Statistical Analysis of Fiber Area in Human Skeletal Muscle

2002 ◽  
Vol 27 (4) ◽  
pp. 415-422 ◽  
Author(s):  
Michael R.M. Mcguigan ◽  
William J. Kraemer ◽  
Michael R. Deschenes ◽  
Scott E. Gordon ◽  
Takashi Kitaura ◽  
...  
Keyword(s):  
Fiber Type ◽  
Cross Sectional Area ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Cross Sectional ◽  
Fiber Area ◽  
Random Block ◽  
Type I Fibers ◽  
Accurate Reflection

Previous research has indicated that 50 fiber measurements per individual for type I and II fibers would be sufficient to characterize the fiber areas. This study replicated the work of McCall et al. (1998) using the three major fiber types (I, IIA, and IIB) and sampling larger populations of fibers. Random blocks of fibers were also examined to investigate how well they correlated with the overall mean average fiber area. Using random blocks of 50 fibers provided an accurate reflection of the type IIB fibers (r = 0.96-0.98) but not for the type I (r = 0.85-0.94) or IIA fibers (r = 0.80-0.91). Type I fibers were consistently reflected by a random block of 150 fibers (r = 0.95-0.98) while type IIA fibers required random blocks of 200 fibers (r = 0.94-0.98), which appeared to provide an accurate reflection of the cross-sectional area. These results indicate that for a needle biopsy different numbers of fibers are needed depending on the fiber type to accurately characterize the mean fiber population. Key words: fiber type, sample size, cross-sectional area, biopsy

Modulation of myonuclear number in functionally overloaded and exercised rat plantaris fibers

1999 ◽  
Vol 87 (2) ◽  
pp. 634-642 ◽  
Author(s):  
Roland R. Roy ◽  
Steven R. Monke ◽  
David L. Allen ◽  
V. Reggie Edgerton
Keyword(s):  
Fiber Type ◽  
Domain Size ◽  
Cross Sectional Area ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Tight Coupling ◽  
Fiber Volume ◽  
Cross Sectional ◽  
Myonuclear Domain

The effects of 10 wk of functional overload (FO), with and without daily treadmill endurance training, on the cross-sectional area, myonuclear number, and myonuclear domain size of mechanically isolated single fiber segments of the adult rat plantaris were determined. The fibers were typed on the basis of high-resolution gel electrophoresis for separation of specific myosin heavy chain (MHC) isoforms and grouped as type I+ (containing some type I MHC with or without any combination of fast MHCs), type IIa+ (containing some type IIa with or without some type IIx and/or IIb but no type I MHC), and type IIx/b (containing only type IIx and/or IIb MHCs). Type I+ fibers had a higher myonuclear number than did both fast types of fibers in the control and FO, but not in the FO and treadmill trained, rats. All fiber types in both FO groups had a significantly larger (36–90%) cross-sectional area and a significantly higher (61–109%) myonuclear number than did control. The average myonuclear domain size of each fiber type was similar among the three groups, except for a smaller domain size in the type IIx/b fibers of the FO compared with control. In general, these data indicate that during hypertrophy the number of myonuclei increase proportionally to the increase in fiber volume. The maintenance of myonuclear domain size near control values suggests that regulatory mechanisms exist that ensure a tight coupling between the quantity of genetic machinery and the protein requirements of a fiber.

scholarly journals Denervation effects on myonuclear domain size of rat diaphragm fibers

2006 ◽  
Vol 100 (5) ◽  
pp. 1617-1622 ◽  
Author(s):  
Bharathi Aravamudan ◽  
Carlos B. Mantilla ◽  
Wen-Zhi Zhan ◽  
Gary C. Sieck
Keyword(s):  
Fiber Type ◽  
Cross Sectional Area ◽  
Diaphragm Muscle ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Rat Diaphragm ◽  
Cross Sectional ◽  
Fiber Size ◽  
Myonuclear Domain

Denervation (DNV) of rat diaphragm muscle (DIAm) leads to selective atrophy of type IIx and IIb fibers, whereas the cross-sectional area of type I and IIa fibers remains unchanged or slightly hypertrophied. DIAm DNV also increases satellite cell mitotic activity and myonuclear apoptosis. Similar to other skeletal muscles, DIAm fibers are multinucleated, and each myonucleus regulates the gene products in a finite fiber volume, i.e., myonuclear domain (MND). MND size varies across DIAm fiber types in rank order, I < IIa < IIx < IIb [fiber type based on myosin heavy chain isoform expression]. We hypothesized that, after DNV, the total number of myonuclei per fiber does not change and, accordingly, that MND changes proportionately to the change in fiber size regardless of fiber type. Adult rats underwent unilateral (right side) DIAm DNV, and after 2 wk single fibers were dissected. Fiber cross-sectional area, myonuclear number, and MND were measured by confocal microscopy, and these values in DNV DIAm were compared with those obtained in controls. After DNV, type I fibers hypertrophied, type IIa fiber size was unchanged, and type IIx and IIb fibers atrophied compared with control. The total number of myonuclei per fiber was not affected by DNV. Accordingly, after DNV, type I fiber MND increased by 25%, whereas it decreased in type IIx and IIb fibers by 50 and 70%, respectively. These results suggest that MND is not maintained after DNV-induced DIAm fiber hypertrophy or atrophy. These results are interpreted with respect to consequent effects of DNV on myonuclear transcriptional activity and protein turnover.

scholarly journals Effect of Sex and Muscle on the Fiber-Type Composition and Cross-Sectional Area of Springbok (Antidorcas marsupialis) Muscle

2017 ◽  
Vol 1 (1) ◽  
Author(s):  
Megan K. North ◽  
Louw C. Hoffman
Keyword(s):  
Fiber Type ◽  
Biceps Femoris ◽  
Cross Sectional Area ◽  
Type I ◽  
Sectional Area ◽  
Cross Sectional ◽  
Fiber Type Composition ◽  
Type Composition ◽  
Type I Fibers ◽  
Antidorcas Marsupialis

This study aimed to compare the fiber-type composition and fiber cross-sectional area (CSA) of male and female springbok (Antidorcas marsupialis) Longissimus thoracis et lumborum (LTL) and Biceps femoris (BF) muscles. Frozen samples from 4 male and 3 female springbok were fiber-typed immunohistochemically using the primary antibodies A4.74, BA-D5 and BF-35. The CSA of the fibers was determined using the software Image J. Type IIX fibers accounted for 64 to 77% of the fibers in all samples, with type IIA (12.7 to 19.1%), type IIAX (6.4 to 9.3%) and type I (2.4 to 8.5%) making smaller (P < 0.001) contributions. Female springboks’ muscles contained more type IIX fibers than males’ (P = 0.004) and the BF contained more type I fibers and fewer type IIA and IIAX fibers than the LTL (P < 0.001). CSA values did not differ between sexes or muscles; however, they increased with apparent fiber glycolytic capacity (I < IIA < IIAX < IIX; P < 0.001). The glycolytic nature suggested by the fiber-type composition of springbok muscle found in this study is in contrast with previous reports on the physicochemical nature of springbok meat. This casts doubt on the application of standard associations between fiber-type and meat quality to this species. However, it may provide some explanation for the low shear force values found for springbok meat in previous studies.

Rostrocaudal pattern of fiber-type changes in an overloaded rat ankle extensor

1991 ◽  
Vol 71 (2) ◽  
pp. 558-564 ◽  
Author(s):  
P. F. Gardiner ◽  
B. J. Jasmin ◽  
P. Corriveau
Keyword(s):  
Fiber Type ◽  
Muscle Length ◽  
Similar Degree ◽  
Complex Nature ◽  
Type I ◽  
Fiber Types ◽  
Type Ii ◽  
Cross Sectional ◽  
Hypertrophic Response ◽  
Type I Fibers

Our aim was to quantify the overload-induced hypertrophy and conversion of fiber types (type II to I) occurring in the medial head of the gastrocnemius muscle (MG). Overload of MG was induced by a bilateral tenotomy/retraction of synergists, followed by 12–18 wk of regular treadmill locomotion (2 h of walking/running per day on 3 of 4 days). We counted all type I fibers and determined type I and II mean fiber areas in eight equidistant sections taken along the length of control and overloaded MG. Increase in muscle weights (31%), as well as in total muscle cross-sectional areas (37%) and fiber areas (type I, 57%; type II, 34%), attested to a significant hypertrophic response in overloaded MG. An increase in type I fiber composition of MG from 7.0 to 11.5% occurred as a result of overload, with the greatest and only statistically significant changes (approximately 70–100%) being found in sections taken from the most rostral 45% of the muscle length. Results of analysis of sections taken from the largest muscle girth showed that it significantly underestimated the extent of fiber conversion that occurred throughout the muscle as a whole. These data obtained on the MG, which possesses a compartmentalization of fiber types, support the notion that all fiber types respond to this model with a similar degree of hypertrophy. Also, they emphasize the complex nature of the adaptive changes that occur in these types of muscles as a result of overload.

Regulation of fiber size, oxidative potential, and capillarization in human muscle by resistance exercise

1999 ◽  
Vol 276 (2) ◽  
pp. R591-R596 ◽  
Author(s):  
H. Green ◽  
C. Goreham ◽  
J. Ouyang ◽  
M. Ball-Burnett ◽  
D. Ranney
Keyword(s):  
Fiber Type ◽  
Vastus Lateralis ◽  
Succinic Dehydrogenase ◽  
Quadriceps Muscle ◽  
Cellular Tissue ◽  
Cross Sectional Area ◽  
Fiber Types ◽  
Sectional Area ◽  
Oxidative Potential ◽  
Cross Sectional

To examine the hypothesis that increases in fiber cross-sectional area mediated by high-resistance training (HRT) would result in a decrease in fiber capillarization and oxidative potential, regardless of fiber type, we studied six untrained males (maximum oxygen consumption, 45.6 ± 2.3 ml ⋅ kg−1 ⋅ min−1; mean ± SE) participating in a 12-wk program designed to produce a progressive hypertrophy of the quadriceps muscle. The training sessions, which were conducted 3 times/wk, consisted of three sets of three exercises, each performed for 6–8 repetitions maximum (RM). Measurements of fiber-type distribution obtained from tissue extracted from the vastus lateralis at 0, 4, 7, and 12 wk indicated reductions ( P < 0.05) in type IIB fibers (15.1 ± 2.1% vs. 7.2 ± 1.3%) by 4 wk in the absence of changes in the other fiber types (types I, IIA, and IIAB). Training culminated in a 17% increase ( P < 0.05) in cross-sectional area by 12 wk with initial increases observed at 4 wk. The increase was independent of fiber type-specific changes. The number of capillaries in contact with each fiber type increased by 12 wk, whereas capillary contacts-to-fiber area ratios remained unchanged. In a defined cross-sectional field, HRT also increased the capillaries per fiber at 12 wk. Training failed to alter cellular oxidative potential, as measured by succinic dehydrogenase (SDH) activity, regardless of fiber type and training duration. It is concluded that modest hypertrophy induced by HRT does not compromise cellular tissue capillarization and oxidative potential regardless of fiber type.

Running during recovery from hindlimb suspension induces transient muscle injury

1990 ◽  
Vol 68 (2) ◽  
pp. 533-539 ◽  
Author(s):  
C. E. Kasper ◽  
T. P. White ◽  
L. C. Maxwell
Keyword(s):  
Soleus Muscle ◽  
Recovery Period ◽  
Morphological Characteristics ◽  
Cross Sectional Area ◽  
Hindlimb Suspension ◽  
Type I ◽  
Sectional Area ◽  
Cross Sectional ◽  
Female Wistar Rats ◽  
Type I Fibers

The objectives were to study morphological adaptations of soleus muscle to decreased loading induced by hindlimb suspension and the effect of run training during the subsequent recovery period. Adult female Wistar rats were kept for 28 days with hindlimbs suspended. For the next 28 days, rats were assigned to a cage-sedentary or daily running group. Compared with control soleus muscles, 28 days of hindlimb suspension reduced the mass and fiber cross-sectional area to 58 and 53% of control values, respectively, and decreased type I fibers from 92 +/- 2 to 81 +/- 2%. During recovery, clusters of damaged fibers were observed in the soleus muscle, and this observation was more pronounced in trained animals. Type IIc fibers appeared transiently during recovery, and their presence was exacerbated with training, as IIc fibers increased to approximately 20% of the total by day 14 of recovery and were no longer evident at day 28. Although muscle wet mass does not differ as a result of mode of recovery at day 14, training transiently decreased the overall fiber area compared with sedentary recovery at this point. By day 28 of recovery the morphological characteristics of soleus muscle in the trained group did not differ from control muscle, whereas in the sedentary group muscle mass and overall fiber cross-sectional area were approximately 14% less than control values.

Effects of starvation and refeeding on adult male rat diaphragm contractility, fatigue, and fiber types

1993 ◽  
Vol 74 (2) ◽  
pp. 742-749 ◽  
Author(s):  
D. J. Prezant ◽  
D. E. Valentine ◽  
H. H. Kim ◽  
E. I. Gentry
Keyword(s):  
Fatigue Resistance ◽  
Cross Sectional Area ◽  
Male Rats ◽  
Male Rat ◽  
Type I ◽  
Fiber Types ◽  
Type Ii ◽  
Sectional Area ◽  
Cross Sectional ◽  
Type Ii Fibers

The effects of 4.5 days of acute starvation, either alone or followed by refeeding (ad libitum), on diaphragm contractility, fatigue, and fiber types were studied in male rats. Contractility and fatigue resistance indexes were measured in an in vitro costal diaphragm strip preparation with direct stimulation at 37 degrees C. Compared with controls, starvation produced a 28 +/- 1% (P < 0.001) reduction in body weight and an 18 +/- 4% (P < 0.001) reduction in costal diaphragm weight. Twitch and tetanic tensions (normalized for weight or cross-sectional area) were not reduced by starvation. Starvation produced significant increases in fatigue resistance indexes after a 5-Hz stimulation paradigm but not after a 100-Hz paradigm, supporting the hypothesis that fatigue resistance is dependent on the energy demand of a given paradigm. The proportions of type I and type II fibers were similar between diaphragms of starved and control rats, but the cross-sectional area of type II fibers decreased significantly by 18 +/- 7% (P < 0.01). Thus, despite the significant decrease in diaphragm weight after starvation, contractility was preserved and fatigue resistance was increased (low-output paradigm). This is consistent with the decrease in type II fiber area. Refeeding restored all parameters so that there were no longer significant differences in body or diaphragm weight, contractility, fatigue, or fiber types.

The Effects of Non-Weight Bearing on Skeletal Muscle in Older Rats: an Interrupted Bout versus an Uninterrupted Bout

2004 ◽  
Vol 5 (3) ◽  
pp. 195-202 ◽  
Author(s):  
Alissa Guildner Gehrke ◽  
Margaret Sheie Krull ◽  
Robin Shotwell McDonald ◽  
Tracy Sparby ◽  
Jessica Thoele ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Weight Bearing ◽  
Cross Sectional Area ◽  
Type I ◽  
Type Ii ◽  
Sectional Area ◽  
Cross Sectional ◽  
Age Related ◽  
Type Ii Fibers

Age-related changes in skeletal muscle, in combination with bed rest, may result in a poorer rehabilitation potential for an elderly patient. The purpose of this study was to determine the effects of non-weight bearing (hind limb unweighting [HU]) on the soleus and extensor digitorum longus (EDL) in older rats. Two non-weight bearing conditions were used: an uninterrupted bout of HU and an interrupted bout of HU. Twenty-one rats were randomly placed into 1 of 3 groups: control, interrupted HU (2 phases of 7 days of HU, separated by a 4-day weight-bearing phase) and an uninterrupted HU (18 uninterrupted days of HU). Following non-weight bearing, the soleus and EDL muscles were removed. Fiber type identification was performed by myofibrillar ATPase and cross-sectional area was determined. The findings suggest that any period of non-weight bearing leads to a decrease in muscle wet weight (19%-45%). Both type I and type II fibers of the soleus showed atrophy (decrease in cross-sectional area, 35%-44%) with an uninterrupted bout of non-weight bearing. Only the type II fibers of the soleus showed recovery with an interrupted bout of weight bearing. In the EDL, type II fibers were more affected by an uninterrupted bout of non-weight bearing (15% decrease in fiber size) compared to the type I fibers. EDL type II fibers showed more atrophy with interrupted bouts of non-weight bearing than with a single bout (a 40% compared to a 15% decrease). This study shows that initial weight bearing after an episode of non-weight bearing may be damaging to type II fibers of the EDL.

Absence of regional differences in the size and oxidative capacity of diaphragm muscle fibers

1987 ◽  
Vol 63 (3) ◽  
pp. 1076-1082 ◽  
Author(s):  
G. C. Sieck ◽  
R. D. Sacks ◽  
C. E. Blanco
Keyword(s):  
Muscle Fibers ◽  
Continuous Distribution ◽  
Oxidative Capacity ◽  
Cross Sectional Area ◽  
Diaphragm Muscle ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Cross Sectional ◽  
Fast Twitch

The oxidative capacity and cross-sectional area of muscle fibers were compared between the costal and crural regions of the cat diaphragm and across the abdominal-thoracic extent of the muscle. Succinate dehydrogenase (SDH) activity of individual fibers was quantified using a microphotometric procedure implemented on an image-processing system. In both costal and crural regions, population distributions of SDH activities were unimodal for both type I and II fibers. The continuous distribution of SDH activities for type II fibers indicated that no clear threshold exists for the subclassification of fibers based on differences in oxidative capacity (e.g., the classification of fast-twitch glycolytic and fast-twitch oxidative glycolytic fiber types). No differences in either SDH activity or cross-sectional area were noted between fiber populations of the costal and crural regions. Differences in SDH activity and cross-sectional area were noted, however, between fiber populations located on the abdominal and thoracic sides of the costal region. Both type I and II fibers on the abdominal side of the costal diaphragm were larger and more oxidative than comparable fibers on the thoracic side.

Aging, muscle fiber type, and contractile function in sprint-trained athletes

2006 ◽  
Vol 101 (3) ◽  
pp. 906-917 ◽  
Author(s):  
Marko T. Korhonen ◽  
Alexander Cristea ◽  
Markku Alén ◽  
Keijo Häkkinen ◽  
Sarianna Sipilä ◽  
...  
Keyword(s):  
Fiber Type ◽  
Cross Sectional Area ◽  
Rate Of Force Development ◽  
Knee Extensors ◽  
Type I ◽  
Sectional Area ◽  
Cross Sectional ◽  
Specific Tension ◽  
Force Development ◽  
Aging Muscle

Biopsy samples were taken from the vastus lateralis of 18- to 84-yr-old male sprinters ( n = 91). Fiber-type distribution, cross-sectional area, and myosin heavy chain (MHC) isoform content were identified using ATPase histochemistry and SDS-PAGE. Specific tension and maximum shortening velocity ( Vo) were determined in 144 single skinned fibers from younger (18–33 yr, n = 8) and older (53–77 yr, n = 9) runners. Force-time characteristics of the knee extensors were determined by using isometric contraction. The cross-sectional area of type I fibers was unchanged with age, whereas that of type II fibers was reduced ( P < 0.001). With age there was an increased MHC I ( P < 0.01) and reduced MHC IIx isoform content ( P < 0.05) but no differences in MHC IIa. Specific tension of type I and IIa MHC fibers did not differ between younger and older subjects. Vo of fibers expressing type I MHC was lower ( P < 0.05) in older than in younger subjects, but there was no difference in Vo of type IIa MHC fibers. An aging-related decline of maximal isometric force ( P < 0.001) and normalized rate of force development ( P < 0.05) of knee extensors was observed. Normalized rate of force development was positively associated with MHC II ( P < 0.05). The sprint-trained athletes experienced the typical aging-related reduction in the size of fast fibers, a shift toward a slower MHC isoform profile, and a lower Vo of type I MHC fibers, which played a role in the decline in explosive force production. However, the muscle characteristics were preserved at a high level in the oldest runners, underlining the favorable impact of sprint exercise on aging muscle.

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