptides ◽  
Physicochemical Descriptors ◽  
Peptide Presentation

AbstractAntigens presented on the cell surface have been subjected to multiple biological processes. Among them, C-terminal antigen processing constitutes one of the main bottlenecks of the peptide presentation pathways, as it delimits the peptidome that will be subjected downstream. Here, we present NetCleave, an open-source and retrainable algorithm for the prediction of the C-terminal antigen processing for both MHC-I and MHC-II pathways. NetCleave architecture consists of a neural network trained on 46 different physicochemical descriptors of the cleavage site amino acids. Our results demonstrate that prediction of C-terminal antigen processing achieves high accuracy on MHC-I (AUC of 0.91), while it remains challenging for MHC-II (AUC of 0.66). Moreover, we evaluated the performance of NetCleave and other prediction tools for the evaluation of four independent immunogenicity datasets (H2-Db, H2-Kb, HLA-A*02:01 and HLA-B:07:02). Overall, we demonstrate that NetCleave stands out as one of the best algorithms for the prediction of C-terminal processing, and we provide one of the first evidence that C-terminal processing predictions may help in the discovery of immunogenic peptides.

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