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Abstract

It has been proposed that training to failure is a necessary strategy to maximize muscle growth. This paper examines the research behind these claims, and attempts to draw evidence-based conclusions as to the practical implications for hypertrophy training.
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... However, there is evidence to suggest that performing repetitions at or close to concentric muscular failure may not be necessary to develop these physical qualities, rather ceasing a set multiple repetitions short of concentric muscular failure may be adequate (10,16). However, the findings from these studies are highly variable (27,38), as observed in recent reviews concerning muscular strength and hypertrophy (5,48) and indicate that the current consensus is inconclusive with more research needed to build on current recommendations (42). ...
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Davies, TB, Halaki, M, Orr, R, Mitchell, L, Helms, ER, Clarke, J, and Hackett, DA. Effect of set structure on upper-body muscular hypertrophy and performance in recreationally trained men and women. J Strength Cond Res 36(8): 2176–2185, 2022—This study explored the effect of volume-equated traditional-set and cluster-set structures on muscular hypertrophy and performance after high-load resistance training manipulating the bench press exercise. Twenty-one recreationally trained subjects (12 men and 9 women) performed a 3-week familiarization phase and were then randomized into one of two 8-week upper-body and lower-body split programs occurring over 3 and then progressing to 4 sessions per week. Subjects performed 4 sets of 5 repetitions at 85% one repetition maximum (1RM) using a traditional-set structure (TRAD, n = 10), which involved 5 minutes of interset rest only, or a cluster-set structure, which included 30-second inter-repetition rest and 3 minutes of interset rest (CLUS, n = 11). A 1RM bench press, repetitions to failure at 70% 1RM, regional muscle thickness, and dual-energy x-ray absorptiometry were used to estimate changes in muscular strength, local muscular endurance, regional muscular hypertrophy, and body composition, respectively. Velocity loss was assessed using a linear position transducer at the intervention midpoint. TRAD demonstrated a significantly greater velocity loss magnitude (g = 1.50) and muscle thickness of the proximal pectoralis major (g = −0.34) compared with CLUS. There were no significant differences between groups for the remaining outcomes, although a small effect size favoring TRAD was observed for the middle region of the pectoralis major (g = −0.25). It seems that the greater velocity losses during sets observed in traditional-set compared with cluster-set structures may promote superior muscular hypertrophy within specific regions of the pectoralis major in recreationally trained subjects.
... In the practice, repetitions to failure are often used to lead to greater total time under tension, possibly increasing the total volume [23]. On the other hand, repetitions to failure may need more time to recover and not be comfortable in less experienced people [45]. Recently, two different meta-analyses compared the effects of repetitions to failure versus not to failure on strength and hypertrophy [23,24]. ...
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Manipulating resistance training variables is crucial to plan the induced stimuli correctly. When reporting the exercise variables in resistance training protocols, sports scientists and practitioners often refer to the load lifted and the total number of repetitions. The present conceptual review explores all within-exercise variables that may influence the strength and hypertrophic gains, and the changes in muscle architecture. Together with the (1) load and (2) the number of repetitions, (3) performing repetitions to failure or not to failure, (4) the displacement of the load or the range of movement (full or partial), (5) the portion of the partial movement to identify the muscle length at which the exercise is performed, (6) the total time under tension, the duration of each phase and the position of the two isometric phases, (7) whether the concentric, eccentric or concentric-eccentric phase is performed, (8) the use of internal or external focus and (9) the inter-set rest may all have repercussions on the adaptations induced by each resistance exercise. Manipulating one or more variable allows to increase, equalize or decrease the stimuli related to each exercise. Sports scientists and practitioners are invited to list all aforementioned variables for each exercise when reporting resistance training protocols.
... 1, 2 Increasing muscle size is one of the main goals of resistance training, and several evidence-based hypertrophy-oriented training guidelines have been established and updated in the past three decades for various training variables such as load/intensity, volume, repetition speed/tempo, and inter-set rest. [3][4][5][6][7] On the other hand, only relatively recently have studies begun to examine the influence of muscle length/joint angle during exercise on muscle hypertrophy. [8][9][10][11][12][13][14][15] Nevertheless, a growing body of evidence suggests that muscle hypertrophy is promoted when resistance training is conducted at long vs. short muscle lengths (see 16 for a recent review), likely attributable, at least in part, to greater metabolic stress 17 and IGF-1 expression 10 associated with exercise at long muscle lengths. ...
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The biarticular triceps brachii long head (TBLong) 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 (14 males and 7 females, age: 23.4 ± 1.6 y, height: 1.69 ± 0.09 m, body mass: 64.5 ± 12.4 kg) 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 TBLong, monoarticular lateral and medial heads (TBLat+Med), 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, P = 0.285), while their absolute values/weights were always lower in Overhead-Arm (-34-39%, P < 0.001). Changes in muscle volume in Overhead-Arm compared to Neutral-Arm were 1.5-fold greater for the TBLong (+28.5% vs. +19.6%, Cohen's d = 1.272, P < 0.001), 1.4-fold greater for the TBLat+Med (+14.6% vs. +10.5%, d = 1.106, P = 0.002), and 1.4-fold greater for the Whole-TB (+19.9% vs. +13.9%, d = 1.427, P < 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.
... In fact, of the 86 empirical studies used within these reviews, SUP was mentioned (or assumed based on specific methods e.g., training on an isokinetic dynamometer) in ~80%. Further reviews have attempted to determine the intensity of effort required to optimise strength and hypertrophic adaptations, primarily by considering resistance training to failure versus not to failure [7][8][9]. However, people are typically poor at predicting proximity to failure based on repetitions in reserve [10], and since reaching muscular failure (MF) seems important in producing continued muscular adaptations [9], SUP might enhance intensity of effort [11,12], and thus be a key stimulus for the adaptations seen in empirical research. ...
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Background: Since many people choose to perform resistance training unsupervised, and a lack of supervision within strength training is reported to result in inadequate workout quality, we aimed to compare outcomes for resistance training with and without supervision. Methods: A systematic review and meta-analysis were performed for performance/functional outcomes and/or body composition measurements. Results: 12 studies were included in the review; 301 and 276 participants were in supervised and unsupervised groups, respectively. The main model for all performance/function effects revealed a small, standardised point estimate favouring SUP (0.28 [95%CI = 0.02 to 0.55]). For sub-grouped outcome types, there was very poor precision of robust estimates for speed, power, function, and endurance. However, for strength there was a moderate effect favouring SUP (0.40 [95%CI = 0.06 to 0.74]). The main model for all body composition effects revealed a trivial standardised point estimate favouring SUP (0.07 [95%CI = -0.01 to 0.15]). Conclusions: Supervised resistance training, compared to unsupervised training, might produce a small effect on increases in performance/function, most likely in strength, but has little impact on body composition outcomes.
... It is worth noting that, because RT is commonly incorporated as a complement to the field-specific training, it seems that soccer players would benefit from RT programs based on low-tomoderate levels of intraset fatigue because they would produce higher performance improvements at a lower time and fatigue (13,37) cost. Nonetheless, it is important to consider that training to failure (or very close to it) has also been found as an effective strategy to generate positive adaptations on strength, but especially on muscle mass gain (16,54). Consequently, this type of stimuli could represent an interesting strategy during specific periods included in soccer plans in which muscle hypertrophy could be the main objective, such as postinjury recovery or preseason phases. ...
... In fact, of the 86 empirical studies used within these reviews', SUP was mentioned (or assumed based on specific methods e.g., training on an isokinetic dynamometer) in ~80%. Further reviews have attempted to determine the intensity of effort required to optimise strength and hypertrophic adaptations, primarily by considering resistance training to failure versus not to failure [7][8][9]. However, people are typically poor at predicting proximity to failure based on repetitions in reserve [10], and since reaching muscular failure (MF) seems important in continued muscular adaptations [9], SUP might enhance intensity of effort [11,12], and thus be a key stimulus for the adaptations seen in empirical research, is an important factor to consider. ...
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Background: The body of resistance training literature appears heavily focused upon investigating efficacy of interventions by dint of most incorporating supervision (SUP). Authors have suggested that a lack of SUP within strength training results in inadequate workout quality and diminished results yet, since many people choose to perform resistance training unsupervised (UNSUP), it seems important to understand effectiveness of resistance training under such ecologically valid conditions. That is, the extent to which SUP might impact adaptation. Objective: To collectively explore the effects of SUP upon performance/function and body composition outcomes. Design: Exploratory systematic review and meta-analysis. Search and Inclusion: A systematic literature search using a Boolean search strategy was conducted with PubMed/MEDLINE, Scopus, and CINAHL in December 2020 and was supplemented with additional ‘snowballing’ searches. To be included in our analysis, studies had to be experimental trials including at least one performance/functional measure (e.g., strength, speed, power, function, endurance, and cardiorespiratory fitness) and/or body composition measure (body fat percentage, fat mass, and fat free mass). After search and screening, 12 studies were eligible for inclusion including 301 participants in SUP groups and a further 276 participants in UNSUP groups. Results: The cluster robust main model for all performance/function effects (57 across 12 clusters [median = 4, range = 1-12 effects per cluster]) revealed a small, standardised point estimate favouring SUP, though with relatively poor precision for the interval estimate that ranged from a trivial to a moderate effect favouring SUP (0.28 [95%CI = 0.02 to 0.55]). For sub-grouped outcome types there was very poor precision of robust estimates for speed, power, function, and endurance, with all ranging from large effects supporting UNSUP to large effects supporting SUP. However, for strength there was a small, standardised point estimate favouring SUP though with moderate precision for the interval estimate that ranged from a trivial effect favouring SUP to a moderate effect favouring SUP (0.40 [95%CI = 0.06 to 0.74]). The cluster robust main model for all body composition effects (18 across 6 clusters [median = 3, range = 1-6 effects per cluster]) revealed a trivial standardised point estimate favouring SUP that was relatively precise in the interval estimate ranging only trivial effects in either direction (0.07 [95%CI = -0.01 to 0.15]). Conclusions: The results of the present systematic review and exploratory meta-analysis suggest that, broadly speaking, SUP resistance training might produce a small effect on increases in performance/function, most likely in strength, compared to UNSUP, and has little to no impact on body composition outcomes. However, the lack of role and purpose within supervision as well as the lack of parity in UNSUP exercise interventions make providing a conclusive and overarching recommendation difficult.
... Controversy exists regarding the need for progressing training to failure to induce neuromuscular adaptation. Although some studies advocate that resistance exercise performed to failure may maximize muscle excitability and stimulate strength and muscle mass gains regardless of the exercise load or BFR (8,11,25,34), others suggest that high-load or low-load training performed to failure with free blood flow does not add benefits to muscle mass and strength gains in both untrained and trained subjects compared with nonfailure training (10, 28,33). This is a relevant discussion because LL-RT performed to failure could cause boredom and result in overtraining and musculoskeletal injury because of the repetitive effort (22,37). ...
Article
Cerqueira, MS, Lira, M, Mendonça Barboza, JA, Burr, JF, Wanderley e Lima, TB, Maciel, DG, and De Brito Vieira, WH. Repetition failure occurs earlier during low-load resistance exercise with high but not low blood flow restriction pressures: a systematic review and meta-analysis. J Strength Cond Res XX(X): 000-000, 2021-High-load and low-load resistance training (LL-RT) performed to failure are considered effective for improving muscle mass and strength. Alternatively, LL-RT with blood flow restriction (LL-BFR) may accelerate repetition failure and has been suggested to be more time efficient than LL-RT. This study explores the evidence for the effects of LL-BFR vs. LL-RT on repetition failure. A systematic literature search was conducted in the PubMed, CINAHL, Web of Science, CENTRAL, Scopus, SPORTDiscus, and PEDro databases. Meta-analyses of mean differences and 95% confidence intervals (CIs) were performed using a random-effects model. Subgroup analyses were conducted for both the high and low blood flow restriction pressures. The search identified n = 10 articles that met the inclusion criteria. The meta-analysis comprised a total of 218 healthy subjects. Low-load resistance training with blood flow restriction with high pressures (≥50% arterial occlusion pressure [AOP]) precipitate repetition failure in ∼14.5 fewer repetitions (95% CI -19.53 to -9.38) compared with LL-RT, whereas the use of low pressures (<50% AOP) stimulated repetition failure with ∼1.4 fewer repetitions (95% CI -3.11 to 0.37); however, this difference was not statistically significant. Repetition failure has been demonstrated to be an important normalizing variable when comparing the hypertrophic and strength effects resulting from resistance training and occurs earlier during low-load resistance exercise with high but not low blood flow restriction pressures.
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Resistance training (RT) is a widely practiced type of training and the number of adherents of this type of physical exercise is increasing each year. Among the most sought objectives of those who initiate RT is muscle hypertrophy, although success in this process depends on a well-designed protocol and good manipulation of training variables. The present study aims to analyze, through a systematic review, the impact of the RT variables (such as intensity, volume, recovery interval, execution speed, and concentric muscle failure) relevant to muscle hypertrophy and if there is an ideal range for each training variable. The research was carried out in the PubMed, Web of Science, Scopus and Scielo databases, from 2000 to 2020, using the terms “resistance training” and “hypertrophy” and “intensity” or “volume” or “recovery interval” or “execution speed” or “muscular failure”. Twenty-three articles were included in the review. The PEDro scale was used to analyze the selected articles quality. It was concluded that the variables intensity and volume must be carefully analyzed in a training program. The other variables, despite of not having a direct impact on hypertrophy, affect the intensity and volume, and must be manipulated according to what is intended with the others.
Thesis
Introdução: Desordens musculoesqueléticas são comuns e podem comprometer a função, o desempenho físico e a qualidade de vida. Dentre as intervenções utilizadas no manejo de desordens musculoesqueléticas, as modalidades de restrição de fluxo sanguíneo (RFS) vêm ganhando espaço na literatura científica. Objetivos: Essa tese teve o propósito de investigar os aspectos fisiológicos, os métodos de prescrição e as aplicações clínicas de modalidades de RFS em diferentes desordens musculoesqueléticas. Métodos e resultados: As modalidades de RFS consideradas foram a RFS passiva (sem exercício concomitante), o pré-condicionamento isquêmico (PCI) e a RFS combinada ao exercício. Como desordens musculoesqueléticas foram consideradas condições que causassem prejuízo funcional, tais como perda de força e de massa muscular, dano muscular induzido por exercício, fadiga muscular e osteoartrite (OA) de joelho. A presente tese é composta por introdução, três capítulos referentes às modalidades de RFS, e considerações finais. Os capítulos 1, 2 e 3 versam, respectivamente, sobre RFS passiva, PCI e RFS combinada ao exercício, e são compostos de sete artigos científicos envolvendo três desenhos de estudo: revisão sistemática (com e sem meta-análise), revisão narrativa e ensaio clínico aleatorizado. O capítulo 1 é uma revisão sistemática (artigo 1) sobre os efeitos da RFS passiva para minimizar perdas de força e de massa muscular (hipotrofia por desuso) em indivíduos submetidos a restrições na descarga de peso em membros inferiores. No capítulo 1 observamos que embora potencialmente útil, o alto risco de viés apresentado nos estudos originais limita a indicação de RFS passiva como modalidade eficaz contra a redução de força e de massa muscular induzida por imobilismo. O capítulo 2 é um ensaio clínico controlado e aleatorizado (artigo 2) que investigou os efeitos do PCI na proteção contra o dano muscular induzido por exercício (DMIE) em pessoas saudáveis. O artigo 2 apontou que o PCI não foi superior ao sham para proteger contra o DMIE. O capítulo 3 aborda aspectos fisiológicos, metodológicos e clínicos da RFS combinada ao exercício físico. O primeiro manuscrito do capítulo 3 (artigo 3) é uma revisão sistemática com meta-análise que analisou a excitação muscular (por eletromiografia de superfície) durante exercício resistido com RFS. O artigo 3 indicou que a excitação muscular durante o exercício de baixa carga com RFS foi maior que durante exercício de carga pareada sem RFS somente quando a falha muscular não foi alcançada. Adicionalmente, exercício de baixa carga com RFS apresentou menor excitação muscular que exercício de alta carga, independentemente de alcançar ou não a falha voluntária. O segundo manuscrito do capítulo 3 (artigo 4) é uma revisão sistemática com meta-análise que mostrou uma viii antecipação da falha muscular durante exercícios de baixa carga com altas pressões de RFS, mas não com baixas pressões. O terceiro manuscrito do capítulo 3 (artigo 5) é uma revisão narrativa que discute a possível necessidade de ajustar a pressão de RFS ao longo das semanas de treinamento. No artigo 5 observamos que a literatura é contraditória, o que dificulta recomendar se tais ajustes na pressão de RFS são necessários. O artigo 6 é um protocolo de ensaio clínico aleatorizado proposto para investigar os efeitos do exercício de baixa carga e volume total reduzido com RFS versus treinamento de alta carga sem RFS no tratamento da OA de joelho. O artigo 7 é o ensaio clínico aleatorizado que apresenta os resultados do protocolo (artigo 6) e mostrou que o treinamento de baixa carga com volume total reduzido e com RFS teve efeito similar ao treinamento de alta carga sem RFS na dor no joelho, desempenho muscular, função física e qualidade de vida de pacientes com OA de joelho, embora a magnitude nos ganhos de força tenha sido maior após treino de alta carga. Conclusões: De forma geral, com exceção do PCI para proteger contra o DMIE, as modalidades de RFS são potencialmente úteis no manejo das disfunções musculoesqueléticas aqui estudadas. Adicionalmente, concluímos que é necessário avançar no entendimento dos mecanismos fisiológicos e no estudo dos métodos de prescrição das diferentes modalidades de restrição de fluxo sanguíneo.
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Repetitions in Reserve' (RIR) scales in resistance training (RT) are used to control effort but assume people accurately predict performance a priori (i.e. the number of possible repetitions to momentary failure (MF)). This study examined the ability of trainees with different experience levels to predict number of repetitions to MF. One hundred and forty-one participants underwent a full body RT session involving single sets to MF and were asked to predict the number of repetitions they could complete before reaching MF on each exercise. Participants underpredicted the number of repetitions they could perform to MF (Standard error of measurements [95% confidence intervals] for combined sample ranged between 2.64 [2.36-2.99] and 3.38 [3.02-3.83]). There was a tendency towards improved accuracy with greater experience. Ability to predict repetitions to MF is not perfectly accurate among most trainees though may improve with experience. Thus, RIR should be used cautiously in prescription of RT. Trainers and trainees should be aware of this as it may have implications for the attainment of training goals, particularly muscular hypertrophy. Subjects Anatomy and Physiology, Kinesiology
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Purpose: To describe the acute and delayed time course of recovery following resistance training (RT) protocols differing in the number of repetitions (R) performed in each set (S) out of the maximum possible number (P). Methods: Ten resistance-trained men undertook three RT protocols [S × R(P)]: (1) 3 × 5(10), (2) 6 × 5(10), and (3) 3 × 10(10) in the bench press (BP) and full squat (SQ) exercises. Selected mechanical and biochemical variables were assessed at seven time points (from - 12 h to + 72 h post-exercise). Countermovement jump height (CMJ) and movement velocity against the load that elicited a 1 m s(-1) mean propulsive velocity (V1) and 75% 1RM in the BP and SQ were used as mechanical indicators of neuromuscular performance. Results: Training to muscle failure in each set [3 × 10(10)], even when compared to completing the same total exercise volume [6 × 5(10)], resulted in a significantly higher acute decline of CMJ and velocity against the V1 and 75% 1RM loads in both BP and SQ. In contrast, recovery from the 3 × 5(10) and 6 × 5(10) protocols was significantly faster between 24 and 48 h post-exercise compared to 3 × 10(10). Markers of acute (ammonia, growth hormone) and delayed (creatine kinase) fatigue showed a markedly different course of recovery between protocols, suggesting that training to failure slows down recovery up to 24-48 h post-exercise. Conclusions: RT leading to failure considerably increases the time needed for the recovery of neuromuscular function and metabolic and hormonal homeostasis. Avoiding failure would allow athletes to be in a better neuromuscular condition to undertake a new training session or competition in a shorter period of time.
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The history of resistance training research began with anecdotal ideas and a slow growth of research from the late 1890s through the 1970s. The mid-1970s were a nexus point when resistance training studies evolved from just strength assessments to importance in physiological systems, physical health, and physical performance capabilities for individuals interested in physical fitness through to those seeking elite athletic performances. The pursuit of understanding program design and what mediated successful programs continues today as new findings, replication of old concepts, and new visions with the latest technologies fuel both our understanding and interest in this modality. This brief review highlights some of the important scientific contributions to the evolution of our scientific study of resistance training and provides a literature base analysis for greater quantification of the origins and expanse of such investigations.
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The purpose of this paper was to conduct a systematic review of the current body of literature and a meta-analysis to compare changes in strength and hypertrophy between low- versus high-load resistance training protocols. Searches of PubMed/MEDLINE, Cochrane Library and Scopus were conducted for studies that met the following criteria: 1) an experimental trial involving both low- (≤60% 1 RM) and high- (>60% 1 RM) load training; 2) with all sets in the training protocols being performed to momentary muscular failure; 3) at least one method of estimating changes in muscle mass and/or dynamic, isometric or isokinetic strength was used; 4) the training protocol lasted for a minimum of 6 weeks; 5) the study involved participants with no known medical conditions or injuries impairing training capacity. A total of 21 studies were ultimately included for analysis. Gains in 1RM strength were significantly greater in favor of high- versus low-load training, while no significant differences were found for isometric strength between conditions. Changes in measures of muscle hypertrophy were similar between conditions. The findings indicate that maximal strength benefits are obtained from the use of heavy loads while muscle hypertrophy can be equally achieved across a spectrum of loading ranges.
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Prior resistance training (RT) recommendations and position stands have discussed variables that can be manipulated when producing RT interventions. However, one variable that has received little discussion is set end points (i.e. the end point of a set of repetitions). Set end points in RT are often considered to be proximity to momentary failure and are thought to be a primary variable determining effort in RT. Further, there has been ambiguity in use and definition of terminology that has created issues in interpretation of research findings. The purpose of this paper is to: 1) provide an overview of the ambiguity in historical terminology around set end points; 2) propose a clearer set of definitions related to set end points; and 3) highlight the issues created by poor terminology and definitions. It is hoped this might permit greater clarity in reporting, interpretation, and application of RT interventions for researchers and practitioners.
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Training frequency is considered an important variable in the hypertrophic response to regimented resistance exercise. The purpose of this paper was to conduct a systematic review and meta-analysis of experimental studies designed to investigate the effects of weekly training frequency on hypertrophic adaptations. Following a systematic search of PubMed/MEDLINE, Scoups, and SPORTDiscus databases, a total of 25 studies were deemed to meet inclusion criteria. Results showed no significant difference between higher and lower frequency on a volume-equated basis. Moreover, no significant differences were seen between frequencies of training across all categories when taking into account direct measures of growth, in those considered resistance-trained, and when segmenting into training for the upper body and lower body. Meta-regression analysis of non-volume-equated studies showed a significant effect favoring higher frequencies, although the overall difference in magnitude of effect between frequencies of 1 and 3+ days per week was modest. In conclusion, there is strong evidence that resistance training frequency does not significantly or meaningfully impact muscle hypertrophy when volume is equated. Thus, for a given training volume, individuals can choose a weekly frequency per muscle groups based on personal preference.
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Pareja-Blanco, F, Rodríguez-Rosell, D, Aagaard, P, Sánchez-Medina, L, Ribas-Serna, J, Mora-Custodio, R, Otero-Esquina, C, Yáñez-García, JM, and González-Badillo, JJ. Time course of recovery from resistance exercise with different set configurations. J Strength Cond Res XX(X): 000-000, 2018-This study analyzed the response to 10 resistance exercise protocols differing in the number of repetitions performed in each set (R) with respect to the maximum predicted number (P). Ten males performed 10 protocols (R(P): 6(12), 12(12), 5(10), 10(10), 4(8), 8(8), 3(6), 6(6), 2(4), and 4(4)). Three sets with 5-minute interset rests were performed in each protocol in bench press and squat. Mechanical muscle function (countermovement jump height and velocity against a 1 m·s load, V1-load) and biochemical plasma profile (testosterone, cortisol, growth hormone, prolactin, IGF-1, and creatine kinase) were assessed at several time points from 24-hour pre-exercise to 48-hour post-exercise. Protocols to failure, especially those in which the number of repetitions performed was high, resulted in larger reductions in mechanical muscle function, which remained reduced up to 48-hour post-exercise. Protocols to failure also showed greater increments in plasma growth hormone, IGF-1, prolactin, and creatine kinase concentrations. In conclusion, resistance exercise to failure resulted in greater fatigue accumulation and slower rates of neuromuscular recovery, as well as higher hormonal responses and greater muscle damage, especially when the maximal number of repetitions in the set was high.
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This study investigated the effects of a 10-week resistance training to failure on neuromuscular adaptations in young women. Eighty-nine active young women were randomly assigned to one of three groups: 1) repetitions to failure (RF; three sets of repetitions to failure); 2) repetitions not to failure with equalized volume (RNFV; four sets of 7 repetitions); and 3) repetitions not to failure (RNF; three sets of 7 repetitions). All groups performed the elbow flexor exercise (bilateral biceps curl) and trained 2 days per week using 70% of 1RM. There were significant increases (p<0.05) in muscle strength after 5 (15.9% for RF, 18.4% for RNF, and 19.9% for RNFV) and 10 (28.3% for RF, 26.8% for RNF, and 28.3% for RNFV) weeks of training, with no significant differences between groups. Additionally, muscular endurance increased after 5 and 10 weeks, with no differences between groups. However, peak torque (PT) increased significantly at 180°.s-1 in the RNFV (13.7%) and RNF (4.1%) groups (p<0.05), whereas no changes were observed in the RF group (-0.5%). Muscle thickness increased significantly (p<0.05) in the RF and RNFV groups after 5 (RF: 8.4% and RNFV: 2.3%) and 10 weeks of training (RF: 17.5%, and RNFV: 8.5%), whereas no significant changes were observed in the RNF group (3.9 and 2.1% after 5 and 10 weeks, respectively). These data suggest that short-term training of repetitions to failure do not yield additional overall neuromuscular improvements in young women.
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The purpose of the present study was to investigate the effects of resistance training (RT) at high- and low-intensities performed to muscle failure or volitional interruption on muscle strength, cross-sectional area (CSA), pennation angle (PA) and muscle activation. Thirty-two untrained men participated in the study. Each leg was allocated in one of four unilateral RT protocols: RT to failure at high (HIRT-F) and low (LIRT-F) intensities, and RT to volitional interruption (repetitions performed to the point in which participants voluntarily interrupted the exercise) at high (HIRT-V) and low (LIRT-V) intensities. Muscle strength (1-RM), CSA, PA and muscle activation by amplitude of the electromyography (EMG) signal were assessed before (Pre), after 6 (6W) and 12 (12W) weeks. 1-RM increased similarly after 6W (range: 15.8 - 18.9%, ES: 0.41- 0.58) and 12W (range: 25.6 - 33.6%, ES: 0.64 - 0.98) for all protocols. All protocols were similarly effective in increasing CSA after 6W (range: 3.0 - 4.6%, ES: 0.10 - 0.24) and 12W (range: 6.1 - 7.5%, ES: 0.22 - 0.26). PA increased after 6W (~3.5) and 12W (~9%; main time effect, P < 0.0001), with no differences between protocols. EMG values were significantly higher for the high-intensity protocols at all times (main intensity effect, P < 0.0001). In conclusion, both high- and low-intensity RT performed to volitional interruption are equally effective in increasing muscle mass, strength and PA when compared to RT performed to muscle failure.