The strength, contractile properties and radiological density of skeletal muscle before and 1 year after gastroplasty

1988 ◽  
Vol 74 (1) ◽  
pp. 79-83 ◽  
Author(s):  
D. J. Newham ◽  
R. A. Harrison ◽  
A. M. Tomkins ◽  
C. G. Clark
Keyword(s):  
Skeletal Muscle ◽  
Fat Content ◽  
Contractile Properties ◽  
Morbidly Obese ◽  
Force Frequency ◽  
Axial Tomography ◽  
Before And After ◽  
Computerized Axial Tomography ◽  
The Mean ◽  
Frequency Relaxation

1. Skeletal muscle strength, contractile properties and radiological composition have been studied in seven morbidly obese adults (six female) before and 1 year after gastroplasty operations. The mean body weight fell from 138.3 kg (sd 25.2) to 99.7 kg (sd 23.0) (P < 0.001). 2. The strength and contractile properties (force/frequency, relaxation rate and fatiguability) of both the adductor pollicis and quadriceps muscles were unaffected by the weight loss. 3. Computerized axial tomography scans obtained 1 year after surgery showed that the quadriceps contained an abnormally high proportion of fat. The mean fat content was 10.8% (range 3.0–30.1%) compared with 1.6% (range 0–5%) for normal muscle. Two individuals were scanned before and after surgery and the fat content of their quadriceps fell from 12.6% and 6.9% to 3.1% and 3.0%, respectively. 4. It is concluded that in obese individuals large amounts of weight can be lost, from both subcutaneous and intramuscular fat stores, without compromising either the strength or contractile properties of skeletal muscles. These results do not support the claim that skeletal muscle contractility is a sensitive indicator of changes in nutritional status.

Effect of caffeine on skeletal muscle function before and after fatigue

1983 ◽  
Vol 54 (5) ◽  
pp. 1303-1305 ◽  
Author(s):  
J. M. Lopes ◽  
M. Aubier ◽  
J. Jardim ◽  
J. V. Aranda ◽  
P. T. Macklem
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Relaxation Rate ◽  
Voluntary Contraction ◽  
Contractile Properties ◽  
Double Blind ◽  
Caffeine Ingestion ◽  
Muscle Contractile Properties ◽  
Before And After ◽  
Muscle Contractile

We studied the effect of caffeine on voluntary and electrically stimulated contractions of the adductor pollicis muscle in five adult volunteers. Caffeine (500 mg) was administered orally in a double-blind fashion. Electrical stimulation of the ulnar nerve was performed at 10, 20, 30, 50, and 100 Hz before and after a sustained voluntary contraction held at 50% of the maximal voluntary contraction (MVC). A brief tetanus at 30 Hz was also performed to calculate relaxation rate in the fresh muscle. Contractile properties, relaxation rate, and endurance were then assessed after caffeine and placebo, as well as the response of the fatigued muscle to different frequencies of stimulation. There was no difference in the maximal tension obtained with electrical stimulation (T100) or in the MVC between placebo and caffeine. The tensions developed with electrical stimulation at lower frequencies increased significantly with caffeine ingestion, shifting the frequency-force curve to the left, both before and after fatigue. Mean plasma caffeine concentration associated with these responses was 12.2 +/- 4.9 mg/l. We conclude that caffeine has a direct effect on skeletal muscle contractile properties both before and after fatigue as demonstrated by electrical stimulation.

Regional skeletal muscle measurement: evaluation of new dual-energy X-ray absorptiometry model

1999 ◽  
Vol 87 (3) ◽  
pp. 1163-1171 ◽  
Author(s):  
Wei Wang ◽  
Zimian Wang ◽  
Myles S. Faith ◽  
Donald Kotler ◽  
Rick Shih ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Mass Measurement ◽  
Dual Energy ◽  
System Level ◽  
Axial Tomography ◽  
X Ray ◽  
Computerized Axial Tomography ◽  
Tissue System ◽  
Immunodeficiency Syndrome

Although there is growing interest in studying muscle distribution, regional skeletal muscle (SM) mass measurement methods remain limited. The aim of the present study was to develop a new dual-energy X-ray absorptiometry (DEXA) model for estimating regional adipose tissue-free skeletal muscle mass (AT-free SM). Relationships were derived from Reference Man data between tissue-system- level components (i.e., AT-free SM, AT, skeleton, and skin) and molecular-level components including fat-free soft tissue, fat, and bone mineral. The proposed DEXA-SM model was evaluated by multiscan computerized axial tomography (CT). Twenty-seven male subjects [age, 36 ± 12 (SD) yr; body mass, 73.2 ± 12.4 kg; 20 were healthy, and 7 had acquired immunodeficiency syndrome] completed DEXA and CT studies. Identical landmarks for DEXA and CT measurements were selected in three regions, including calves, thighs, and forearms. There was a strong correlation for AT-free SM estimates between the new DEXA and CT methods (e.g., sum of three regions, r= 0.86, P < 0.001). Regional AT-free SM measured in the 27 subjects by DEXA and CT, respectively, were 3.44 ± 0.60 and 3.47 ± 0.55 kg (difference 0.9%, P > 0.05) for calves, 10.49 ± 1.77 and 10.05 ± 1.79 kg (difference 4.4%, P < 0.05) for thighs, 1.36 ± 0.49 and 1.20 ± 0.41 kg (difference 13.3%, P < 0.01) for forearms, and 15.29 ± 2.33 and 14.72 ± 2.33 kg (difference 3.9%, P < 0.05) for the sum all three regions. Although the suggested DEXA-SM model needs minor refinements, this is a promising in vivo approach for measurement of regional SM, because DEXA is widely available, relatively inexpensive, and radiation exposure is low.

Contractile properties of single-skinned skeletal muscle fibres of the extensor digitorum longus muscle of the Australian short-nosed echidna

2005 ◽  
Vol 53 (4) ◽  
pp. 237
Author(s):  
Anthony J. Bakker ◽  
Ann L. Parkinson ◽  
Stewart I. Head
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Contractile Properties ◽  
Extensor Digitorum ◽  
Muscle Fibres ◽  
Force Response ◽  
Response Data ◽  
The Mean ◽  
Fast Twitch ◽  
Skeletal Muscle Fibres

Eutherian mammal fast-twitch muscle fibres share similar contractile activation properties, suggesting that these properties are highly conserved in mammals. To investigate this hypothesis, we examined the contractile properties of skeletal muscle from the order Monotremata, a mammalian order that separated from eutherians 150 million years ago. The Ca2+- and Sr2+-activation properties of single mechanically skinned skeletal muscle fibres from the extensor digitorum longus (EDL) muscle of the short-nosed echidna were determined. Sigmoidal curves fitted to force response data plotted as a function of pCa (–log[Ca2+]), had a mean slope of 4.32 ± 0.28 and a mean pCa50 and pCa10 value of 6.18 ± 0.01 and 6.41 ± 0.02 respectively (n = 20). The mean pSr50, pSr10 and slope values of curves fitted to the force-response data after activation with Sr2+ were 4.80 ± 0.03, 5.29 ± 0.07 and 2.75 ± 0.18 respectively (n = 20). The mean pCa50–pSr50 value for the echidna EDL fibres was 1.37 ± 0.04. In five of the echidna fibres, exposure to submaximal Ca2+ concentrations produced myofibrillar force oscillations (mean frequency, 0.13 ± 0.01 Hz), a phenomenon found only in eutherian slow and intermediate muscle fibres. These results show that echidna EDL fibres generally have similar contractile properties to eutherian fast-twitch skeletal muscle fibres, such as those found in the EDL of the rat.

Microgravity-induced transformations of myosin isoforms and contractile properties of skeletal muscle

1996 ◽  
Vol 81 (1) ◽  
pp. 123-132 ◽  
Author(s):  
V. J. Caiozzo ◽  
F. Haddad ◽  
M. J. Baker ◽  
R. E. Herrick ◽  
N. Prietto ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Level ◽  
Muscle Fibers ◽  
Contractile Properties ◽  
Protein Isoforms ◽  
Control Group ◽  
Type I ◽  
Myosin Isoforms ◽  
Force Frequency ◽  
Mrna Isoform

This study examined the effects of microgravity (14 days) on 1) the contractile properties of the soleus (Sol), an antigravity skeletal muscle; and 2) the myosin heavy chain (MHC) protein and mRNA isoform content of the Sol, vastus intermedius (VI), plantaris (Plan), and tibialis anterior (TA) muscles. The force-velocity relationships of the flight Sol muscles had a significant reduction in maximal isometric tension (-37%) and a corresponding increase in maximal shortening velocity (+20%). Additionally, the force-frequency relationship of the flight Sol muscles was shifted to the right of the ground-based control group. Microgravity had the greatest effect on muscle fiber composition in the Sol muscle, with a reduction in slow muscle fibers and a corresponding increase in muscle fibers categorized as hybrid fibers. The estimated absolute MHC isoform content was altered to the greatest extent in the Sol and VI muscles, with significant decreases and elevations in the slow type I and fast type IIX MHC protein isoforms, respectively. Consistent with the protein data, both the flight Sol and VI muscles exhibited significant elevations in the fast type IIX MHC mRNA isoform. In contrast, however, the flight Plan and TA groups had significant increases in the fast type IIB MHC mRNA isoform content without corresponding changes at the protein level. The results of this study suggest that spaceflight of even short duration produces important changes in the contractile properties of antigravity skeletal muscle. These changes are mediated by alterations in MHC phenotype and reductions in muscle mass. In some instances, the alterations in MHC mRNA isoform content seemed to be uncoupled from those occurring at the protein level. This apparent uncoupling between mRNA and protein expression demonstrates that the effects of microgravity must be better understood at the transcriptional, translational, and post-translational levels.

Relationship between carbohydrate oxidation and G-1,6-P2 in human skeletal muscle during euglycemic hyperinsulinemia

1991 ◽  
Vol 260 (1) ◽  
pp. R113-R119 ◽  
Author(s):  
A. Katz ◽  
C. Bogardus
Keyword(s):  
Skeletal Muscle ◽  
Carbohydrate Oxidation ◽  
Whole Body ◽  
Glucose Disposal ◽  
Dependent Diabetes Mellitus ◽  
Insulin Resistant ◽  
Before And After ◽  
The Mean ◽  
Fructose 1,6 Bisphosphate ◽  
Rate Limiting

Euglycemic (approximately 5.5 mM) hyperinsulinemic clamps were performed on normoglycemic insulin-sensitive (NIS) men and men who were normoglycemic but insulin resistant (NIR) and hyperglycemic and insulin resistant (HIR) (i.e., noninsulin-dependent diabetes mellitus). Insulin was infused at successive rates of 40 and 400 mU.m-2.min-1, and biopsies were obtained from the quadriceps femoris muscles before and after insulin and analyzed for regulators of phosphofructokinase, a rate-limiting enzyme for glycolysis. Glucose disposal and whole body carbohydrate oxidation were markedly lower in NIR and HIR vs. NIS (P less than 0.001 for disposal and oxidation). The alpha-D-glucose 1,6-bisphosphate (G-1,6-P2) content increased almost twofold during the 40-mU insulin infusion (P less than 0.001) without any further change during the 400-mU infusion in NIS men. The increase in G-1,6-P2 in NIR and HIR was only approximately 25 and 50% of the increase observed in NIS during the 40- and 400-mU infusions, respectively. The mean content of G-1,6-P2 was strongly related to the mean rate of carbohydrate oxidation (r = 0.99; P less than 0.001). Because during euglycemic hyperinsulinemia approximately 90% of the glucose utilization is accounted for by skeletal muscle (J. Clin. Invest. 76: 149, 1985), it is likely that whole body carbohydrate oxidation is proportional to carbohydrate oxidation and glycolysis in muscle. The different rates of carbohydrate oxidation between NIS and insulin-resistant men could not be associated with differences in fructose 6-phosphate, fructose 1,6-bisphosphate, fructose 2,6-bisphosphate, Pi, free ADP and free AMP (activators of phosphofructokinase), or ATP and citrate (inhibitors of phosphofructokinase).

scholarly journals Positive adaptations to weight-lifting training in the elderly

1990 ◽  
Vol 69 (5) ◽  
pp. 1725-1733 ◽  
Author(s):  
A. B. Brown ◽  
N. McCartney ◽  
D. G. Sale
Keyword(s):  
Biceps Brachii ◽  
Weight Lifting ◽  
Contractile Properties ◽  
Isometric Strength ◽  
Elbow Flexors ◽  
Cross Sectional ◽  
Maximal Load ◽  
Before And After ◽  
Isokinetic Torque ◽  
The Mean

Maximal weight-lifting performance, isometric strength, isokinetic torque, whole muscle and individual fiber cross-sectional areas, and muscle evoked contractile properties were assessed in 14 elderly males before and after 12 wk of weight-lifting training. Dynamic elbow flexion training of one arm resulted in a significant 48% mean increase in the maximal load that could be lifted once (1 RM) and a smaller improvement in isokinetic torque (8.8%) but no change in isometric strength. In the contralateral control arm, 1 RM and isokinetic torque increased by 12.7 and 6.5%, respectively, but isometric strength did not change. The interpolated twitch technique confirmed complete motor unit activation during a maximal isometric contraction of the elbow flexors before and after the training. Bilateral leg press training effected mean increases of 17 and 23% in isokinetic torque and dynamic lifting capacity, respectively. The mean maximal cross-sectional area of the elbow flexors (biceps brachii and brachialis) increased by 17.4% in the trained arm but did not change the control arm. The increase in the mean area of type II fibers in the biceps brachii muscle in the trained arm (30.2%) was greater than the corresponding change in the control arm (10.7%, P less than 0.05). The most significant change in the evoked contractile properties of the trained elbow flexors was the increase in twitch half-relaxation time. It is concluded that older individuals retain the potential for significant increases in strength performance and upper limb muscle hypertrophy in response to overload training.

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