Article

Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training

November 1996
Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology 81(5):2004-2012

DOI:10.1152/jappl.1996.81.5.2004

Authors:

University of Puget Sound

McCall, G. E., W. C. Byrnes, A. Dickinson, P. M. Pattany, and S. J. Fleck. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training. J. Appl. Physiol. 81(5): 2004–2012, 1996.—Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% ( P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 ± 2.7 to 13.3 ± 2.6 cm ² ; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases ( P < 0.05) in fiber areas for type I (from 4,196 ± 859 to 4,617 ± 1,116 μm ² ; n = 11) and II fibers (from 6,378 ± 1,552 to 7,474 ± 2,017 μm ² ; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 ± 61.5 × 10 ³ pretraining; 297.5 ± 69.5 × 10 ³ posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly ( P < 0.05) for both type I (from 4.9 ± 0.6 to 5.5 ± 0.7; n = 10) and II fibers (from 5.1 ± 0.8 to 6.2 ± 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.

Progression and perceptual responses to blood flow restriction resistance training among people with multiple sclerosis

Article

Full-text available

Aug 2024
EUR J APPL PHYSIOL

Purpose Resistance exercise can attenuate muscular impairments associated with multiple sclerosis (MS), and blood flow restriction (BFR) may provide a viable alternative to prescribing heavy training loads. The purpose of this investigation was to examine the progression of upper and lower body low-load (30% of one-repetition maximum [1RM]) resistance training (RT) with BFR applied intermittently during the exercise intervals (RT + BFR) versus volume-matched heavy-load (65% of 1RM) RT. Methods Men and women with MS (n = 16) were randomly assigned to low-load RT + BFR (applied intermittently) or heavy-load RT and completed 12 weeks (2 × /week) of RT that consisted of bilateral chest press, seated row, shoulder press, leg press, leg extension, and leg curl exercises. Exercise load, tonnage, and rating of perceived exertion were assessed at baseline and every 6 weeks. Results Training load increased to a greater extent and sometimes earlier for RT + BFR (57.7–106.3%) than heavy-load RT (42.3–54.3%) during chest press, seated row, and leg curl exercises, while there were similar increases (63.5–101.1%) for shoulder press, leg extension, and leg press exercises. Exercise tonnage was greater across all exercises for RT + BFR than heavy-load RT, although tonnage only increased during the chest press (70.7–80.0%) and leg extension (89.1%) exercises. Perceptions of exertion (4.8–7.2 au) and compliance (97.9–99.0%) were similar for both interventions. Conclusion The training-induced increases in load, high compliance, and moderate levels of exertion suggested that RT + BFR and heavy-load RT are viable interventions among people with MS. RT + BFR may be a preferred modality if heavy loads are not well tolerated and/or to promote early-phase training responses.

Microvascular Reactivity Is Greater Following Blood Flow Restriction Resistance Exercise Compared with Traditional Resistance Exercise

Article

Jul 2024
J STRENGTH COND RES

Perlet, MR, Hosick, PA, Licameli, N, and Matthews, EL. Microvascular reactivity is greater following blood flow restriction resistance exercise compared with traditional resistance exercise. J Strength Cond Res XX(X): 000–000, 2024—Chronic blood flow restriction (BFR) resistance exercise can improve muscular strength, hypertrophy, and microvasculature function, but the acute microvascular effects are unknown. We aimed to test the effects of acute BFR resistance exercise on postexercise microvascular reactivity in an exercising muscle and nonexercising muscle compared with traditional resistance exercise (TRE). Twenty-five adults (men = 14, women = 11, age: 22 ± 3 years, body mass: 71.69 ± 14.49 kg, height: 170 ± 10 cm) completed barbell back squat 1-repetition maximum (1RM) testing followed by 2 randomized and counterbalanced resistance exercise visits separated by ≥48 hours. The 2 visits involved either BFR (4 sets of 30-15-15-15 repetitions at 30% 1RM, with 60-second rest intervals) or TRE (4 sets of 10 repetitions at 70% 1RM, 60-second rest intervals). During each exercise visit, a pre- and postbarbell back squat vascular occlusion test was performed using near-infrared spectroscopy to measure skeletal muscle oxygen (SmO 2 ) in the vastus lateralis (VL) and flexor carpi radialis (FCR). Two-way repeated-measures ANOVA found an interaction effect ( p = 0.020) for SmO 2 reactivity in the VL. Post hoc analysis found greater reactive hyperemia postexercise in the VL for the BFR condition ( p < 0.001) but not the TRE condition ( p ≥ 0.05). There were no time, condition, or interaction effects (all p > 0.05) for the same analysis in the FCR. This analysis suggests that BFR, but not TRE, lead to acutely improved microvasculature function. Moreover, it suggests that the effects of BFR resistance exercise are local to the exercised or occluded limb and not systemic.

Long-Term Resistance Trained Human Muscles Have More Fibers, More Myofibrils, and Tighter Myofilament Packing Than Untrained

Article

Full-text available

Jun 2024
MED SCI SPORT EXER

Introduction Increases in skeletal muscle size occur in response to prolonged exposure to resistance training that is typically ascribed to increased muscle fibre size. Whether muscle fibre number also changes remains controversial, and a paucity of data exists about myofibrillar structure. This cross-sectional study compared muscle fibre and myofibril characteristics in long-term resistance-trained (LRT) versus untrained (UNT) individuals. Methods The maximal anatomical cross-sectional area (ACSAmax) of the biceps brachii muscle was measured by MRI in 16 LRT (5.9 ± 3.5 years’ experience) and 13 UNT males. A muscle biopsy was taken from the biceps brachii to measure muscle fibre area, myofibril area and myosin spacing. Muscle fibre number, myofibril number in total and per fibre were estimated by dividing ACSAmax by muscle fibre area or myofibril area, and muscle fibre area by myofibril area, respectively. Results Compared to UNT, LRT individuals had greater ACSAmax (+70%, P < 0.001), fibre area (+29%, P = 0.028), fibre number (+34%, P = 0.013), and myofibril number per fibre (+49%, P = 0.034) and in total (+105%, P < 0.001). LRT individuals also had smaller myosin spacing (-7%, P = 0.004; i.e. greater packing density) and a tendency towards smaller myofibril area (-16%, P = 0.074). ACSAmax was positively correlated with fibre area ( r = 0.526), fibre number ( r = 0.445) and myofibril number (in total r = 0.873 and per fibre r = 0.566), and negatively correlated with myofibril area ( r = -0.456) and myosin spacing ( r = -0.382) (all P < 0.05). Conclusions The larger muscles of LRT individuals exhibited more fibres in cross-section and larger muscle fibres, which contained substantially more total myofibrils and more packed myofilaments than UNT participants, suggesting plasticity of muscle ultrastructure.

Muscle fibre type, size and satellite cell pool in male volleyball players

Article

Jun 2022

Introduction. Longitudinal volleyball training stimuli can cause an increase in muscle strength that is brought about by neurological and morphological adaptations, such as changes in muscle fibre composition percentage and cross-sectional area (CSA). Aim of Study. The aim of this study was to examine the biological adaptations of volleyball-players in terms of muscle fiber type composition, cross-sectional area, myonuclei and satellite cell pool in comparison to physically active controls. Material and Methods. Ten professional volleyball-players (VG) and five physically active-persons (CG) participated in this study. Muscle biopsies were obtained from the vastus-lateralis of the dominant leg. Results. Immunohistochemical analysis revealed that although MHC I and MHC IIC muscle fibre distribution was not different between the groups, MHC IIX and MHC IIAX were totally absent in VG and appeared only in the CG. The cross-sectional area revealed a slightly different pattern as both MHC I and IIA were larger for the volleyball players. In accordance, MHC II myonuclei number was moderately larger in the volleyball players, while the satellite cells and their ratio to number of fibres had a large and very large difference, respectively. Conclusions. In conclusion, our study reveals that volleyball training-induced hypertrophy for both type I and II muscle fibres in the vastus lateralis of volleyball players and resulted in a specific shift in muscle fibres containing MHC II isoforms. This hypertrophy of the muscle fibres is associated with an increase in the myonuclear number and satellite cells.

Neuromuscular Electrical Stimulation in Muscular Adaptations in Exercise: A Narrative Review

Article

Nov 2022

Daniel Tarmast

A Systematic Review of Electromagnetic Treatments for Body Contouring

Article

Full-text available

Dec 2022
ANN PLAS SURG

Eric Swanson

Background: Energy-based treatments include ultrasound, lasers, cryolipolysis, and radiofrequency. The most recent energy treatment for noninvasive body contouring is electromagnetic treatments-a hot topic in plastic surgery today. A systematic review to assess efficacy and safety has not been published. Methods: An electronic search was performed using PubMed to identify the literature describing electromagnetic treatments. Measurements from imaging studies were tabulated and compared. Results: Fourteen clinical studies were evaluated. Two studies included simultaneous radiofrequency treatments. In 11 studies, the Emsculpt device was used; in 2 studies, the Emsculpt-Neo device was used. One study included a sham group of patients. The usual protocol was 4 treatments given over a 2-week period. No complications were reported. Eight studies included abdominal measurement data obtained using magnetic resonance imaging, computed tomography, or ultrasound. Photographic results were typically modest. Photographs showing more dramatic results also showed unexplained reductions in untreated areas.Measurement variances were high. The mean reduction in fat thickness was 5.5 mm. The mean increment in muscle thickness was 2.2 mm. The mean decrease in muscle separation was 2.9 mm (P = 0.19). Early posttreatment ultrasound images in 1 study showed an echolucent muscle layer, compared with a more echodense layer at the baseline, consistent with tissue swelling after exercise. Almost all studies were authored by medical advisors for the device manufacturer. Discussion: Measurement data show small reductions in fat thickness, occurring almost immediately after the treatments. Adipocyte removal without tissue swelling would be unique among energy-based treatments. Similarly, muscle hypertrophy is not known to occur acutely after exercise; muscle swelling likely accounts for an early increment in muscle thickness. Any improvement in the diastasis recti is likely fictitious. Conclusions: Electromagnetic treatments, either administered alone or in combination with radiofrequency, are safe. However, the evidence for efficacy is tenuous. Measured treatment effects are very small (<5 mm). Conflict of interest and publication bias are major factors in studies evaluating energy-based alternatives. The evidence-based physician may not be satisfied that an equivocal treatment benefit justifies the time and expense for patients.

Neuromuscular Electrical Stimulation in Muscular Adaptations in Exercise: A Narrative Review

Article

Full-text available

Nov 2022

Daniel Tarmast

Nowadays, sports science uses scientific methods and medical devices to assist people with any improvements in sports. Muscle adaptations have significantly benefited as a result of the use of these advanced devices. It has been shown that neuromuscular electrical stimulation (NMES) devices effectively improve muscle function. The use of NMES devices in exercise physiology shows that neuromuscular adaptation is a current research area in both athletes and non-athletes. This narrative review aims to address neuromuscular adaptations and describe neuromuscular changes based on research using NMES. Many researchers and sports trainers will benefit from the results of this article by better understanding neuromuscular adaptations. NMES training has been shown to be an effective way to improve muscle growth, maximum voluntary strength, neuronal drive, oxidative metabolism, and antioxidant defense systems. In addition, NMES is capable of regulating the homeostasis of muscle proteins and increasing oxidative enzyme activity. In animal models, it has also been shown to increase axonal outgrowth, fiber reinnervation, and motor axon regeneration. Various NMES methods may decrease age-related muscle atrophy and functional deterioration. The use of NMES, which is one of the most successful strategies for increasing athletic performance through neuromuscular adaptations, is one of the most promising areas of research.

Angewandtes Hypertrophietraining – Überprüfung traditioneller und neuer Ansätze

Thesis

Full-text available

Jan 2021

Simon Gavanda

Summary of the doctoral thesis Introduction: In many sports, strength is considered an important basis for performance. One factor affecting strength is muscle mass. Therefore, it may be necessary to increase muscle mass in athletes through resistance training. However, the most effective strategy to gain muscle mass has not yet been clearly identified. Many methods used in practice are based on anecdotal evidence rather than empirical data. For this reason, different approaches to hypertrophy training were examined in this thesis based on three studies. The methods and most important results of these studies are summarized in the following. Methods: In the first study, adolescent American football players completed a 12-week resistance training program with three total-body training sessions per week using either Block Periodization (BLOCK) or Daily Undulating Periodization (DUP). The aim was to investigate the effects of the different periodization strategies on muscle mass and athletic performance. The second study assessed the impact of a three-week detraining period (DTR) on anthropometric measures and sport performance. In a third study, highly trained male subjects completed a six-week low-intensity calf resistance training intervention either without (noBFR) or with blood flow restriction (BFR). Before and after the intervention, 1-RM calf raise, calf volume, muscle thickness of the gastrocnemius, and leg stiffness were recorded. Results: At the end of the first intervention, both periodization groups showed significantly higher muscle mass and thickness, as well as athletic performance without differences between groups. Following DTR, fat mass increased significantly, and fat-free mass was reduced. All other measures were unchanged after DTR. Both BFR and NoBFR training resulted in significant increases in 1-RM and muscle thickness without differences between groups. Calf volume and leg stiffness remained unchanged in both conditions. Conclusions: In adolescent American football players, the structure of periodization does not appear to have any effect on muscle growth. Furthermore, a three weeks DTR does not result in negative effects. Both results provide new insights that can be helpful when creating training programs as well as for planning training-free periods. The currently frequently investigated BFR training does not show higher effects on muscle growth of the lower extremities than conventional low-intensity resistance training.

A SIMULATION STUDY ON NEUROMUSCULAR FACTORS AFFECTING CONSECUTIVE MOTOR UNIT ACTION POTENTIAL WAVESHAPE

Article

Dec 2020

Quantification of consecutive motor unit potential (MUP) is used to diagnose and monitor the progress of neuromuscular pathologies in clinical applications. In this study, a detailed motor unit simulation was conducted to reveal and understand the factors affecting MUPs. Using a volume conductor model and real muscle parameters, normal and pathologic MUPs were created. The shape changes observed in consecutive MUPs, called jiggle, are calculated with a quantification method. Increased jitter duration and re-innervation percentage commonly observed during motor unit loss increase the jiggle value proportionally. Moreover, increasing fiber density changing different regions of a muscle bundle decreases the jiggle value. The blocking phenomena generally observed in re-innervated fibers affects the jiggle value similar to jitter duration. But, higher blocking levels (50%) of re-innervated motor fiber do not have an effect on jiggle value as lower levels of blocking (20%). In conclusion, simulation of pathological MUPs showed that it is useful for clinicians to understand the progress of a neuromuscular pathology and the factors affecting consecutive MUP wave shape.

High-Volume Resistance Training Improves Double-Poling Peak Oxygen Uptake in Youth Elite Cross-Country Skiers and Biathletes: A Pilot Study

Article

Full-text available

Mar 2024

A total of nineteen elite youth cross-country skiers (16 ± 2 years) were divided into three groups: a low-load group (LL, n = 6) performing 15–20 repetitions per exercise, a high-load group (HL, n = 9) executing 6–12 repetitions, and a control group (CON, n = 4) exclusively engaging in endurance training. Testing included 1RM in upper-body exercises, VO2max running tests, and double-poling (DP) ergometer exhaustion and sprint tests to determine peak oxygen uptake (VO2peak-DP) and peak power (PP). The results indicated that HL and LL showed significant increases in VO2peak-DP, both in absolute values (d = −1.2 and −1.2, p < 0.05) and when normalized to body mass (d = 0.93 and 1.3, p < 0.05). Although there were no group*time effects for VO2peak-DP, PP during DP tests to exhaustion increased in both HL (d = −1.6, p < 0.05) and LL (d = 1.4, p < 0.05) compared to CON. Standardized to body mass, only HL showed significant improvements in PP during the sprint test (d = 1.7, p < 0.05). During the sprint test, both absolute and body-mass-normalized peak power increased only in the high-load group (d = −1.0 and 0.93, p < 0.05). In conclusion, high-load resistance training resulted in the greatest improvements in strength, DP performance, and VO2peak-DP, indicating a dose–response relationship to the load magnitude of resistance training.

Increasing trend of angiogenic indices following Traditional and Circuit Resistance Training in sedentary men

Preprint

Full-text available

Sep 2023

Background Angiogenesis is a beneficial process leading to capillary enhancement, which can trigger in response to physical training. Aims The present study aimed to investigate the changes in physiological factors involved in angiogenesis in response to circuit or traditional resistance training. Methods Following the pre-test, Thirty-six healthy sedentary students (age: 21.1 ± 2.3 years; height: 172.7 ± 5.1 cm) were randomly divided into Circuit Resistance Training (CRT) (4 circles/3 times a week/8 weeks circuit performance/50–55% 1 Repetition Maximum; n = 12), Traditional Resistance Training (TRT) (8 repetition/3 set/3 time per week/8 weeks of same movements with 75% 1RM followed by 2 minutes break between the sets; n = 12) and the control group (n = 12). We examined the responses of Vascular Endothelial Growth Factor (VEGF), plasma level of growth hormone (GH), and basic Fibroblast Growth Factor (bFGF). Results Both of CRT and TRT protocols resulted in significant increases in post-test compared to pre-test, in VEGF (p = 0.00), GH (p = 0.04), and bFGF (p = 0.00). In addition, the magnitude of changes in VEGF and GH were significantly greater than the control group in post-test (p = 0.03, and 0.001, respectively). In addition, there was a strong correlation between absolute value of GH and VEGF (r = 0.74 and r = 0.71) following CRT (p = 0.01) and TRT (p = 0.02). Conclusions This study demonstrated that CRT and TRT might enhance angiogenesis through increase in VEGF, bFGF and GH.

Mechanisms of mechanical overload-induced skeletal muscle hypertrophy: current understanding and future directions

Article

Full-text available

Jun 2023
PHYSIOL REV

Mechanisms underlying mechanical overload-induced skeletal muscle hypertrophy have been extensively researched since the landmark report by Morpurgo (1897) of "work-induced hypertrophy" in dogs that were treadmill-trained. Much of the pre-clinical rodent and human resistance training research to date supports that involved mechanisms include enhanced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, an expansion in translational capacity through ribosome biogenesis, increased satellite cell abundance and myonuclear accretion, and post-exercise elevations in muscle protein synthesis rates. However, several lines of past and emerging evidence suggest additional mechanisms that feed into or are independent of these processes are also involved. This review will first provide a historical account as to how mechanistic research into skeletal muscle hypertrophy has progressed. A comprehensive list of mechanisms associated with skeletal muscle hypertrophy is then outlined and areas of disagreement involving these mechanisms are presented. Finally, future research directions involving many of the discussed mechanisms will be proposed.

Can muscle typology explain the inter‐individual variability in resistance training adaptations?

Article

Full-text available

Apr 2023
J PHYSIOL-LONDON

Considerable inter‐individual heterogeneity exists in the muscular adaptations to resistance training. It has been proposed that fast‐twitch fibres are more sensitive to hypertrophic stimuli and thus that variation in muscle fibre type composition is a contributing factor to the magnitude of training response. This study investigated if the inter‐individual variability in resistance training adaptations is determined by muscle typology and if the most appropriate weekly training frequency depends on muscle typology. In strength‐training novices, 11 slow (ST) and 10 fast typology (FT) individuals were selected by measuring muscle carnosine with proton magnetic resonance spectroscopy. Participants trained both upper arm and leg muscles to failure at 60% of one‐repetition maximum (1RM) for 10 weeks, whereby one arm and leg trained 3×/week and the contralateral arm and leg 2×/week. Muscle volume (MRI‐based 3D segmentation), maximal dynamic strength (1RM) and fibre type‐specific cross‐sectional area (vastus lateralis biopsies) were evaluated. The training response for total muscle volume (+3 to +14%), fibre size (−19 to +22%) and strength (+17 to +47%) showed considerable inter‐individual variability, but these could not be attributed to differences in muscle typology. However, ST individuals performed a significantly higher training volume to gain these similar adaptations than FT individuals. The limb that trained 3×/week had generally more pronounced hypertrophy than the limb that trained 2×/week, and there was no interaction with muscle typology. In conclusion, muscle typology cannot explain the high variability in resistance training adaptations when training is performed to failure at 60% of 1RM. image Key points This study investigated the influence of muscle typology (muscle fibre type composition) on the variability in resistance training adaptations and on its role in the individualization of resistance training frequency. We demonstrate that an individual's muscle typology cannot explain the inter‐individual variability in resistance training‐induced increases in muscle volume, maximal dynamic strength and fibre cross‐sectional area when repetitions are performed to failure. Importantly, slow typology individuals performed a significantly higher training volume to obtain similar adaptations compared to fast typology individuals. Muscle typology does not determine the most appropriate resistance training frequency. However, regardless of muscle typology, an additional weekly training (3×/week vs. 2×/week) increases muscle hypertrophy but not maximal dynamic strength. These findings expand on our understanding of the underlying mechanisms for the large inter‐individual variability in resistance training adaptations.

Exercise-induced skeletal muscle angiogenesis: impact of age, sex, angiocrines and cellular mediators

Article

Full-text available

Jan 2023
EUR J APPL PHYSIOL

Exercise-induced skeletal muscle angiogenesis is a well-known physiological adaptation that occurs in humans in response to exercise training and can lead to endurance performance benefits, as well as improvements in cardiovascular and skeletal tissue health. An increase in capillary density in skeletal muscle improves diffusive oxygen exchange and waste extraction, and thus greater fatigue resistance, which has application to athletes but also to the general population. Exercise-induced angiogenesis can significantly contribute to improvements in cardiovascular and metabolic health, such as the increase in muscle glucose uptake, important for the prevention of diabetes. Recently, our understanding of the mechanisms by which angiogenesis occurs with exercise has grown substantially. This review will detail the biochemical, cellular and biomechanical signals for exercise-induced skeletal muscle angiogenesis, including recent work on extracellular vesicles and circulating angiogenic cells. In addition, the influence of age, sex, exercise intensity/duration, as well as recent observations with the use of blood flow restricted exercise, will also be discussed in detail. This review will provide academics and practitioners with mechanistic and applied evidence for optimising training interventions to promote physical performance through manipulating capillarisation in skeletal muscle.

Handgrip Strength Is Not Associated With High Blood Pressure and Does Not Have Good Discriminatory Power for High Blood Pressure in Adolescents

Article

Nov 2022
J STRENGTH COND RES

de Lima, TR and Silva, DAS. Handgrip strength is not associated with high blood pressure and does not have good discriminatory power for high blood pressure in adolescents. J Strength Cond Res 37(1): 46-54, 2023-Muscle strength measured by handgrip strength (HGS) was inversely and independently associated with high blood pressure (HBP). In addition, HGS has been used as a valuable indicator for monitoring pediatric health. This study aimed to investigate the association between HGS indexes and HBP, verify the discriminatory capacity of HGS to identify HBP in adolescents, and propose cut-points for HGS to be used in the early identification of HBP if good discriminatory power is identified between the variables. This was a cross-sectional study comprising 811 adolescents (male: 48.9%; age: 16.4 ± 1.3 years) from southern Brazil. Blood pressure was measured by the oscillometric method. Handgrip strength was assessed by a hand dynamometer and 3 different approaches were adopted: (a) HGS in kilogram-force, (b) normalized HGS (HGS/body mass), and (c) allometric HGS (HGS/body mass-0.67). Binary logistic regression was used to verify the association between HGS indexes and HBP, and the receiver operating characteristic (ROC) was used to determine the possible use of HGS as a diagnostic tool for HBP. Handgrip strength indexes were not associated with HBP (p > 0.05), and ROC analyses showed a nonsignificant discriminating accuracy for most of the HGS indexes analyzed (p > 0.05) in identifying HBP in boys and girls. The area under curve (AUC) values ranged from 0.499 (95% CI [0.403-0.596] for allometric HGS among overweight or obese boys) to 0.595 (95% CI [0.546-0.643] for HGS among boys). Handgrip strength was not associated with HBP, and its use in the screening of HBP in adolescents is not recommended.

Análise de Ciclo de Vida (ACV) de óleos refrigerantes para transformadores

Chapter

Dec 2022

Physical activity during aging – role of physical activity in muscle atrophy and physical impairment during aging

Article

Full-text available

Aug 2020

Regular physical activity and exercise have many beneficial effects for physical and mental health in almost every population. Regular exercises may induce reduction of age-related lean body mass loss and decrease risk of bone fractures. Furthermore it has been observed that regular physical activity may reduce the risk for several chronic diseases including metabolic syndrome, hypertension, diabetes mellitus type 2, and depression. Exercise, however, especially in elderly populations are not done very often. This is due to the lack of awareness of their beneficial effect and the lack of ideas for such type of activity. The aim of this review is to summarize current knowledge regarding to role and effects of physical exercises on muscle functioning and coordination specially during aging. Before a final recommendation can be made with respect to the possible therapeutically role of physical training in aged people, there is a substantial need for further studies to be performed on this topic.

Changes in microvascular perfusion of heart and skeletal muscle in sheep around the time of birth

Article

Full-text available

Nov 2022
EXP PHYSIOL

Microvascular perfusion of striated muscle is an important determinant of health throughout life. Birth is a transition with profound effects on the growth and function of striated muscle, but the regulation of microvascular perfusion around this transition is poorly understood. We used contrast‐enhanced ultrasound perfusion imaging (CEUS) to study the perfusion of left ventricular myocardium and hindlimb biceps femoris, which are populations of muscle with different degrees of change in pre‐ to postnatal workloads and different capacities for postnatal proliferative growth. We studied separate groups of lambs in late gestation (135 days’ gestational age; 92% of term) and shortly after birth (5 days’ postnatal age). We used CEUS to quantify baseline perfusion, perfusion during hyperaemia induced by adenosine infusion (myocardium) or electrically stimulated unloaded exercise (skeletal muscle), flow reserve and oxygen delivery. We found heart‐to‐body weight ratio was greater in neonates than fetuses. Microvascular volume and overall perfusion were lower in neonates than fetuses in both muscle groups at baseline and with hyperaemia. Flux rate differed with muscle group, with myocardial flux being faster in neonates than fetuses, but skeletal muscle flux being slower. Oxygen delivery to skeletal muscle at baseline was lower in neonates than fetuses, but was not significantly different in myocardium. Flow reserve was not different between ages. Given the significant somatic growth, and the transition from hyperplastic to hypertrophic myocyte growth occurring in the perinatal period, we postulate that the primary driver of lower neonatal striated muscle perfusion is faster growth of myofibres than their associated capillary networks.

Handgrip strength is not associated with high blood pressure and does not have good discriminatory power for high blood pressure in adolescents

Article

Full-text available

Aug 2022
J STRENGTH COND RES

A relevância da educação para a saúde coletiva

Chapter

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Aug 2022

Temos o prazer de lançar o primeiro livro da coletânea voltada às ciências da saúde, que tem como título Coletânea Internacional de Pesquisa em Ciências da Saúde. V.1, essa obra é editada pela Seven Publicações Ltda, tendo a composição de mais de 67 capítulos voltados ao desenvolvimento e disseminação do conhecimento na área da saúde.

Effect of Exercise and Non-exercise Interventions on Cardiac Angiogenesis in Diabetes Mellitus Patients: A Review

Article

Full-text available

Jan 2022

Reza Sabzevari Rad

Manipulating Resistance Training Variables to Induce Muscle Strength and Hypertrophy: A Brief Narrative Review

Article

Full-text available

Jul 2022

International Journal of Exercise Science 15(4): 910-933, 2022. The regular practice of resistance training (RT) has been shown to induce relevant increases in both muscle strength and size. In order to maximize these adaptations, the proper manipulation of RT variables is warranted. In this sense, the aim of the present study was to review the available literature that has examined the application of the acute training variables and their influence on strength and morphological adaptations of healthy young adults. The information presented in this study may represent a relevant approach to proper training design. Therefore, strength and conditioning coaches may acquire a fundamental understanding of RT-variables and the relevance of their practical application within exercise prescription.

Manipulating Resistance Training Variables to Induce Muscle Strength and Hypertrophy: A Brief Narrative Review

Article

Full-text available

Jul 2022

International Journal of Exercise Science 15(4): X-Y, 2022. The regular practice of resistance training (RT) has been shown to induce relevant increases in both muscle strength and size. In order to maximize these adaptations, the proper manipulation of RT variables is warranted. In this sense, the aim of the present study was to review the available literature that has examined the application of the acute training variables and their influence on strength and morphological adaptations of healthy young adults. The information presented in this study may represent a relevant approach to proper training design. Therefore, strength and conditioning coaches may acquire a fundamental understanding of RT-variables and the relevance of their practical application within exercise prescription.

PHYSIOLOGICAL MECHANISMS OF MUSCLE HYPERTROPHY

Article

Full-text available

Jan 2022

Nandrolone decanoate reduces the positive effects of resistance training on cognition, anxious behavior, and hippocampal morphology in rats

Article

Full-text available

Jun 2022

AAs became popular among competitive athletes and the general population for recreational and performance purposes. The indiscriminate use of AAs occurs in supraphysiological doses and negatively affects cognition. Moreover, nandrolone decanoate (DECA) abuse may reduce the beneficial effects of resistance training (RT) on health. Objective: We aimed to investigate if DECA administration in supraphysiological doses interferes with the positive effects of RT on anxious behavior, memory, and morphology of neurons in the hippocampus of rats. Materials and Methods: Rats were randomly assigned into four groups (N= 12): Control (C); DECA (D); Trained (T) Trained+DECA (TD). EAA DECA was administered in daily supraphysiological doses of 15mg/kg during the 8 weeks of the RT protocol. All groups performed a maximum load test before and after the RT protocol; anxious behavior and memory tests were performed, and thereafter, rats were euthanized for morphologic analyses of the hippocampus. DECA produced an anxiogenic effect, worsened cognition and reduced the thickness of the grainy layer of the DG in the hippocampus. Moreover, DECA reduced the positive effects of RT on cognition and DG neurons. This is the first study showing that suprapharmacological doses of DECA reduce the positive effects of RT on memory and the thickness of the granular layer of the DG.

Resistance Training Improves Muscle Strength and Function, Regardless of Protein Supplementation, in the Mid- to Long-Term Period after Gastric Bypass

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Full-text available

Dec 2021

Inadequate protein intake and low levels of physical activity are common long-term sequelae after bariatric surgery and can negatively affect muscle strength (MS) and physical function (PF). The study investigated the effects of resistance training with or without protein supplementation on MS and PF. The study, which involved a 12-week controlled trial (n = 61) of individuals 2–7 years post-Roux-en-Y gastric bypass (RYGB), comprised four groups: whey protein supplementation (PRO; n = 18), maltodextrin placebo (control [CON]; n = 17), resistance training combined with placebo (RTP; n = 11), and resistance training combined with whey protein supplementation (RTP+PRO; n = 15). An isokinetic dynamometer was used to measure MS (peak torque at 60°/s and 180°/s). PF was measured with the 30-s sit-to-stand (30-STS), 6-min walk (6-MWT), and timed up-and-go (TUG) tests. There were improvements in the absolute and relative-to-bodyweight peak torque at 60°/s and 180°/s, TUG, 6-MWT and 30-STS in the RTP and RTP+PRO groups, but not in the CON and PRO groups. Changes in MS were significantly correlated with changes in PF between the pre- and post-intervention periods. A supervised resistance training program, regardless of protein supplementation, improved MS and PF in the mid-to-long-term period after RYGB and can lead to clinical benefits and improved quality of life.

Indices reflecting muscle contraction performance during exercise based on a combined electromyography and mechanomyography approach

Article

Full-text available

Oct 2021

Electromyography (EMG) and mechanomyography (MMG) have been used to directly evaluate muscle function through the electromechanical aspect of muscle contraction. The purpose of this study was to establish new absolute indices to describe muscle contraction performance during dynamic exercise by combining EMG and displacement MMG (dMMG) measured simultaneously using our previously developed MMG/EMG hybrid transducer system. Study participants were eight healthy male non-athletes (controls) and eight male athletes. EMG and dMMG of the vastus medialis were measured for 30 s during four cycles of recumbent bicycle pedaling (30, 60, 90, and 120 W) and on passive joint movement. Total powers were calculated based on the time domain waveforms of both signals. Muscle contraction performance was verified with the slope of regression line (SRL) and the residual sum of squares (RSS) obtained from EMG and dMMG correlation. EMG and dMMG has increased with the work rate. Force and EMG were similar between groups, but dMMG showed a significant difference with load increase. Athletes had significantly higher SRL and significantly lower RSS than controls. The average value divided by SRL and RSS was higher in athletes than in controls. The indices presented by the combined approach of EMG and dMMG showed a clear contrast between the investigated groups and may be parameters that reflect muscle contraction performance during dynamic exercise.

Effects of Resistance Training Performed with Different Loads in Untrained and Trained Male Adult Individuals on Maximal Strength and Muscle Hypertrophy: A Systematic Review

Article

Full-text available

Oct 2021
Int J Environ Res Publ Health

The load in resistance training is considered to be a critical variable for neuromuscular adaptations. Therefore, it is important to assess the effects of applying different loads on the development of maximal strength and muscular hypertrophy. The aim of this study was to systematically review the literature and compare the effects of resistance training that was performed with low loads versus moderate and high loads in untrained and trained healthy adult males on the development of maximal strength and muscle hypertrophy during randomized experimental designs. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (2021) were followed with the eligibility criteria defined according to participants, interventions, comparators, outcomes, and study design (PICOS): (P) healthy males between 18 and 40 years old, (I) interventions performed with low loads, (C) interventions performed with moderate or high loads, (O) development of maximal strength and muscle hypertrophy, and (S) randomized experimental studies with between-or within-subject parallel designs. The literature search strategy was performed in three electronic databases (Embase, PubMed, and Web of Science) on 22 August 2021. Results: Twenty-three studies with a total of 563 participants (80.6% untrained and 19.4% trained) were selected. The studies included both relative and absolute loads. All studies were classified as being moderate-to-high methodological quality, although only two studies had a score higher than six points. The main findings indicated that the load magnitude that was used during resistance training influenced the dynamic strength and isometric strength gains. In general, comparisons between the groups (i.e., low, moderate, and high loads) showed higher gains in 1RM and maximal voluntary isometric contraction when moderate and high loads were used. In contrast, regarding muscle hypertrophy, most studies showed that when resistance training was performed to muscle failure, the load used had less influence on muscle hypertrophy. The current literature shows that gains in maximal strength are more pronounced with high and moderate loads compared to low loads in healthy adult male populations. However, for muscle hypertrophy, studies indicate that a wide spectrum of loads (i.e., 30 to 90% 1RM) may be used for healthy adult male populations. Citation: Lacio, M.; Vieira, J.G.; Trybulski, R.; Campos, Y.; Santana, D.; Filho, J.E.; Novaes, J.; Vianna, J.; Wilk, M. Effects of Resistance Training

Comparison of Shifts in Skeletal Muscle Plasticity Parameters in Horses in Three Different Muscles, in Answer to 8 Weeks of Harness Training

Article

Full-text available

Oct 2021

Training-induced follow-up of multiple muscle plasticity parameters in postural stability vs. locomotion muscles provides an integrative physiological view on shifts in the muscular metabolic machinery. It can be expected that not all muscle plasticity parameters show the same expression time profile across muscles. This knowledge is important to underpin results of metabolomic studies. Twelve non-competing Standardbred mares were subjected to standardized harness training. Muscle biopsies were taken on a non-training day before and after 8 weeks. Shifts in muscle fiber type composition and muscle fiber cross-sectional area (CSA) were compared in the m. pectoralis, the m. vastus lateralis, and the m. semitendinosus. In the m. vastus lateralis, which showed most pronounced training-induced plasticity, two additional muscle plasticity parameters (capillarization and mitochondrial density) were assessed. In the m. semitendinosus, additionally the mean minimum Feret's diameter was assessed. There was a significant difference in baseline profiles. The m. semitendinosus contained less type I and more type IIX fibers compatible with the most pronounced anaerobic profile. Though no baseline fiber type-specific and overall mean CSA differences could be detected, there was a clear post-training decrease in fiber type specific CSA, most pronounced for the m. vastus lateralis, and this was accompanied by a clear increase in capillary supply. No shifts in mitochondrial density were detected. The m. semitendinosus showed a decrease in fiber type specific CSA of type IIAX fibers and a decrease of type I fiber Feret's diameter as well as mean minimum Feret's diameter. The training-induced increased capillary supply in conjunction with a significant decrease in muscle fiber CSA suggests that the muscular machinery models itself toward an optimal smaller individual muscle fiber structure to receive and process fuels that can be swiftly delivered by the circulatory system. These results are interesting in view of the recently identified important fuel candidates such as branched-chain amino acids, aromatic amino acids, and gut microbiome-related xenobiotics, which need a rapid gut–muscle gateway to reach these fibers and are less challenging for the mitochondrial system. More research is needed with that respect. Results also show important differences between muscle groups with respect to baseline and training-specific modulation.

The relevance of muscle fibre typology in sports

Thesis

Jan 2021

Eline Lievens

The human skeletal muscle consists of two major cell types, slow-twitch fibers (also called type I fibers) and fast-twitch fibers (or type II fibers). These fibers have distinct characteristics, as fast-twitch fibers are able to generate a large amount of power at high shortening velocities, while slow-twitch fibers have a better energy efficiency, a higher resistance to fatigue and a more robust structural integrity. On average, most humans will dispose of a 50% slow-twitch and a 50% fast-twitch distribution. However a big heterogeneity exists, what results in people with predominantly slow or fast muscle fibers. The typology of a person is mostly genetically determined and is present across most muscles of the body. Taken together, the fact that muscle fibers have distinct characteristics and that muscle typologies range over the whole continuum from predominantly slow to fast in human, will have important implications for sports performance. Nevertheless, these typologies are currently not used in the daily coaching practice. This is probably due to the invasiveness of the current ‘gold’ standard to measure the muscle typology: a muscle biopsy, which is a labor intensive method and harbors a low generalizability. In 2011, our group introduced a non-invasive way to estimate the muscle fiber type composition through the measurement of carnosine – a metabolite which is abundantly available in fast-twitch fibers – using proton magnetic resonance spectroscopy (1H-MRS). The non-invasiveness of this technique enables the use in both the sports practice and science, and renews the interest of the muscle typology in sports. In the first study, the 1H-MRS method to determine the muscle typology was further optimized with the ultimate goal to make it applicable on various scanner systems of multiple vendors. 1H-MRS was found to be a reliable method to quantify carnosine in the muscle. Furthermore, best practices were proposed to prevent often encountered methodological problems and step by step guidelines were developed to allow broader utilization of this technique. Secondly, we investigated if pre-puberty carnosine measurements could give insights in the post-puberty carnosine concentrations, which would allow application of this technique in early specialization sports (study 2). Carnosine was shown to be a trackable metabolite through the disruptive puberty period (R2=0.249-0.670), which confirms the potential of the current technique to scan both future talents and elite athletes. Next to the methodological optimization, the relevance of the muscle typology for talent identification was examined. Before the start of the thesis, the construct validity of our method was already confirmed in athletics, in which clear differences were determined in the muscle typology of either sprint or endurance disciplines. Despite the fact that a comparable distribution of the muscle typologies could be expected in other cyclic sports such as cycling and swimming, this was not yet investigated in elite athletes. Therefore, study 3 established the muscle typologies of 80 world-class cyclists. Clear differences were found in the muscle typology between cycling events. Keirin, bicycle motocross racing (BMX), sprint and 500 m to 1 km time trial cyclists can be considered as fast typology athletes. Time trial, points race, scratch, and omnium consist of intermediate typology athletes, while most individual pursuit, single-stage, cyclo-cross, mountain bike, and multistage cyclists have a slow typology. Nevertheless, this distribution was not present in 73 elite swimmers (study 4), as no clear differences in the muscle typology were detected between short and long distance swimming events in the different strokes. However, there was some evidence to suggest that truly world-class sprint swimmers had a faster muscle fiber type composition when compared to elite swimmers competing at the international level. Moreover, breaststroke swimmers were identified to have a faster muscle typology in comparison to the either freestyle, backstroke or butterfly swimmers. Elite soccer players (n=118) were found to have an on average intermediate typology, which matches with the intermittent nature of this sport (study 6). In contrary to our hypothesis, no differences in the muscle typology were detected between different positions (keeper, defender, midfielder and striker). A big heterogeneity was established over all positions, indicating that the muscle typology is not of major importance for talent identification in soccer. To determine the influence of the muscle typology on individualized training and recovery cycles, we investigated if fatigue and recovery were different when both slow and fast typology subjects were exposed to the same high-intensity training (study 5). Fatigue during three Wingate tests, determined by the power drop, was 20% higher in fast typology athletes. Even though the same work was done during these Wingate tests, also the recovery from these Wingate tests was found to be 15 times slower in fast typology athletes (20 min in slow typology vs. longer than 5 h in fast typology). If a training plan would be composed with a minimum of recovery in between the training sessions, recovery might be insufficient for fast typology athletes, possibly rendering them with a higher risk for muscle strains. In study 6, we studied if the muscle typology is a risk factor for muscle strains in elite soccer players. We discovered that fast typology soccer players had a 5.3 times higher chance to get a hamstring injury, when compared to slow typology soccer players during a prospective longitudinal follow-up study over three seasons. Next to a higher accumulation of fatigue, a higher vulnerability in fast typology players could be expected due to the lower structural integrity in fast fibers. Bringing together, the muscle typology is an important characteristic, which could be non-invasively monitored using 1H-MRS. This technique could help athletes to make a scientific based decision on their ideal discipline during talent orientation. Moreover, it could help coaches tailoring training to enlarge the athletes’ muscle potential and to prevent fatigue accumulation. This endeavor might partly prevent fast typology athletes to be at a higher risk for strain injuries. Consequently, we believe that measuring the muscle fiber typology of athletes should be considered as a valuable procedure to help athletes to fully develop their potential based on the smart use of muscle profiling.

Effect of online low-intensity exercise training on fitness and cardiovascular parameters

Article

Aug 2021

Online exercise is undoubtedly useful and important; however, chronic adaptations to online exercise, particularly strength gain, muscle hypertrophy, and cardiovascular parameters, remain unclear. We investigated the effect of online exercise training using Zoom on fitness parameters compared with the same exercises supervised directly. In the present study, 34 subjects (age: 42.9±14.4 years) were included. Twenty-three subjects performed eight weeks of body mass-based exercise training online using Zoom, and eleven subjects performed the same exercise supervised directly as the control group. The subjects performed low-load resistance exercises twice a week for 8 weeks for a total of 16 sessions. The sessions included 9 exercises: leg raises, squats, rear raises, shoulder presses, rowing, dips, lunges, Romanian dead lifts, and push-ups. Chair-stand, push-up, and sit-and-reach tests were performed on all subjects. Overall, the home exercise program effectively increased strength and muscle mass and decreased blood pressure and arterial stiffness, but there were no differences between the groups. Changes in chair-stand and sit-and-reach test results were higher in the control group than in the online group. Our results show that there is a similar training response to body mass-based training in both groups, even with virtual experiences using Zoom.

Indices Reflecting Muscle Contraction Performance During Exercise Based on a Combined Electromyography and Mechanomyography Approach

Preprint

Full-text available

Jun 2021

Influence of Myosin Heavy Chain Protein Isoforms on Akt/mTOR Signaling and mRNA Expression Following Resistance Exercise in Trained Men

Article

Apr 2015

Effekte einer Blockperiodisierung im Vergleich zu einer kontinuierlichen Wellenperiodisierung auf die Maximal- und Schnellkraft kompetitiver Athleten - Systematisches Review und Meta-Analyse

Article

Apr 2021

From Myth to Reality: Resistance Training in Children

Article

Full-text available

Feb 2021

Children have been participating in sports with the increasing numbers day by day. With the increasing rivalry, they are trying to find the ways to improve their performance to the best possible. As a result, the number of children who are adding resistance training to their training routines is also increasing. This raises myths about the harmful and risky nature of resistance training on children with many questions about its safety and effectiveness. Recent studies can remove doubts about the risk of injury, uselessness and ineffectiveness. With the proves from many studies for some decades, it is now accepted that properly controlled and supervised resistance training during childhood is not only safe and effective but also recommended by the world's leading healthcare and sports organizations for improving health and athletic performance. In the light of the scientific data, possible benefits, risks and application areas of resistance training for child athletes are discussed in this review.

Body Contouring With Electromagnetic Treatment Plus Radiofrequency: A Review

Article

Nov 2024
ANN PLAS SURG

Eric Swanson

Background Electromagnetic treatments have recently been combined with radiofrequency to reduce the fat layer and simultaneously increase muscle thickness. Studies report treatment efficacy, using photographs and imaging methods. Methods A literature review was conducted. Measurement data were tabulated. The EmSculpt Neo device (BTL Industries, Boston, MA) was used in all studies. Results Seven studies evaluated the fat thickness and muscle thickness using either ultrasound (1 study) or magnetic resonance imaging methods (6 studies). The abdomen was treated in 2 studies. The other studies treated the lateral thighs, flanks, buttocks, inner thighs, and upper arms. The mean reduction in fat thickness was 8.0 mm, and the mean increase in muscle thickness was 5.5 mm. All 7 studies were authored by BTL medical advisors. Measured changes were likely within the margin of error and of questionable clinical relevance. Few adverse events were reported. Discussion Photographs were frequently not standardized, showing changes in treated areas, but unexplained changes in nontreated areas as well. The magnetic resonance imaging scans were affected by differing levels of the axial slice. Measured changes were incremental and likely not indicative of a true treatment effect. The scientific basis for efficacy is tenuous, both for fat reduction and muscle hypertrophy. Conclusions A scientific evaluation of the results fails to produce reliable evidence of a clinically meaningful result for this combination energy-based treatment. Financial conflict is a major factor. Liposuction remains the gold standard.

Temporal expression of mitochondrial life cycle markers during acute and chronic overload of rat plantaris muscles

Article

Full-text available

Aug 2024

Skeletal muscle hypertrophy is generally associated with a fast-to-slow phenotypic adaptation in both human and rodent models. Paradoxically, this phenotypic shift is not paralleled by a concomitant increase in mitochondrial content and aerobic markers that would be expected to accompany a slow muscle phenotype. To understand the temporal response of the mitochondrial life cycle (i.e., biogenesis, oxidative phosphorylation, fission/fusion, and mitophagy/autophagy) to hypertrophic stimuli, in this study, we used the functional overload (FO) model in adult female rats and examined the plantaris muscle responses at 1 and 10 weeks. As expected, the absolute plantaris muscle mass increased by ∼12 and 26% at 1 and 10 weeks following the FO procedure, respectively. Myosin heavy-chain isoform types I and IIa significantly increased by 116% and 17%, respectively, in 10-week FO plantaris muscles. Although there was a general increase in protein markers associated with mitochondrial biogenesis in acute FO muscles, this response was unexpectedly sustained under 10-week FO conditions after muscle hypertrophy begins to plateau. Furthermore, the early increase in mito/autophagy markers observed under acute FO conditions was normalized by 10 weeks, suggesting a cellular environment favoring mitochondrial biogenesis to accommodate the aerobic demands of the plantaris muscle. We also observed a significant increase in the expression of mitochondrial-, but not nuclear-, encoded oxidative phosphorylation (OXPHOS) proteins and peptides (i.e., humanin and MOTS-c) under chronic, but not acute, FO conditions. Taken together, the temporal response of markers related to the mitochondrial life cycle indicates a pattern of promoting biogenesis and mitochondrial protein expression to support the energy demands and/or enhanced neural recruitment of chronically overloaded skeletal muscle.

Making the case for resistance training in improving vascular function and skeletal muscle capillarization

Article

Full-text available

Feb 2024

Through decades of empirical data, it has become evident that resistance training (RT) can improve strength/power and skeletal muscle hypertrophy. Yet, until recently, vascular outcomes have historically been underemphasized in RT studies, which is underscored by several exercise-related reviews supporting the benefits of endurance training on vascular measures. Several lines of evidence suggest large artery diameter and blood flow velocity increase after a single bout of resistance exercise, and these events are mediated by vasoactive substances released from endothelial cells and myofibers (e.g., nitric oxide). Weeks to months of RT can also improve basal limb blood flow and arterial diameter while lowering blood pressure. Although several older investigations suggested RT reduces skeletal muscle capillary density, this is likely due to most of these studies being cross-sectional in nature. Critically, newer evidence from longitudinal studies contradicts these findings, and a growing body of mechanistic rodent and human data suggest skeletal muscle capillarity is related to mechanical overload-induced skeletal muscle hypertrophy. In this review, we will discuss methods used by our laboratories and others to assess large artery size/function and skeletal muscle capillary characteristics. Next, we will discuss data by our groups and others examining large artery and capillary responses to a single bout of resistance exercise and chronic RT paradigms. Finally, we will discuss RT-induced mechanisms associated with acute and chronic vascular outcomes.

Effects of Resistance Exercise Training on Aged Skeletal Muscle: Potential Role of Muscle Stem Cells

Article

Full-text available

May 2023

PURPOSE: The prevalence of sarcopenia, which can lead to disability, hospitalization, and death, is increasing among older populations. Resistance exercise training (RT) is currently the most effective strategy for combating sarcopenia by stimulating hypertrophy and increasing strength. This review describes the underlying mechanisms of aging skeletal muscle and whether RT attenuates aging-related loss of muscle function and mass.METHODS: We reviewed and summarized previous research using PubMed, Science Direct, and Google Scholar databases.RESULTS: Load-induced muscle growth is a complex phenomenon that depends on various physiological systems and signaling pathways. Muscle growth occurs through signaling events arising from mechanical stress and consequent muscle protein turnover controlled by the balance between protein synthesis and degradation, which is negatively affected by aging. The authors used the myonuclear domains mediated by muscle satellite cells to explain the molecular machinery of exercise-induced muscle growth and recovery in aging muscles.CONCLUSIONS: Despite a blunted molecular response to an exercise bout, aging muscle cells demonstrated remarkable plasticity, with substantial improvements in myofibril size and strength during RT. More studies are necessary to elucidate the specific mechanisms by which RT activates muscle satellite cells and mitogenic and myogenic signaling in aged muscles.

BİLATERAL TOTAL DİZ PROTEZİ SONRASI ERKEN İLERLEYİCİ KAPALI KİNETİK ZİNCİR EGZERSİZLERİNİN STANDART EGZERSİZ PROGRAMINA GÖRE ETKİLERİ - RANDOMİZE KONTROLLÜ ÇALIŞMAEARLY PROGRESSIVE CLOSED CHAIN EXERCISE VERSUS STANDARD EXERCISE PROGRAM FOLLOWING BILATERAL TOTAL KNEE ARTHROPLASTY: A RANDOMIZED CONTROLLED TRIAL

Article

Full-text available

Feb 2023

Amaç: Total diz protezlerinden (TDP) sonra hastaların cerrahi öncesi fonksiyonel duruma dönmelerinde post-akut erken dönem dirençli egzersizler büyük önem taşımaktadır. Bu çalışma ilerleyici kapalı kinetik zincir egzersiz (KKZE) programının, açık kinetik pozisyonda verilen standart egzersiz programına göre bilateral TDP hastalarında ağrı şiddeti, diz bölgesi ödem, eklem hareket açıklığı ve fonksiyonel durum üzerine kısa dönem etkilerini belirlemek amacıyla yapıldı. Yöntem: Çalışmaya yaş ortalaması 65,22 (51-79) yıl olan ve bilateral TDP uygulanan toplam 36 hasta (72 diz) dahil edildi. Hastalar basit-rastgele örnekleme yöntemi ile KKZE grubu (KKZE, n=16) ve standart egzersizlerden oluşan kontrol grubu (KG, n=16) olarak ayrıldı. Postoperatif 1. hafta (3 gün hastanede, 4 gün evde) tüm hastalara hastane içi aynı akut fizyoterapi programı uygulandı. Post-operatif 2. haftada (7-8.günlerde) ilk kontrollerine çağrılan hastalar randomize edilerek gruplarına uygun dirençli egzersiz eğitimine başladı. Haftada 3 gün ve toplamda 6 hafta uygulanan programlarda hastaların ağrı (VAS), ödem (çevre ölçümü), eklem hareket açıklığı (evrensel goniyometre) ölçümleri, başlangıçta (post-operatif 2.hafta) ve post-operatif 4. ve 7. haftada yapıldı. Fonksiyonel durum (WOMAC) değerlendirmesi ise sadece son ölçümde yapıldı. Sonuçlar: Her iki grupta da ağrı, ödem, diz eklemi hareketlerinde 6 hafta sonunda istatistiksel olarak anlamlı iyileşmeler oldu (p

Myofiber hypertrophy adaptations following 6-weeks of low load resistance training with blood flow restriction in untrained males and females

Article

Full-text available

Apr 2023
J APPL PHYSIOL

The effects of low load resistance training with blood flow restriction (BFR) on hypertrophy of type I/II myofibers remains unclear, especially in females. The purpose of the present study is to examine changes in type I/II myofiber cross-sectional area (fCSA) and muscle CSA (mCSA) of the vastus lateralis (VL) pre- to post-6 weeks of high load resistance training (HL, n=15, 8 females) and low load resistance training with BFR (n=16, 8 females). Mixed-effects models were used to analyze fCSA with group (HL, BFR), sex (M, F), fiber type (I, II), and time (Pre-, Post-) included as factors. mCSA increased pre- to post-training (p<0.001, d=0.91) and was greater in males compared to females (p<0.001, d=2.26). Type II fCSA increased pre- to post-HL (p<0.05, d=0.46) and was greater in males compared to females (p<0.05, d=0.78). There were no significant increases in fCSA pre- to post-BFR for either fiber type or sex. Cohen's d, however, revealed moderate effect sizes in type I and II fCSA for males (d=0.59 & 0.67), although this did not hold true for females (d=0.29 & 0.34). Conversely, the increase in type II fCSA was greater for females than males following HL. In conclusion, low load resistance training with BFR may not promote myofiber hypertrophy to the level of HL resistance training, and similar responses were generally observed for males and females. In contrast, comparable effect sizes for mCSA and 1RM between groups suggest that BFR could play a role in a resistance training program.

Effecten van krachttraining

Chapter

Mar 2023

Effect of selected plyometric training on arm and leg strength of volleyball players

Article

Full-text available

Dec 2022

Aarif Majeed

To achieve the purpose of this study 40 male college level volleyball players who were in various colleges of tehsil Devsar of district Kulgam, Jammu and Kashmir were randomly selected as subjects. The age ranged from 17-23. The selected subjects were divided into two groups and each group consists of 20 subjects, that is 20 subjects for experimental group and 20 subjects for control group.

Implantation of Decellularized Extracellular Matrix with Resistance Training Effectively Repairs a Volumetric Muscle Loss

Article

Full-text available

Aug 2022

PURPOSE: Skeletal muscle has remarkable regenerative capacity in most minor injuries induced by mechanical laceration, overstretching, and toxins. However, volumetric muscle loss (VML) injury, a large volume of muscle loss beyond the self-repair capacity, causes functional disability and morphological deformities. This study investigated the effects of myofiber injection into a decellularized extracellular matrix (ECM) and resistance training (RT) on skeletal muscle regeneration following VML injury.METHODS: 6-months-old male Fischer CDF rats and 2-months-old F344-Tg (UBC-EGFP) rats (myofiber donors) were used in this study. Approximately 20% of the mass of the lateral gastrocnemius (LGAS) was excised and replaced by ECM of similar dimensions. Thirty myofibers were injected into the injured region seven days post-injury. Ladder climbing (RT) was allowed 10 days post-defect surgery, and the rats were subjected to ladder climbing with a weight every third day for 6 weeks.RESULTS: After 56 days of recovery and exercise training, the cross-sectional area (CSA) of intact muscle in the EXE group (5,104±92 μm²) increased significantly compared to that in the ECM (4,657±79 μm²) group. The number of blood vessels larger than 20 μm in diameter, capillaries excluded, showed a significant difference between the ECM+EXE (34.25±4.2) and ECM (21.75±3.89) groups. A significant reduction of fibrosis in the ECM+EXE (44.50±1.6%) group was observed compared to the ECM (69.25±1.9%) and ECM+FIB+EXE (63.00±1.7%) groups. Moreover, the small muscle fiber area within the transplanted ECM was significantly larger in the ECM+EXE (1.37±0.03 mm²) than in both the ECM (0.49±0.01 mm²) and ECM+FIB (0.62±0.01 mm²) groups.CONCLUSIONS: These data suggest that ECM transplantation with RT effectively repairs VML by enhancing hypertrophy, angiogenesis, and myofiber infiltration throughout the entire ECM.

Effects of obesity and acute resistance exercise on skeletal muscle angiogenic communication pathways

Article

May 2022

New findings: What are the central questions of this study? Do obesity and acute resistance exercise alter the regulation of muscle intercellular communication pathways consistent with inadequate compensatory angiogenesis in response to muscle loading present in individuals with obesity? What is the main finding and its importance? Obesity is associated with differences in both pro- and anti-angiogenic signaling consistent with lower muscle capillarization. Acute resistance exercise increases the release of skeletal muscle small extracellular vesicles independent of body mass. These results identify novel cellular factors associated with impaired angiogenesis in obesity and the positive effects of acute resistance exercise in lean and obese skeletal muscle. Abstract: Introduction Obesity (OB) impairs cell-to-cell communication signaling. Small extracellular vesicles (EVs), which includes exosomes, are released by skeletal muscle and participate in cell-to-cell communications including the regulation of angiogenesis. Resistance exercise (REx) increases muscle fiber size and capillarization. However, while obesity increases muscle fiber size, there is an inadequate increase in capillarization such that capillary density is reduced. It was hypothesized that REx induced angiogenic signaling and EV biogenesis would be lower with obesity. Methods Sedentary lean (LN) and individuals with obesity (OB) (n = 8/group) performed three sets of single leg, knee extension REx at 80% of maximum. Muscle biopsies were obtained at rest, 15 min, and 3 hr post-exercise and analyzed for angiogenic and EV biogenesis mRNA and protein. Results In OB, muscle fiber size was ∼20% greater and capillary density with type II fibers was ∼25% lower compared to LN (p<0.001) . In response to REx, increased vascular endothelial growth factor (VEGF) mRNA (pro-angiogenic) was similar (3-fold) between groups, while thrombospondin-1 (TSP-1) mRNA (anti-angiogenic) increased ∼2.5-fold in OB only (p = 0.010). miR-130a (pro-angiogenic) was ∼1.4-fold (p = 0.011) and miR-503 (anti-angiogenic) was ∼1.8-fold (p = 0.017) greater in OB compared to LN across all time points. In both groups acute REx decreased the EV surface protein Alix ∼50% consistent with the release of exosomes (p = 0.016). Conclusion Acute resistance exercise appears to induce the release of skeletal muscle small EVs independent of body mass. However, with obesity there is predominantly impaired angiogenic signaling consistent with inadequate angiogenesis in response to basal muscle hypertrophy. This article is protected by copyright. All rights reserved.

Implication of satellite cell behaviors in capillary growth via VEGF expression-independent mechanism in response to mechanical loading in HeyL-null mice

Article

Jan 2022

Angiogenesis and muscle satellite cell (SC)-mediated myonuclear accretion are considered essential for the robust response of contraction-induced muscle hypertrophy. Moreover, both myonucleus and SCs are physically adjacent to capillaries and are the major sites for the expression of proangiogenic factors, such as VEGF, in the skeletal muscle. Thus, events involving the addition of new myonuclei via activation of SCs may play an important role in angiogenesis during muscle hypertrophy. However, the relevance among myonuclei number, capillary density, and angiogenesis factor is not demonstrated. The Notch effector HeyL is specifically expressed in SCs in skeletal muscle and is crucial for SC proliferation by inhibiting MyoD in overload-induced muscle hypertrophy. Here, we tested whether the addition of new myonuclei by SC in overloaded muscle is associated with angiogenic adaptation by reanalyzing skeletal muscle from HeyL knockout (KO) mice, which show blunted responses of SC proliferation, myonucleus addition, and overload-induced muscle hypertrophy. Reanalysis confirmed blunted SC proliferation and myonuclear accretion in the plantaris muscle of HeyL-KO mice 9 weeks after synergist ablation. Interestingly, the increase in capillary-fiber ratio observed in WT mice was impaired in HeyL-KO mice. In both WT and HeyL-KO mice, the expression of VEGFA and VEGFB was similarly increased in response to overload. In addition, the expression pattern of TSP-1, a negative regulator of angiogenesis, was also not changed between WT and HeyL-KO mice. Collectively, these results suggest that SCs activation-myonuclear accretion plays a crucial role in angiogenesis during overload-induced muscle hypertrophy via independent of angiogenesis regulators.

Distribution of motor unit properties across human muscles

Article

Oct 2021

The purpose of our review was to compare the distribution of motor unit properties across human muscles of different sizes and recruitment ranges. Although motor units can be distinguished based on several different attributes, we focused on four key parameters that have a significant influence on the force produced by muscle during voluntary contractions: the number of motor units, average innervation number, and the distributions of contractile characteristics and discharge rates within motor unit pools. Despite relatively few publications on this topic, current data indicate that the most influential factor in the distribution of these motor unit properties between muscles is innervation number. Nonetheless, despite a five-fold difference in innervation number between a hand muscle (first dorsal interosseus) and a lower leg muscle (tibialis anterior), the general organization of their motor unit pools and the range of discharge rates appears to be relatively similar. These observations provide foundational knowledge for studies on the control of movement and the changes that occur with ageing and neurological disorders.

Controlling High Blood through Nutrition Nutritional Supplements Lifestyle and Drugs

Book

May 2021

The effect of glenoid lateralization and glenosphere size in reverse shoulder arthroplasty on deltoid muscle tension: A biomechanical cadaveric study

Article

Apr 2021

Purpose Use of a relatively larger glenosphere with some larger overhang helps to minimize posterior impingement and some degree of glenoid lateralization is also beneficial in reverse shoulder arthroplasty (RSA). The optimal amounts of inferior overhang and lateralization are not agreed upon. The purpose of this in-vitro biomechanical study is to analyze the effect of glenosphere size and glenoid lateralization on deltoid load, focusing on differences in its three distinct heads. Methods Reverse shoulder arthroplasty (DeltaXtend, Fa. Depuy/Synthes) was performed on six cadaveric specimens. The load on each head of the deltoid muscle (spinalis, acromialis, and clavicularis) was measured indirectly by transferring deformation (μm/m) via strain gauges (Fa. Vishay) with stepwise lateralization: +0 mm (subgroup I), +5 mm (subgroup II), +10 mm (subgroup III). Each scenario was done with a 38 mm (group A) and a 42 mm (group B) glenosphere. Results In group A as well in group B, the mean measured deformation in the respective titanium omega increased with lateralization in the clavicular (AI: 119.6 μm/m, AIII: 307.3 μm/m; BI: 173.3 μm/m, BIII: 358.5 μm/m), in the spinal (AI: 85.3 μm/m, AIII: 188.5 μm/m; BI: 138.8 μm/m, BIII 261.2 μm/m) and in the acromial head (AI: 340.5 μm/μ; AIII: 454.2 μm/m; BI: 388.5 μm/m, BIII: 538.8 μm/m). A significant difference between the subgroups in the spinal (p = .048) and clavicular heads (p = .028) was found. The use of a 42 mm glenosphere increased significantly the load in each segment. Conclusion Lateralization and glenosphere size increased significantly deltoid muscle loading, especially in the clavicular head. According to these in-vitro data, the high variability in the amount of lateralization influences the soft-tissue balance in reverse shoulder arthroplasty. Level of evidence Basic science study.

Zihinsel Antrenman

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Full-text available

Jan 2021

Capillary supply in heavy-resistance trained non-postural human skeletal muscle

Article

Full-text available

Jan 1983

Peter Schantz

Protein and Amino Acid Needs of the Strength Athlete

Article

Full-text available

Jul 1991
Int J Sport Nutr

Peter W R Lemon

The debate regarding optimal protein/amino acid needs of strength athletes is an old one. Recent evidence indicates that actual requirements are higher than those of more sedentary individuals, although this is not widely recognized. Some data even suggest that high protein/amino acid diets can enhance the development of muscle mass and strength when combined with heavy resistance exercise training. Novices may have higher needs than experienced strength athletes, and substantial interindividual variability exists. Perhaps the most important single factor determining absolute protein/amino acid need is the adequacy of energy intake. Present data indicate that strength athletes should consume approximately 12-15% of their daily total energy intake as protein, or about 1.5-2.0 g protein/kg.d-1 (approximately 188-250% of the U.S. recommended dietary allowance). Although routinely consumed by many strength athletes, higher protein intakes have not been shown to be consistently effective and may even be associated with some health risks.

Evidence of fibre hyperplasia in human skeletal muscles from healthy young men? A left-right comparison of the fibre number in whole anterior tibialis muscles

Article

Full-text available

Feb 1991
Eur J Appl Physiol Occup Physiol

Cross-sections (thickness 10 microns) of whole autopsied left and right anterior tibialis muscles of seven young previously healthy right-handed men (mean age 23 years, range 18-32 years) were prepared for light-microscope enzyme histochemistry. Muscle cross-sectional area and total number of fibres, mean fibre size (indirectly determined) and proportion of the different fibre types (type 1 and type 2 on basis of myofibrillar adenosine triphosphatase characteristics), in each muscle cross-section were determined. The analysis showed that the cross-sectional area of the left muscle was significantly larger (P less than 0.05), and the total number of fibres was significantly higher (P less than 0.05), than for the corresponding right muscle. There was no significant difference for the mean fibre size or the proportion of the two fibre types. The results imply that long-term asymmetrical low-level daily demands on muscles of the left and the right lower leg in right-handed individuals provide enough stimuli to induce an enlargement of the muscles on the left side, and that this enlargement is due to an increase in the number of muscle fibres (fibre hyperplasia). Calculations based on the data also explain why the underlying process of hyperplasia is difficult, or even impossible, to detect in standard muscle biopsies.

Muscle hypertrophy in men and women

Article

Full-text available

Sep 1988

It is widely believed that women experience less skeletal muscle hypertrophy consequent to heavy-resistance training than men. The purpose of this study was to test this hypothesis using both traditional indirect indicators as well as a direct measure of muscle size. Seven male experimental (ME), 8 female experimental (FE), and 7 control subjects were studied before and after a 16-wk weight training program, in which ME and FE trained 3 days.wk-1 at 70 to 90% of maximum voluntary contraction using exercise designed to produce hypertrophy of the upper arm and thigh. Strength increased significantly (P less than 0.05) in ME and FE, respectively, on elbow flexion (36.2 and 59.2%), elbow extension (32.6 and 41.7%), knee flexion (12.8 and 24.4%), and knee extension (28.8 and 33.9%) tests. Absolute changes were significantly greater in ME than FE in 2 of the 4 tests, whereas percentage changes were not significantly different. Substantial muscle hypertrophy occurred in the upper arms of both ME and FE as evidenced by significant increases in upper arm circumference (7.9 and 7.9%), bone-plus-muscle (B+M) cross-sectional area (CSA) estimated by anthropometry (17.5 and 20.4%), and muscle CSA determined from computed tomography scanning (15.9 and 22.8%). Changes by ME and FE were not significantly different, except for the absolute increase in estimated B+M CSA, which was significantly greater in ME (11.2 vs 7.4 cm2). No muscle hypertrophy occurred in the thigh of either ME and FE as evidenced by non-significant changes in thigh circumference (1.7 and 2.3%), B+M CSA (4.9 and 6.1%), and muscle CSA (2.9 and 2.9%). Changes by ME and FE in body weight, fat-free weight, and fat weight were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of different fibre types in human skeletal muscles. I. Method for the preparation and analysis of cross-sections of whole tibialis anterior

Article

Full-text available

Mar 1983

The aim of this study was to examine whether small biopsy specimens are representative of the whole human skeletal muscle or whether the different fibre types are unevenly distributed at different depths of the muscle. Ten micrometre thick cross-sections of whole human tibialis anterior were prepared using LKB PMV Cryo-Microtomes with a stroke length of 160 to 480 mm and the sections were stained for myofibrillar ATPase according to a modified procedure. The total and relative number of different fibres (Types 1 and 2) was determined in every 9th mm2 of the section. The data obtained were analysed by means of a computer program, which allowed assessment of bivariate data in the form of contour plots. The total number of fibres varied greatly between individuals (from 96 000 to 162 000; five individuals). The relative number of different fibres varied systematically in all individuals as a function of depth in the muscle. There was a gradual, often dramatic, relative increase in Type 2 fibre occurrence from the surface of the muscle (about 10–25%) towards the deeper regions (30–50%), the maximum being approximately along a line slightly posterior to the middle of the muscle. Additionally, superficial peaks were seen in places. In conclusion, the fibre type distribution in the tibialis anterior is not random. These results point to the importance of defining biopsy depth.

Distribution of different fibre types in human skeletal muscles. 2. A study of cross-sections of whole m. vastus lateralis

Article

Full-text available

Feb 1983

In order to determine the total number of fibres and the extent to which the relative occurrence of different fibre types varies within m. vastus lateralis, 15 micrometers thick cross-sections of whole muscles were prepared. The total number of type 1 and type 2 fibres was determined in every 48th square millimetre of the section, and the results thus obtained were analysed using a computer program allowing an assessment of bivariate data in the form of contour plots. The total number of fibres varied both in proximal to distal direction in the same muscle and between individuals. No obvious correlation existed between the mean fibre area and the muscle cross-sectional area. The proportion of type 1 fibres in the whole muscle varied between individuals (from 44% to 57%) with a mean value for all five of 52%. The distribution of different fibre types varied within the muscle, mainly as a function of depth, with a predominance to type 2 fibres at the surface and type 1 fibres in deeper regions of the muscle. Thus, the fibre type distribution in m. vastus lateralis is not random. This must be taken into consideration when data on fibre type composition are compared with functional variables.

Capillary supply in hypertrophied human skeletal muscle

Article

Full-text available

May 1982

Peter Schantz

An increase in capillary supply is a well-documented feature of endurance-training. There is, however, a paucity of information regarding capillary supply in connection with heavy-resistance training. In order to obtain more information on this matter, the capillary supply in heavy-resistance trained subjects with greatly hypertrophied muscles has been characterized and compared with untrained and endurance trained subjects.

8 The Plasticity of Skeletal Muscle

Article

Jan 1991

Capillarity of elite cross-country skiers: A lectin (Ulex europaeus I) marker

Article

Jan 2007
SCAND J MED SCI SPOR

Capillary morphometries in human skeletal muscle has been limited by technical problems in visualization. The purpose of this study was to develop a method for identifying capillary endothelium at the light level of resolution and to reassess the skeletal muscle capillarity in trained and untrained subjects. A lectin system of biotinylated Ulex europaeus I (UEA-I), a vascular endothelial marker, provided a stain dense enough for direct computer-aided image analysis. A morphometric comparison was made between Andersen's periodic acid-Schiff and the UEA-I capillary stains on tissue sections of human skeletal muscle. When identical fibers from adjacent sections were compared, the capillary density was 6% and cap fiber was 9% greater using die lectin method. Biopsies from 17 cross-country skiers were compared with those of 8 age-matched sedentary controls. The capillary density in the triceps muscle for the skiers was 536.1 ± 33.1 compared with 296 ± 17.7 for the controls. Longitudinal profiles that appear in skeletal muscle cross-sections suggest a more isotropic (random orientation) configuration of the capillary bed than proposed by the Krogh model. There were 50.6% more longitudinal profiles in the trained samples. The UEA-I lectin appears to be a valid and potentially useful marker for computerized image analysis of non-pathological vascular endothelium, and tie differences in capillarity between trained and untrained individuals may be greater than previously reported.

Capillary Density in Skeletal Muscle of Man

Article

Dec 2008
Acta Physiol Scand

Per Andersen

The effect of weight-lifting exercise related to muscle fiber cross-sectional area in humans

Article

Feb 1979
Eur J Appl Physiol Occup Physiol

Isometric and dynamic strength and endurance of knee extensors were tested in 18 young males. The relative composition of slow (ST) and fast twitch (FT) fibers in the vastus lateralis muscle was registered from needle biopsies. Thigh muscle volume was evaluated from ultrasonic measurements. Six subjects served as controls, six trained with 50%, and six with 80% dynamic strength three times per week for 7 weeks with 20 and 12 repetitions per session, respectively. The training load was adjusted to the increases in strength observed during training. Dynamic strength increased by 42.3% in the 80% group (p< 0.01). In the control group and 50% group no significant increases were observed. Dynamic endurance: Controls showed no change. There was an over-all increase in the 50% group, while the 80% group only increased dynamic endurance for heavier loads. Isometric strength and endurance and fiber composition did not change in any group. In the 50% group the area of FT-realtive to ST-fibers increased 12.4% (p>0.05). Dynamic strength relative to muscle cross section increased by 30% in the 80% group (p<0.01) positively correlated to relative content of FT fibers. The present results confirm the specificity of training and indicate that a high content of FT fibers is a prerequisite for a successful strength training.

Neural Factors Versus Hypertrophy in the Time Course of Muscle Strength Gain

Article

Jul 1979
Am J Phys Med

The time course of strength gain with respect to the contributions of neural factors and hypertrophy was studied in seven young males and eight females during the course of an 8 week regimen of isotonic strength training. The results indicated that neural factors accounted for the larger proportion of the initial strength increment and thereafter both neural factors and hypertrophy took part in the further increase in strength, with hypertrophy becoming the dominant factor after the first 3 to 5 weeks. Our data regarding the untrained contralateral arm flexors provide further support for the concept of cross education. It was suggested that the nature of this cross education effect may entirely rest on the neural factors presumably acting at various levels of the nervous system which could result in increasing the maximal level of muscle activation.

Changes in muscle fibre type distribution in man after physical training. A sign of fibre type transformation?

Article

Nov 1978

The aim of the present study was to throw further light on questions concerning fibre type transformation by studying long-term effects of different types of physical training on the percentages of different fibre types. Four long-distance runners participated in the study. Needle biopsies were taken from vastus lateralis after both training periods. After 'anaerobic' training, all subjects had a lower percentage type I and a higher percentage type II C fibres than after 'aerobic' training. Three subjects also had a higher percentage type II A + II B fibres and an increased II B/II A ratio after 'anaerobic' training. Thus, it seems reasonable to assume that a conversion of type I to type II C fibres had occurred in subjects 1 and 2 due to 'anaerobic' training and that a conversion in the opposite direction had occurred in subjects 3 and 4 due to 'aerobic' training. The type II C fibres might be fibres in transformation from type I to type II A or in the reversed direction.

Effects of resistance training on elbow flexors of highly competitive bodybuilders

Article

May 1992

The influence of gender on muscular adaptation of the elbow flexors to 24 wk of heavy resistance training was studied in five male bodybuilders (MB) and five female bodybuilders (FB) who were highly competitive. Muscle cross-sectional area (CSA), fiber area, and fiber number were determined from the biceps brachii, and voluntary elbow flexor torque was obtained at velocities of contraction between 0 and 300 degrees/s. Biceps and flexor CSA was 75.8 and 81% greater, respectively, in MB than in FB, but muscle CSA was not significantly altered by the training program in either group. Because estimated fiber number and the volume density of nonmuscle tissue were similar in MB and FB, most of the gender difference in muscle CSA appeared to be due to greater absolute mean fiber areas in MB (10.51 and 10.68 x 10(3) microns 2 pre- and posttraining, respectively) than in FB (5.33 and 5.96 x 10(3) microns 2 pre- and posttraining, respectively). In neither MB nor FB did fiber type achieve further hypertrophy during the 24-wk training program. These data suggest that the extent of any change in muscle mass or muscle fiber characteristics is minimal after a bodybuilder of either gender has attained a high degree of muscle mass and a highly competitive status.

Influence of eccentric action of skeletal muscle adaptations to resistance training

Article

Nov 1991

Three different training regimens were performed to study the influence of eccentric muscle actions on skeletal muscle adaptive responses to heavy resistance exercise. Middle-aged males performed the leg press and leg extension exercises two days each week. The resistance was selected to induce failure within six to twelve repetitions of each set. Group CON/ECC (n = 8) performed coupled concentric and eccentric actions while group CON (n = 8) used concentric actions only. They did four or five sets of each exercise. Group CON/CON (n = 10) performed twice as many sets with only concentric actions. Eight subjects did not train and served as controls. Tissue samples were obtained from m. vastus lateralis using the biopsy technique before and after 19 weeks of training, and after four weeks of detraining. Histochemical analyses were performed to assess fibre type composition, fibre area and capillarization. Training increased (P less than 0.05) Type IIA and decreased (P less than 0.05) Type IIB fibre percentage. Only group CON/ECC increased Type I area (14%, P less than 0.05). Type II area increased (P less than 0.05) 32 and 27%, respectively, in groups CON/ECC and CON/CON, but not in group CON. Mean fibre area increased (P less than 0.05) 25 and 20% in groups CON/ECC and CON/CON, respectively. Capillaries per fibre increased (P less than 0.05) equally for Type I and Type II fibres. Capillaries per fibre area for both fibre types, however, increased (P less than 0.05) only in groups CON and CON/CON. The changes in fibre type composition and capillary frequency were manifest after detraining.(ABSTRACT TRUNCATED AT 250 WORDS)

The plasticity of skeletal muscle: Effects of neuromuscular activity

Article

Feb 1991

Effects of eccentric and concentric resistance training on skeletal muscle substrates, enzyme activities and capillary supply

Article

Jan 1991

This study compared the skeletal muscle metabolic adaptations in response to combined eccentric and concentric or concentric resistance training regimens. Twenty-six physically active males were assigned to either the combined eccentric and concentric group (n = 10), the concentric group (n = 10) or the control group (n = 6). The combined eccentric and concentric and the concentric groups performed four to five sets of maximal, voluntary bilateral quadriceps muscle actions at 1.05 rad s-1 using a speed-controlled dynamometer three times per week for 12 weeks. The concentric group performed 12 concentric actions per set, whereas the combined eccentric and concentric group performed six coupled eccentric and concentric actions per set. Bilateral percutaneous muscle biopsies were obtained from m. vastus lateralis at rest pre- and post-training. Tissue samples were analysed for contents of adenosine triphosphate, creatine phosphate and creatine and for enzyme activities of citrate synthase, lactate dehydrogenase, myokinase, phosphofructokinase, hexokinase and Mg2(+)-ATPase using fluorometric techniques. Histochemical staining procedures were employed to determine capillary supply. The overall increase (P less than 0.05) in muscle strength was greater (P less than 0.05) for the combined eccentric and concentric group than for the concentric group. Enzyme or substrate contents and capillary supply were unaltered after either type of training. It is suggested that substantial increases in muscle strength may occur in response to resistance training without enhancing or compromising metabolic function of skeletal muscle.

Brown AB, McCartney N, Sale DG. Positive adaptations to weight-lifting training in the elderly

Article

Dec 1990

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.

Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women

Article

Feb 1990
Eur J Appl Physiol Occup Physiol

Twenty-four women completed a 20-week heavy-resistance weight training program for the lower extremity. Workouts were twice a week and consisted of warm-up exercises followed by three sets each of full squats, vertical leg presses, leg extensions, and leg curls. All exercises were performed to failure using 6-8 RM (repetition maximum). Weight training caused a significant increase in maximal isotonic strength (1 RM) for each exercise. After training, there was a decrease in body fat percentage (p less than 0.05), and an increase in lean body mass (p less than 0.05) with no overall change in thigh girth. Biopsies were obtained before and after training from the superficial portion of the vastus lateralis muscle. Sections were prepared for histological and histochemical examination. Six fiber types (I, IC, IIC, IIA, IIAB, and IIB) were distinguished following routine myofibrillar adenosine triphosphatase histochemistry. Areas were determined for fiber types I, IIA, and IIAB + IIB. The heavy-resistance training resulted in significant hypertrophy of all three groups: I (15%), IIA (45%), and IIAB + IIB (57%). These data are similar to those in men and suggest considerable hypertrophy of all major fiber types is also possible in women if exercise intensity and duration are sufficient. In addition, the training resulted in a significant decrease in the percentage of IIB with a concomitant increase in IIA fibers, suggesting that strength training may lead to fiber conversions.

Contrasts in muscle and myofibers of elite male and female bodybuilders

Article

Aug 1989

Muscle cross-sectional area (CSA), fiber area, and fiber number were determined from the biceps brachii of eight elite male bodybuilders (MB) and five elite female bodybuilders (FB) who had similar training characteristics. Biceps CSA was obtained from computer tomographic scanning and corrected for noncontractile tissue. Biceps CSA was twofold greater in MB relative to FB and strongly correlated to lean body mass (R = 0.93). Biceps CSA expressed per kilogram lean body mass (LBM) or per centimeter body height (BH) was 35% greater in MB compared with FB. Most of the gender difference in muscle CSA was because of greater absolute mean fiber areas in MB (9,607 microns2) relative to FB (5,386 microns2); however, MB also had a significantly greater population of small type II fibers (less than 2,000 microns2) compared with FB. Type II fiber area/LBM averaged 1.6-fold greater in MB compared with FB; however, type I fiber area/LBM was similar between groups. Biceps CSA was positively correlated to fiber CSA (R = 0.75) and fiber number (R = 0.55). This suggests that adaptations to resistance training may be complex and involve fiber hypertrophy and fiber number (e.g., proliferation). Alternatively, since the muscle characteristics before training are not known, these apparent adaptations might be genetically determined attributes.

Structural Changes in Skeletal Muscle Tissue with Heavy-Resistance Exercise*

Article

Jul 1986

Muscle strength, muscle cross-sectional area, fiber size, fiber type distribution, capillarity, and mitochondrial volume were estimated before and after 6 weeks of heavy-resistance exercise. Isokinetic torque production of the knee extensor muscles increased by a total of 17.6%, mainly during the first half of the training period. The cross-sectional area of the vastus lateralis muscle increased by 8.4%, mainly during the second half of the training period. Morphometrically determined fiber size, fiber type distribution, and capillarity from biopsies of vastus lateralis did not change significantly with training. Likewise, the surface densities of inner and outer mitochondrial membranes as well as the volume density of myofibrils remained unchanged. In contrast, the volume density of mitochondria decreased by 9.6%. However, due to the increase in total muscle volume, the calculated absolute volume of mitochondria remained constant, whereas the absolute volume of myofibrils increased by 10%. It is concluded that strength training of short duration in previously untrained young male subjects does not change the ultrastructural composition of mitochondria and that the apparent dilution of mitochondria can quantitatively be accounted for by the increase in myofibrillar volume.

Isokinetic strength training protocols: Do they induce skeletal muscle fiber hypertrophy?

Article

May 1988
ARCH PHYS MED REHAB

Sedentary subjects were submitted to repeated concentric isokinetic strength training protocols separated by a 50-day detraining period. Peak torque output of the quadriceps muscle group increased by 54% after the first ten-week training protocol. No significant changes in mean skeletal muscle fiber area were observed while a significant increase in percent fiber type and percent fiber area was noticed for type IIa fibers. The activities of the enzymes hexokinase, malate dehydrogenase, 3-hydroxyacyl CoA dehydrogenase, and oxoglutarate dehydrogenase were also increased significantly. Fifty days without training induced a significant decline in peak torque output. All the enzymes that responded to the first training protocol maintained their elevated activities over the detraining period except for the enzyme oxoglutarate dehydrogenase. A second training protocol administered to the same subjects following the 50-day inactivity period did not result in any significant increase in maximum torque output and fiber area. It is concluded that the isokinetic strength training protocol used can increase the functional capacity of skeletal muscle, but this effect does not appear to be related to skeletal muscle fiber hypertrophy.

Exercise-Induced Skeletal Muscle Growth

Article

May 1986

Postnatal skeletal muscle growth in humans is generally ascribed to enlargement of existing muscle fibres rather than to cellular proliferation. Some evidence of muscle fibre division or splitting was provided in the nineteenth century. This evidence has more recently been supported by fibres obtained from regenerating muscle, and from muscle which has undergone stress-induced growth. Numerous investigators have reported indirect evidence for exercise-induced hypertrophy and hyperplasia. These findings are largely founded on secondary observations of fibre size or number differences expressed relative to muscle cross-sectional area. Since these observations in humans are open to methodological criticism, researchers have developed 3 animal models to represent exercise-induced human muscle growth. These include compensatory hypertrophy, stretch-induced hypertrophy, and weight lifting in trained animals. The results and criticisms of the experiments which have used these models are discussed in this review. In studies of muscle cross-sectional area, errors are created by fibres terminating intrafascicularly. Longitudinal growth of such fibres result in an overestimation of fibre number, and with the use of penniform muscles where fibres do not run parallel to the longitudinal axis of the muscle, the error is compounded. It was concluded that hyperplasia is not yet substantiated, and that new fibres, if present, may be the result of the development of satellite cells. Further experiments are required before a definitive answer can be provided. It is suggested that rigidly controlled exercise studies using contralateral control, fusiform muscles with analysis of individually teased muscle fibres be performed.

Voluntary strength and muscle characteristics in untrained men and women and male bodybuilders

Article

Jun 1987

Eight untrained women (F), 13 untrained men (M), and 11 male bodybuilders (BB) did maximal elbow flexions on an isokinetic dynamometer at velocities of 30, 120, 180, 240, and 300 degrees/s, from which impact torque (IT), peak torque (PT), and work (W) were measured. Biceps and total flexor cross-sectional area (CSA) were measured by computerized tomographic scanning. Muscle fiber area, fiber composition, and collagen volume density were determined from single needle biopsies of biceps brachii. Biceps fiber number was estimated as the ratio of biceps CSA (corrected for connective tissue) to mean fiber area. PT and W decreased at higher velocities in M and BB but not in F; consequently, the correlation between CSA and PT and W was lower at 300 degrees/s (r = 0.58, 0.60) than 30 degrees/s (r = 0.80, 0.79). The ratio of PT to flexor CSA was similar in all groups at 30 degrees/s, whereas F had greater ratios than M and BB at the remaining velocities. F had greater W/CSA ratios than M and BB at all velocities. IT increased at higher velocities in all groups; the increase was greater in F and M than in BB. In contrast to PT and W, the correlation between IT and CSA was greater at 300 degrees/s (r = 0.67) than 30 degrees/s (r = 0.58), and there were no differences among groups in the IT/CSA ratios. Flexor CSA correlated negatively with the ratio of IT, PT, and W to CSA. Muscle fiber composition failed to correlate with any measure of strength. M and BB had greater biceps area, fiber number, and fiber area than F.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle Fiber Types: How Many and What Kind?

Article

Nov 1970
ARCH NEUROL-CHICAGO

STUDIES on normal and pathological striated muscle are increasingly clouded by inconsistencies in the definition of fiber types and lack of correlation between different systems of nomenclature. The purpose of the present communication is to point out some of the problems involved in the classification of fibers and to add new information of value in the analysis of human biopsy material. The histochemical reaction for myosin adenosine triphosphatase (ATPase) and the pH lability of this reaction is used to characterize the various types of fibers. Material and Methods Muscle was obtained by biopsy in man, rat, and rabbit. Gastrocnemius and soleus were investigated in the animals. The human biopsies were taken from the biceps. The methods used for histochemical analysis have been given elsewhere.1 In summary, unfixed frozen material was sectioned at 10μ thickness in the cryostat and the following histochemical reactions were carried out: (1) reduced diphosphopyridine

Variability of fibre distribution within human muscles

Article

Jan 1983

The variability of fiber type distributions between different regions of the same human muscle is believed to be small, based on the sampling of between two and four sites. The objective of the present investigation was to determine the variability of slow-twitch (ST) and fast-twitch (FT) fiber distributions using a more extensive sampling technique than those previously employed. The soleus, biceps, triceps, and vastus lateralis muscles were excised from each of four young men who had died suddenly. Between 13 and 17 sites were sampled from each of the muscles; 3 transverse areas were then examined within each sample. Fiber type distributions were determined from photographs of sections stained for myofibrillar adenosine triphosphatase at pH 10.3, 10.0, or 4.3. The numbers of fibers counted in the four muscles ranged between a mean of 13,660 and a mean of 21,601. The variability in fiber type distributions observed between sites and areas within a site were statistically greater (P less than 0.01) than could be expected from muscles whose fiber type distributions are equally distributed throughout the muscle. It was concluded that sampling between 3 and 5 sites in the different muscles was necessary to reduce the between-site standard deviation to 5%.

Muscle fiber number in biceps brachii in bodybuilders and control subjects

Article

Dec 1984

Muscle fiber numbers were estimated in vivo in biceps brachii in 5 elite male bodybuilders, 7 intermediate caliber bodybuilders, and 13 age-matched controls. Mean fiber area and collagen volume density were calculated from needle biopsies and muscle cross-sectional area by computerized tomographic scanning. Contralateral measurements in a subsample of seven subjects indicated the method for estimation of fiber numbers to have adequate reliability. There was a wide interindividual range for fiber numbers in biceps (172,085-418,884), but despite large differences in muscle size both bodybuilder groups possessed the same number of muscle fibers as the group of untrained controls. Although there was a high correlation between average cross-sectional fiber area and total muscle cross-sectional area within each group, many of the subjects with the largest muscles also tended to have a large number of fibers. Since there were equally well-trained subjects with fewer than normal fiber numbers, we interpret this finding to be due to genetic endowment rather than to training-induced hyperplasia. The proportion of muscle comprised of connective and other noncontractile tissue was the same for all subjects (approximately 13%), thus indicating greater absolute amounts of connective tissue in the trained subjects. We conclude that in humans, heavy resistance training directed toward achieving maximum size in skeletal muscle does not result in an increase in fiber numbers.

Muscle capillary supply and fiber type characteristics in weight and power lifters

Article

Feb 1984

Muscle tissue samples were obtained from vastus lateralis muscle of elite weight/power lifters (WL/PL, n = 8), endurance athletes (EA, n = 8), and nonathletes (NA, n = 8). Histochemical stainings for myofibrillar ATPase, NADH-tetrazolium reductase, and amylase-periodic acid-Schiff, respectively, were undertaken to assess relative distribution of fast-twitch (FT) and slow-twitch (ST) muscle fiber types, fiber size, and capillary supply [capillaries per fiber (cap X fib-1) and capillaries per mm2 (cap X mm-2)]. Fiber type distribution in WL/PL, EA, and NA averaged 59 +/- 6 (SD), 40 +/- 11, and 61 +/- 10% FT. Values for mean fiber area and FT/ST area were significantly greater in WL/PL compared with values obtained in EA and NA. Similar values for cap X fib-1 were observed WL/PL (2.06 +/- 0.74) and NA (2.16 +/- 0.34). EA exhibited greater cap X fib-1 (3.11 +/- 0.73) than WL/PL (NS) and NA (P less than 0.01). However, cap X mm-2 in WL/PL (199 +/- 29) was lower than in EA (401 +/- 61, P less than 0.001) and NA (306 +/- 29, P less than 0.01). It is suggested that heavy resistance training in contrast to endurance training does not result in increased capillary density. Instead, as a consequence of fiber hypertrophy induced by muscle overloading, capillary density is decreased.

Regional adipose cellularity and reliability of adipose cell size determination

Article

Dec 1980

Regional adipose cell size was assessed in 18 males ranging in age from 20 to 36 years. These measures were correlated to total body fat determined by hydrostatic weighing. Adipose samples were removed from the gluteal, abdominal, and subscapular regions using a needle aspiration technique. The tissue was incubated in collagenase to release individual cells that were immediately photographed under a microscope. To establish the reliability of adipose cell size assessment over time, fat biopsies were secured on 2 separate days. No significant difference was found for any region between day 1 and 2 adipose cell measures. Gluteal cell diameter (90.3 mu) was significantly larger than the abdominal (81.0 mu) and subscapular (78.6 mu) cell diameter (90.3 mu) was significantly larger than the abdominal (81.0 mu) and subscapular (78.6 mu) cell diameters. Total body fat correlated highest with gluteal cell size (r = 0.76) compared with the abdominal (r = 0.67) or subscapular (r = 0.70) regions. This study also examined the number of adipose cells required to subscapular (r = 0.70) regions. This study also examined the number of adipose cells required to obtain a reliable and representative mean value of adipose cell size. Using a sequential estimation analysis it was found that adipose cell diameters of the abdominal, gluteal, or subscapular regions can be reliably estimated with fewer than 100 cells.

Suction applied to a biopsy maximizes sample size

Article

Feb 1982

A method for increasing the size of a percutaneous needle biopsy specimen of skeletal muscle is described. Suction (700 TORR) is applied to the inner bore of the biopsy needle after the needle has been inserted into the subject's muscle. The suction pulls the surrounding muscle tissue into the needle, thus insuring the taking of a larger piece (X = 78.5 mg). In most cases, this technique will eliminate the need for repeated biopsies because of inadequate muscle sample size and enhance the validity of subsequent analysis procedures.

Muscle ultrastructure characteristics of elite powerlifters and bodybuilders

Article

Feb 1982
Eur J Appl Physiol Occup Physiol

Muscle ultrastructure of a group of subjects possessing extreme hypertrophy was compared with that of a control group which had undergone 6 months of heavy resistance training. Two needle biopsies were taken from triceps brachii of two international calibre powerlifters and five elite bodybuilders. In addition, samples were taken from five healthy volunteers before and after 6 months of training of the elbow extensors. One biopsy was prepared for electron microscopy and analyzed stereologically, and the other was stained for myosin ATPase activity and photographed under the light microscope. Despite large differences in elbow extension strength and arm girth there was no significant difference in fibre areas or percentages of fibre types between the elite group and the trained controls. This suggests that the elite group possessed a greater total number of muscle fibres than the controls did. Mitochondrial volume density of the elite group was similar to that of the control group following training but significantly less (p less than 0.05) than the pretraining control measurements. Myofibrillar volume density was significantly lower and cytoplasmic volume density significantly higher in the elite group than in the trained controls. There was a considerably higher incidence of structural abnormalities including central nuclei and atrophied fibres in the elite group than in the control group, which might possibly have been associated with the use of anabolic steroids by the elite group.

Measurement of cardiorespiratory fitness and body composition in the clinical setting

Article

Oct 1980
Compr Ther

With increased interest and participation in physical activity, particularly in activities that develop and maintain cardiorespiratory fitness and control body weight and fat, evaluation of physical fitness has become an important aspect of preventive and rehabilitative medicine. The term physical fitness has many meanings; cardiorespiratory fitness, body composition, muscular strength, endurance, and flexibility are considered the most important components when assessing the average adult. A close estimate of fitness enables the practitioner to make sound decisions concerning exercise prescription and health management. Energy expenditure in treadmill exercise, bicycle ergometry and in the step test are discussed. Information on the measurement of body composition is also presented.

Skeletal muscle fiber hyperplasia

Article

Jan 1994

Skeletal muscle enlargement in adult animals has been ascribed primarily to changes in fiber cross-sectional area (i.e., fiber hypertrophy); however, recent evidence from several laboratories suggests strongly that fiber hyperplasia contributes to muscle mass increases in adult animals and possibly human athletes. Scientists have used three models to study the cellular mechanisms of muscle enlargement: compensatory hypertrophy, stretch, and exercise. Each of these models has provided direct as well as indirect evidence supporting the occurrence of muscle fiber hyperplasia. Direct counts of muscle fibers using nitric acid digestion techniques have shown that both exercise and stretch overload result in significant increases (range = 9-52%) in fiber number. Indirect fiber counts using histological cross-sections have suggested fiber hyperplasia (range = 10-82%) in all three models. Additionally, the expression of embryonic myosin isoforms have provided indirect evidence for new fiber formation in stretch overloaded muscle. Furthermore, satellite cells have been shown to be involved in muscle fiber hyperplasia in stretch and exercise.

Exercise-induced skeletal muscle growth. Hypertrophy or hyperplasia? Sports Med

Jan 1986
190-200

N A Taylor
J G Wilkinson

Taylor, N. A., and J. G. Wilkinson. Exercise-induced skeletal muscle growth. Hypertrophy or hyperplasia? Sports Med. 3: 190-200, 1986.

Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training

Abstract

No full-text available

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