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Physiological Reviews Jul 2023Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle... (Review)
Review
Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive individuals with low levels of endurance and strength to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation, and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a "trial-and-error" approach, with the experience and practices of successful coaches and athletes often providing the bases for "post hoc" scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and interindividual differences in exercise capacity and performance, with special consideration given to aging athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise and how such adaptations translate from "molecules to medals."
Topics: Humans; Athletes; Exercise; Resistance Training; Adaptation, Physiological; Muscle, Skeletal; Awards and Prizes; Physical Endurance
PubMed: 36603158
DOI: 10.1152/physrev.00017.2022 -
Circulation Jan 2024Resistance training not only can improve or maintain muscle mass and strength, but also has favorable physiological and clinical effects on cardiovascular disease and... (Review)
Review
Resistance training not only can improve or maintain muscle mass and strength, but also has favorable physiological and clinical effects on cardiovascular disease and risk factors. This scientific statement is an update of the previous (2007) American Heart Association scientific statement regarding resistance training and cardiovascular disease. Since 2007, accumulating evidence suggests resistance training is a safe and effective approach for improving cardiovascular health in adults with and without cardiovascular disease. This scientific statement summarizes the benefits of resistance training alone or in combination with aerobic training for improving traditional and nontraditional cardiovascular disease risk factors. We also address the utility of resistance training for promoting cardiovascular health in varied healthy and clinical populations. Because less than one-third of US adults report participating in the recommended 2 days per week of resistance training activities, this scientific statement provides practical strategies for the promotion and prescription of resistance training.
Topics: Adult; United States; Humans; Cardiovascular Diseases; Resistance Training; American Heart Association; Exercise; Risk Factors
PubMed: 38059362
DOI: 10.1161/CIR.0000000000001189 -
Diabetologia Oct 2023Type 2 diabetes in people in the healthy weight BMI category (<25 kg/m), herein defined as 'normal-weight type 2 diabetes', is associated with sarcopenia (low muscle... (Randomized Controlled Trial)
Randomized Controlled Trial
Strength training is more effective than aerobic exercise for improving glycaemic control and body composition in people with normal-weight type 2 diabetes: a randomised controlled trial.
AIMS/HYPOTHESIS
Type 2 diabetes in people in the healthy weight BMI category (<25 kg/m), herein defined as 'normal-weight type 2 diabetes', is associated with sarcopenia (low muscle mass). Given this unique body composition, the optimal exercise regimen for this population is unknown.
METHODS
We conducted a parallel-group RCT in individuals with type 2 diabetes (age 18-80 years, HbA 47.5-118.56 mmol/mol [6.5-13.0%]) and BMI <25 kg/m). Participants were recruited in outpatient clinics or through advertisements and randomly assigned to a 9 month exercise programme of strength training alone (ST), aerobic training alone (AER) or both interventions combined (COMB). We used stratified block randomisation with a randomly selected block size. Researchers and caregivers were blinded to participants' treatment group; however, participants themselves were not. Exercise interventions were conducted at community-based fitness centres. The primary outcome was absolute change in HbA level within and across the three groups at 3, 6 and 9 months. Secondary outcomes included changes in body composition at 9 months. Per adherence to recommended exercise protocol (PP) analysis included participants who completed at least 50% of the sessions.
RESULTS
Among 186 individuals (ST, n=63; AER, n=58; COMB, n=65) analysed, the median (IQR) age was 59 (53-66) years, 60% were men and 83% were Asian. The mean (SD) HbA level at baseline was 59.6 (13.1) mmol/mol (7.6% [1.2%]). In intention-to-treat analysis, the ST group showed a significant decrease in HbA levels (mean [95% CI] -0.44 percentage points [-0.78, -0.12], p=0.002), while no significant change was observed in either the COMB group (-0.35 percentage points, p=0.13) or the AER group (-0.24 percentage points, p=0.10). The ST group had a greater improvement in HbA levels than the AER group (p=0.01). Appendicular lean mass relative to fat mass increased only in the ST group (p=0.0008), which was an independent predictor of HbA change (beta coefficient -7.16, p=0.01). Similar results were observed in PP analysis. Only one adverse event, in the COMB group, was considered to be possibly associated with the exercise intervention.
CONCLUSIONS/INTERPRETATION
In normal-weight type 2 diabetes, strength training was superior to aerobic training alone, while no significant difference was observed between strength training and combination training for HbA reduction. Increased lean mass relative to decreased fat mass was an independent predictor of reduction in HbA level.
TRIAL REGISTRATION
ClinicalTrials.gov NCT02448498.
FUNDING
This study was funded by the National Institutes of Health (NIH; R01DK081371).
Topics: Male; Humans; Adolescent; Young Adult; Adult; Middle Aged; Aged; Aged, 80 and over; Female; Diabetes Mellitus, Type 2; Glycemic Control; Resistance Training; Blood Glucose; Glycated Hemoglobin; Body Composition
PubMed: 37493759
DOI: 10.1007/s00125-023-05958-9 -
Journal of Sport and Health Science Jan 2024The aim of this umbrella review was to determine the impact of resistance training (RT) and individual RT prescription variables on muscle mass, strength, and physical... (Review)
Review
PURPOSE
The aim of this umbrella review was to determine the impact of resistance training (RT) and individual RT prescription variables on muscle mass, strength, and physical function in healthy adults.
METHODS
Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically searched and screened eligible systematic reviews reporting the effects of differing RT prescription variables on muscle mass (or its proxies), strength, and/or physical function in healthy adults aged >18 years.
RESULTS
We identified 44 systematic reviews that met our inclusion criteria. The methodological quality of these reviews was assessed using A Measurement Tool to Assess Systematic Reviews; standardized effectiveness statements were generated. We found that RT was consistently a potent stimulus for increasing skeletal muscle mass (4/4 reviews provide some or sufficient evidence), strength (4/6 reviews provided some or sufficient evidence), and physical function (1/1 review provided some evidence). RT load (6/8 reviews provided some or sufficient evidence), weekly frequency (2/4 reviews provided some or sufficient evidence), volume (3/7 reviews provided some or sufficient evidence), and exercise order (1/1 review provided some evidence) impacted RT-induced increases in muscular strength. We discovered that 2/3 reviews provided some or sufficient evidence that RT volume and contraction velocity influenced skeletal muscle mass, while 4/7 reviews provided insufficient evidence in favor of RT load impacting skeletal muscle mass. There was insufficient evidence to conclude that time of day, periodization, inter-set rest, set configuration, set end point, contraction velocity/time under tension, or exercise order (only pertaining to hypertrophy) influenced skeletal muscle adaptations. A paucity of data limited insights into the impact of RT prescription variables on physical function.
CONCLUSION
Overall, RT increased muscle mass, strength, and physical function compared to no exercise. RT intensity (load) and weekly frequency impacted RT-induced increases in muscular strength but not muscle hypertrophy. RT volume (number of sets) influenced muscular strength and hypertrophy.
Topics: Adult; Humans; Resistance Training; Exercise Therapy; Exercise; Hypertrophy; Muscle, Skeletal
PubMed: 37385345
DOI: 10.1016/j.jshs.2023.06.005 -
Journal of Functional Morphology and... Dec 2023Regimented resistance training (RT) has been shown to promote increases in muscle size. When engaging in RT, practitioners often emphasize the importance of appropriate... (Review)
Review
Regimented resistance training (RT) has been shown to promote increases in muscle size. When engaging in RT, practitioners often emphasize the importance of appropriate exercise technique, especially when trying to maximize training adaptations (e.g., hypertrophy). This narrative review aims to synthesize existing evidence on what constitutes proper RT exercise technique for maximizing muscle hypertrophy, focusing on variables such as exercise-specific kinematics, contraction type, repetition tempo, and range of motion (ROM). We recommend that when trying to maximize hypertrophy, one should employ a ROM that emphasizes training at long muscle lengths while also employing a repetition tempo between 2 and 8 s. More research is needed to determine whether manipulating the duration of either the eccentric or concentric phase further enhances hypertrophy. Guidelines for body positioning and movement patterns are generally based on implied theory from applied anatomy and biomechanics. However, existing research on the impact of manipulating these aspects of exercise technique and their effect on hypertrophy is limited; it is therefore suggested that universal exercise-specific kinematic guidelines are followed and adopted in accordance with the above recommendations. Future research should investigate the impact of stricter versus more lenient exercise technique variations on hypertrophy.
PubMed: 38249086
DOI: 10.3390/jfmk9010009 -
British Journal of Sports Medicine Sep 2023To determine how distinct combinations of resistance training prescription (RTx) variables (load, sets and frequency) affect muscle strength and hypertrophy. (Meta-Analysis)
Meta-Analysis
OBJECTIVE
To determine how distinct combinations of resistance training prescription (RTx) variables (load, sets and frequency) affect muscle strength and hypertrophy.
DATA SOURCES
MEDLINE, Embase, Emcare, SPORTDiscus, CINAHL, and Web of Science were searched until February 2022.
ELIGIBILITY CRITERIA
Randomised trials that included healthy adults, compared at least 2 predefined conditions (non-exercise control (CTRL) and 12 RTx, differentiated by load, sets and/or weekly frequency), and reported muscle strength and/or hypertrophy were included.
ANALYSES
Systematic review and Bayesian network meta-analysis methodology was used to compare RTxs and CTRL. Surface under the cumulative ranking curve values were used to rank conditions. Confidence was assessed with threshold analysis.
RESULTS
The strength network included 178 studies (n=5097; women=45%). The hypertrophy network included 119 studies (n=3364; women=47%). All RTxs were superior to CTRL for muscle strength and hypertrophy. Higher-load (>80% of single repetition maximum) prescriptions maximised strength gains, and all prescriptions comparably promoted muscle hypertrophy. While the calculated effects of many prescriptions were similar, higher-load, multiset, thrice-weekly training (standardised mean difference (95% credible interval); 1.60 (1.38 to 1.82) vs CTRL) was the highest-ranked RTx for strength, and higher-load, multiset, twice-weekly training (0.66 (0.47 to 0.85) vs CTRL) was the highest-ranked RTx for hypertrophy. Threshold analysis demonstrated these results were extremely robust.
CONCLUSION
All RTx promoted strength and hypertrophy compared with no exercise. The highest-ranked prescriptions for strength involved higher loads, whereas the highest-ranked prescriptions for hypertrophy included multiple sets.
PROSPERO REGISTRATION NUMBER
CRD42021259663 and CRD42021258902.
Topics: Humans; Adult; Female; Resistance Training; Bayes Theorem; Network Meta-Analysis; Muscle, Skeletal; Muscle Strength; Hypertrophy; Prescriptions
PubMed: 37414459
DOI: 10.1136/bjsports-2023-106807 -
Sports Medicine (Auckland, N.Z.) Nov 2023Increasing muscle strength and cross-sectional area is of crucial importance to improve or maintain physical function in musculoskeletal rehabilitation and sports... (Review)
Review
Increasing muscle strength and cross-sectional area is of crucial importance to improve or maintain physical function in musculoskeletal rehabilitation and sports performance. Decreases in muscular performance are experienced in phases of reduced physical activity or immobilization. These decrements highlight the need for alternative, easily accessible training regimens for a sedentary population to improve rehabilitation and injury prevention routines. Commonly, muscle hypertrophy and strength increases are associated with resistance training, typically performed in a training facility. Mechanical tension, which is usually induced with resistance machines and devices, is known to be an important factor that stimulates the underlying signaling pathways to enhance protein synthesis. Findings from animal studies suggest an alternative means to induce mechanical tension to enhance protein synthesis, and therefore muscle hypertrophy by inducing high-volume stretching. Thus, this narrative review discusses mechanical tension-induced physiological adaptations and their impact on muscle hypertrophy and strength gains. Furthermore, research addressing stretch-induced hypertrophy is critically analyzed. Derived from animal research, the stretching literature exploring the impact of static stretching on morphological and functional adaptations was reviewed and critically discussed. No studies have investigated the underlying physiological mechanisms in humans yet, and thus the underlying mechanisms remain speculative and must be discussed in the light of animal research. However, studies that reported functional and morphological increases in humans commonly used stretching durations of > 30 min per session of the plantar flexors, indicating the importance of high stretching volume, if the aim is to increase muscle mass and maximum strength. Therefore, the practical applicability seems limited to settings without access to resistance training (e.g., in an immobilized state at the start of rehabilitation), as resistance training seems to be more time efficient. Nevertheless, further research is needed to generate evidence in different human populations (athletes, sedentary individuals, and rehabilitation patients) and to quantify stretching intensity.
PubMed: 37556026
DOI: 10.1007/s40279-023-01898-x -
British Journal of Sports Medicine Oct 2023To investigate potential moderating effects of resistance exercise dose components including intensity, volume and frequency, for the management of common tendinopathies. (Meta-Analysis)
Meta-Analysis
OBJECTIVE
To investigate potential moderating effects of resistance exercise dose components including intensity, volume and frequency, for the management of common tendinopathies.
DESIGN
Systematic review with meta-analysis and meta-regressions.
DATA SOURCES
Including but not limited to: MEDLINE, CINAHL, SPORTDiscus, ClinicalTrials.gov and ISRCTN Registry.
ELIGIBILITY CRITERIA FOR SELECTING STUDIES
Randomised and non-randomised controlled trials investigating resistance exercise as the dominant treatment class, reporting sufficient information regarding ≥2 components of exercise dose.
RESULTS
A total of 110 studies were included in meta-analyses (148 treatment arms (TAs), 3953 participants), reporting on five tendinopathy locations (rotator cuff: 48 TAs; Achilles: 43 TAs; lateral elbow: 29 TAs; patellar: 24 TAs; gluteal: 4 TAs). Meta-regressions provided consistent evidence of greater pooled mean effect sizes for higher intensity therapies comprising additional external resistance compared with body mass only (large effect size domains: = 0.50 (95% credible interval (CrI): 0.15 to 0.84; p=0.998); small effect size domains ( = 0.04 (95% CrI: -0.21 to 0.31; p=0.619)) when combined across tendinopathy locations or analysed separately. Greater pooled mean effect sizes were also identified for the lowest frequency (less than daily) compared with mid (daily) and high frequencies (more than once per day) for both effect size domains when combined or analysed separately (p≥0.976). Evidence for associations between training volume and pooled mean effect sizes was minimal and inconsistent.
SUMMARY/CONCLUSION
Resistance exercise dose is poorly reported within tendinopathy management literature. However, this large meta-analysis identified some consistent patterns indicating greater efficacy on average with therapies prescribing higher intensities (through inclusion of additional loads) and lower frequencies, potentially creating stronger stimuli and facilitating adequate recovery.
Topics: Humans; Resistance Training; Rotator Cuff; Exercise Therapy; Patella; Tendinopathy
PubMed: 37169370
DOI: 10.1136/bjsports-2022-105754 -
European Journal of Sport Science Jul 2023The biarticular triceps brachii long head (TB) is lengthened more in the overhead than neutral arm position. We compared triceps brachii hypertrophy after elbow...
The biarticular triceps brachii long head (TB) is lengthened more in the overhead than neutral arm position. We compared triceps brachii hypertrophy after elbow extension training performed in the overhead vs. neutral arm position. Using a cable machine, 21 adults conducted elbow extensions (90-0°) with one arm in the overhead (Overhead-Arm) and the other arm in the neutral (Neutral-Arm) position at 70% one-repetition maximum (1RM), 10 reps/set, 5 sets/session, 2 sessions/week for 12 weeks. Training load was gradually increased (+5% 1RM/session) when the preceding session was completed without repetition failure. 1RM of the assigned condition and MRI-measured muscle volume of the TB, monoarticular lateral and medial heads (TB), and whole triceps brachii (Whole-TB) were assessed pre- and post-training. Training load and 1RM increased in both arms similarly (+62-71% at post, = 0.285), while their absolute values/weights were always lower in Overhead-Arm (-34-39%, < 0.001). Changes in muscle volume in Overhead-Arm compared to Neutral-Arm were 1.5-fold greater for the TB (+28.5% vs. +19.6%, Cohen's = 0.61, < 0.001), 1.4-fold greater for the TB (+14.6% vs. +10.5%, = 0.39, = 0.002), and 1.4-fold greater for the Whole-TB (+19.9% vs. +13.9%, = 0.54, < 0.001). In conclusion, triceps brachii hypertrophy was substantially greater after elbow extension training performed in the overhead versus neutral arm position, even with lower absolute loads used during the training.Growing evidence suggests that resistance training at long muscle lengths promotes muscle hypertrophy, but its practical applications are yet to be explored.Triceps brachii muscle hypertrophy was substantially greater after cable elbow extension training performed in the overhead than neutral arm position, particularly in the biarticular triceps brachii long head, even with lower absolute loads lifted (i.e. lower mechanical stress to muscles/joints).Cable elbow extension training should be performed in the overhead rather than neutral arm position if one aims to maximise muscle hypertrophy of the triceps brachii or to prevent atrophy of this muscle.
Topics: Adult; Humans; Elbow; Elbow Joint; Muscle, Skeletal; Resistance Training; Hypertrophy
PubMed: 35819335
DOI: 10.1080/17461391.2022.2100279 -
Scientific Reports Jun 2023Aerobic training (AT) is suggested to be an effective anti-aging strategy for skin aging. However, the respective effects of resistance training (RT) have not been...
Aerobic training (AT) is suggested to be an effective anti-aging strategy for skin aging. However, the respective effects of resistance training (RT) have not been studied. Therefore, we compared the effects of AT and RT on skin aging in a 16-week intervention in 61 healthy sedentary middle-aged Japanese women. Data from 56 women were available for analysis. Both interventions significantly improved skin elasticity and upper dermal structure, and RT also improved dermal thickness. After the training intervention, expression of dermal extracellular matrix-related genes was increased in normal human primary dermal fibroblasts. AT and RT had different effects on circulating levels of factors, such as cytokines, hormones in serum, and metabolites, and RT increased dermal biglycan (BGN). To our knowledge, this is the first report to show different effects of AT and RT on skin aging and identify the key factors involved in RT-induced skin rejuvenation.
Topics: Middle Aged; Humans; Female; Skin Aging; Resistance Training; Skin; Extracellular Matrix; Aging; Fibroblasts
PubMed: 37353523
DOI: 10.1038/s41598-023-37207-9