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.

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.

Contractile, biochemical, and histochemical properties of thyrotoxic rat soleus muscle

1980 ◽  
Vol 238 (1) ◽  
pp. C15-C20 ◽  
Author(s):  
R. H. Fitts ◽  
W. W. Winder ◽  
M. H. Brooke ◽  
K. K. Kaiser ◽  
J. O. Holloszy
Keyword(s):  
Relaxation Time ◽  
Sarcoplasmic Reticulum ◽  
Soleus Muscle ◽  
Biochemical Properties ◽  
Contractile Properties ◽  
Contraction Time ◽  
Shortening Velocity ◽  
Actomyosin Atpase ◽  
Atpase Reaction ◽  
Isometric Twitch

The effects of thyrotoxicosis on the contractile properties of soleus muscle were examined in rats given 3 mg of T4 and 1 mg of T3 per kg of diet for 6–8 wk. Thyrotoxicosis induced significant decreases in isometric twitch contraction time (CT), one-half relaxation time, and peak twitch tension. The Ca2+ uptake activity of the sarcoplasmic reticulum (SR) was increased in the thyrotoxic muscles; this adaptation in the SR provides a possible mechanism for the alterations in isometric contractile properties. Thyrotoxicosis induced a large increase in fibers classified as type 2, on the basis of an alkali-stable histochemical reaction for ATPase, in the soleus. Although this reaction is commonly interpreted as indicating that a muscle is fast, maximum shortening velocity (Vmax) and Mg2+ activated actomyosin ATPase activity were unaffected in the thyrotoxic soleus. Our findings provide evidence that CT and Vmax can vary independently and that the histochemical ATPase reaction may not always reflect the biochemical properties that make myosin fast or slow. actomyosin ATPase; histochemical ATPase reaction; isometric contraction time; maximum shortening velocity; one-half relaxation time; sarcoplasmic reticulum; skeletal muscle Submitted on April 13, 1979 Accepted on August 7, 1979

Length dependence of staircase potentiation: interactions with caffeine and dantrolene sodium

2000 ◽  
Vol 78 (4) ◽  
pp. 350-357 ◽  
Author(s):  
Dilson E Rassier ◽  
Brian R MacIntosh
Keyword(s):  
Skeletal Muscle ◽  
Gastrocnemius Muscle ◽  
Repetitive Stimulation ◽  
Mammalian Skeletal Muscle ◽  
Optimal Length ◽  
Dantrolene Sodium ◽  
Length Dependence ◽  
Before And After ◽  
Isometric Twitch

In skeletal muscle, there is a length dependence of staircase potentiation for which the mechanism is unclear. In this study we tested the hypothesis that abolition of this length dependence by caffeine is effected by a mechanism independent of enhanced Ca2+ release. To test this hypothesis we have used caffeine, which abolishes length dependence of potentiation, and dantrolene sodium, which inhibits Ca2+ release. In situ isometric twitch contractions of rat gastrocnemius muscle before and after 20 s of repetitive stimulation at 5 Hz were analyzed at optimal length (Lo), Lo - 10%, and Lo + 10%. Potentiation was observed to be length dependent, with an increase in developed tension (DT) of 78 ± 12, 51 ± 5, and 34 ± 9% (mean ± SEM), at Lo - 10%, Lo, and Lo + 10%, respectively. Caffeine diminished the length dependence of activation and suppressed the length dependence of staircase potentiation, giving increases in DT of 65±13, 53 ± 11, and 45 ± 12% for Lo - 10%, Lo, and Lo + 10%, respectively. Dantrolene administered after caffeine did not reverse this effect. Dantrolene alone depressed the potentiation response, but did not affect the length dependence of staircase potentiation, with increases in DT of 58 ± 17, 26 ± 8, and 18 ± 7%, respectively. This study confirms that there is a length dependence of staircase potentiation in mammalian skeletal muscle which is suppressed by caffeine. Since dantrolene did not alter this suppression of the length dependence of potentiation by caffeine, it is apparently not directly modulated by Ca2+ availability in the myoplasm.

Recovery in skeletal muscle contractile function after prolonged hindlimb immobilization

1985 ◽  
Vol 59 (3) ◽  
pp. 916-923 ◽  
Author(s):  
R. H. Fitts ◽  
C. J. Brimmer
Keyword(s):  
Contractile Function ◽  
Vastus Lateralis ◽  
Weight Ratio ◽  
Contractile Properties ◽  
Shortening Velocity ◽  
Slow Twitch ◽  
Isometric Twitch ◽  
Fast Twitch ◽  
Muscle Contractile

Contractile properties of slow-twitch soleus (SOL), fast-twitch extensor digitorum longus (EDL), and fast-twitch superficial region of the vastus lateralis were determined in vitro (22 degrees C) in rats remobilized after prolonged (3 mo) hindlimb immobilization (IM). For all muscles the muscle-to-body weight ratio was significantly depressed by IM, and the ratios failed to completely recover even after 90 days. The contractile properties of the fast-twitch muscles were less affected by IM than the slow-twitch SOL. The IM shortened the SOL isometric twitch duration due to a reduced contraction and half-relaxation time. These parameters returned to control levels by the 14th day of recovery. Peak tetanic tension (Po, g/cm2) declined with IM by 46% in the SOL but showed no significant change in the fast-twitch muscles. After IM the SOL Po (g/cm2) recovered to control values by 28 days. The recovery of Po in absolute units (g) was considerably slower and did not return to control levels until 60 (SOL) to 90 (EDL) days. The maximum shortening velocity was not altered by IM in any of the muscles studied. These results demonstrate that both fast- and slow-twitch skeletal muscles possess the ability to completely recover normal contractile function following prolonged periods of hindlimb IM.

Nasal vestibule wall elasticity: interactions with a nasal dilator strip

1999 ◽  
Vol 86 (5) ◽  
pp. 1638-1643 ◽  
Author(s):  
T. C. Amis ◽  
J. P. Kirkness ◽  
E. di Somma ◽  
J. R. Wheatley
Keyword(s):  
Elastic Properties ◽  
Cross Sectional Area ◽  
Horizontal Direction ◽  
Sectional Area ◽  
Cross Sectional ◽  
Nasal Vestibule ◽  
Wall Displacement ◽  
Recoil Force ◽  
Wall Compliance

We studied the effect of an adhesive external nasal dilator strip (ENDS) on external nasal geometry in 20 healthy Caucasian adults (10 men, 10 women; age 21–45 yr). The recoil force exerted by ENDS was estimated by bending the device ( n = 10) with known weights. In the horizontal direction, a small/medium-sized ENDS in situ exerted a unilateral recoil force of 21.4–22.6 g. Application of ENDS resulted in a displacement of the lateral nasal vestibule walls that had both anterosuperior and horizontal components and that was maintained over an 8-h period. The resultant unilateral nasal vestibule wall displacement at the tip of the device was at 47.6 ± 2.0° to the horizontal (as related to the plane of the device when in situ) and had a magnitude of 3.5 ± 0.1 mm. ENDS increased external nasal cross-sectional area by 23.0–65.3 mm2. Nasal vestibule wall compliance was estimated at 0.05–0.16 mm/g. Thus ENDS applies a relatively constant abducting force irrespective of nasal width. Variable responsiveness to ENDS may be related to differences in elastic properties of the nasal vestibule wall.

Salbutamol enhances isotonic contractile properties of rat diaphragm muscle

1998 ◽  
Vol 85 (2) ◽  
pp. 525-529 ◽  
Author(s):  
H. F. M. Van Der Heijden ◽  
W. Z. Zhan ◽  
Y. S. Prakash ◽  
P. N. R. Dekhuijzen ◽  
G. C. Sieck
Keyword(s):  
Power Output ◽  
Maximum Power ◽  
Contractile Properties ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Maximum Power Output ◽  
Isometric Twitch ◽  
Camp Levels

The effects of the β2-adrenoceptor agonist salbutamol (Slb) on isometric and isotonic contractile properties of the rat diaphragm muscle (Diamus) were examined. A loading dose of 25 μg/kg Slb was administered intracardially before Diamus excision to ensure adequate diffusion. Studies were then performed with 0.05 μM Slb in the in vitro tissue chamber. cAMP levels were determined by radioimmunoassay. Compared with controls (Ctl), cAMP levels were elevated after Slb treatment. In Slb-treated rats, isometric twitch and maximum tetanic force were increased by ∼40 and ∼20%, respectively. Maximum shortening velocity increased by ∼15% after Slb treatment, and maximum power output increased by ∼25%. During repeated isotonic activation, the rate of fatigue was faster in the Slb-treated Diamus, but both Slb-treated and Ctl Diamusfatigued to the same maximum power output. Still, endurance time during repetitive isotonic contractions was ∼10% shorter in the Slb-treated Diamus. These results are consistent with the hypothesis that β-adrenoceptor stimulation by Slb enhances Diamus contractility and that these effects of Slb are likely mediated, at least in part, by elevated cAMP.

scholarly journals Soleus fiber force and maximal shortening velocity after non-weight bearing with intermittent activity

1996 ◽  
Vol 80 (3) ◽  
pp. 981-987 ◽  
Author(s):  
J. J. Widrick ◽  
J. J. Bangart ◽  
M. Karhanek ◽  
R. H. Fitts
Keyword(s):  
Isometric Force ◽  
Weight Bearing ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Cross Sectional Area ◽  
Type I ◽  
Sectional Area ◽  
Shortening Velocity ◽  
Adult Rats ◽  
Cross Sectional

This study examined the effectiveness of intermittent weight bearing (IWB) as a countermeasure to non-weight-bearing (NWB)-induced alterations in soleus type I fiber force (in mN), tension (Po; force per fiber cross-sectional area in kN/m-2), and maximal unloaded shortening velocity (Vo, in fiber lengths/s). Adult rats were assigned to one of the following groups: normal weight bearing (WB), 14 days of hindlimb NWB (NWB group), and 14 days of hindlimb NWB with IWB treatments (IWB group). The IWB treatment consisted of four 10-min periods of standing WB each day. Single, chemically permeabilized soleus fiber segments were mounted between a force transducer and position motor and were studied at maximal Ca2+ activation, after which type I fiber myosin heavy-chain composition was confirmed by sodium dodecyl sufate-polyacrylamide gel electrophoresis. NWB resulted in a loss in relative soleus mass (-45%), with type I fibers displaying reductions in diameter (-28%) and peak isometric force (-55%) and an increase in Vo (+33%). In addition, NWB induced a 16% reduction in type I fiber Po, a 41% reduction in type I fiber peak elastic modulus [Eo, defined as (delta force/delta length) x (fiber length/fiber cross-sectional area] and a significant increase in the Po/Eo ratio. In contrast to NWB, IWB reduced the loss of relative soleus mass (by 22%) and attenuated alterations in type I fiber diameter (by 36%), peak force (by 29%), and Vo (by 48%) but had no significant effect on Po, Eo, or Po/Eo. These results indicate that a modest restoration of WB activity during 14 days of NWB is sufficient to attenuate type I fiber atrophy and to partially restore type I peak isometric force and Vo to WB levels. However, the NWB-induced reductions in Po and Eo, which we hypothesize to be due to a decline in the number and stiffness of cross bridges, respectively, are considerably less responsive to this countermeasure treatment.

Changes in the human muscle force-velocity relationship in response to resistance training and subsequent detraining

2005 ◽  
Vol 99 (1) ◽  
pp. 87-94 ◽  
Author(s):  
Lars L. Andersen ◽  
Jesper L. Andersen ◽  
S. Peter Magnusson ◽  
Charlotte Suetta ◽  
Jørgen L. Madsen ◽  
...  
Keyword(s):  
Resistance Training ◽  
Knee Extension ◽  
Limb Movement ◽  
Cross Sectional Area ◽  
Contractile Properties ◽  
Type I ◽  
Maximal Velocity ◽  
Sectional Area ◽  
Cross Sectional ◽  
Muscle Cross Sectional Area

Previous studies show that cessation of resistance training, commonly known as “detraining,” is associated with strength loss, decreased neural drive, and muscular atrophy. Detraining may also increase the expression of fast muscle myosin heavy chain (MHC) isoforms. The present study examined the effect of detraining subsequent to resistance training on contractile performance during slow-to-medium velocity isokinetic muscle contraction vs. performance of maximal velocity “unloaded” limb movement (i.e., no external loading of the limb). Maximal knee extensor strength was measured in an isokinetic dynamometer at 30 and 240°/s, and performance of maximal velocity limb movement was measured with a goniometer during maximal unloaded knee extension. Muscle cross-sectional area was determined with MRI. Electromyographic signals were measured in the quadriceps and hamstring muscles. Twitch contractions were evoked in the passive vastus lateralis muscle. MHC isoform composition was determined with SDS-PAGE. Isokinetic muscle strength increased 18% ( P < 0.01) and 10% ( P < 0.05) at slow and medium velocities, respectively, along with gains in muscle cross-sectional area and increased electromyogram in response to 3 mo of resistance training. After 3 mo of detraining these gains were lost, whereas in contrast maximal unloaded knee extension velocity and power increased 14% ( P < 0.05) and 44% ( P < 0.05), respectively. Additionally, faster muscle twitch contractile properties along with an increased and decreased amount of MHC type II and MHC type I isoforms, respectively, were observed. In conclusion, detraining subsequent to resistance training increases maximal unloaded movement speed and power in previously untrained subjects. A phenotypic shift toward faster muscle MHC isoforms (I → IIA → IIX) and faster electrically evoked muscle contractile properties in response to detraining may explain the present results.

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.

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