Effects of fatigue and recovery on electromyographic and isometric force- and relaxation-time characteristics of human skeletal muscle

1986 ◽  
Vol 55 (6) ◽  
pp. 588-596 ◽  
Author(s):  
Keijo H�kkinen ◽  
Paavo V. Komi
Keyword(s):  
Skeletal Muscle ◽  
Relaxation Time ◽  
Human Skeletal Muscle ◽  
Isometric Force

scholarly journals Glucose formation in human skeletal muscle. Influence of glycogen content

1989 ◽  
Vol 258 (3) ◽  
pp. 911-913 ◽  
Author(s):  
K Sahlin ◽  
S Broberg ◽  
A Katz
Keyword(s):  
Skeletal Muscle ◽  
Relative Intensity ◽  
Human Skeletal Muscle ◽  
Glycogen Content ◽  
Isometric Force ◽  
Debranching Enzyme ◽  
Glycogen Store ◽  
Glycolytic Intermediates ◽  
Glucose Formation ◽  
Maximal Isometric Force

Eight men exercised at 66% of their maximal isometric force to fatigue after prior decrease in the glycogen store in one leg (low-glycogen, LG). The exercise was repeated with the contralateral leg (control) at the same relative intensity and for the same duration. Muscle (quadriceps femoris) glycogen content decreased in the LG leg from 199 +/- 17 (mean +/- S.E.M.) to 163 +/- 16 mmol of glucosyl units/kg dry wt. (P less than 0.05), and in the control leg from 311 +/- 23 to 270 +/- 18 mmol/kg (P less than 0.05). The decrease in glycogen corresponded to a similar accumulation of glycolytic intermediates. Muscle glucose increased in the LG leg during the contraction, from 1.8 +/- 0.1 to 4.3 +/- 0.6 mmol/kg dry wt. (P less than 0.01), whereas no significant increase occurred in the control leg (P greater than 0.05). It is concluded that during exercise glucose is formed from glycogen through the debranching enzyme when muscle glycogen is decreased to values below about 200 mmol/kg dry wt.

scholarly journals Excitability and contractility of skeletal muscle engineered from primary cultures and cell lines

2001 ◽  
Vol 280 (2) ◽  
pp. C288-C295 ◽  
Author(s):  
Robert G. Dennis ◽  
Paul E. Kosnik ◽  
Mark E. Gilbert ◽  
John A. Faulkner
Keyword(s):  
Skeletal Muscle ◽  
Relaxation Time ◽  
Cell Lines ◽  
Isometric Force ◽  
Cross Sectional Area ◽  
Specific Force ◽  
Sectional Area ◽  
Cross Sectional ◽  
Peak Tension ◽  
Time To Peak

The purpose of this study was to compare the excitability and contractility of three-dimensional skeletal muscle constructs, termed myooids, engineered from C2C12 myoblast and 10T½ fibroblast cell lines, primary muscle cultures from adult C3H mice, and neonatal and adult Sprague-Dawley rats. Myooids were 12 mm long, with diameters of 0.1–1 mm, were excitable by transverse electrical stimulation, and contracted to produce force. After ∼30 days in culture, myooid cross-sectional area, rheobase, chronaxie, resting baseline force, twitch force, time to peak tension, one-half relaxation time, and peak isometric force were measured. Specific force was calculated by dividing peak isometric force by cross-sectional area. The specific force generated by the myooids was 2–8% of that generated by skeletal muscles of control adult rodents. Myooids engineered from C2C12-10T½ cells exhibited greater rheobase, time to peak tension, and one-half relaxation time than myooids engineered from adult rodent cultures, and myooids from C2C12-10T½ and neonatal rat cells had greater resting baseline forces than myooids from adult rodent cultures.

scholarly journals Chimpanzee super strength and human skeletal muscle evolution

2017 ◽  
Vol 114 (28) ◽  
pp. 7343-7348 ◽  
Author(s):  
Matthew C. O’Neill ◽  
Brian R. Umberger ◽  
Nicholas B. Holowka ◽  
Susan G. Larson ◽  
Peter J. Reiser
Keyword(s):  
Skeletal Muscle ◽  
Power Output ◽  
Human Skeletal Muscle ◽  
Isometric Force ◽  
Low Cost ◽  
Human Muscle ◽  
Dynamic Force ◽  
Muscular Performance ◽  
In The Wild ◽  
Species Specific

Since at least the 1920s, it has been reported that common chimpanzees (Pan troglodytes) differ from humans in being capable of exceptional feats of “super strength,” both in the wild and in captive environments. A mix of anecdotal and more controlled studies provides some support for this view; however, a critical review of available data suggests that chimpanzee mass-specific muscular performance is a more modest 1.5 times greater than humans on average. Hypotheses for the muscular basis of this performance differential have included greater isometric force-generating capabilities, faster maximum shortening velocities, and/or a difference in myosin heavy chain (MHC) isoform content in chimpanzee relative to human skeletal muscle. Here, we show that chimpanzee muscle is similar to human muscle in its single-fiber contractile properties, but exhibits a much higher fraction of MHC II isoforms. Unlike humans, chimpanzee muscle is composed of ∼67% fast-twitch fibers (MHC IIa+IId). Computer simulations of species-specific whole-muscle models indicate that maximum dynamic force and power output is 1.35 times higher in a chimpanzee muscle than a human muscle of similar size. Thus, the superior mass-specific muscular performance of chimpanzees does not stem from differences in isometric force-generating capabilities or maximum shortening velocities—as has long been suggested—but rather is due in part to differences in MHC isoform content and fiber length. We propose that the hominin lineage experienced a decline in maximum dynamic force and power output during the past 7–8 million years in response to selection for repetitive, low-cost contractile behavior.

TGFß regulates metabolism of human skeletal muscle cells by miRNAs

2018 ◽  
Author(s):  
S Höckele ◽  
P Huypens ◽  
C Hoffmann ◽  
T Jeske ◽  
M Hastreiter ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Human Skeletal Muscle Cells

IRAK-1/IRS-1 Signaling Cross Talk in Human Skeletal Muscle—Role in Insulin Resistance

Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 159-OR
Author(s):  
THEODORE P. CIARALDI ◽  
SUNDER MUDALIAR ◽  
LIWU LI ◽  
ROSARIO SCALIA ◽  
XIAO JIAN SUN ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Cross Talk ◽  
Human Skeletal Muscle

1891-P: Palmitate-Enriched Lipid Ingestion Acutely Induces Insulin Resistance Associated with PKCγ Activation and Impaired Mitochondrial Function in Human Skeletal Muscle

Diabetes ◽  
2020 ◽  
Vol 69 (Supplement 1) ◽  
pp. 1891-P
Author(s):  
THERESIA SARABHAI ◽  
CHRYSI KOLIAKI ◽  
SABINE KAHL ◽  
DOMINIK PESTA ◽  
LUCIA MASTROTOTARO ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Mitochondrial Function ◽  
Human Skeletal Muscle
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