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The use of hormone replacement and myostatin-based therapies in clinical trials – aimed at promoting muscle hypertrophy – has not resulted in notable advancements in muscle strength or functional performance. The decline in sex hormones that occurs with aging is closely tied to the development of sarcopenia. However, the potential adverse effects of sex hormone replacement therapy outweigh its modest advantages in mitigating muscle aging. There is no conclusive association between circulating myostatin level and muscle aging, and myostatin-based therapy does not affect muscle aging. While effective in promoting muscle growth, hypertrophic signaling compromises muscle protein quality control, exacerbating age-related muscle dysfunction. An alternative intervention to refine mechanistic target of rapamycin (mTOR) functions is proposed to benefit muscle health in the elderly. A healthy lifespan relies on independent living, in which active skeletal muscle is a critical element. The cost of not recognizing and acting earlier on unhealthy or aging muscle could be detrimental, since muscular weakness is inversely associated with all-cause mortality. Sarcopenia is characterized by a decline in skeletal muscle mass and strength and is associated with aging. Exercise is the only effective therapy to delay sarcopenia development and improve muscle health in older adults. Although numerous interventions have been proposed to reduce sarcopenia, none has yet succeeded in clinical trials. This review evaluates the biological gap between recent clinical trials targeting sarcopenia and the preclinical studies on which they are based, and suggests an alternative approach to bridge the discrepancy. [ABSTRACT FROM AUTHOR]

Simple Summary: In fish farming, protein is the most expensive macronutrient in the diet. Research on the physiology of fish nutrition has focused on the relationships between nutrient intake and animal development and metabolism. The dynamics of protein metabolism are influenced by the body's nutrient needs and dietary protein and energy intake. The Amazonian Pintado, a crossbred hybrid of Pseudoplatystoma reticulatum × Leiarius marmoratus, is farmed due to its growth rate, feed conversion efficiency, carcass yield, and absence of intramuscular bones. This study aimed to evaluate the effects of dietary digestible protein levels on muscle growth dynamics and oxidative stress in the white muscle of Amazonian Pintado. The results revealed that high dietary levels of digestible protein, despite increasing protein and free amino acid concentrations in the muscle, restrict muscle hypertrophy and increase tissue exposure to oxidative damage in Amazonian Pintado farming. This study aimed to evaluate the effects of dietary digestible protein levels on the growth dynamics and oxidative stress status of white muscle fibers in Amazonian Pintado (Pseudoplatystoma reticulatum × Leiarius marmoratus). Four hundred and fifty-five juveniles of Amazonian Pintado were fed diets containing varying digestible protein levels (225, 250, 275, 300, 325, 350, or 375 g kg−1) for 75 days. At the end of the experiment, the fish were fasted for 24 h, anesthetized, and euthanized to obtain muscle samples. The linear and quadratic effects of dietary digestible protein levels on white muscle fiber diameter, metabolite concentrations, and oxidative stress were assessed. The results revealed that increasing dietary digestible protein levels linearly raised the concentrations of free amino acids and total proteins in muscle tissue but also led to elevated levels of TBARS, indicating increased oxidative stress. Notably, the average area of muscle fibers with a cell area greater than 1133 µm2 decreased, reflecting restricted muscle hypertrophy, whereas glycogen and glucose levels also declined. These findings suggest that although high dietary digestible protein enhances protein and free amino acid concentrations in muscle tissue, it may compromise muscle hypertrophy and increase oxidative damage in Amazonian Pintado, underscoring the complexity of optimizing diet formulation. [ABSTRACT FROM AUTHOR]

Introduction: Increases in skeletal muscle size occur in response to prolonged exposure to resistance training that is typically ascribed to increased muscle fiber size. Whether muscle fiber number also changes remains controversial, and a paucity of data exists about myofibrillar structure. This cross-sectional study compared muscle fiber 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 magnetic resonance imaging in 16 LRT (5.9 ± 3.5 yr’ experience) and 13 UNT males. A muscle biopsy was taken from the biceps brachii to measure muscle fiber area, myofibril area, and myosin spacing. Muscle fiber number, and myofibril number in total and per fiber were estimated by dividing ACSAmax by muscle fiber area or myofibril area, and muscle fiber area by myofibril area, respectively. Results: Compared with UNT, LRT individuals had greater ACSAmax (+70%, P < 0.001), fiber area (+29%, P = 0.028), fiber number (+34%, P = 0.013), and myofibril number per fiber (+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 toward smaller myofibril area (−16%, P = 0.074). ACSAmax was positively correlated with fiber area (r = 0.526), fiber number (r = 0.445), and myofibril number (in total r = 0.873 and per fiber 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 fibers in cross-section and larger muscle fibers, which contained substantially more total myofibrils and more packed myofilaments than UNT participants, suggesting plasticity of muscle ultrastructure. [ABSTRACT FROM AUTHOR]

We aimed to compare the effects of periodic resistance training (RT) and continuous RT on muscle strength and size. Fifty‐five healthy, untrained participants (age 32 ± 5 years) were randomized to periodic (PRT, n = 20 completed the study, 45% females) or continuous (CRT, n = 22 completed the study, 45% females) groups. PRT completed a 10‐week RT, a 10‐week detraining, and a second identical 10‐week RT. CRT began with a 10‐week non‐RT, followed by a 20‐week RT. RT included twice‐weekly supervised whole‐body RT sessions. Leg press (LP) and biceps curl (BC) one repetition maximum (1RM), countermovement jump (CMJ) height, muscle cross‐sectional area (CSA) of vastus lateralis (VL), and biceps brachii (BB) using ultrasound imaging were measured twice at the beginning and every fifth week during the intervention. Both groups increased (p < 0.001) 1RM in LP and BC, CSA in VL and BB, and CMJ height with no differences between the groups. In PRT, 1RM in LP and BC, CSA in VL and BB, and CMJ height decreased during detraining (p < 0.05). During the first 5 weeks of retraining in PRT, increases in LP 1RM, and VL and BB CSA were greater than in CRT during Weeks 10–15 of their CRT (p < 0.01). PRT and CTR ended up in similar postintervention adaptations, as decreased muscle strength and size during detraining in PRT regained rapidly during retraining. Our results therefore suggest that trainees should not be too concerned about occasional short‐term training breaks in their daily lives when it comes to lifelong strength training. Trial Registration:ClinicalTrials.gov identifier: NCT05553769 [ABSTRACT FROM AUTHOR]

Skeletal muscle mass plays a pivotal role in metabolic function, but conditions such as bed rest or injury often render resistance training impractical. The beta2‐adrenergic receptor has been highlighted as a potential target to promote muscle hypertrophy and treat atrophic conditions. Here, we investigate the proteomic changes associated with beta2‐adrenergic‐mediated muscle hypertrophy, using resistance training as a hypertrophic comparator. We utilize MS‐based proteomics to map skeletal muscle proteome remodeling in response to beta2‐adrenergic stimulation or resistance training as well as cell model validation. We report that beta2‐adrenergic stimulation mimics multiple features of resistance training in proteome‐wide remodeling, comprising systematic upregulation of ribosomal subunits and concomitant downregulation of mitochondrial proteins. Approximately 20% of proteins were regulated in both conditions, comprising proteins involved in steroid metabolism (AKR1C1, AKR1C2, AKRC1C3), protein‐folding (SERPINB1), and extracellular matrix organization (COL1A1, COL1A2). Among overall most significantly upregulated proteins were kelch‐like family members (KLHL) 40 and 41. In follow‐up experiments, we identify KLHL41 as having novel implications for beta2‐adrenergic‐mediated muscle hypertrophy. Treating C2C12 cells with beta2‐agonist for 96 h increased myotube diameter by 48% (p < 0.001). This anabolic effect was abolished by prior knockdown of KLHL41. Using siRNA, KLHL41 abundance was decreased by 60%, and the anabolic response to beta2‐agonist was diminished (+ 15%, i.e., greater in the presence of KLHL41, knock‐down × treatment: p = 0.004). In conclusion, protein‐wide remodeling induced by beta2‐adrenergic stimulation mimics multiple features of resistance training, and thus the beta2‐adrenergic receptor may be a target with therapeutic potential in the treatment of muscle wasting conditions without imposing mechanical load. [ABSTRACT FROM AUTHOR]

Introduction: When you perform an exercise to only one joint of your body, a change in the axis line can have significant effects on the extent that agonist muscle is activated. In this review, the authors critically present an analysis of potential injury risks by certain triceps brachii exercises. Hand positioning (pronation/supination) was suggested to influence activation of the long, medial and lateral heads of the Triceps Brachii. Yet, assessing the medial head activation with surface electromyography is still impossible as it cannot be recorded because of its anatomical situation. Secondly, some exercises can strain or damage passive tissues that are hard to be felt and thus will not alarm the exception but may deteriorate as time goes by until an injury is generated. Materials and Methods: The aim of this review to illustrate beneficial and contrary hand position changes, during different triceps brachii exercises with appropirate health aspects. This type of analysis aims to maximize congruence and coaxial alignment across joints, taking into account any overloading effects on certain ligaments which could potentially increase injury risk. Results: There is currently limited evidence in the literature supporting that one grip hand (pronated or supinated) target certain heads of the triceps brachii either more than other heads. However, a neutral hand grip might reduce injury risk and provide the most stability. As a result this positioning might additionally have advantage Conclusions: The single-joint triceps brachii strengthening exercises were categorized into three levels (good, moderate to good and poor) according joint safety and efficacy in this review. Nevertheless, the analysis did not account for stretch placement through exercises which may have stronger potential to increase hypertrophy. [ABSTRACT FROM AUTHOR]

The aim of this investigation was to study how autoregulation impacted training volume, performance, and muscle size on a 10-week mixed session periodized (MSP) resistance training program, characterized by the inclusion of different training foci in each session. Twenty-four resistance trained men were assigned to an autoregulated mixed session periodized (AMSP group; n = 13; age = 26.2 ± 4.9 y; body mass = 82.0 ± 8.7 kg; height = 176.8 ± 6.0 cm) or into an MSP (n = 11; age = 24.0 ± 2.6; body mass = 81.3 ± 10.5 kg; height = 174.0 ± 5.4 cm) group. Subjects in both groups trained 5 days per week for 10 weeks and performed the same exercises. The difference between the groups consisted in the use of a perceived recovery-based scale to adjust the individual training volume in the AMSP program. Maximal strength (bench press and squat 1 repetition maximum), power (bench press throw and countermovement jump), and muscle architecture (muscle thickness [MT] of biceps brachii, trapezius, vastus lateralis and vastus medialis) were collected before and after the 10-week training period. In addition, training volume and session load were calculated for each training session. A higher total training volume (p < 0.001) was seen in AMSP program compared with MSP program, but no differences (p > 0.05) were noted in the average session load. No significant differences between the groups were detected for MT of both upper-body and lower-body muscles (p's > 0.05) and lean body mass (p = 0.681). No significant differences between the groups were detected for any strength or power measurements. Results of this study indicate that a perceived recovery-based AMSP training program was not more effective than an MSP training program for increasing muscle size and performance in resistance trained men. [ABSTRACT FROM AUTHOR]

Purpose: Resistance training (RT) induces muscle growth at varying rates across RT phases, and evidence suggests that the muscle-molecular responses to training bouts become refined or attenuated in the trained state. This study examined how proteolysis-related biomarkers and extracellular matrix (ECM) remodeling factors respond to a bout of RT in the untrained (UT) and trained (T) state. Methods: Participants (19 women and 19 men) underwent 10 weeks of RT. Biopsies of vastus lateralis were collected before and after (24 h) the first (UT) and last (T) sessions. Vastus lateralis cross-sectional area (CSA) was assessed before and after the experimental period. Results: There were increases in muscle and type II fiber CSAs. In both the UT and T states, calpain activity was upregulated and calpain-1/-2 protein expression was downregulated from Pre to 24 h. Calpain-2 was higher in the T state. Proteasome activity and 20S proteasome protein expression were upregulated from Pre to 24 h in both the UT and T. However, proteasome activity levels were lower in the T state. The expression of poly-ubiquitinated proteins was unchanged. MMP activity was downregulated, and MMP-9 protein expression was elevated from Pre to 24 h in UT and T. Although MMP-14 protein expression was acutely unchanged, this marker was lower in T state. TIMP-1 protein levels were reduced Pre to 24 h in UT and T, while TIMP-2 protein levels were unchanged. Conclusion: Our results are the first to show that RT does not attenuate the acute-induced response of proteolysis and ECM remodeling-related biomarkers. [ABSTRACT FROM AUTHOR]

Abstract Background Glycative stress, characterized by the formation and accumulation of advanced glycation end products (AGEs) associated with protein glycation reactions, has been implicated in inducing a decline of muscle function. Although the inverse correlation between glycative stress and muscle mass and strength has been demonstrated, the underlying molecular mechanisms are not fully understood. This study aimed to elucidate how glycative stress affects the skeletal muscle, particularly the adaptive muscle response to hypertrophic stimuli and its molecular mechanism. Methods Male C57BL/6NCr mice were randomly divided into the following two groups: the bovine serum albumin (BSA)‐treated and AGE‐treated groups. Mice in the AGE‐treated group were intraperitoneally administered AGEs (0.5 mg/g) once daily, whereas those in the BSA‐treated group received an equal amount of BSA (0.5 mg/g) as the vehicle control. After 7 days of continuous administration, the right leg plantaris muscle of mice in each group underwent functional overload treatment by synergist ablation for 7 days to induce muscle hypertrophy. In in vitro studies, cultured C2C12 myocytes were treated with AGEs (1 mg/mL) to examine cell adhesion and cell membrane permeability. Results Continuous AGE administration increased the levels of fluorescent AGEs, Nε‐(carboxymethyl) lysine, and methylglyoxal‐derived hydroimidazolone‐1 in both plasma and skeletal muscle. Plantaris muscle weight, muscle fibre cross‐sectional area, protein synthesis rate, and the number of myonuclei increased with functional overload in both groups; however, the increase was significantly reduced by AGE treatment. Some muscles of AGE‐treated mice were destroyed by functional overload. Proteomic analysis was performed to explore the mechanisms of muscle hypertrophy suppression and myofibre destruction by AGEs. When principal component analysis was performed on 4659 data obtained by proteomic analysis, AGE treatment was observed to affect protein expression only in functionally overloaded muscles. Enrichment analysis of the 436 proteins extracted using the K‐means method further identified a group of proteins involved in cell adhesion. Consistent with this finding, dystrophin–glycoprotein complex proteins and cell adhesion‐related proteins were confirmed to increase with functional overload; however, this was attenuated by AGE treatment. Additionally, the treatment of C2C12 muscle cells with AGEs inhibited their ability to adhere and increased cell membrane permeability. Conclusions This study indicates that glycative stress may be a novel pathogenic factor in skeletal muscle dysfunctions by causing loss of membrane integrity and preventing muscle mass gain.

Many athletes desire weight gain, ideally as lean body mass (LBM), to improve athletic performance. These athletes are commonly encouraged to increase energy intake by ~500 kcal·d-1 with emphasis on adequate protein, carbohydrate, and judicious inclusion of healthy fatcontaining energy-dense foods, such as peanuts/peanut butter, along with rigorous resistance training (RT). These guidelines target gains of ~0.23 kg·wk-1. However, little is known about the efficacy of such regimens. Purpose: The purpose of this study is to evaluate the outcomes of a 10-wk diet and exercise regimen designed to promote healthy weight gain with excess energy from peanut-containing or highcarbohydrate foods. Methods: Nineteen male and 13 female athletes were randomly assigned to receive an additional 500 kcal·d-1 above typical intake through provision of either peanut-based whole foods/snacks (PNT group) or a similar, high-carbohydrate, peanut-free snack (CHO group) alongwith supervised, whole-body RT (3 d·wk-1 for 60-120 min). Body composition was assessed by dual-energyx-ray absorptiometry at baseline and postintervention. Results: Total bodymass (TBM) increased 2.2 ± 1.3 kg with 1.5 ± 1.1 kg as LBMafter week 10. The PNT group (n = 16; 27 ± 7 yr; 10 men, 6 women) gained less TBM than the CHO group (n = 16; 23 ± 3 yr; 9 men, 7 women) (1.6 ± 1.1 kg vs 2.7 ± 1.2 kg, respectively, P = 0.007) with no differences in LBM (1.2 ± 1.1 kg vs 1.9 ± 1.0 kg, P= 0.136). Conclusions: These results suggest that the addition of 500 kcal·d-1 from whole foods/snacks in combination with a rigorous RT program promotes a similar weight gain of ~0.22 kg·wk-1, primarily as LBM, over 10 wk in both male and female athletes. However, snack macronutrient content may impact the effectiveness of this regimen. [ABSTRACT FROM AUTHOR]

Walking is a low-impact form of physical activity feasible, acceptable, and safe for load-compromised individuals, such as older adults. Options available to increase the potency of this exercise exerto promote training adaptations are generally limited to manipulation of speed, gradient, and duration. How-Comever, emerging studies have suggested that blood flow restriction BFR) combined with walking is a method that can accentuate training-Emerginduced adaptations compared with walking alone. This narrative review aimed to examine the effectiveness and safety of BFR walking in older adults according to the existing literature. Of the limited evidence available on this topic, it appears that BFR walking compared with walking alone can induce significant increases in muscular hypertrophy and strength. Therefore, implementing BFR walking may be a feasible and safe option for older adults to enhance the effectiveness of their walking interventions, at least from a musculoskeletal perspective. [ABSTRACT FROM AUTHOR]

Resistance training or strength training has become one of the most popular forms of exercise, because it is the only method capable of improving physical fitness and increasing muscle mass simultaneously. Among the variables of training, the relationship between intensity and volume has been extensively addressed to enhance exercise-induced muscular hypertrophy. For many, mechanical stress is seen as a factor of greater relevance and, because high loads promote greater crossmechanical tension and high intensities subare traditionally used to increase muscle mass. However, evidence has shown greater safety and similar results through training based on lower intensities and increased training volume. Thus, this narrative review aimed to search the current literature for evidence on using different training loads to promote muscle hypertrophy. An extensive nonsystematic literature review was conducted in the PubMed, Google Scholar and Scielo databases. It was possible to conclude that the use of high and low intensity promotes similar results in muscle hypertrophy in all groups, leading to the belief that there is greater safety and adherence to the use of lower intensities compared with close effort to concentric failure. [ABSTRACT FROM AUTHOR]

The greater muscle fiber cross-sectional area (CSA) is associated with greater skeletal muscle mass and strength, whereas muscle fiber atrophy is considered a major feature of sarcopenia. Muscle fiber size is a polygenic trait influenced by both environmental and genetic factors. However, the genetic variants underlying inter-individual differences in muscle fiber size remain largely unknown. The aim of our study was to determine whether 1535 genetic variants previously identified in a genome-wide association study of appendicular lean mass are associated with the CSA of fast-twitch muscle fibers (which better predict muscle strength) in the m. vastus lateralis of 148 physically active individuals (19 power-trained and 28 endurance-trained females, age 28.0 ± 1.1; 28 power-trained and 73 endurance-trained males, age 31.1 ± 0.8). Fifty-seven single-nucleotide polymorphisms (SNPs) were identified as having an association with muscle fiber size (p < 0.05). Of these 57 SNPs, 31 variants were also associated with handgrip strength in the UK Biobank cohort (n = 359,729). Furthermore, using East Asian and East European athletic (n = 731) and non-athletic (n = 515) cohorts, we identified 16 SNPs associated with athlete statuses (sprinter, wrestler, strength, and speed–strength athlete) and weightlifting performance. All SNPs had the same direction of association, i.e., the lean mass-increasing allele was positively associated with the CSA of muscle fibers, handgrip strength, weightlifting performance, and power athlete status. In conclusion, we identified 57 genetic variants associated with both appendicular lean mass and fast-twitch muscle fiber size of m. vastus lateralis that may, in part, contribute to a greater predisposition to power sports. [ABSTRACT FROM AUTHOR]

Key Clinical Message: Botulinum toxin (BTX) injection can be an effective treatment for persistent pain and functional impairment associated with hypertrophy of the first dorsal interosseous muscle. It offers a non‐surgical and minimally invasive alternative for those who have failed conservative treatment, showcasing the therapeutic promise of BTX for addressing similar musculoskeletal conditions. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the effect of two long-term reduced concurrent training modalities, in which participants performed one training session every either 7 or 14 days, after 12 weeks of systematic concurrent resistance and aerobic training, on lower extremities' muscle strength, power, and morphology in young females. After the 12-week training period, participants were assigned into three groups and performed either one training session every 7 days (G7) or once every 14 days (G14), or detraining (GD), for 12 weeks, followed by 12 additional weeks of detraining. The following were measured before, after the systematic training period, after the end of the reduced training frequency period, and after the end of complete detraining: body composition, leg press 1-RM, countermovement jump, quadriceps cross-sectional area (CSA), vastus lateralis muscle architecture, and maximum aerobic power. Performance and muscle mass increased after the initial 12-week training period. Thereafter, leg press 1-RM, quadriceps CSA, and aerobic power remained unchanged in the G7 group, but decreased in G14 (−4.4 ± 3.5%; −5.9 ± 1.8%; −9.0 ± 7.8%, respectively, p < 0.05), maintaining 95.6 ± 3.5%, 94.1 ± 1.8%, and 91.0 ± 7.8% of the initial training adaptations, respectively. In conclusion, performing one training session every 2 weeks for 3 months may preserve 90 to 95% of the muscle mass/strength and aerobic power adaptations achieved with systematic concurrent training. [ABSTRACT FROM AUTHOR]

Osteoarthritis is associated with high risks of sarcopenia in older populations. Exercise interventions are promising treatments for musculoskeletal impairments in knee osteoarthritis (KOA). The purpose of this study was to identify the comparative effects of exercise monotherapy and its adjunct treatments on muscle volume and serum inflammation for older individuals with KOA. A literature search in the electronic databases was comprehensively performed from this study's inception until April 2024 to identify relevant randomized controlled trials (RCTs) that reported muscle morphology and inflammation outcomes after exercise. The included RCTs were analyzed through a frequentist network meta-analysis (NMA). The standard mean difference (SMD) with a 95% confidence interval was estimated for treatment effects on muscle morphology and inflammation biomarkers. The relative effects on each main outcome among all treatment arms were compared using surface under the cumulative ranking (SUCRA) scores. The certainty of evidence (CoE) was assessed by the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) ranking system. Probable moderators of the treatment efficacy were investigated by network meta-regression analysis. This study included 52 RCTs (4255 patients) for NMA. Among the 27 identified treatment arms, isokinetic training plus physical modality as well as low-load resistance training plus blood-flow restriction yielded the most optimal treatment for inflammation reduction (−1.89; SUCRA = 0.97; CoE = high) and muscle hypertrophy (SMD = 1.28; SUCRA = 0.94; CoE = high). The patient's age (β = −0.73), the intervention time (β = −0.45), and the follow-up duration (β = −0.47) were identified as significant determinants of treatment efficacy on muscle hypertrophy. Exercise therapy in combination with noninvasive agents exert additional effects on inflammation reduction and muscle hypertrophy compared to its corresponding monotherapies for the KOA population. However, such treatment efficacy is likely moderated by the patient's age, the intervention time, and the follow-up duration. [ABSTRACT FROM AUTHOR]

Multiple intramuscular variables have been proposed to explain the high variability in resistance training induced muscle hypertrophy across humans. This study investigated if muscular androgen receptor (AR), estrogen receptor α (ERα) and β (ERβ) content and fiber capillarization are associated with fiber and whole‐muscle hypertrophy after chronic resistance training. Male (n = 11) and female (n = 10) resistance training novices (22.1 ± 2.2 years) trained their knee extensors 3×/week for 10 weeks. Vastus lateralis biopsies were taken at baseline and post the training period to determine changes in fiber type specific cross‐sectional area (CSA) and fiber capillarization by immunohistochemistry and, intramuscular AR, ERα and ERβ content by Western blotting. Vastus lateralis volume was quantified by MRI‐based 3D segmentation. Vastus lateralis muscle volume significantly increased over the training period (+7.22%; range: −1.82 to +18.8%, p < 0.0001) but no changes occurred in all fiber (+1.64%; range: −21 to +34%, p = 0.869), type I fiber (+1.33%; range: −24 to +41%, p = 0.952) and type II fiber CSA (+2.19%; range: −23 to +29%, p = 0.838). However, wide inter‐individual ranges were found. Resistance training increased the protein expression of ERα but not ERβ and AR, and the increase in ERα content was positively related to changes in fiber CSA. Only for the type II fibers, the baseline capillary‐to‐fiber‐perimeter index was positively related to type II fiber hypertrophy but not to whole muscle responsiveness. In conclusion, an upregulation of ERα content and an adequate initial fiber capillarization may be contributing factors implicated in muscle fiber hypertrophy responsiveness after chronic resistance training. [ABSTRACT FROM AUTHOR]

Purpose: Lactate has recently been the focus of research for its hypertrophic effects. The aim of this study was to introduce lacto-resistance exercise, emphasizing lactate production during exercise, and compare its hypertrophic effects with traditional resistance training in professional bodybuilders. Methods: Twenty-four participants performed traditional and lacto-resistance exercises in two separate sessions. Blood lactate concentrations and metabolic stress, estimated by plasma ammonia levels (PAL) and muscle oxygen saturation (SmO2), were compared between two exercises. The participants were then matched based on their rectus femoris muscle cross-sectional area (RFCSA) and allocated to the control (C, n = 8), traditional resistance training (TRT, n = 8), and lacto-resistance training (La-RT, n = 8) groups. The TRT and La-RT groups completed their own four-week resistance training program and RFCSA and one-repetition maximum (1RM) changes were compared between the groups. Results: The average changes in blood lactate concentrations (1.38-fold), SmO2 (0.86-fold), and PAL (1.16-fold) from rest to post-exercise were significantly higher in the lacto-resistance exercise compared to those obtained following traditional resistance exercise (all P < 0.05). After four weeks of resistance training, the values of 1RM squat (TRT: 1.14-fold, P < 0.05; La-RT: 1.2-fold induction, P < 0.05) and 1RM leg press (TRT: 1.11-fold, P < 0.05; La-RT: 1.20-fold, P < 0.05) were significantly higher than in the C group. Post-training values of RFCSA in La-RT group were significantly higher than in the C group (1.22-fold, P < 0.01), but not in the TRT group. Conclusion: Lacto-resistance training, therefore, is a useful hypertrophy-oriented exercise, even for professional athletes who hardly experience muscle mass gains with traditional resistance training. [ABSTRACT FROM AUTHOR]

Lean body mass (LBM) is correlated with powerlifting performance in athletes competing in different bodyweight classes. However, it remains unknown whether changes in LBM are correlated with performance changes in powerlifters preparing for a competition. The aim of this study was to investigate the changes in LBM and performance in powerlifters preparing for a competition. Eight male powerlifters (age 31.7 ± 9.8 years, height 1.77 ± 0.06 m, weight 99.2 ± 14.6 kg) and three female powerlifters (age 32.7 ± 16.3 years, height 1.54 ± 0.06 m, weight 66.6 ± 20.9 kg) participated in the study. The athletes followed individualized periodized training programs for 12 weeks, aiming to maximize their performance for the national championship. The maximum strength (1-RM) in the squat, bench press, and deadlift, body composition, handgrip strength, anaerobic power, quadriceps' cross-sectional area and vastus lateralis muscle architecture were measured before and after the training period. Significant increases were found after the training period in the squat (5.8 ± 7.0%, p < 0.05), bench press (4.9 ± 9.8%, p = 0.05) and deadlift (8.3 ± 16.7%, p < 0.05). Significant correlations were found between the 1-RM and LBM before and after the training period (r > 0.75, p < 0.05). The changes in the 1-RM after the training intervention correlated with the changes in the total LBM (p < 0.05). These results suggest that individual changes in LBM due to systematic resistance training for a competition may dictate increases in the 1-RM strength in powerlifters. [ABSTRACT FROM AUTHOR]

Introduction and Objective: Alcohol is a prevalent substance in many cultures, often associated with socializing, relaxation, and even post-exercise rituals. Despite its widespread use, the effects of alcohol on muscle recovery and hypertrophy are not well understood by the general public. Emerging research suggests that alcohol may have negative health effects on these factors. Understanding the interaction between alcohol consumption and resistance training is crucial for athletes and individuals aiming to optimize their fitness outcomes. The main aim of this article is to show clinicians, patients and, above all, athletes, the negative effects of alcohol on training and leading a healthy lifestyle. Review and Methods: Review and summary of studies and meta-analysis of studies available in open-source format on Google Scholar, Web of Science and PubMed. Abbreviated Description of the State of Knowledge: Resistance training is a proven method for increasing muscle mass and strength through the process of hypertrophy, where muscle protein synthesis (MPS) exceeds muscle protein breakdown (MPB). The mechanistic/mammalian target of rapamycin (mTOR) signaling pathway plays a key role in regulating MPS and hypertrophy. Summary: Alcohol has been shown to impair muscle protein synthesis, primarily through its negative effects on the mTOR signaling pathway, which is crucial for muscle growth. Additionally, alcohol disrupts sleep quality, further hindering recovery and performance.

Abstract Background Gut microbiota and their metabolites play a regulatory role in skeletal muscle growth and development, which be known as gut-muscle axis. 3-phenylpropionic acid (3-PPA), a metabolite produced by colonic microorganisms from phenylalanine in the gut, presents in large quantities in the blood circulation. But few study revealed its function in skeletal muscle development. Results Here, we demonstrated the beneficial effects of 3-PPA on muscle mass increase and myotubes hypertrophy both in vivo and vitro. Further, we discovered the 3-PPA effectively inhibited protein degradation and promoted protein acetylation in C2C12 and chick embryo primary skeletal muscle myotubes. Mechanistically, we supported that 3-PPA reduced NAD+ synthesis and subsequently suppressed tricarboxylic acid cycle and the mRNA expression of SIRT1/3, thus promoting the acetylation of total protein and Foxo3. Moreover, 3-PPA may inhibit Foxo3 activity by directly binding. Conclusions This study firstly revealed the effect of 3-PPA on skeletal muscle growth and development, and newly discovered the interaction between 3-PPA and Foxo3/NAD+ which mechanically promote myotubes hypertrophy. These results expand new understanding for the regulation of gut microbiota metabolites on skeletal muscle growth and development.

Primary objective of this study was to examine the interplay between grip strength, a functional marker of hypertrophy, and its connection to the Firmicutes to Bacteroidetes ratio in the gut microbiome. Twenty-five male Wistar rats were divided into five groups using a computerized randomizer: old and young control groups (OC, YC), old resistance training group (OR), old supplement group (OS), and old resistance training combined with supplement group (ORS). Rats in the OR and ORS cohorts underwent eight weeks of ladder-climbing resistance training three times a week, while those in the OS group were given supplements 5 times per week after the intervention. Muscle samples were collected from all rats two days’ post-intervention. FOXO1, BAX, and cytochrome C, were assessed using PCR-real time. Analysis of the data was carried out using one-way ANOVA and post-hoc Tukey testing. The results revealed a decrease in FOXO1 and apoptotic gene expression post-intervention, with a more pronounced reduction observed in the ORS group compared to the other groups (p

Creatine (Cr) supplementation is a well-established strategy to enhance gains in strength, lean body mass, and power from a period of resistance training. However, the effectiveness of creatyl-L-leucine (CLL), a purported Cr amide, is unknown. Therefore, the purpose of this study was to assess the effects of CLL on muscle Cr content. Twenty-nine healthy men (n = 17) and women (n = 12) consumed 5 g/day of either Cr monohydrate (n = 8; 28.5 ± 7.3 years, 172.1 ± 11.0 cm, 76.6 ± 10.7 kg), CLL (n = 11; 29.2 ± 9.3 years, 170.3 ± 10.5 cm, 71.9 ± 14.5 kg), or placebo (n = 10; 30.3 ± 6.9 years, 167.8 ± 9.9 cm, 69.9 ± 11.1 kg) for 14 days in a randomized, double-blind design. Participants completed three bouts of supervised resistance exercise per week. Muscle biopsies were collected before and after the intervention for quantification of muscle Cr. Cr monohydrate supplementation which significantly increased muscle Cr content with 14 days of supplementation. No changes in muscle Cr were observed for the placebo or CLL groups. Cr monohydrate supplementation is an effective strategy to augment muscle Cr content while CLL is not. [ABSTRACT FROM AUTHOR]

Pectoral muscle development is an important economic trait. According to the different essence, muscle development can be divided into 2 processes: embryonic muscle fiber generation and postnatal muscle fiber hypertrophy, and postnatal muscle fiber hypertrophy has a greater impact on muscle development than the number of muscle fibers formed during the embryonic phase in poultry. However, the underlying mechanisms regulating the hypertrophy of goose pectoral muscles have not been elucidated. Therefore, the purpose of the present study was to conduct transcriptome sequencing in pectoral muscles of both Landes (LD) and Sichuan White (SW) geese at 6, 10, and 30 weeks of age to reveal the molecular mechanisms regulating pectoral muscle hypertrophy through intra-breed and inter-breed bioinformatics analyses. Phenotypically, the pectoral muscle weight/index of LD and SW geese increased from 6 to 30 weeks of age, and except for the pectoral muscle index at 10 weeks of age (P = 0.962), at the same age, the pectoral muscle weight/index of LD geese were significantly higher than that of SW geese (P < 0.05). In transcriptional regulation, intra-breed bioinformatics analysis identified 3331 genes whose expression levels were opposite to the trend of pectoral muscle hypertrophy both in LD and SW geese, and the 3331 genes were mainly enriched into abundant KEGG pathways related to lipid metabolism, proliferation/apoptosis, and immune response. Moreover, 23 genes (including SLC2A10, TNFRSF1A, PRKAA1, SLC27A4, ITGB2, THY1, RHOA, MYL10, ACTB, PRKCB, PIK3R2, RAC2, DMD, LATS2, YAP1, WWTR1, SMAD7, CTGF, FGF1, AXIN2, GLI2, ID2, and CCND2) who were enriched in 6 crosstalk pathways named viral myocarditis, insulin resistance, sphingolipid signaling pathway, hippo signaling pathway, chemokine signaling pathway, and leukocyte transendothelial migration were identified as the key candidate genes regulating the hypertrophy of goose pectoral muscles. In inter-breed bioinformatics analysis, abundant different expression genes (DEGs) related to lipid metabolism, immune response, and proliferation/apoptosis were identified between LD and SW geese too, and compared with SW geese, the expression level of MYL10 in LD geese was lower, while the expression levels of GLI2/CTGF/SMAD7 in LD geese were higher. These results suggested that the hypertrophy of goose pectoral muscles might be achieved through more lipid deposition and less leukocyte infiltration to promote the proliferation of cells within the muscles, and the low expression of MYL10 and high expressions of GLI2/CTGF/SMAD7 might the keys to induce the pectoral muscle hypertrophy of LD geese from 6 to 30 weeks of age over that of SW geese. All data the present study obtained will provide new insights into the molecular mechanisms regulating the hypertrophy of goose pectoral muscles.

Unilateral hypertrophy of the tensor fasciae latae (TFL) is an uncommon radiologic finding that may present as a palpable soft tissue mass in the thigh. Accurate radiologic diagnosis can circumvent unnecessary biopsy for this benign finding. We report two cases of unilateral hypertrophy of tensor fasciae latae muscles, both of which presented as a proximal thigh mass. We provide examples of sonographic, computed tomography (CT), and magnetic resonance imaging (MRI) features.

Background: Gut microbiota and their metabolites play a regulatory role in skeletal muscle growth and development, which be known as gut-muscle axis. 3-phenylpropionic acid (3-PPA), a metabolite produced by colonic microorganisms from phenylalanine in the gut, presents in large quantities in the blood circulation. But few study revealed its function in skeletal muscle development. Results: Here, we demonstrated the beneficial effects of 3-PPA on muscle mass increase and myotubes hypertrophy both in vivo and vitro. Further, we discovered the 3-PPA effectively inhibited protein degradation and promoted protein acetylation in C2C12 and chick embryo primary skeletal muscle myotubes. Mechanistically, we supported that 3-PPA reduced NAD+ synthesis and subsequently suppressed tricarboxylic acid cycle and the mRNA expression of SIRT1/3, thus promoting the acetylation of total protein and Foxo3. Moreover, 3-PPA may inhibit Foxo3 activity by directly binding. Conclusions: This study firstly revealed the effect of 3-PPA on skeletal muscle growth and development, and newly discovered the interaction between 3-PPA and Foxo3/NAD+ which mechanically promote myotubes hypertrophy. These results expand new understanding for the regulation of gut microbiota metabolites on skeletal muscle growth and development. [ABSTRACT FROM AUTHOR]

Background and Aim: Given the significant relationship between muscle cross-sectional area (CSA) and muscle strength, the primary objective for athletes involved in resistance training is to enhance muscle mass and strength. Proper manipulation of training variables such as intensity, volume, frequency, exercise selection, rest interval, and tempo are essential for maximizing exercise-induced muscle hypertrophy. The present study examined the effects of weekly variations in resistance training on muscle thickness (MT) and strength adaptations in young men. Methods: This research included 30 participants (age: 21.37 ± 1.37 years, height: 174.48 ± 3.34 cm, weight: 72.13 ± 3.45 kg). They were randomly assigned into varying training groups whose training routine changed every week (VAR) or traditional training groups that did not change (TRAD) for ten weeks. For the VAR group training weeks were labeled as adaptation, metabolic stress, mechanical tension, muscle damage, and de-load week 2 cycles of this change occurred through the training intervention for them, but the TRAD group training routine did not change through the study. Results: Both the TRAD and VAR groups showed significant increases in the MT of the biceps brachii muscle (BB) (VAR: P = 0.001; TRAD: P = 0.007), significant differences were observed between groups (P = 0.012). Vastus lateralis (VL) MT increased significantly in both groups (P = 0.001), no significant difference was observed between the two groups (P>0.05). Among the groups, lean body mass (LBM) increased significantly (P = 0.001), TRAD group showed a significant decrease in body fat (P = 0.49), there was no significant change in BMI of both groups (P>0.05). Both groups showed significant increase in bench press and back squat 1-RM strength test (P = 0.001). Back squat showed a trivial non-significant difference between the groups (P = 0.072). Conclusion: The results showed that changing resistance training methods weekly was more effective than traditional resistance training for biceps hypertrophy. Nevertheless, the effects of VAR and TRAD exercises are similar in the case of the latissimus dorsi muscle. [ABSTRACT FROM AUTHOR]

To systematically review and analyze the effects of resistance-based exercise programs and potential moderators of change in body fat percentage, whole-body fat and lean mass, muscle hypertrophy, muscle strength, and muscle power/rapid force in healthy young women (between 18 and 35 years). A systematic search was undertaken in 7 databases from inception to May 2022. Eligible randomized controlled trials examined the effects of resistance-based exercise programs on outcomes of interest in healthy young women. Meta-analysis was undertaken with a 3-level mixed-effects model. Associations between standardized mean difference (SMD) and potential moderators (number of sessions, weekly volume, and intensity) were tested by meta-regression models. Statistical significance was set at an a level of 0.05, whereas an a level of 0.05-0.10 was also considered for potential moderators of resistance training effects. Forty articles (n = 1,312) were included. Resistance-based exercise programs resulted in a significant improvement of 0.4 SMD (95% confidence intervals [95% CI]: 0.2 to 0.5, p < 0.001) in lean mass/muscle hypertrophy and 1.2 SMD (95% CI: 0.9 to 1.5, p < 0.001) in muscle strength. A higher number of sessions was associated with changes in lean mass/muscle hypertrophy (β = 0.01 ± 0.00, p = 0.009), whereas a higher weekly volume approached statistical significance to moderate changes in muscle strength (β = 0.01 ± 0.01, p = 0.053). Body fat percentage (-0.4 SMD, 95% CI: -0.6 to -0.1, p = 0.006) and muscle power/rapid force (0.6 SMD, 95% CI: 0.2 to 1.1, p = 0.011) were significantly improved. In conclusion, a higher resistance training volume was associated with greater improvements in lean mass/muscle hypertrophy, muscle strength, and body fat percentage, whereas muscle power/rapid force improvements were observed irrespective of prescription characteristics. These findings may help in designing resistance training programs for muscle hypertrophy, strength and power, and body fat percentage in healthy women. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the effect of progressively adding sets for the lower limb every 2 wk versus performing a constant set volume in resistance-trained males. Methods: Thirty-one resistance-trained males (age = 24.4 ± 2.9 yr, height = 175.5 ± 6.5 cm, body mass = 80.1 ± 9.4 kg, body fat = 14.4% ± 3.1%, resistance training [RT] experience = 5.1 ± 2.2 yr; one-repetition maximum [1RM] barbell back squat: body mass ratio = 1.7 ± 0.1 a.u.) were randomly allocated into a constant group (CG, n = 10), a four-set progression group (4SG, n = 10) or a six-set progression group (6SG, n = 11). After a 2-wk washout period and another 2-wk familiarization period, participants performed a lower-limb training program twice a week for 12 wk. Maximum dynamic strength (1RM) in the barbell back squat, vastus lateralis cross-sectional area, and the sum of lateral thigh muscle thickness at 30%, 50%, and 70% of the femur length were assessed at baseline and after the 12-wk training program. Results: Regarding 1RM, multiple comparisons revealed that 6SG elicited higher muscle strength gains than 4SG (P = 0.002) and CG (P < 0.0001), and 4SG had greater improvements than CG (P = 0.023). Cross-sectional area and sum of lateral thigh muscle thickness showed no between-group differences (P = 0.067 and P = 0.076, respectively). However, an inspection of 95% confidence intervals suggests a potential dose–response relationship, with results appearing to plateau in the higher volume conditions. Conclusions: Our results suggest that progressively adding four or six sets per week every 2 wk elicited greater lower-limb strength in resistance-trained individuals over a 12-wk training period. Although our findings indicate a possible small benefit for higher volume conditions regarding hypertrophic adaptations in this population, the limited certainty of our findings warrants caution. [ABSTRACT FROM AUTHOR]

Aim: We compared muscular metabolic stress during exercise performed at multiple intensities, from very low to moderate, with blood flow restriction (BFR) adjusted by the same work volume. Methods: Twenty‐five healthy young adults performed unilateral plantar flexion at 1 repetition/2 s in a magnetic resonance system. The BFR exercise protocols were as follows: (A) exercise with 10% of one repetition maximum (1‐RM) for 360 s, (B) 15% 1‐RM for 240 s, (C) 20% 1‐RM for 180 s, (D) 30% 1‐RM for 120 s, and (E) 40% 1‐RM for 90 s. All protocols had the same total work volume (load × repetitions = 1800). A high‐intensity protocol at 65% 1‐RM without BFR (60 s) was also performed for comparison. We used 31P‐magnetic resonance spectroscopy to evaluate the muscular metabolic stress in the subjects' calf muscle, defined as decreases in phosphocreatine and intramuscular pH. Results: The phosphocreatine depletion (A: 15.6 ± 0.7, B: 14.8 ± 0.8, C: 15.2 ± 0.6, D: 14.3 ± 0.6, E: 10.9 ± 0.5 mM; no significant difference [ns]) and the intramuscular pH decrease (A: 6.82 ± 0.02, B: 6.84 ± 0.01, C: 6.83 ± 0.02, D: 6.83 ± 0.02, E: 6.77 ± 0.02; ns) at the end of each exercise were similar and greater than those produced by the 65% 1‐RM without BFR. Conclusion: If the total work volumes are equal, the metabolic stress in exercising muscle may reach similar levels at the end of exercise with BFR and could provide similar successful training effects. [ABSTRACT FROM AUTHOR]

Regarding skeletal muscle hypertrophy, resistance training and nutrition, the most often discussed and proposed supplements include proteins. Although, the correct amount, quality, and daily distribution of proteins is of paramount importance for skeletal muscle hypertrophy, there are many other nutritional supplements that can help and support the physiological response of skeletal muscle to resistance training in terms of muscle hypertrophy. A healthy muscle environment and a correct whole muscle metabolism response to the stress of training is a prerequisite for the increase in muscle protein synthesis and, therefore, muscle hypertrophy. In this review, we discuss the role of different nutritional supplements such as carbohydrates, vitamins, minerals, creatine, omega-3, polyphenols, and probiotics as a support and complementary factors to the main supplement i.e., protein. The different mechanisms are discussed in the light of recent evidence. [ABSTRACT FROM AUTHOR]

Key Clinical Message Botulinum toxin (BTX) injection can be an effective treatment for persistent pain and functional impairment associated with hypertrophy of the first dorsal interosseous muscle. It offers a non‐surgical and minimally invasive alternative for those who have failed conservative treatment, showcasing the therapeutic promise of BTX for addressing similar musculoskeletal conditions.

Purpose: To compare the effect of 4 velocity-loss (VL) thresholds—0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50)—on strength gains, neuromuscular adaptations, and muscle hypertrophy during the bench press (BP) exercise using intensities ranging from 55% to 70% of 1-repetition maximum (1RM). Methods: Fifty resistance-trained men were randomly assigned to 4 groups that followed an 8-week (16 sessions) BP training program at 55% to 70% 1RM but differed in the VL allowed in each set (VL0, VL15, VL25, and VL50). Assessments performed before (pre) and after (post) the training program included (1) cross-sectional area of pectoralis major muscle, (2) maximal isometric test, (3) progressive loading test, and (4) fatigue test in the BP exercise. Results: A significant group × time interaction was found for 1RM (P =.01), where all groups except VL0 showed significant gains in 1RM strength (P <.001). The VL25 group attained the greatest gains in 1RM strength and most load–velocity relationship parameters analyzed. A significant group × time interaction was observed for EMG root mean square in pectoralis major (P =.03) where only the VL25 group showed significant increases (P =.02). VL50 showed decreased EMG root mean square in triceps brachii (P =.006). Only the VL50 group showed significant increases in cross-sectional area (P <.001). Conclusions: These findings indicate that a VL threshold of about 25% with intensities from 55% to 70% 1RM in BP provides an optimal training stimulus to maximize dynamic strength performance and neuromuscular adaptations, while higher VL thresholds promote higher muscle hypertrophy. [ABSTRACT FROM AUTHOR]

Abstract Murine exercise models are developed to study the molecular and cellular mechanisms regulating muscle mass. A progressive weighted wheel running model, named ‘PoWeR’, was previously developed to serve as a more translatable alternative to involuntary resistance‐type exercise models in rodents, such as synergist ablation. However, mice still run great distances despite the added resistance as evidenced by a large glycolytic‐to‐oxidative shift in muscle fibre type. Thus, PoWeR reflects a blended resistance/endurance model. In an attempt to bias PoWeR further towards resistance‐type exercise, we developed a novel heavy PoWeR model (hPoWeR) utilizing higher wheel loads (max of 12.5 g vs 6 g). Adult male C57BL/6 mice voluntarily performed an 8‐week progressive loading protocol (PoWeR or hPoWeR). Running distance peaked at ∼5–6 km day−1 in both treatments and was maintained by PoWeR mice, but declined in the hPoWeR mice as load increased beyond 7.5 g. Peak isometric force of the gastrocnemius–soleus–plantaris complex tended to increase in wheel running treatments. Soleus mass increased by 19% and 24% in PoWeR and hPoWeR treatments, respectively, and plantaris fibre cross‐sectional area was greater in hPoWeR, compared to PoWeR. There were fewer glycolytic and more oxidative fibres in the soleus and plantaris muscles in the PoWeR treatment, but not hPoWeR. Collectively, these data suggest hPoWeR may modestly alter skeletal muscle supporting the aim of better reflecting typical resistance training adaptations, in line with decreased running volume and exposure to higher resistance. Regardless, PoWeR remains an effective hypertrophic concurrent training model in mice.

Abstract Background Climbing is an intricate sport composed of various disciplines, holds, styles, distances between holds, and levels of difficulty. In highly skilled climbers the potential for further strength-specific adaptations to increase performance may be marginal in elite climbers. With an eye on the upcoming 2024 Paris Olympics, more climbers are trying to maximize performance and improve training strategies. The relationships between muscular strength and climbing performance, as well as the role of strength in injury prevention, remain to be fully elucidated. This narrative review seeks to discuss the current literature regarding the effect of resistance training in improving maximal strength, muscle hypertrophy, muscular power, and local muscular endurance on climbing performance, and as a strategy to prevent injuries. Main Body Since sport climbing requires exerting forces against gravity to maintain grip and move the body along the route, it is generally accepted that a climber`s absolute and relative muscular strength are important for climbing performance. Performance characteristics of forearm flexor muscles (hang-time on ledge, force output, rate of force development, and oxidative capacity) discriminate between climbing performance level, climbing styles, and between climbers and non-climbers. Strength of the hand and wrist flexors, shoulders and upper limbs has gained much attention in the scientific literature, and it has been suggested that both general and specific strength training should be part of a climber`s training program. Furthermore, the ability to generate sub-maximal force in different work-rest ratios has proved useful, in examining finger flexor endurance capacity while trying to mimic real-world climbing demands. Importantly, fingers and shoulders are the most frequent injury locations in climbing. Due to the high mechanical stress and load on the finger flexors, fingerboard and campus board training should be limited in lower-graded climbers. Coaches should address, acknowledge, and screen for amenorrhea and disordered eating in climbers. Conclusion Structured low-volume high-resistance training, twice per week hanging from small ledges or a fingerboard, is a feasible approach for climbers. The current injury prevention training aims to increase the level of performance through building tolerance to performance-relevant load exposure and promoting this approach in the climbing field.

Objective: This study aims to compare, through quantitative analysis, the effectiveness of different endurance training types on increasing lower limb strength and muscle cross-sectional area (MCSA) in concurrent training. Methods: This systematic literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) [PROSPERO ID: CRD42023396886]. Web of Science, SportDiscuss, Pubmed, Cochrane, and Scopus were systematically searched from their inception date to October 20, 2023. Results: A total of 40 studies (841 participants) were included in this meta-analysis. MCSA analysis showed that, compared to resistance training alone, concurrent high-intensity interval running training and resistance training and concurrent moderate-intensity continuous cycling training and resistance training were more effective (SMD = 0.15, 95% CI = −0.46 to 0.76, and SMD = 0.07, 95% CI = −0.24 to 0.38 respectively), while other modalities of concurrent training not. Lower body maximal strength analysis showed that all modalities of concurrent training were inferior to resistance training alone, but concurrent high-intensity interval training and resistance training showed an advantage in four different concurrent training modalities (SMD = −0.08, 95% CI = −0.25 to 0.08). For explosive strength, only concurrent high-intensity interval training and resistance training was superior to resistance training (SMD = 0.06, 95% CI = −0.21 to 0.33). Conclusion: Different endurance training types have an impact on the effectiveness of concurrent training, particularly on lower limb strength. Adopting high-intensity interval running as the endurance training type in concurrent training can effectively minimize the adverse effects on lower limb strength and MCSA.

Host associated probiotics (HAPs) provide health benefits to the host when administered as dietary supplement. However, a short-term probiotics application strategy has yet to be optimized. A 90-days study was conducted to evaluate the response of Malaysian mahseer, Tor tambroides post larvae fed with basal diet enriched HAPs for 30-days, and its response following another 60-days feeding with only basal diet. Three experimental diets (Enterococcus faecalis strain 2674 (T1), Aeromonas sp. strain A8-29 (T2) and E. faecalis strain FC11682 (T3)) were prepared by spray-coating each HAPs on a basal diet at 1 × 108 CFU/g feed. Differences in growth performances, whole-body proximate and fatty acid composition, muscle morphometry, and gut morphology were evaluated. Results showed that after 30 days, T3 fish produced highest growth. All HAP treatment groups showed better muscle distribution profile, improved fatty acid composition, and higher villus length, width and area, than control group. After 90 days, the growth of T3 fish was still the highest. Muscle distribution profile and villus growth were higher in HAP treatments, although only total n-6 PUFA, total MUFA, linoleic acids, and linolenic acids in HAP treated fish remained high after probiotics withdrawal. No difference in whole-body proximate composition was observed in both 30 and 90 days. Collective findings demonstrated that short-term application of HAPs at an early stage could be used to boost T. tambroides growth, with E. faecalis strain FC11682 showing the best efficacy.

Background and Study Aim. In the context of the growing importance of strength training, the analysis of the impact of strength loads on muscle hypertrophy becomes increasingly significant. Therefore, it is critical to comprehend both the effects of strength training on stimulating muscle growth and the potential ramifications. This study aimed to systematically analyze and collate the existing scientific evidence on the effects of weight training on muscle hypertrophy. Material and Methods. The research method involved the source selection of relevant studies from various databases, with predefined inclusion criteria. A thorough literature search was conducted, followed by data extraction focusing on study design, subject population, type of weight training, duration, and outcome measures of muscle hypertrophy. Databases such as PubMed, Google Scholar and Scopus were the primary sources of literature searches. Results. The results of this systematic review indicated evidence supporting the positive effect of weight training on muscle hypertrophy in most of the studies included. However, some studies produced controversial findings or even showed no significant impact. Factors such as variations in exercise type, intensity, and frequency also influence the outcome of weight training on muscle growth. Conclusions. While weight training has the potential to stimulate muscle hypertrophy, its effects may vary based on various factors. Therefore, selecting the correct type of exercise, setting the appropriate intensity, and planning the frequency of activity is essential in achieving optimal results. This study has strong relevance in fostering effective and safe exercise programs.It can also serve as a basis for further research in exploring other factors that may influence weight training-induced muscle hypertrophy outcomes.

This study aimed to evaluate the effects of dietary digestible protein levels on the growth dynamics and oxidative stress status of white muscle fibers in Amazonian Pintado (Pseudoplatystoma reticulatum × Leiarius marmoratus). Four hundred and fifty-five juveniles of Amazonian Pintado were fed diets containing varying digestible protein levels (225, 250, 275, 300, 325, 350, or 375 g kg−1) for 75 days. At the end of the experiment, the fish were fasted for 24 h, anesthetized, and euthanized to obtain muscle samples. The linear and quadratic effects of dietary digestible protein levels on white muscle fiber diameter, metabolite concentrations, and oxidative stress were assessed. The results revealed that increasing dietary digestible protein levels linearly raised the concentrations of free amino acids and total proteins in muscle tissue but also led to elevated levels of TBARS, indicating increased oxidative stress. Notably, the average area of muscle fibers with a cell area greater than 1133 µm2 decreased, reflecting restricted muscle hypertrophy, whereas glycogen and glucose levels also declined. These findings suggest that although high dietary digestible protein enhances protein and free amino acid concentrations in muscle tissue, it may compromise muscle hypertrophy and increase oxidative damage in Amazonian Pintado, underscoring the complexity of optimizing diet formulation.

The acute response of muscle protein synthesis (MPS) to resistance exercise and nutrition is often used to inform recommendations for exercise programming and dietary interventions, particularly protein nutrition, to support and enhance muscle growth with training. Those recommendations are worthwhile only if there is a predictive relationship between the acute response of MPS and subsequent muscle hypertrophy during resistance exercise training. The metabolic basis for muscle hypertrophy is the dynamic balance between the synthesis and degradation of myofibrillar proteins in muscle. There is ample evidence that the process of MPS is much more responsive to exercise and nutrition interventions than muscle protein breakdown. Thus, it is intuitively satisfying to translate the acute changes in MPS to muscle hypertrophy with training over a longer time frame. Our aim is to examine and critically evaluate the strength and nature of this relationship. Moreover, we examine the methodological and physiological factors related to measurement of MPS and changes in muscle hypertrophy that contribute to uncertainty regarding this relationship. Finally, we attempt to offer recommendations for practical and contextually relevant application of the information available from studies of the acute response of MPS to optimize muscle hypertrophy with training. [ABSTRACT FROM AUTHOR]

Sarcopenia is a process of progressive aging‐associated loss of skeletal muscle mass (SMM) recognized as a serious global health issue contributing to frailty and increased all‐cause mortality. Exercise and nutritional interventions (particularly intake of dairy products and milk) demonstrate good efficacy, safety, and broad applicability. Here, we propose that at least some of the well‐documented favorable effects of milk and milk‐derived protein supplements on SMM might be mediated by D‐galactose, a monosaccharide present in large quantities in milk in the form of disaccharide lactose (milk sugar). We suggest that ingestion of dairy products results in exposure to D‐galactose in concentrations metabolized primarily via the Leloir pathway with the potential to (i) promote anabolic signaling via maintenance of growth factor (e.g., insulin‐like growth factor 1 [IGF‐1]) receptor mature glycosylation patterns; and (ii) provide extracellular (liver glycogen) and intracellular substrates for short (muscle glycolysis) and long‐term (muscle glycogen, intramyocellular lipids) energy availability. Additionally, D‐galactose might optimize the metabolic function of skeletal muscles by increasing mitochondrial content and stimulating glucose and fatty acid utilization. The proposed potential of D‐galactose to promote the accretion of SMM is discussed in the context of its therapeutic potential in sarcopenia. [ABSTRACT FROM AUTHOR]

Murine exercise models are developed to study the molecular and cellular mechanisms regulating muscle mass. A progressive weighted wheel running model, named 'PoWeR', was previously developed to serve as a more translatable alternative to involuntary resistance‐type exercise models in rodents, such as synergist ablation. However, mice still run great distances despite the added resistance as evidenced by a large glycolytic‐to‐oxidative shift in muscle fibre type. Thus, PoWeR reflects a blended resistance/endurance model. In an attempt to bias PoWeR further towards resistance‐type exercise, we developed a novel heavy PoWeR model (hPoWeR) utilizing higher wheel loads (max of 12.5 g vs 6 g). Adult male C57BL/6 mice voluntarily performed an 8‐week progressive loading protocol (PoWeR or hPoWeR). Running distance peaked at ∼5–6 km day−1 in both treatments and was maintained by PoWeR mice, but declined in the hPoWeR mice as load increased beyond 7.5 g. Peak isometric force of the gastrocnemius–soleus–plantaris complex tended to increase in wheel running treatments. Soleus mass increased by 19% and 24% in PoWeR and hPoWeR treatments, respectively, and plantaris fibre cross‐sectional area was greater in hPoWeR, compared to PoWeR. There were fewer glycolytic and more oxidative fibres in the soleus and plantaris muscles in the PoWeR treatment, but not hPoWeR. Collectively, these data suggest hPoWeR may modestly alter skeletal muscle supporting the aim of better reflecting typical resistance training adaptations, in line with decreased running volume and exposure to higher resistance. Regardless, PoWeR remains an effective hypertrophic concurrent training model in mice. What is the central question of this study?Can utilizing a heavier loading protocol, compared to the previously developed progressive weighted wheel running (PoWeR) exercise model, bias skeletal muscle adaptations further towards resistance‐type exercise in mice?What is the main finding and its importance?Utilizing a significantly heavier wheel loading protocol, which may better reflect traditional resistance‐type exercise training, only modestly alters skeletal muscle adaptations. These results intuitively demonstrate decreased running distance with exposure to higher resistance, compared to PoWeR; however, murine wheel running models may always inherently possess a strong endurance training component. [ABSTRACT FROM AUTHOR]

Background: Climbing is an intricate sport composed of various disciplines, holds, styles, distances between holds, and levels of difficulty. In highly skilled climbers the potential for further strength-specific adaptations to increase performance may be marginal in elite climbers. With an eye on the upcoming 2024 Paris Olympics, more climbers are trying to maximize performance and improve training strategies. The relationships between muscular strength and climbing performance, as well as the role of strength in injury prevention, remain to be fully elucidated. This narrative review seeks to discuss the current literature regarding the effect of resistance training in improving maximal strength, muscle hypertrophy, muscular power, and local muscular endurance on climbing performance, and as a strategy to prevent injuries. Main Body: Since sport climbing requires exerting forces against gravity to maintain grip and move the body along the route, it is generally accepted that a climber's absolute and relative muscular strength are important for climbing performance. Performance characteristics of forearm flexor muscles (hang-time on ledge, force output, rate of force development, and oxidative capacity) discriminate between climbing performance level, climbing styles, and between climbers and non-climbers. Strength of the hand and wrist flexors, shoulders and upper limbs has gained much attention in the scientific literature, and it has been suggested that both general and specific strength training should be part of a climber's training program. Furthermore, the ability to generate sub-maximal force in different work-rest ratios has proved useful, in examining finger flexor endurance capacity while trying to mimic real-world climbing demands. Importantly, fingers and shoulders are the most frequent injury locations in climbing. Due to the high mechanical stress and load on the finger flexors, fingerboard and campus board training should be limited in lower-graded climbers. Coaches should address, acknowledge, and screen for amenorrhea and disordered eating in climbers. Conclusion: Structured low-volume high-resistance training, twice per week hanging from small ledges or a fingerboard, is a feasible approach for climbers. The current injury prevention training aims to increase the level of performance through building tolerance to performance-relevant load exposure and promoting this approach in the climbing field. Key Points: Altering the mechanical and metabolic stress, by using different intensities or varying the number of repetitions and sets, and training frequency per week are the most significant variables in manipulating the overall training volume and the variables requiring emphasis in planning incorporation of resistance training (RT) in climbers. Structured low-volume training at high resistance, twice per week, is a feasible approach to RT in climbers. The following classifications are proposed in climbing: > 15 reps (or hang time > 30 s) strength endurance bias; 8–15 RM (or 3–30 s hang time) hypertrophic bias; 1- 5 RM (or 1–5 s hang time) maximal strength bias. Improving maximal finger and shoulder girdle strength may decrease injury risk; as a result of reducing percentage of maximum strength generated in each move, the overall loading stress in a session is also diminished. Upper body RT programs have proven efficient for improving performance in climbing-specific tests among lower- and intermediate-grade climbers, but whether this training approach may improve climbing performance among advanced or elite climbers remains to be elucidated. [ABSTRACT FROM AUTHOR]

This study examined the influence of resistance training (RT) proximity-to-failure, determined by repetitions-in-reserve (RIR), on quadriceps hypertrophy and neuromuscular fatigue. Resistance-trained males (n = 12) and females (n = 6) completed an 8-week intervention involving two RT sessions per week. Lower limbs were randomised to perform the leg press and leg extension exercises either to i) momentary muscular failure (FAIL), or ii) a perceived 2-RIR and 1-RIR, respectively (RIR). Muscle thickness of the quadriceps [rectus femoris (RF) and vastus lateralis (VL)] and acute neuromuscular fatigue (i.e., repetition and lifting velocity loss) were assessed. Data was analysed with Bayesian linear mixed-effect models. Increases in quadriceps thickness (average of RF and VL) from pre- to post-intervention were similar for FAIL [0.181 cm (HDI: 0.119 to 0.243)] and RIR [0.182 cm (HDI: 0.115 to 0.247)]. Between-protocol differences in RF thickness slightly favoured RIR [−0.036 cm (HDI: −0.113 to 0.047)], but VL thickness slightly favoured FAIL [0.033 cm (HDI: −0.046 to 0.116)]. Mean volume was similar across the RT intervention between FAIL and RIR. Lifting velocity and repetition loss were consistently greater for FAIL versus RIR, with the magnitude of difference influenced by the exercise and the stage of the RT intervention. Terminating RT sets with a close proximity-to-failure (e.g., 1- to 2-RIR) can be sufficient to promote similar hypertrophy of the quadriceps as reaching momentary muscular failure in resistance-trained individuals over eight weeks, but the overall influence of proximity-to-failure on muscle-specific hypertrophy may also depend on other factors (e.g., exercise selection, order, and subsequent musculature targeted). Due to high repetition loss (from the first to final set) when sets are terminated at momentary muscular failure, performing RT with 1- to 2-RIR allows for similar volume load and repetition volume accumulation as reaching momentary muscular failure across eight weeks, possibly influencing the overall RT stimulus achieved. Performing RT to momentary muscular failure consistently induces higher levels of acute neuromuscular fatigue versus RT performed with 1- to 2-RIR; however, improved fatigue resistance overtime may attenuate acute neuromuscular fatigue and subsequent repetition loss (but may depend on the exercise performed). [ABSTRACT FROM AUTHOR]