Stretch-induced growth in chicken wing muscles: a new model of stretch hypertrophy

1980 ◽  
Vol 238 (1) ◽  
pp. C62-C71 ◽  
Author(s):  
R. G. Holly ◽  
J. G. Barnett ◽  
C. R. Ashmore ◽  
R. G. Taylor ◽  
P. A. Mole
Keyword(s):  
Cross Section ◽  
Muscle Activity ◽  
Enzyme Activities ◽  
Latissimus Dorsi ◽  
Capillary Density ◽  
Oxidative Enzyme ◽  
Longitudinal Growth ◽  
Mitochondrial Enzyme ◽  
New Model ◽  
Anterior Latissimus Dorsi

A new model of stretch-induced growth is evaluated in four chicken wing muscles stretched to different extents by a spring-loaded tubular assembly. Muscles grew in length and cross section in proportion to the extent to which they were stretched. Longitudinal growth was essentially completed within 1 wk, while muscles grew in cross section through at least 5 wk of stretch. The muscles were neither denervated nor immobilized, and muscle activity as measured by EMG was not increased. Oxidative enzyme activities increased substantially with stretch in the patagialis (PAT), a twitch muscle, but were relatively unchanged in the slow-tonic anterior latissimus dorsi (ALD). Stretch altered mitochondrial enzyme proportions in the PAT, but had little effect in the ALD. Capillary density was unchanged with stretch in the PAT, but decreased in the ALD. Capillary density was unchanged with stretch in the PAT, but decreased in the ALD. Capillary-to-fiber ratio, however, increased in both muscles. We conclude that muscles grow and adapt enzymatically due to stretch, but that these responses are dissimilar in twitch and tonic muscles.

Anatomic capillarization is elevated in the medial gastrocnemius muscle of mighty mini mice

2009 ◽  
Vol 106 (5) ◽  
pp. 1660-1667 ◽  
Author(s):  
Lisa E. Wong ◽  
Theodore Garland ◽  
Sharon L. Rowan ◽  
Russell T. Hepple
Keyword(s):  
Cross Sections ◽  
Enzyme Activities ◽  
Gastrocnemius Muscle ◽  
Wheel Running ◽  
Fiber Type ◽  
Capillary Density ◽  
Medial Gastrocnemius ◽  
Mitochondrial Enzyme ◽  
Small Muscle ◽  
Medial Gastrocnemius Muscle

House mice selectively bred for high voluntary wheel running display a mini-muscle (MM) phenotype wherein mass-specific mitochondrial enzyme activities are double that of normal, but muscle mass is reduced by half. In addition, mini-muscles are characterized by small muscle fibers in the superficial region of the plantaris and medial gastrocnemius muscles. To determine the structural alterations facilitating aerobic metabolism in these mini-muscles, cross-sections of the medial gastrocnemius muscle of normal (N; n = 6) and mini-muscle (MM; n = 6) mice were histo- and immunochemically labeled and analyzed for fiber size, capillarization, and fiber type. On the basis of the higher mitochondrial enzyme activities in muscles of MM mice, we hypothesized that they would have greater fiber capillarization in the medial gastrocnemius than N mice. Furthermore, we hypothesized that augmented capillarization in MM would principally be a function of the smaller fibers in the superficial aspect of this muscle. On average, MM had higher capillary-to-fiber ratio and higher capillary density. Binning fibers according to size revealed that it was primarily the normal-sized fibers of the MM that had higher capillarity. The small fibers seen in the superficial region of MM were distinct from N mice in that they had heterogeneous myofibrillar ATPase staining and patchy succinate dehydrogenase staining in the interior of the fibers. These results support the hypothesis that the MM have higher indexes of capillarity, caused primarily by greater capillary number around normally sized fibers. These alterations are consistent with the superior mass-specific aerobic function of these muscles.

Satellite cell activation in the stretch-enlarged anterior latissimus dorsi muscle of the adult quail

1991 ◽  
Vol 260 (2) ◽  
pp. C206-C212 ◽  
Author(s):  
P. K. Winchester ◽  
M. E. Davis ◽  
S. E. Alway ◽  
W. J. Gonyea
Keyword(s):  
Satellite Cell ◽  
Satellite Cells ◽  
Latissimus Dorsi ◽  
Tritiated Thymidine ◽  
Cell Activity ◽  
Muscle Length ◽  
Latissimus Dorsi Muscle ◽  
Cell Labeling ◽  
Dorsi Muscle ◽  
Anterior Latissimus Dorsi

Satellite cell activity was examined in the stretch-enlarge anterior latissimus dorsi muscle (ALD) of the adult quail. Thirty-seven birds had a weight equal to 10% of their body mass attached to one wing while the contralateral wing served as an intra-animal control. At various time intervals after application of the wing weight (from 1 to 30 days), the birds were injected with tritiated thymidine and killed 1 h later. Stretched muscle length was greater by day 1 and mass by day 3 when compared with the contralateral muscle. Satellite cells actively synthesizing DNA were quantitated in fiber segments of the control and stretched ALD. A minimum of 1,500 muscle nuclei (satellite cell nuclei and myonuclei) were counted in each muscle. Labeling in stretched muscle was expressed by the percent labeled nuclei per total nuclei counted. Satellite cell labeling was initiated by day 1, peaked between days 3 and 7, and was not statistically different from control values at day 30. These results demonstrate that satellite cells are induced to enter the cell cycle in the stretch-enlarged ALD muscle from the adult quail, and the peak of proliferative activity is within the first week of stretch.

Long waves in a straight channel with non-uniform cross-section

2015 ◽  
Vol 770 ◽  
pp. 156-188 ◽  
Author(s):  
Patricio Winckler ◽  
Philip L.-F. Liu
Keyword(s):  
Boundary Layer ◽  
Wave Propagation ◽  
Cross Section ◽  
Three Dimensional ◽  
Channel Cross Section ◽  
Cross Sectional ◽  
New Model ◽  
One Dimensional ◽  
Uniform Channel ◽  
The Cross

A cross-sectionally averaged one-dimensional long-wave model is developed. Three-dimensional equations of motion for inviscid and incompressible fluid are first integrated over a channel cross-section. To express the resulting one-dimensional equations in terms of the cross-sectional-averaged longitudinal velocity and spanwise-averaged free-surface elevation, the characteristic depth and width of the channel cross-section are assumed to be smaller than the typical wavelength, resulting in Boussinesq-type equations. Viscous effects are also considered. The new model is, therefore, adequate for describing weakly nonlinear and weakly dispersive wave propagation along a non-uniform channel with arbitrary cross-section. More specifically, the new model has the following new properties: (i) the arbitrary channel cross-section can be asymmetric with respect to the direction of wave propagation, (ii) the channel cross-section can change appreciably within a wavelength, (iii) the effects of viscosity inside the bottom boundary layer can be considered, and (iv) the three-dimensional flow features can be recovered from the perturbation solutions. Analytical and numerical examples for uniform channels, channels where the cross-sectional geometry changes slowly and channels where the depth and width variation is appreciable within the wavelength scale are discussed to illustrate the validity and capability of the present model. With the consideration of viscous boundary layer effects, the present theory agrees reasonably well with experimental results presented by Chang et al. (J. Fluid Mech., vol. 95, 1979, pp. 401–414) for converging/diverging channels and those of Liu et al. (Coast. Engng, vol. 53, 2006, pp. 181–190) for a uniform channel with a sloping beach. The numerical results for a solitary wave propagating in a channel where the width variation is appreciable within a wavelength are discussed.

scholarly journals Electromyographic Analysis of Traditional and Nontraditional Abdominal Exercises: Implications for Rehabilitation and Training

2006 ◽  
Vol 86 (5) ◽  
pp. 656-671 ◽  
Author(s):  
Rafael F Escamilla ◽  
Eric Babb ◽  
Ryan DeWitt ◽  
Patrick Jew ◽  
Peter Kelleher ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Latissimus Dorsi ◽  
Rectus Femoris ◽  
Rectus Abdominis ◽  
Oblique Muscle ◽  
Emg Activity ◽  
Internal Oblique ◽  
Rectus Femoris Muscle ◽  
Femoris Muscle ◽  
Roll Out

Abstract Background and Purpose. Performing nontraditional abdominal exercises with devices such as abdominal straps, the Power Wheel, and the Ab Revolutionizer has been suggested as a way to activate abdominal and extraneous (nonabdominal) musculature as effectively as more traditional abdominal exercises, such as the crunch and bent-knee sit-up. The purpose of this study was to test the effectiveness of traditional and nontraditional abdominal exercises in activating abdominal and extraneous musculature. Subjects. Twenty-one men and women who were healthy and between 23 and 43 years of age were recruited for this study. Methods. Surface electromyography (EMG) was used to assess muscle activity from the upper and lower rectus abdominis, external and internal oblique, rectus femoris, latissimus dorsi, and lumbar paraspinal muscles while each exercise was performed. The EMG data were normalized to maximum voluntary muscle contractions. Differences in muscle activity were assessed by a 1-way, repeated-measures analysis of variance. Results. Upper and lower rectus abdominis, internal oblique, and latissimus dorsi muscle EMG activity were highest for the Power Wheel (pike, knee-up, and roll-out), hanging knee-up with straps, and reverse crunch inclined 30 degrees. External oblique muscle EMG activity was highest for the Power Wheel (pike, knee-up, and roll-out) and hanging knee-up with straps. Rectus femoris muscle EMG activity was highest for the Power Wheel (pike and knee-up), reverse crunch inclined 30 degrees, and bent-knee sit-up. Lumbar paraspinal muscle EMG activity was low and similar among exercises. Discussion and Conclusion. The Power Wheel (pike, knee-up, and roll-out), hanging knee-up with straps, and reverse crunch inclined 30 degrees not only were the most effective exercises in activating abdominal musculature but also were the most effective in activating extraneous musculature. The relatively high rectus femoris muscle activity obtained with the Power Wheel (pike and knee-up), reverse crunch inclined 30 degrees, and bent-knee sit-up may be problematic for some people with low back problems.

Regionalized adaptations and muscle fiber proliferation in stretch-induced enlargement

1989 ◽  
Vol 66 (2) ◽  
pp. 771-781 ◽  
Author(s):  
S. E. Alway ◽  
P. K. Winchester ◽  
M. E. Davis ◽  
W. J. Gonyea
Keyword(s):  
Muscle Fiber ◽  
Latissimus Dorsi ◽  
Volume Density ◽  
Cross Sectional ◽  
Adult Skeletal Muscle ◽  
Relative Contribution ◽  
Anterior Latissimus Dorsi ◽  
Fiber Number ◽  
Nitric Acid Digestion ◽  
Alpha Type

The relative contribution of increases in fiber area to stretch-induced muscle enlargement was evaluated in the slow tonic fibers of the anterior latissimus dorsi of adult Japanese quails. A weight corresponding to 10% of the bird's body mass was attached to one wing. Thirty days of stretch in 34 birds averaged 171.8 +/- 13.5% increase in muscle mass and 23.5 +/- 0.8% increase in muscle fiber length. The volume density of noncontractile tissue increased in middle and distal regions of stretch-enlarged muscles. Mean fiber cross-sectional area increased 56.7 +/- 12.3% in the midregion of stretched muscles. Further analysis indicated slow beta-fiber hypertrophy occurred in proximal, middle, and distal regions; however, fast alpha-type fiber hypertrophy was limited to middle regions of stretched muscles. Stretched muscles had a significant increase in the frequency of slow beta-fibers that were less than 500 microns 2 in all regions and fast alpha-type fibers in middle and distal regions. Total fiber number was determined after nitric acid digestion of connective tissue in 10 birds. Fiber number increased 51.8 +/- 19.4% in stretched muscle. These results are the first to clearly show that muscle fiber proliferation contributes substantially to adult skeletal muscle stretch-induced enlargement, although we do not know whether the responses of the slow tonic anterior latissimus dorsi might be similar or different from mammalian twitch muscle.

Progressive stretch overload of skeletal muscle results in hypertrophy before hyperplasia

1993 ◽  
Vol 75 (3) ◽  
pp. 1263-1271 ◽  
Author(s):  
J. Antonio ◽  
W. J. Gonyea
Keyword(s):  
Latissimus Dorsi ◽  
Critical Size ◽  
Muscle Length ◽  
Progressive Increase ◽  
Right Wing ◽  
Left Wing ◽  
Anterior Latissimus Dorsi ◽  
Fiber Number ◽  
The Right ◽  
Large Muscle

Intermittent stretch of the anterior latissimus dorsi (ALD) muscle produces fiber hypertrophy without fiber hyperplasia (J. Appl. Physiol. 74: 1893–1898, 1993). This study was undertaken to determine if a progressive increase in load and duration of stretch would induce extremely large muscle fiber areas or if the fibers would reach a critical size before the onset of fiber hyperplasia. Weights ranging from 10 to 35% of the bird's mass were attached to the right wing of 26 adult quail while the left wing served as the intra-animal control. The stretch protocol was as follows: day 1 (10% wt), days 2 and 3 (rest), day 4 (15% wt), days 5–7 (rest), day 8 (20% wt), days 9 and 10 (rest), days 11–14 (25% wt), days 15 and 16 (rest), and days 17–38 (35% wt). Birds were killed after 12, 16, 20, 24, and 28 days of stretch not including rest days. Muscle mass increased 174% (12 days), 196% (16 days), 225% (20 days), 264% (24 days), and 318% (28 days). Muscle length increased 60% (12 days), 34% (16 days), 59% (20 days), 50% (24 days), and 51% (28 days). Mean fiber area increased 111% (12 days), 142% (16 days), 75% (20 days), 90% (24 days), and 39% (28 days). Fiber number, which was measured histologically, increased significantly by 82% only in the 28 days of stretch group. The percentage of slow tonic fibers did not change for any of the time points examined.(ABSTRACT TRUNCATED AT 250 WORDS)

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