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.

Contractile properties of rat, rhesus monkey, and human type I muscle fibers

1997 ◽  
Vol 272 (1) ◽  
pp. R34-R42 ◽  
Author(s):  
J. J. Widrick ◽  
J. G. Romatowski ◽  
M. Karhanek ◽  
R. H. Fitts
Keyword(s):  
Rhesus Monkey ◽  
Body Mass ◽  
Fiber Length ◽  
Peak Power ◽  
Cross Sectional Area ◽  
Contractile Properties ◽  
Type I ◽  
Sectional Area ◽  
Shortening Velocity ◽  
Cross Sectional

It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

Single muscle fiber contractile properties of young competitive distance runners

2008 ◽  
Vol 105 (2) ◽  
pp. 629-636 ◽  
Author(s):  
Matthew Harber ◽  
Scott Trappe
Keyword(s):  
Fiber Type ◽  
Peak Force ◽  
Contractile Properties ◽  
Fiber Types ◽  
Distance Runners ◽  
Cross Sectional ◽  
Mhc I ◽  
Contraction Velocity ◽  
Fast Twitch ◽  
Mhc Iia

The purpose of this investigation was to characterize the contractile properties of individual slow- and fast-twitch myofibers from highly trained distance runners. Muscle biopsies were obtained from the gastrocnemius of eight competitive runners (Run) and eight recreationally active individuals (Rec). Slow-twitch [myosin heavy chain (MHC) I] and fast-twitch (MHC IIa) myofibers were isolated and analyzed for diameter (μm), peak force (Po; mN), unloaded contraction velocity ( Vo; fiber lengths/s), and power. Maximum oxygen uptake was higher ( P < 0.05) in Run (71 ± 1 vs. 47 ± 2 ml·kg−1·min−1). Diameter of MHC I and MHC IIa fibers from Run subjects was ∼20% greater ( P < 0.05) than Rec. Peak force of the MHC IIa fibers was 31% higher ( P < 0.05) in Run, whereas Po of MHC I fibers was not different between groups. No differences for specific tension (Po/cross-sectional area) were present between groups for either fiber type. Vo was higher ( P < 0.05) in MHC I (+70%) and MHC IIa (+18%) fibers from Run subjects. In vitro peak absolute power (μN·s−1) of both fiber types was greater ( P < 0.05) in Run (131 and 85% for MHC I and MHC IIa, respectively). Additionally, normalized power (W/l) of the MHC I fibers was 64% higher in Run, whereas no differences were noted for normalized power of MHC IIa fibers. These data indicate that highly trained endurance runners have elevated contraction velocity in both slow- and fast-twitch myofibers. These characteristics of the fast-twitch muscle fibers have not been previously reported in competitive endurance athletes and may contribute to the high level of running performance in these athletes.

Functional significance of compensatory overloaded rat fast muscle

1982 ◽  
Vol 52 (2) ◽  
pp. 473-478 ◽  
Author(s):  
R. R. Roy ◽  
I. D. Meadows ◽  
K. M. Baldwin ◽  
V. R. Edgerton
Keyword(s):  
Biochemical Properties ◽  
Slow Muscle ◽  
Repetitive Stimulation ◽  
Contractile Properties ◽  
Sectional Area ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Time To Peak ◽  
Isometric Twitch

Chronic overload of a skeletal muscle by removing its synergists produces hypertrophy and marked changes in its metabolic and biochemical properties. In this study alterations in the contractile properties of the plantaris 12–14 wk after bilateral removal of the soleus and gastrocnemius were investigated. In situ isometric and isotonic contractile properties of overloaded plantaris (OP), normal plantaris (NP), and normal soleus (NS) were tested at 33 +/- 1 degree C. Op were 97% heavier than NP and produced 43 and 46% higher twitch (Pt) and tetanic (Po) tensions. However, NP produced more tension per cross-sectional area than OP (mean 26.2 vs. 21.6 N/cm2; P less than 0.001). Isometric twitch time to peak tension (TPT) and half-relaxation time (1/2RT) were significantly longer in OP (mean 36.4 vs. 32.5 ms and 23.9 vs. 18.4 ms). Mean maximum shortening velocity (Vmax, mm/s per 1,000 sarcomeres) were 34.1 for NP and 18.1 for OP (P less than 0.001). The degree of conversion toward the Vmax of NS was 74% compared with only 19 and 14% for TPT and 1/2RT. OP produced a higher proportion of Po at a given stimulation frequency than NP and showed less fatigue than NP after repetitive stimulation. Chronic overload of the fast plantaris modified to varying degrees the contractile properties studied toward that resembling a slow muscle. Although the maximum tension of OP was markedly enhanced it was not in proportion to the increase in muscle mass.

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.

scholarly journals Human vastus lateralis and soleus muscles display divergent cellular contractile properties

2008 ◽  
Vol 295 (5) ◽  
pp. R1593-R1598 ◽  
Author(s):  
Nicholas Luden ◽  
Kiril Minchev ◽  
Erik Hayes ◽  
Emily Louis ◽  
Todd Trappe ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Contractile Function ◽  
Vastus Lateralis ◽  
Single Fiber ◽  
Muscle Adaptation ◽  
Shortening Velocity ◽  
Mhc I ◽  
Myosin Heavy Chain Isoform ◽  
I 18 ◽  
Mhc Iia

The purpose of this study was to investigate potential differences in single-fiber contractile physiology of fibers with the same myosin heavy chain isoform (MHC I and MHC IIa) originating from different muscles. Vastus lateralis (VL) and soleus biopsies were obtained from 27 recreationally active females (31 ± 1 yr, 59 ± 1 kg). A total of 943 single fibers (MHC I = 562; MHC IIa = 301) were isolated and examined for diameter, peak tension (Po), shortening velocity (Vo), and power. The soleus had larger ( P < 0.05) fibers (MHC I +18%; MHC IIa +19%), higher MHC I Vo (+13%), and higher MHC I Po (+18%) compared with fibers from the VL. In contrast, fibers from the VL had higher ( P < 0.05) specific tension (MHC I +18%; MHC IIa +20%), and MHC I normalized power (+25%) compared with the soleus. There was a trend for MHC IIa soleus fibers to have higher Vo [MHC IIa +13% ( P = 0.058)], whereas VL MHC IIa fibers showed a trend for higher normalized power compared with soleus fibers [MHC IIa +33% ( P = 0.079)]. No differences in absolute power were detected between muscles. These data highlight muscle-specific differences in single-fiber contractile function that should serve as a scientific basis for consideration when extending observations of skeletal muscle tissue from one muscle of interest to other muscles of origin. This is important when examining skeletal muscle adaptation to physical states such as aging, unloading, and training.

Contractile properties and myosin expression in rats born and reared in hypergravity

2002 ◽  
Vol 282 (6) ◽  
pp. R1687-R1695 ◽  
Author(s):  
F. Picquet ◽  
V. Bouet ◽  
M. H. Canu ◽  
L. Stevens ◽  
Y. Mounier ◽  
...  
Keyword(s):  
Contractile Properties ◽  
Fiber Types ◽  
Hybrid Fiber ◽  
Plantaris Muscle ◽  
Muscle Weight ◽  
Cross Sectional ◽  
Mhc I ◽  
Contractile Parameters ◽  
Wet Weight ◽  
Muscle Types

The effects of hypergravity (HG) on soleus and plantaris muscles were studied in Long Evans rats aged 100 days, born and reared in 2- g conditions (HG group). The morphological and contractile properties and the myosin heavy chain (MHC) content were examined in whole muscles and compared with terrestrial control (Cont) age-paired rats. The growth of HG rats was slowed compared with Cont rats. A decrease in absolute muscle weight was observed. An increase in fiber cross-sectional area/muscle wet weight was demonstrated, associated with an increase in relative maximal tension. The soleus muscle changed into a slower type both in contractile parameters and in MHC content, since HG soleus contained only the MHC I isoform. The HG plantaris muscle presented a faster contractile behavior. Moreover, the diversity of hybrid fiber types expressing multiple MHC isoforms (including MHC IIB and MHC IIX isoforms) was increased in plantaris muscle after HG. Thus the HG environment appears as an important inductor of muscular plasticity both in slow and fast muscle types.

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.

Maximal and submaximal forces of slow fibers in human soleus after bed rest

2001 ◽  
Vol 91 (1) ◽  
pp. 417-424 ◽  
Author(s):  
Katsumasa Yamashita-Goto ◽  
Ryoko Okuyama ◽  
Masanori Honda ◽  
Kensuke Kawasaki ◽  
Kazuhiko Fujita ◽  
...  
Keyword(s):  
Bed Rest ◽  
Knee Extension ◽  
Contractile Properties ◽  
Plantar Flexors ◽  
Shortening Velocity ◽  
Gravitational Unloading ◽  
Cross Sectional ◽  
Fiber Size ◽  
Before And After ◽  
Elastic Loading

The effects of 2 and 4 mo of bed rest, with or without exercise countermeasures, on the contractile properties of slow fibers in the human soleus muscle were examined. Mean fiber diameters were 8 and 36% smaller after 2 and 4 mo of bed rest, respectively, than the pre-bed rest level. Maximum tetanic force (Po), maximum activated force (Fmax) per cross-sectional area (CSA), and the common-logarithm value of free Ca2+concentration required for half-maximal activation (pCa50) also decreased after 2 and 4 mo of bed rest. In contrast, maximum unloaded shortening velocity ( V o) was increased after 2 and 4 mo of bed rest. After 1 mo of recovery, fiber diameters, Po, Fmax per CSA ( P > 0.05), and pCa50 were increased and V odecreased toward pre-bed rest levels. Effects of knee extension/flexion exercise by wearing an anti-G Penguin suit for 10 h daily, and the effects of loading or unloading of the plantar flexors with (Penguin-1) or without (Penguin-2) placing the elastic loading elements of the suit, respectively, were investigated during ∼2 mo of bed rest. In the Penguin-1 group, mean fiber diameter, Po, Fmax per CSA, V o, and pCa50 were similar before and after bed rest. However, the responses of fiber size and contractile properties to bed rest were not prevented in the Penguin-2 group, although the degree of the changes was less than those induced by bed rest without any countermeasure. These results indicate that long-term bed rest results in reductions of fiber size, force-generation capacity, and Ca2+sensitivity, and enhancement of shortening velocity in slow fibers of the soleus. The data indicate that continuous mechanical loading on muscle, such as stretching of muscle, is an effective countermeasure for the prevention of muscular adaptations to gravitational unloading.

scholarly journals Aerobic exercise training improves whole muscle and single myofiber size and function in older women

2009 ◽  
Vol 297 (5) ◽  
pp. R1452-R1459 ◽  
Author(s):  
Matthew P. Harber ◽  
Adam R. Konopka ◽  
Matthew D. Douglass ◽  
Kiril Minchev ◽  
Leonard A. Kaminsky ◽  
...  
Keyword(s):  
Exercise Training ◽  
Aerobic Exercise ◽  
Older Women ◽  
Peak Power ◽  
Protein Concentration ◽  
Aerobic Exercise Training ◽  
Mhc I ◽  
Fiber Size ◽  
And Function ◽  
Mhc Iia

To comprehensively assess the influence of aerobic training on muscle size and function, we examined seven older women (71 ± 2 yr) before and after 12 wk of cycle ergometer training. The training program increased ( P < 0.05) aerobic capacity by 30 ± 6%. Quadriceps muscle volume, determined by magnetic resonance imaging (MRI), was 12 ± 2% greater ( P < 0.05) after training and knee extensor power increased 55 ± 7% ( P < 0.05). Muscle biopsies were obtained from the vastus lateralis to determine size and contractile properties of individual slow (MHC I) and fast (MHC IIa) myofibers, myosin light chain (MLC) composition, and muscle protein concentration. Aerobic training increased ( P < 0.05) MHC I fiber size 16 ± 5%, while MHC IIa fiber size was unchanged. MHC I peak power was elevated 21 ± 8% ( P < 0.05) after training, while MHC IIa peak power was unaltered. Peak force (Po) was unchanged in both fiber types, while normalized force (Po/cross-sectional area) was 10% lower ( P < 0.05) for both MHC I and MHC IIa fibers after training. The decrease in normalized force was likely related to a reduction ( P < 0.05) in myofibrillar protein concentration after training. In the absence of an increase in Po, the increase in MHC I peak power was mediated through an increased ( P < 0.05) maximum contraction velocity (Vo) of MHC I fibers only. The relative proportion of MLC1s (Pre: 0.62 ± 0.01; Post: 0.58 ± 0.01) was lower ( P < 0.05) in MHC I myofibers after training, while no differences were present for MLC2s and MLC3f isoforms. These data indicate that aerobic exercise training improves muscle function through remodeling the contractile properties at the myofiber level, in addition to pronounced muscle hypertrophy. Progressive aerobic exercise training should be considered a viable exercise modality to combat sarcopenia in the elderly population.

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