Jozo Grgic

Jozo Grgic
Victoria University Melbourne | VU · Institute of Sport, Exercise and Active Living (ISEAL)

About

110
Publications
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Introduction
A PhD student who works at the Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne. Areas of interest include neuromuscular adaptations to resistance training, the effects of sports supplements (caffeine in particular) on performance and physical activity research.

Publications

Publications (110)
Article
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Background Rest interval (RI) duration is an important resistance-training variable underlying gain in muscular strength. Recommendations for optimal RI duration for gains in muscular strength are largely inferred from studies examining the acute resistance training effects, and the generalizability of such findings to chronic adaptations is uncert...
Article
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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 exper...
Article
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The goal of this randomized, double-blind, cross-over study was to assess the acute effects of caffeine ingestion on muscular strength and power, muscular endurance, rate of perceived exertion (RPE), and pain perception (PP) in resistance-trained men. Seventeen volunteers (mean ± SD: age = 26 ± 6 years, stature = 182 ± 9 cm, body mass = 84 ± 9 kg,...
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The aim of this study was to explore tapering practices among 10 Croatian open-class powerlifting champions (mean ± SD: age 29.2 ± 3.2 years; Wilks coefficient 355.1 ± 54.8). The athletes were interviewed about their tapering practices using a semi-structured interview, after which the audio content was transcribed. The athletes reported decreasing...
Article
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Background: Values of resting metabolic rate are very important for determining optimal daily caloric intake. Body fat percentage is one of the most important indicators of health. However, there are possibilities for making mistakes in estimating these values. This study aimed to investigate possible variations in metabolism and body composition e...
Article
The present meta-analysis examined the effects of resistance training on increasing the rate of force development (RFD), followed by exploring the changes in RFD occurring during training cessation. Five databases were searched to find eligible studies. Their methodological quality was evaluated using the Downs and Black checklist. The data were po...
Article
Objective To investigate the effects of high-intensity interval training (HIIT) and sprint interval training (SIT) on fat oxidation during exercise (FatOx) and how they compare with the effects of moderate-intensity continuous training (MICT). Design Systematic review and meta-analysis. Data sources Academic Search Ultimate, CINAHL, Networked Dig...
Article
The interest in the benefits of caffeine in combat sports has grown exponentially in the last few years, evidenced by the significant rise of post-competition urine caffeine concentration. We conduct a systematic review and meta-analysis on the effects of caffeine on different performance variables in combat sports athletes. In total, we included 2...
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Purpose While several studies have examined the reliability of the EUROFIT test battery, the findings are conflicting. Therefore, this paper aimed to conduct a review of studies that explored the reliability of the EUROFIT test battery. Methods Seven databases were searched to find studies that investigated the reliability of the EUROFIT test batt...
Article
We performed a systematic review and meta-analysis comparing the effects of single-joint (SJ) and multijoint (MJ) resistance exercises on muscle hypertrophy of the limb muscles. A systematic search was performed to identify randomized trials that directly compared hypertrophic changes between SJ and MJ resistance exercises, as well as combinations...
Article
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This review aimed to conduct a meta-analysis of studies examining the effects of caffeine on rate of force development (RFD). Ten databases were searched to find relevant studies. Risk of bias (RoB) of the included studies was evaluated. Data were analyzed in a random-effects meta-analysis. Eleven studies with “some concerns” regarding RoB were inc...
Article
Purpose – Caffeine is a popular ergogenic aid, but its effects on swimming performance are not yet fully clear. Therefore, the aim of this review was to examine the effects of caffeine on swimming performance. Design/methodology/approach – Crossover placebo-controlled studies that explored the effects of caffeine on swimming performance were inclu...
Article
Purpose – The aim of this review was to explore the effects of low doses of caffeine (<3 mg/kg) on jumping performance using a meta-analysis. Design/methodology/approach – The search for eligible studies was performed through six databases, with additional backward and forward citation tracking. A random-effects meta-analysis was performed to compa...
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In recent years, studies have explored the effects of paracetamol (acetaminophen) ingestion on exercise performance. However, due to the contrasting findings, there is still no consensus on this topic. This article provides an overview of the effects of paracetamol on endurance, sprinting, and resistance exercise performance. Studies have reported...
Article
The aim of this review was to perform a meta-analysis examining the effects of CWI coupled with resistance training on gains in muscular strength. Four databases were searched to find relevant studies. Their methodological quality and risk of bias were evaluated using the PEDro checklist. The effects of CWI vs. control on muscular strength were exa...
Article
Objectives: Caffeine ingestion has well-established ergogenic effects for resistance exercise performance. However, the concept of a minimum effective caffeine dose has not yet been thoroughly examined in the literature. Therefore, this review aimed to explore the minimum ergogenic dose of caffeine on resistance exercise outcomes, such as muscular...
Article
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We aimed to examine the effects of mental fatigue on the Yo-Yo test and Loughborough soccer passing and shooting tests performance using a meta-analysis. The search for studies was performed through eight bibliographic databases (Academic Search Elite, AUSPORT, Cochrane Library, PsycInfo, PubMed/MEDLINE, Scopus, SPORTDiscus, and Web of Science). Th...
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Several studies explored the effects of attentional focus on resistance exercise, but their analysed outcomes most commonly involved surface electromyography variables. Therefore, the effects of attentional focus on resistance exercise performance remain unclear. The aim of this review was to perform a meta-analysis examining the acute effects of e...
Article
Objective: Several studies explored the effects of caffeine on isometric handgrip strength, but their findings varied. Therefore, the aim of this review was to perform a meta-analysis of studies exploring the effects of caffeine on isometric handgrip strength. Methods: Search for studies was performed through five databases (Academic Search Elite,...
Article
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Purpose: To conduct a systematic review and multilevel meta-analysis of the current literature as to the effects of interval training (IT) vs moderate intensity continuous training (MICT) on measures of body composition, both on a whole-body and regional level. Methods: We searched English-language papers on PubMed/MEDLINE, Scopus, CINAHL, and s...
Article
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Background We aimed to perform an umbrella review of meta-analyses examining the effects of sodium bicarbonate supplementation on exercise performance. Methods We systematically searched for meta-analyses that examined the effects of sodium bicarbonate supplementation on exercise performance. The methodological quality of the included reviews was...
Article
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This review aimed to perform a meta-analysis examining the following: (a) acute effects of adopting an internal focus vs. external focus of attention on muscular strength; and (b) long-term effects of adopting an internal focus vs. external focus of attention during resistance training on gains in muscular strength. We searched through five databas...
Article
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In the last few years, a plethora of studies explored the effects of caffeine on resistance exercise, demonstrating that this field of research is growing fast. This review evaluated and summarized the most recent findings. Given that toxic doses of caffeine are needed to increase skeletal muscle contractility, the binding of caffeine to adenosine...
Article
This review aimed to summarize and critically evaluate the research on the effects of music on resistance exercise performance. Research in the field has consistently demonstrated an ergogenic effect of music on resistance exercise performance. Specifically, studies have demonstrated that listening to music pre-exercise or during exercise may enhan...
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Background: There is a growing body of research examining the effects of plyometric jump training (PJT) on repeated sprint ability (RSA) in athletes. However, available studies produced conflicting findings and the literature has not yet been systematically reviewed. Therefore, the effects of PJT on RSA indices remain unclear. Objective: To explor...
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Objective In this review, we critically evaluate studies directly comparing the effects of plyometric vs. resistance training on skeletal muscle hypertrophy. Methods We conducted electronic searches of PubMed/MEDLINE, Scopus, SPORTDiscus, and Web of Science to find studies that explored the effects of plyometric vs. resistance training on muscle...
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The present study uniquely examined the effect of 3 mg·kg−1 chronic caffeine consumption on training adaptations induced by 7-weeks resistance training and assessed the potential for habituation to caffeine’s ergogenicity. Thirty non-specifically resistance-trained university standard male rugby union players (age (years): 20 ± 2; height (cm): 181...
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Based on a comprehensive review and critical analysis of the literature regarding the effects of sodium bicarbonate supplementation on exercise performance, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Sup...
Article
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Several studies explored the effects of paracetamol (acetaminophen) ingestion on endurance performance, but their findings are conflicting. Therefore, this review aimed to conduct a meta-analysis examining the effects of paracetamol ingestion on endurance performance. Five databases were searched to find relevant studies. The PEDro checklist was us...
Article
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Hypertrophy can be operationally defined as an increase in the axial cross-sectional area of a muscle fiber or whole muscle, and is due to increases in the size of pre-existing muscle fibers. Hypertrophy is a desired outcome in many sports. For some athletes, muscular bulk and, conceivably, the accompanying increase in strength/power, are desirable...
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Background: The objective of this review was to synthesize previous findings on the test-retest reliability of the 30-15 Intermittent Fitness Test (IFT). Methods: The literature searches were performed in eight databases. Studies that examined the test-retest reliability of the 30-15 IFT and presented intraclass correlation coefficient (ICC) and/o...
Preprint
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Objectives: To conduct a systematic review and multilevel meta-analysis of the current literature as to the effects of interval training (IT) vs moderate intensity continuous training (MICT) on measures of body composition, both on a whole-body and regional level. Design: Systematic review and meta-analysis. Data sources: English-language searches...
Article
This paper aimed to: (a) critically review studies that explored the isolated and combined effects of caffeine and sodium bicarbonate ingestion on exercise performance; (b) discuss some of the possible reasons for the discrepancy in findings; and, (c) provide suggestions for future studies. Out of the eight studies that examined this topic, only on...
Article
This meta-analysis explored the effects of sodium bicarbonate supplementation on swimming performance. Seven databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed to analyze the data. Nine studies were included in the review. There was no significant difference between...
Article
The aim of this study was to conduct a comprehensive examination of caffeine’s effects on countermovement jump (CMJ) performance. In this randomized, double-blind, crossover study, twenty-two resistance-trained men (age: 28 ± 5 years; height: 183 ± 5 cm; weight: 79 ± 10 kg; habitual caffeine intake: 127 ± 102 mg/day) performed the CMJ test on two o...
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This meta-analysis aimed to explore the effects of caffeine ingestion on muscular endurance and muscular strength in women. Five databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed for data analysis. Subgroup meta-analyses explored the effects of caffeine on upper-bod...
Article
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Purpose: To systematically review studies that examined the influence of the CYP1A2 −163C>A polymorphism on the ergogenic effects of caffeine and to discuss some of the reasons for the discrepancies in findings between the studies. Methods: This review was performed in accordance with the PRISMA guidelines. The search for studies was performed thro...
Article
Objective: The aim of this meta-analysis was to explore the effects of beta-alanine supplementation on Yo-Yo test performance. Methods: Nine databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed for data analysis. Subgroup meta-analyses were conducted to explore the eff...
Article
Purpose: To compare the acute effects of caffeine and placebo ingestion with a control condition (i.e., no supplementation) on vertical jump performance. Methods: The sample for this study consisted of 26 recreationally trained males. Following the familiarization visit, the subjects were randomized in a double-blind fashion to three main condition...
Article
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The aim of this systematic review was to explore the test-retest reliability of isometric mid-thigh pull maximum strength assessment. We searched through five databases to find studies that examined the test-retest reliability of peak force in the isometric mid-thigh pull exercise. From each included study, we extracted intra-class correlation coef...
Article
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The objectives of this paper were to: (a) systematically review studies that explored the effects of exercise order (EO) on muscular strength and/or hypertrophy; (b) pool their results using a meta-analysis; and (c) provide recommendations for the prescription of EO in resistance training (RT) programmes. A literature search was performed in four d...
Article
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Loading recommendations for resistance training are typically prescribed along what has come to be known as the “repetition continuum”, which proposes that the number of repetitions performed at a given magnitude of load will result in specific adaptations. Specifically, the theory postulates that heavy load training optimizes increases maximal str...
Article
Caffeine is a well-established ergogenic aid, with its performance-enhancing effects demonstrated across a variety of sports and exercise types. As a result of caffeine's ergogenic properties, it is widely utilised by athletes at all levels around both competition and training. Caffeine exerts its performance benefits through a variety of mechanism...
Article
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Objective We aimed to perform a systematic review and meta-analysis of the effects of training to muscle failure or non-failure on muscular strength and hypertrophy. Methods Meta-analyses of effect sizes (ESs) explored the effects of training to failure vs. non-failure on strength and hypertrophy. Subgroup meta-analyses explored potential moderatin...
Article
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Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: 1. Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. Small to moderate benefits of caffeine use...
Article
The review aimed to perform a meta-analysis of studies exploring the acute effects of sodium bicarbonate on Wingate test performance. Ten databases were searched to find studies that examined the effects of sodium bicarbonate on single and repeated Wingate tests. Meta-analyses were performed using the random-effects model. Ten studies were included...
Article
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Background: Effects of resistance training on muscle strength and hypertrophy are well-established in adults and younger elderly. However, less is currently known about these effects in the very elderly (i.e., 75 years of age and older). Objective: To examine the effects of resistance training on muscle size and strength in very elderly individuals...
Article
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The aim of this meta-analysis was to explore the effects of low-load vs. high-load resistance training on type I and type II muscle fiber hypertrophy. Searches for studies were performed through ten databases. Studies were included if they: (a) compared the effects of low-load vs. high-load resistance training (performed to momentary muscular failu...
Article
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We aimed to examine the effects of placebo and caffeine compared to a control condition on mean velocity in the bench press exercise. Twenty-five resistance-trained men participated in this randomized, crossover, double-blind study. The participants performed the bench press with loads of 50%, 75%, and 90% of one-repetition maximum (1RM), after no...
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We explored the test-retest reliability of velocity and power assessed by the GymAware PowerTool system (GYM) in the deadlift and squat by simulating a context with and without a familiarization session. Sixteen resistance-trained individuals completed three testing sessions. In all sessions, velocity and power were assessed by the GYM system in th...
Article
We carried out a prospective case study in a high-level amateur natural male bodybuilder throughout preparation for 4 competitions and during the ensuing post-contest recovery period. Laboratory testing was conducted monthly over a 1-year period, which included the following assessments: B-mode ultrasound evaluation of muscle thickness (MT), multi-...
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Background: The test-retest reliability of the one-repetition maximum (1RM) test varied across different studies. Given the inconsistent findings, it is unclear what the true reliability of the 1RM test is, and to what extent it is affected by measurement-related factors, such as exercise selection for the test, the number of familiarization trials...
Article
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Background: The effects of sodium bicarbonate on muscular strength and muscular endurance are commonly acknowledged as unclear due to the contrasting evidence on the topic. Objective: To conduct a systematic review and meta-analysis of studies exploring the acute effects of sodium bicarbonate supplementation on muscular strength and endurance. Meth...
Article
This study explored the influence of habitual caffeine intake on the acute effects of caffeine ingestion on resistance exercise, jumping, and Wingate performance. Twenty-four resistance-trained males were tested following the ingestion of caffeine (3 mg/kg) and placebo (3 mg/kg of dextrose). Participants were classified as low caffeine users (n = 1...
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It has been proposed that superior muscle hypertrophy may be obtained by training muscles predominant in type I fibers with lighter loads and those predominant in type II fibers with heavier loads. Purpose: To evaluate longitudinal changes in muscle strength and hypertrophy of the soleus (a predominantly slow-twitch muscle) and gastrocnemius (muscl...
Article
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Background: It has been suggested that polymorphisms within CYP1A2 impact inter-individual variation in the response to caffeine. The purpose of this study was to explore the acute effects of caffeine on resistance exercise, jumping, and sprinting performance in a sample of resistance-trained men, and to examine the influence of genetic variation o...
Article
Purpose: To explore the effects of three doses of caffeine on muscle strength and muscle endurance. Methods: Twenty-eight resistance-trained men completed the testing sessions under five conditions: no-placebo control, placebo-control, and with caffeine doses of 2, 4, and 6 mg.kg−1. Muscle strength was assessed using the one-repetition maximum (1RM...
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Background Several studies investigated the effects of caffeine supplementation on movement velocity in resistance exercise. However, these studies presented inconsistent findings. Objective This paper aimed to: (a) review the studies that explored the effects of caffeine supplementation on movement velocity in resistance exercise; and (b) pool th...
Article
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Caffeine's ergogenic effects on exercise performance are generally explained by its ability to bind to adenosine receptors. ADORA2A is the gene that encodes A2A subtypes of adenosine receptors. It has been suggested that ADORA2A gene polymorphisms may be responsible for the inter-individual variations in the effects of caffeine on exercise performa...
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The purpose of this paper was to conduct a systematic review and a meta-analysis of studies examining the acute effects of caffeine ingestion on measures of rowing performance. Crossover and placebo-controlled experiments that investigated the effects of caffeine ingestion on measures of rowing performance were included. The PEDro checklist was use...
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We aimed to investigate the effects of resistance training (RT) combined with no-load isometric actions (iso-holds) during the inter-set recovery period versus RT that involves passive inter-set rest on muscular strength, muscular hypertrophy, and muscular endurance in resistance-trained men. Twenty-seven resistance-trained male volunteers were ran...
Article
OBJECTIVES: To conduct a systematic review and a meta-analysis of studies exploring the effects of caffeine and/or sodium bicarbonate on performance in the Yo-Yo test. DESIGN: Systematic review/meta-analysis. METHODS: A total of six databases were searched, and random-effects meta-analyses were performed examining the isolated effects of caffeine...
Article
Caffeine is a well-established ergogenic aid, with its performance-enhancing effects demonstrated across a wide variety of exercise modalities. Athletes tend to frequently consume caffeine as a performance enhancement method in training and competition. There are a number of methods available as a means of consuming caffeine around exercise, includ...
Article
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The purpose of this study was to systematically review the literature as to the effects of performing exercise with a full vs. partial range of motion (ROM) during dynamic, longitudinal resistance training (RT) programs on changes in muscle hypertrophy. Based on the available evidence, we aimed to draw evidence-based recommendations for RT prescrip...
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Background Raw bioelectrical values can be used to assess physiological outcomes, though limited information is available concerning the relationships between changes in these values and changes in other variables of interest. Methods This investigation quantified the relationships between total and segmental changes in raw bioelectrical variable...
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Elite athlete status is a partially heritable trait, as are many of the underpinning physiological, anthropometrical, and psychological traits that contribute to elite performance. In recent years, our understanding of the specific genetic variants that contribute to these traits has grown, such that there is considerable interest in attempting to...
Article
Objective To investigate the association of running participation and the dose of running with the risk of all-cause, cardiovascular and cancer mortality. Design Systematic review and meta-analysis. Data sources Journal articles, conference papers and doctoral theses indexed in Academic Search Ultimate, CINAHL, Health Source: Nursing/Academic Edi...
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Background The Yo-Yo test is widely used both in the practical and research contexts; however, its true test-retest reliability remains unclear. Objective The present systematic review aims to identify studies that have examined the test-retest reliability of the Yo-Yo test and summarize their results. Methods A search of ten databases was performe...
Article
We thank Mr. Mizelman for his letter to the editor (1) and interest in our study (2). The author contends that the power analysis for our study was incorrect. We ran the power analysis using G*power, F tests for ANOVA with repeated measures, and within-between interaction. Note that our original statistical analysis was based on this statistical mo...
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This study aimed to investigate the fluctuations of muscle performance in the Smith machine half-squat exercise during three different phases of the menstrual cycle. Thirteen resistance-trained and eumenorrheic women volunteered to participate in the study (58.6 ± 7.8 kg, 31.1 ± 5.5 years). In a pre-experimental test, the half-squat one-repetition...
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In this paper, we review the effects of caffeine on muscle strength and provide suggestions for caffeine supplementation in powerlifting competitions. The currently available studies indicate that caffeine ingestion may enhance strength in two powerlifting competition events, the squat and the bench press. For the deadlift, the same might be expect...
Article
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Resistance training volume, determined by the number of sets performed (set-volume) is considered one of the key variables in promoting muscle hypertrophy. To better guide resistance exercise prescription for weekly per-muscle training volume, the purpose of this paper is to provide evidence-based considerations for set-volume ratios between multi-...