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Journal of Strength and Conditioning... Sep 2022Diniz, RCR, Tourino, FD, Lacerda, LT, Martins-Costa, HC, Lanza, MB, Lima, FV, and Chagas, MH. Does the muscle action duration induce different regional muscle...
Diniz, RCR, Tourino, FD, Lacerda, LT, Martins-Costa, HC, Lanza, MB, Lima, FV, and Chagas, MH. Does the muscle action duration induce different regional muscle hypertrophy in matched resistance training protocols? J Strength Cond Res 36(9): 2371-2380, 2022-The manipulation of the muscle action duration (MAD) can influence the instantaneous torque along the range of motion, which can lead to adaptations of regional muscle hypertrophy. The aim of this study was to compare the effects of matched resistance training (RT) on the knee extension machine with different MAD in the cross-sectional area (CSA) responses within the quadriceps femoris (QF) and its muscles. Forty-four subjects were allocated into a control and 3 experimental groups. For a period of 10 weeks, subjects in the experimental groups performed the training protocols that were different only by the MAD: group 5c1e (5s concentric action [CON] and 1s eccentric action [ECC]; group 3c3e (3s CON and 3s ECC) and group 1c5e (1s CON and 5s ECC). Magnetic resonance imaging was performed (before and after the intervention) to determine the relative change (%) in CSA of the QF muscles along proximal (30%), middle (50%), and distal regions (70% distal of the femur). The change in CSA of the rectus femoris at the middle region are greater in 5c1e (6.8 ± 6.5%) and 1c5e (7.4 ± 6.0%) groups than 3c3e (3.4 ± 6.6%) and control groups (0.2 ± 1.8%). In addition, vastus lateralis at the distal region (5c1e = 15.9 ± 11.8%; 1c5e = 14.4 ± 10.0%) presenting greater increases in change of CSA than the others vastus only 5c1e (vastus lateralis [VI] = 5.0 ± 4.7%; vastus medialis [VM] = 4.2 ± 3.2%) and 1c5e groups (VI = 4.7 ± 3.6%; VM = 3.4 ± 3.1%). In conclusion, this study showed that matched RT protocols with different MAD resulted in different region-specific muscle hypertrophic across the individual muscles of QF.
Topics: Humans; Hypertrophy; Knee; Muscle, Skeletal; Quadriceps Muscle; Resistance Training; Torque
PubMed: 33306588
DOI: 10.1519/JSC.0000000000003883 -
Journal of Cranio-maxillo-facial... May 2023This study aims to confirm the effectiveness and safety of a prabotulinumtoxin type A (praBTX-A) injection in patients with bruxism and masseter hypertrophy. The study...
This study aims to confirm the effectiveness and safety of a prabotulinumtoxin type A (praBTX-A) injection in patients with bruxism and masseter hypertrophy. The study included patients who ground or clenched their teeth while sleeping and had computed tomography (CT) scans that showed a maximum thickness of the masseter muscle of 15 mm or more. The praBTX-A was administered bilaterally into the masseter muscles; 15 U/side for group 1, 25 U/side for group 2, and 35 U/side for group 3. CT scans and bruxism questionnaires were conducted before and eight weeks after the injection. Thirty-seven patients were enrolled, but three dropped out due to loss of follow-up. After injection, masseter thickness decreased to 15.1 ± 2.0 mm for group 1, 14.3 ± 2.9 mm for group 2, and 13.4 ± 1.8 mm for group 3 (p = 0.043). Group 3 showed a statistically significant lower masseter thickness compared to group 1 (p = 0.039). Both subjective and objective frequencies of bruxism decreased for all groups, but there were no significant differences in either subjective (p = 0.396) or objective frequencies (p = 0.87) between the groups after the injection. The results of this study suggest that praBTX-A injection is a safe and effective treatment for bruxism and masseter hypertrophy. A dosage of 35 IU/side can effectively decrease masseter thickness and relieve bruxism symptoms. Even the minimum dosage of 15 IU/side can contribute to improvements in bruxism symptoms. This investigation provides valuable information for managing bruxism that is associated with hypertrophic masseter muscles.
Topics: Humans; Masseter Muscle; Neuromuscular Agents; Bruxism; Prospective Studies; Injections, Intramuscular; Botulinum Toxins, Type A; Hypertrophy
PubMed: 37353404
DOI: 10.1016/j.jcms.2023.05.005 -
The Journal of the Acoustical Society... Jul 2022The male and female southern black drum possess highly specialized, bilateral, striated sonic muscles used in sound production during courtship by males and in the...
The male and female southern black drum possess highly specialized, bilateral, striated sonic muscles used in sound production during courtship by males and in the production of disturbance calls by both males and females. Androgen-driven hypertrophy of the sonic muscles in males during the late spring spawning period results in increased growth of sonic muscle mass followed by post-spawning atrophy of sonic muscles. We examined changes in sonic muscle morphology and in the sound characteristics of males and females underlying seasonal changes in sonic muscle mass and muscle contraction as measured by sound production. In males, the sound pressure level increased while sound pulse duration decreased with increasing sonic muscle mass, indicating that sonic muscle fibers contract with greater force and shorter duration during the spawning season. Interpulse interval and the total number of pulses varied seasonally with muscle mass, which suggests that the effects of steroids on male southern black drum sound characteristics are more pronounced peripherally than in the central nervous system. In females, no increase in sonic muscle mass was found, and therefore, a change was not observed in the acoustic variables analyzed. Seasonal sonic muscle hypertrophy in males likely functions as a secondary sexual characteristic that maximizes vocalization amplitude or loudness during the spawning period.
Topics: Animals; Atrophy; Female; Hypertrophy; Male; Muscles; Perciformes; Sound; Vocalization, Animal
PubMed: 35931508
DOI: 10.1121/10.0012690 -
Acta Physiologica (Oxford, England) May 2022To describe ribosome biogenesis during resistance training, its relation to training volume and muscle growth.
AIM
To describe ribosome biogenesis during resistance training, its relation to training volume and muscle growth.
METHODS
A training group (n = 11) performed 12 sessions (3-4 sessions per week) of unilateral knee extension with constant and variable volume (6 and 3-9 sets per session respectively) allocated to either leg. Ribosome abundance and biogenesis markers were assessed from vastus lateralis biopsies obtained at baseline, 48 hours after sessions 1, 4, 5, 8, 9 and 12, and after eight days of de-training, and from a control group (n = 8). Muscle thickness was measured before and after the intervention.
RESULTS
Training led to muscle growth (3.9% over baseline values, 95% CrI: [0.2, 7.5] vs. control) with concomitant increases in total RNA, ribosomal RNA, upstream binding factor (UBF) and ribosomal protein S6 with no differences between volume conditions. Total RNA increased rapidly in response to the first four sessions (8.6% [5.6, 11.7] per session), followed by a plateau and peak values after session 8 (49.5% [34.5, 66.5] above baseline). Total RNA abundance was associated with UBF protein levels (5.0% [0.2, 10.2] per unit UBF), and the rate of increase in total RNA levels predicted hypertrophy (0.3 mm [0.1, 0.4] per %-point increase in total RNA per session). After de-training, total RNA decreased (-19.3% [-29.0, -8.1]) without muscle mass changes indicating halted biosynthesis of ribosomes.
CONCLUSION
Ribosomes accumulate in the initial phase of resistance training with abundances sensitive to training cessation and associated with UBF protein levels. The average accumulation rate predicts muscle training-induced hypertrophy.
Topics: Humans; Hypertrophy; Muscle, Skeletal; RNA; Resistance Training; Ribosomes
PubMed: 35213791
DOI: 10.1111/apha.13806 -
Acta Physiologica (Oxford, England) Sep 2019
Topics: Aged, 80 and over; Female; Humans; Hypertrophy; Male; Muscle Fibers, Skeletal; Resistance Training
PubMed: 31009166
DOI: 10.1111/apha.13287 -
Journal of Applied Physiology... May 2020It is well established that testosterone administration induces muscle fiber hypertrophy and myonuclear addition in men; however, it remains to be determined whether... (Randomized Controlled Trial)
Randomized Controlled Trial
It is well established that testosterone administration induces muscle fiber hypertrophy and myonuclear addition in men; however, it remains to be determined whether similar morphological adaptations can be achieved in women. The aim of the present study was therefore to investigate whether exogenously administered testosterone alters muscle fiber morphology in skeletal muscle of young healthy, physically active women. Thirty-five young (20-35 yr), recreationally trained women were randomly assigned to either 10-wk testosterone administration (10 mg daily) or placebo. Before and after the intervention, hormone concentrations and body composition were assessed, and muscle biopsies were obtained from the vastus lateralis. Fiber type composition, fiber size, satellite cell and myonuclei content, as well as muscle capillarization were assessed in a fiber type-specific manner by immunohistochemistry. After the intervention, testosterone administration elevated serum testosterone concentration (5.1-fold increase, = 0.001) and induced significant accretion of total lean mass (+1.9%, = 0.002) and leg lean mass (+2.4%, = 0.001). On the muscle fiber level, testosterone increased mixed-fiber cross-sectional area (+8.2%, = 0.001), an effect primarily driven by increases in type II fiber size (9.2%, = 0.006). Whereas myonuclei content remained unchanged, a numerical increase (+30.8%) was found for satellite cells associated with type II fibers in the Testosterone group. In parallel with fiber hypertrophy, testosterone significantly increased capillary contacts (+7.5%, = 0.015) and capillary-to-fiber ratio (+9.2%, = 0.001) in type II muscle fibers. The present study provides novel insight into fiber type-specific adaptations present already after 10 wk of only moderately elevated testosterone levels in women. We have recently demonstrated performance-enhancing effects of moderately elevated testosterone concentrations in young women. Here we present novel evidence that testosterone alters muscle morphology in these women, resulting in type II fiber hypertrophy and improved capillarization. Our findings suggest that low doses of testosterone potently impact skeletal muscle after only 10 wk. These data provide unique insights into muscle adaptation and support the performance-enhancing role of testosterone in women on the muscle fiber level.
Topics: Female; Humans; Hypertrophy; Male; Muscle Fibers, Skeletal; Muscle, Skeletal; Resistance Training; Satellite Cells, Skeletal Muscle; Testosterone
PubMed: 32191598
DOI: 10.1152/japplphysiol.00893.2019 -
Life Sciences Oct 2014Pathologic and physiologic factors acting on the heart can produce consistent pressure changes, volume overload, or increased cardiac output. These changes may then lead... (Review)
Review
Pathologic and physiologic factors acting on the heart can produce consistent pressure changes, volume overload, or increased cardiac output. These changes may then lead to cardiac remodeling, ultimately resulting in cardiac hypertrophy. Exercise can also induce hypertrophy, primarily physiologic in nature. To determine the mechanisms responsible for each type of remodeling, it is important to examine the heart at the functional unit, the cardiomyocyte. Tests of individual cardiomyocyte function in vitro provide a deeper understanding of the changes occurring within the heart during hypertrophy. Examination of cardiomyocyte function during exercise primarily follows one of two pathways: the addition of hypertrophic inducing agents in vitro to normal cardiomyocytes, or the use of trained animal models and isolating cells following the development of hypertrophy in vivo. Due to the short lifespan of adult cardiomyocytes, a proportionately scant amount of research exists involving the direct stimulation of cells in vitro to induce hypertrophy. These attempts provide the only current evidence, as it is difficult to gather extensive data demonstrating cell growth as a result of in vitro physical stimulation. Researchers have created ways to combine skeletal myocytes with cardiomyocytes to produce functional muscle cells used to repair pathologic heart tissue, but continue to struggle with the short lifespan of these cells. While there have been promising findings regarding the mechanisms that surround cardiac hypertrophy in vitro, the translation of in vitro findings to in vivo function is not consistent. Therefore, the focus of this review is to highlight recent studies that have investigated the effect of exercise on the heart, both in vitro and in vivo.
Topics: Adult; Animals; Cardiac Output; Cardiomegaly; Disease Models, Animal; Exercise; Humans; Models, Biological; Muscle Fibers, Skeletal; Myocytes, Cardiac; Ventricular Remodeling
PubMed: 25218762
DOI: 10.1016/j.lfs.2014.08.015 -
Calcified Tissue International Mar 2015In a mature (weight neutral) animal, an increase in muscle mass only occurs when the muscle is loaded sufficiently to cause an increase in myofibrillar protein balance.... (Review)
Review
In a mature (weight neutral) animal, an increase in muscle mass only occurs when the muscle is loaded sufficiently to cause an increase in myofibrillar protein balance. A tight relationship between muscle hypertrophy, acute increases in protein balance, and the activity of the mechanistic target of rapamycin complex 1 (mTORC1) was demonstrated 15 years ago. Since then, our understanding of the signals that regulate load-induced hypertrophy has evolved considerably. For example, we now know that mechanical load activates mTORC1 in the same way as growth factors, by moving TSC2 (a primary inhibitor of mTORC1) away from its target (the mTORC activator) Rheb. However, the kinase that phosphorylates and moves TSC2 is different in the two processes. Similarly, we have learned that a distinct pathway exists whereby amino acids activate mTORC1 by moving it to Rheb. While mTORC1 remains at the forefront of load-induced hypertrophy, the importance of other pathways that regulate muscle mass are becoming clearer. Myostatin, is best known for its control of developmental muscle size. However, new mechanisms to explain how loading regulates this process are suggesting that it could play an important role in hypertrophic muscle growth as well. Last, new mechanisms are highlighted for how β2 receptor agonists could be involved in load-induced muscle growth and why these agents are being developed as non-exercise-based therapies for muscle atrophy. Overall, the results highlight how studying the mechanism of load-induced skeletal muscle mass is leading the development of pharmaceutical interventions to promote muscle growth in those unwilling or unable to perform resistance exercise.
Topics: Animals; Humans; Hypertrophy; Muscle, Skeletal; Resistance Training
PubMed: 25359125
DOI: 10.1007/s00223-014-9925-9 -
Sports Medicine (Auckland, N.Z.) Mar 2022Concurrent training incorporates dual exercise modalities, typically resistance and aerobic-based exercise, either in a single session or as part of a periodized... (Review)
Review
Concurrent training incorporates dual exercise modalities, typically resistance and aerobic-based exercise, either in a single session or as part of a periodized training program, that can promote muscle strength, mass, power/force and aerobic capacity adaptations for the purposes of sports performance or general health/wellbeing. Despite multiple health and exercise performance-related benefits, diminished muscle hypertrophy, strength and power have been reported with concurrent training compared to resistance training in isolation. Dietary protein is well-established to facilitate skeletal muscle growth, repair and regeneration during recovery from exercise. The degree to which increased protein intake can amplify adaptation responses with resistance exercise, and to a lesser extent aerobic exercise, has been highly studied. In contrast, much less focus has been directed toward the capacity for protein to enhance anabolic and metabolic responses with divergent contractile stimuli inherent to concurrent training and potentially negate interference in muscle strength, power and hypertrophy. This review consolidates available literature investigating increased protein intake on rates of muscle protein synthesis, hypertrophy, strength and force/power adaptations following acute and chronic concurrent training. Acute concurrent exercise studies provide evidence for the significant stimulation of myofibrillar protein synthesis with protein compared to placebo ingestion. High protein intake can also augment increases in lean mass with chronic concurrent training, although these increases do not appear to translate into further improvements in strength adaptations. Similarly, the available evidence indicates protein intake twice the recommended intake and beyond does not rescue decrements in selective aspects of muscle force and power production with concurrent training.
Topics: Adaptation, Physiological; Humans; Hypertrophy; Muscle Strength; Muscle, Skeletal; Resistance Training
PubMed: 34822138
DOI: 10.1007/s40279-021-01585-9 -
Physiological Measurement Mar 2019The purpose of this investigation was to examine the ability of the electromyographic (EMG) and mechanomyographic (MMG) amplitude versus torque relationships to track...
OBJECTIVE
The purpose of this investigation was to examine the ability of the electromyographic (EMG) and mechanomyographic (MMG) amplitude versus torque relationships to track group and individual changes in muscle hypertrophy as a result of resistance training.
APPROACH
Twelve women performed four weeks of forearm flexion blood flow restriction (BFR) resistance training at a frequency of three times per week. The training was performed at an isokinetic velocity of 120° · s with a training load that corresponded to 30% of concentric peak torque. Muscle hypertrophy was determined using ultrasound-based assessments of muscle cross-sectional area from the biceps brachii. Training-induced changes in the slope coefficients of the EMG amplitude and MMG amplitude versus torque relationships were determined from the biceps brachii during incremental (10%-100% of maximum) isometric muscle actions.
MAIN RESULTS
There was a significant (p < 0.001; d = 2.15) mean training-induced increase in muscle cross-sectional area from 0 week (mean ± SD = 5.86 ± 0.65 cm) to 4 weeks (7.42 ± 0.80 cm), a significant (p = 0.023; d = 0.36) decrease in the EMG amplitude versus torque relationship (50.70 ± 20.41 to 43.82 ± 17.76 µV · Nm), but no significant (p = 0.192; d = 0.17) change in the MMG amplitude versus torque relationship (0.018 ± 0.009 to 0.020 ± 0.009 m · s · Nm). There was, however, great variability for the individual responses for the EMG and MMG amplitude versus torque relationships.
SIGNIFICANCE
The results of the present study indicated that the EMG amplitude, but not the MMG amplitude versus torque relationship was sensitive to mean changes in muscle cross-sectional area during the early-phase of resistance training. There was, however, great variability for the individual EMG amplitude versus torque relationships that limits its application for identifying individual changes in muscle hypertrophy as a result of BFR.
Topics: Adaptation, Physiological; Biomechanical Phenomena; Electromyography; Female; Humans; Hypertrophy; Male; Mechanical Phenomena; Muscles; Resistance Training; Torque; Young Adult
PubMed: 30736032
DOI: 10.1088/1361-6579/ab057e