Carbohydrate ingestion and single muscle fiber glycogen metabolism during prolonged running in men

1996 ◽  
Vol 81 (2) ◽  
pp. 801-809 ◽  
Author(s):  
O. K. Tsintzas ◽  
C. Williams ◽  
L. Boobis ◽  
P. Greenhaff
Keyword(s):  
Fiber Type ◽  
Vastus Lateralis ◽  
Time To Exhaustion ◽  
Endurance Capacity ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Glycogen Depletion ◽  
Carbohydrate Ingestion ◽  
Atp Production ◽  
Type I Fibers

The aim of this study was to examine the effect of carbohydrate (CHO) ingestion on glycogen degradation in type I and type II muscle fibers during prolonged running by using a quantitative biochemical method. To this end, eight male subjects ran at 70% maximal oxygen uptake to exhaustion on a motorized treadmill on two occasions, 1 wk apart. On each occasion, the subjects ingested 8 ml/kg body wt of either placebo (Pl) or a 5.5% CHO-electrolyte solution (CHO-E) immediately before the start of the run and 2 ml/kg body wt every 20 min thereafter. Needle biopsy samples were obtained from the vastus lateralis muscle before and after each trial and also at the time coinciding with Pl exhaustion in the CHO-E trial. Running time to exhaustion was longer (P < 0.01) in the CHO-E trial compared with the Pl trial (132.4 +/- 12.3 and 104.3 +/- 8.6 min, respectively). A 25% reduction in glycogen utilization in type I fibers only was observed in the CHO-E trial compared with the Pl trial (215.2 +/- 27.5 vs. 285.4 +/- 30.1 mmol/kg dry wt; P < 0.01). Furthermore, in the CHO-E trial, in contrast to the Pl trial, both muscle ATP and phosphocreatine concentrations were well maintained throughout exercise. Therefore, because in both the Pl and CHO-E trials the type I fibers were glycogen depleted at the point of exhaustion (31.6 +/- 10.3 and 28.1 +/- 7.1 mmol/kg dry wt, respectively), it is proposed that CHO ingestion improved endurance capacity by contributing to oxidative ATP production specifically in type I fibers and by doing so delayed the development of glycogen depletion in this fiber type.

Muscle metabolism during prolonged exercise in humans: influence of carbohydrate availability

1999 ◽  
Vol 87 (3) ◽  
pp. 1083-1086 ◽  
Author(s):  
G. McConell ◽  
R. J. Snow ◽  
J. Proietto ◽  
M. Hargreaves
Keyword(s):  
Oxygen Uptake ◽  
Vastus Lateralis ◽  
Time To Exhaustion ◽  
Endurance Capacity ◽  
Vastus Lateralis Muscle ◽  
Double Blind ◽  
Muscle Lactate ◽  
Carbohydrate Ingestion ◽  
Inosine Monophosphate ◽  
Muscle Energy

Eight endurance-trained men cycled to volitional exhaustion at 69 ± 1% peak oxygen uptake on two occasions to examine the effect of carbohydrate supplementation during exercise on muscle energy metabolism. Subjects ingested an 8% carbohydrate solution (CHO trial) or a sweet placebo (Con trial) in a double-blind, randomized order, with vastus lateralis muscle biopsies ( n = 7) obtained before and immediately after exercise. No differences in oxygen uptake, heart rate, or respiratory exchange ratio during exercise were observed between the trials. Exercise time to exhaustion was increased by ∼30% when carbohydrate was ingested [199 ± 21 vs. 152 ± 9 (SE) min, P < 0.05]. Plasma glucose and insulin levels during exercise were higher and plasma free fatty acids lower in the CHO trial. No differences between trials were observed in the decreases in muscle glycogen and phosphocreatine or the increases in muscle lactate due to exercise. Muscle ATP levels were not altered by exercise in either trial. There was a small but significant increase in muscle inosine monophosphate levels at the point of exhaustion in both trials, and despite the subjects in CHO trial cycling 47 min longer, their muscle inosine monophosphate level was significantly lower than in the Con trial (CHO: 0.16 ± 0.08, Con: 0.23 ± 0.09 mmol/kg dry muscle). These data suggest that carbohydrate ingestion may increase endurance capacity, at least in part, by improving muscle energy balance.

Fiber type-specific muscle glycogen sparing due to carbohydrate intake before and during exercise

2007 ◽  
Vol 102 (1) ◽  
pp. 183-188 ◽  
Author(s):  
K. De Bock ◽  
W. Derave ◽  
M. Ramaekers ◽  
E. A. Richter ◽  
P. Hespel
Keyword(s):  
Muscle Glycogen ◽  
Glycogen Content ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Periodic Acid ◽  
Carbohydrate Intake ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Type I Fibers ◽  
Glycogen Sparing

The effect of carbohydrate intake before and during exercise on muscle glycogen content was investigated. According to a randomized crossover study design, eight young healthy volunteers ( n = 8) participated in two experimental sessions with an interval of 3 wk. In each session subjects performed 2 h of constant-load bicycle exercise (∼75% maximal oxygen uptake). On one occasion (CHO), they received carbohydrates before (∼150 g) and during (1 g·kg body weight−1·h−1) exercise. On the other occasion they exercised after an overnight fast (F). Fiber type-specific relative glycogen content was determined by periodic acid Schiff staining combined with immunofluorescence in needle biopsies from the vastus lateralis muscle before and immediately after exercise. Preexercise glycogen content was higher in type IIa fibers [9.1 ± 1 × 10−2 optical density (OD)/μm2] than in type I fibers (8.0 ± 1 × 10−2 OD/μm2; P < 0.0001). Type IIa fiber glycogen content decreased during F from 9.6 ± 1 × 10−2 OD/μm2 to 4.5 ± 1 × 10−2 OD/μm2 ( P = 0.001), but it did not significantly change during CHO ( P = 0.29). Conversely, in type I fibers during CHO and F the exercise bout decreased glycogen content to the same degree. We conclude that the combination of carbohydrate intake both before and during moderate- to high-intensity endurance exercise results in glycogen sparing in type IIa muscle fibers.

Influence of complete spinal cord injury on skeletal muscle within 6 mo of injury

1999 ◽  
Vol 86 (1) ◽  
pp. 350-358 ◽  
Author(s):  
Michael J. Castro ◽  
David F. Apple ◽  
Robert S. Staron ◽  
Gerson E. R. Campos ◽  
Gary A. Dudley
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Cord Injury ◽  
Lateralis Muscle ◽  
Type I Fibers ◽  
Femoris Muscle ◽  
Over Time

This study examined the influence of spinal cord injury (SCI) on affected skeletal muscle. The right vastus lateralis muscle was biopsied in 12 patients as soon as they were clinically stable (average 6 wk after SCI), and 11 and 24 wk after injury. Samples were also taken from nine able-bodied controls at two time points 18 wk apart. Surface electrical stimulation (ES) was applied to the left quadriceps femoris muscle to assess fatigue at these same time intervals. Biopsies were analyzed for fiber type percent and cross-sectional area (CSA), fiber type-specific succinic dehydrogenase (SDH) and α-glycerophosphate dehydrogenase (GPDH) activities, and myosin heavy chain percent. Controls showed no change in any variable over time. Patients showed 27–56% atrophy ( P = 0.000) of type I, IIa, and IIax+IIx fibers from 6 to 24 wk after injury, resulting in fiber CSA approximately one-third that of controls. Their fiber type specific SDH and GPDH activities increased ( P ≤ 0.001) from 32 to 90% over the 18 wk, thereby approaching or surpassing control values. The relative CSA of type I fibers and percentage of myosin heavy chain type I did not change. There was apparent conversion among type II fiber subtypes; type IIa decreased and type IIax+IIx increased ( P ≤ 0.012). Force loss during ES did not change over time for either group but was greater ( P = 0.000) for SCI patients than for controls overall (27 vs. 9%). The results indicate that vastus lateralis muscle shows marked fiber atrophy, no change in the proportion of type I fibers, and a relative independence of metabolic enzyme levels from activation during the first 24 wk after clinically complete SCI. Over this time, quadriceps femoris muscle showed moderately greater force loss during ES in patients than in controls. It is suggested that the predominant response of mixed human skeletal muscle within 6 mo of SCI is loss of contractile protein. Therapeutic interventions could take advantage of this to increase muscle mass.

In vitro human masseter muscle hypersensitivity: a possible explanation for increase in masseter tone

1996 ◽  
Vol 80 (5) ◽  
pp. 1547-1553 ◽  
Author(s):  
P. J. Adnet ◽  
H. Reyford ◽  
B. M. Tavernier ◽  
T. Etchrivi ◽  
I. Krivosic ◽  
...  
Keyword(s):  
Masseter Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Threshold Concentration ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Cross Sectional ◽  
Significant Difference ◽  
Maximal Tension

To determine whether a difference in fiber-type caffeine and Ca2+ sensitivities exists between human masseter and vastus lateralis skeletal muscle, we compared the fiber-type caffeine sensitivities in chemically skinned muscle fibers from 13 masseter and 18 vastus lateralis muscles. Caffeine sensitivity was defined as the threshold concentration inducing > 10% of the maximal tension obtained after the fiber was loaded with a 1.6 x 10(-2) mM Ca2+ solution for 30 s. Significant difference in the mean caffeine sensitivity was found between type I masseter fibers [2.57 +/- 1.32 (SD) mM] vs. type I (6.02 +/- 1.74 mM) and type II vastus lateralis fibers (11.25 +/- 3.13 mM). Maximal Ca(2+)-activated force per cross-sectional area was significantly different between masseter and vastus lateralis fibers. However, the Ca2+ concentration corresponding to half-maximal tension (pCa50) was not significantly different between type I masseter (pCa50 5.9 +/- 0.02) and type I vastus lateralis muscle (pCa50 6.01 +/- 0.08). These results suggest that the increase in caffeine sensitivity of masseter muscle reflects the presence of a low reactivity threshold of the sarcoplasmic reticulum.

Gene Polymorphisms and Fiber-Type Composition of Human Skeletal Muscle

2012 ◽  
Vol 22 (4) ◽  
pp. 292-303 ◽  
Author(s):  
Ildus I. Ahmetov ◽  
Olga L. Vinogradova ◽  
Alun G. Williams
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fiber ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Fiber Types ◽  
Fiber Type Composition ◽  
Type Composition ◽  
Type I Fibers

The ability to perform aerobic or anaerobic exercise varies widely among individuals, partially depending on their muscle-fiber composition. Variability in the proportion of skeletal-muscle fiber types may also explain marked differences in aspects of certain chronic disease states including obesity, insulin resistance, and hypertension. In untrained individuals, the proportion of slow-twitch (Type I) fibers in the vastus lateralis muscle is typically around 50% (range 5–90%), and it is unusual for them to undergo conversion to fast-twitch fibers. It has been suggested that the genetic component for the observed variability in the proportion of Type I fibers in human muscles is on the order of 40–50%, indicating that muscle fiber-type composition is determined by both genotype and environment. This article briefly reviews current progress in the understanding of genetic determinism of fiber-type proportion in human skeletal muscle. Several polymorphisms of genes involved in the calcineurin–NFAT pathway, mitochondrial biogenesis, glucose and lipid metabolism, cytoskeletal function, hypoxia and angiogenesis, and circulatory homeostasis have been associated with fiber-type composition. As muscle is a major contributor to metabolism and physical strength and can readily adapt, it is not surprising that many of these gene variants have been associated with physical performance and athlete status, as well as metabolic and cardiovascular diseases. Genetic variants associated with fiber-type proportions have important implications for our understanding of muscle function in both health and disease.

Carnitine metabolism in human muscle fiber types during submaximal dynamic exercise

1996 ◽  
Vol 80 (3) ◽  
pp. 1061-1064 ◽  
Author(s):  
D. Constantin-Teodosiu ◽  
S. Howell ◽  
P. L. Greenhaff
Keyword(s):  
Muscle Fiber ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Group Formation ◽  
Free Carnitine ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Carnitine Metabolism ◽  
Type I Fibers

The effect of prolonged exhaustive exercise on free carnitine and acetylcarnitine concentrations in mixed-fiber skeletal muscle and in type I and II muscle fibers was investigated in humans. Needle biopsy samples were obtained from the vastus lateralis of six subjects immediately after exhaustive one-legged cycling at approximately 75% of maximal O2 uptake from both the exercised and nonexercised (control) legs. In the resting (control) leg, there was no difference in the free carnitine concentration between type I and II fibers (20.36 +/- 1.25 and 20.51 +/- 1.16 mmol/kg dry muscle, respectively) despite the greater potential for fat oxidation in type I fibers. However, the acetylcarnitine concentration was slightly greater in type I fibers (P < 0.01). During exercise, acetylcarnitine accumulation occurred in both muscle fiber types, but accumulation was greatest in type I fibers (P < 0.005). Correspondingly, the concentration of free carnitine was significantly lower in type I fibers at the end of exercise (P < 0.001). The sum of free carnitine and acetylcarnitine concentrations in type I and II fibers at rest was similar and was unchanged by exercise. In conclusion, the findings of the present study support the suggestion that carnitine buffers excess acetyl group formation during exercise and that this occurs in both type I and II fibers. However, the greater accumulation of acetylcarnitine in type I fibers during prolonged exercise probably reflects the greater mitochondrial content of this fiber type.

Calcium-activated force of human muscle fibers following a standardized eccentric contraction

2010 ◽  
Vol 299 (6) ◽  
pp. C1409-C1417 ◽  
Author(s):  
Seung Jun Choi ◽  
Jeffrey J. Widrick
Keyword(s):  
Fiber Type ◽  
Vastus Lateralis ◽  
Mechanical Strain ◽  
Eccentric Contraction ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Specific Force ◽  
Shortening Velocity ◽  
Hybrid Fibers ◽  
Fixed End

Peak Ca2+-activated specific force (force/fiber cross-sectional area) of human chemically skinned vastus lateralis muscle fiber segments was determined before and after a fixed-end contraction or an eccentric contraction of standardized magnitude (+0.25 optimal fiber length) and velocity (0.50 unloaded shortening velocity). Fiber myosin heavy chain (MHC) isoform content was assayed by SDS-PAGE. Posteccentric force deficit, a marker of damage, was similar for type I and IIa fibers but threefold greater for type IIa/IIx hybrid fibers. A fixed-end contraction had no significant effect on force. Multiple linear regression revealed that posteccentric force was explained by a model consisting of a fiber type-independent and a fiber type-specific component ( r2 = 0.91). Preeccentric specific force was directly associated with a greater posteccentric force deficit. When preeccentric force was held constant, type I and IIa fibers showed identical susceptibility to damage, while type IIa/IIx fibers showed a significantly greater force loss. This heightened sensitivity to damage was directly related to the amount of type IIx MHC in the hybrid fiber. Our model reveals a fiber-type sensitivity of the myofilament lattice or cytoskeleton to mechanical strain that can be described as follows: type IIa/IIx > type IIa = type I. If these properties extend to fibers in vivo, then alterations in the number of type IIa/IIx fibers may modify a muscle's susceptibility to eccentric damage.

Do skeletal muscle phenotypic characteristics of Xhosa and Caucasian endurance runners differ when matched for training and racing distances?

2007 ◽  
Vol 103 (3) ◽  
pp. 932-940 ◽  
Author(s):  
Tertius A. Kohn ◽  
Birgitta Essén-Gustavsson ◽  
Kathryn H. Myburgh
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Dry Weight ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Endurance Running ◽  
Exercise Tests ◽  
Black And White ◽  
Endurance Runners

Although East African black athletes dominate endurance running events, it is unknown whether black and white endurance runners with similar racing ability, matched for training, may differ in their skeletal muscle biochemical phenotype. Thirteen Xhosa (XR) and 13 Caucasian (CR) endurance runners were recruited and matched for 10-km performance, average preferred racing distance (PRDA), and training volume. Submaximal and maximal exercise tests were done, and vastus lateralis muscle biopsies were taken. XR were significantly lighter and shorter than CR athletes but had similar maximum oxygen consumption corrected for body weight and peak treadmill speed (PTS). XR had lower plasma lactate concentrations at 80% PTS ( P < 0.05) compared with CR. Also, XR had more type IIA (42.4 ± 9.2 vs. 31.3 ± 11.5%, P < 0.05) and less type I fibers (47.8 ± 10.9 vs. 63.1 ± 13.2%, P < 0.05), although oxidative enzyme activities did not differ. Furthermore, XR compared with CR had higher lactate dehydrogenase (LDH) activity in homogenate muscle samples (383 ± 99 vs. 229 ± 85 μmol·min−1·g dry weight−1, P < 0.05) and in both type IIa ( P < 0.05) and type I ( P = 0.05) single-fiber pools. A marked difference ( P < 0.05) in the composition of LDH isoform content was found between the two groups with XR having higher levels of LDH5-4 isoforms (skeletal muscle isozymes; LDH-M) than CR, which was not accounted for by fiber-type differences alone. These results confirm differences in muscle phenotype and physiological characteristics, particularly associated with high-intensity running.

Phosphocreatine content in single fibers of human muscle after sustained submaximal exercise

1997 ◽  
Vol 273 (1) ◽  
pp. C172-C178 ◽  
Author(s):  
K. Sahlin ◽  
K. Soderlund ◽  
M. Tonkonogi ◽  
K. Hirakoba
Keyword(s):  
Vastus Lateralis ◽  
Submaximal Exercise ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Fiber Types ◽  
Slow Recovery ◽  
Muscle Energetics ◽  
Single Fibers ◽  
Rapid Reversal ◽  
Type I Fibers

The effect of sustained submaximal exercise on muscle energetics has been studied on the single-fiber level in human skeletal muscle. Seven subjects cycled to fatigue (mean 77 min) at a work rate corresponding to approximately 75% of maximal O2 uptake. Biopsies were taken from the vastus lateralis muscle at rest, at fatigue, and after 5 min of recovery. Muscle glycogen decreased from 444 +/- 40 (SE) mmol glucosyl units/kg dry wt at rest to 94 +/- 16. Postexercise glycogen was inversely correlated (P < 0.01) to muscle content of inosine monophosphate, a catabolite of ATP. Phosphocreatine (PCr) in mixed-fiber muscle decreased at fatigue to 37% but was restored above the initial value (106.5%, P < 0.025) after 5 min of recovery. The overshoot was localized to type I fibers. The rapid reversal of PCr is in contrast to the slow recovery in contraction force. Pi increased at fatigue but less than that expected from the changes in PCr and other phosphate compounds. Mean PCr at rest was approximately 20% higher in type II than in type I fibers (86.4 +/- 3.6 and 71.6 +/- 1.8 mmol/kg dry wt, respectively, P < 0.05), but at fatigue similar PCr contents were observed in the two fiber types. Reduction in PCr in all fibers at fatigue suggests that all fibers were recruited at the end of exercise. PCr content in single fibers showed a great variability in samples at rest, exercise, and recovery. The variability was more pronounced than for ATP, and the data suggest that it is due to interfiber physiological-biochemical differences. At fatigue ATP was maintained relatively high in all single fibers, but a pronounced depletion of PCr was observed in a large number of fibers, and this may contribute to fatigue through the associated increases in Pi or/and free ADP. It is noteworthy that the increase in calculated free ADP at fatigue was similar to that after high-intensity exercise.

Training-induced alterations in muscle glycogen utilization in fibre-specific types during prolonged exercise

1990 ◽  
Vol 68 (10) ◽  
pp. 1372-1376 ◽  
Author(s):  
H. J. Green ◽  
D. Smith ◽  
P. Murphy ◽  
I. Fraser
Keyword(s):  
Prolonged Exercise ◽  
Vastus Lateralis ◽  
Fibre Types ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Glycogen Depletion ◽  
Recruitment Pattern ◽  
Intensive Training ◽  
Glycogen Concentration ◽  
The Face

Using the glycogen depletion technique, we have examined utilization of specific fibre types during prolonged submaximal exercise to investigate the recruitment pattern employed by the central nervous system to sustain force generation in the face of a progressive glycogen depletion. Six male subjects ([Formula: see text] max, 52.8 ± 2.5 mL∙kg−1∙min−1,[Formula: see text]) cycled at 59% of pretraining [Formula: see text] max (the same absolute power output) for 99.5 ± 6 min on two occasions, before training and after 10–12 days of intensive training, involving 2 h of cycling per day. Prior to the training, glycogen concentration during exercise in the type I and type IIA fibres of the vastus lateralis muscle as measured by microphotometric techniques was progressively reduced during exercise. The pattern of depletion in both of these fibre types was parallel and showed an early marked depletion amounting to 51 (p < 0.05) and 35% (p < 0.05) in the type I and type IIA fibres, respectively, during the first 15 min of exercise. At the end of exercise, glycogen levels in type I and type IIA fibres were reduced to 9 and 44% of initial levels, respectively. In contrast, glycogen concentration in type IIB fibres was not significantly (p < 0.05) altered throughout the exercise. Following training, a pronounced glycogen sparing occurred that was conspicuous in only the type I and type IIA fibres, which was most pronounced during the first 15 min of the exercise. Similar to pretraining, glycogen concentrations in type IIB fibres were unaffected by either exercise or training. These results support the hypothesis that the muscle fibre recruitment patterns are established early in exercise and that even in the face of extensive glycogen loss observed late in exercise in the lower threshold type I and type IIA fibres, the higher threshold type IIB fibres are not recruited.Key words: recruitment, fibre types (I, IIA, and IIB), prolonged exercise, glycogen depletion.

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