Hormonal control of muscle growth

Florini, James R.

doi:10.1002/mus.880100702

Cited by 293 publications

(142 citation statements)

References 194 publications

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“…The increase in length is due to the addition of sarcomeres in series within the myofibril and not the result of an increase in average sarcomere length (Close 1972 (Florini 1987;White & Esser 1989).…”

Section: Normal Developmental Growth Of Myofibersmentioning

confidence: 99%

Gender differences in strength and muscle fiber characteristics

Miller

MacDougall

Tarnopolsky

et al. 1993

Europ. J. Appl. Physiol.

866

591

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A gender difference in absolute muscle strength is well documented.The e'xtent to which quantitative (fiber area and number) and qualitative (specific tension) differences in muscle contribute to this is not well understood. The purpose of this study was to examine a variety of muscle characteristics in the biceps brachii and vastus lateralis in a sample of males (n-8) and females (n=8) The difference in type II fiber area in the biceps brachii was not statistically significant despite the fact that these fibers were almost twice as large in the males as in 2 the females (8207 vs. 4306 urn). No significant gender difference was found in biceps fiber number (180,620 vs.l56,872) or muscle area to fiber area ratio in the vastus lateralis (451,468 vs. 465,007).No significant gender differences were found in any of the motor unit characteristics.The results indicate that the primary determinant of the greater muscle strength of males is their larger mean fiber areas which results in greater muscle cross-sectional areas.iv ACKNOWLEDGEMENTS

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Section: Normal Developmental Growth Of Myofibersmentioning

confidence: 99%

Gender differences in strength and muscle fiber characteristics

Miller

MacDougall

Tarnopolsky

et al. 1993

Europ. J. Appl. Physiol.

866

591

View full text Add to dashboard Cite

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“…Binding of insulin to the insulin-IGF-1 receptor activates the PI3K-Akt-mTOR pathway, which increases the rate of protein translation and inhibits the expression of E3 ubiquitin ligases [7,34]. Furthermore, insulin and IGF-1 are also involved in the regulation of proliferation and differentiation of myoblasts and satellite cells [11,15]. The present finding that insulin exclusively does not induce hypertrophy of mature muscle fibres but does so in the presence of albumin indicates that hypertrophy of mature muscle fibres occurred via a synergistic effect of insulin and albumin.…”

Section: Albumin Preserves E-c Couplingmentioning

confidence: 99%

Hypertrophy of mature Xenopus muscle fibres in culture induced by synergy of albumin and insulin

Jaspers

Beek-Harmsen

Blankenstein

et al. 2008

Pflugers Arch - Eur J Physiol

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The aim of this study was to investigate effects of albumin and insulin separately as well as in combination on mature muscle fibres during long-term culture. Single muscle fibres were dissected from m. iliofibularis of Xenopus laevis and attached to a force transducer in a culture chamber. Fibres were cultured in a serum-free medium at slack length (mean sarcomere length 2.3 μm) for 8 to 22 days. The medium was supplemented with (final concentrations): (1) bovine insulin (6 nmol/L or 200-600 nmol/L), (2) 0.2% bovine albumin or (3) 0.2% bovine albumin in combination with insulin (120 nmol/L). In culture medium with insulin, 50% of the muscle fibres became in-excitable within 7-12 days, whereas the other 50% were stable. Caffeine contractures of in-excitable muscle fibres produced 80.4±2.4% of initial peak tetanic force, indicating impaired excitation-contraction (E-C) coupling in in-excitable fibres. In the presence of albumin, all cultured muscle fibres were stable for at least 10 days. Muscle fibres cultured in medium with insulin or albumin exclusively did not hypertrophy or change the number of sarcomeres in series. In contrast, muscle fibres cultured with both albumin and insulin showed an increase in tetanic force and fibre cross-sectional area of 19.6±2.8% and 32.5±4.9%, respectively, (means±SEM.; P=0.007) after 16.3±1.7 days, whereas the number of sarcomeres in series remained unchanged. We conclude that albumin prevents muscle fibre damage and preserves E-C coupling in culture. Furthermore, albumin is important in regulating muscle fibre adaptation by a synergistic action with growth factors like insulin.

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“…Among endocrine factors, actions of anabolic hormones such as growth hormone (GH) and testosterone (TES) have been clearly shown to stimulate protein synthesis and to promote muscle hypertrophy [Florini (1987)]. From this viewpoint, a number of studies have investigated acute anabolic hormone responses in males and females [Kraemer et al (1990[Kraemer et al ( , 1993], and young and elderly subjects [Häkkinen & Pakarinen (1995)].…”

Section: Introductionmentioning

confidence: 99%

Growth Hormone Response to Training Regimen with Combined High-and Low-Intensity Resistance Exercises

Goto

Ishii

Takamatsu

2004

Int. J. Sport Health Sci.

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We had previously shown that performing a single set of resistance exercise at 50% of 1 repetition maximum (RM) added after a high-intensity, low-repetition exercise (strength-type regimen) greatly enhanced growth hormone (GH) secretion [Goto et al. (2003)]. The present study aimed to investigate the effect of an additional set at 50% to 20% of 1RM after a strength-type regimen on anabolic hormone secretion. Eight male subjects performed bilateral knee extension exercises using a strength-type regimen (5 sets at 90% of 1RM, with 3-min rests), and other 3 types of regimens, in which 1 set of exercise at either 50%, 30% or 20% of 1RM was added immediately after the strength-type regimen (defined as C50-type, C30-type and C20-type regimens, respectively). Concentrations of serum GH, testosterone and blood lactate were measured before and after exercises. The number of repetitions in the added set showed a significant dependence on the exercise intensity: 82.3 times in C20-type > 46.1 times in C30-type > 22.6 times in C50-type (p ≤ 0.05). Post-exercise GH concentrations were significantly (p ≤ 0.05) higher in C50-and C30-type regimens than in the strength-type regimen, whereas no significant difference was observed between C20-and strength-type regimens. Testosterone did not change in any types of regimen. These results indicated that performing a single set of exercise at low intensity added after a strength-type regimen caused a significant increase in GH concentration. However, such an effect might be diminished when the intensity of the additional exercise was extremely low (below 20% of 1RM).

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Hormonal control of muscle growth

Cited by 293 publications

References 194 publications

Gender differences in strength and muscle fiber characteristics

Gender differences in strength and muscle fiber characteristics

Hypertrophy of mature Xenopus muscle fibres in culture induced by synergy of albumin and insulin

Growth Hormone Response to Training Regimen with Combined High-and Low-Intensity Resistance Exercises

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