James Krieger

• University of Florida

Background A goal of many who perform resistance training (RT) is to increase muscle mass and strength. An energy surplus is commonly advised to support such gains; however, if too large, it could cause unwanted fat gain without augmenting adaptation. Thus, we randomized 21 trained lifters into maintenance energy (MAIN), 5% (MOD), and 15% (HIGH) en...

Athletes undergoing energy restriction for weight/fat reduction sometimes apply ‘diet breaks’ involving increased energy intake, but there is little empirical evidence of effects on outcomes. Twenty-six resistance-trained athletes (11/26 or 42% female) who had completed 12 weeks of intermittent energy restriction participated in this study. Partici...

Introduction: Can intermittent energy restriction (IER) improve fat loss and fat-free mass retention compared with continuous energy restriction (CER) in resistance-trained adults? Methods: Sixty-one adults (32 women) with mean (SD) age 28.7 (6.5) years, body weight 77.2 (16.1) kg and body fat 25.5 (6.1)% were randomized to 12 weeks of (1) 4 x 3...

Resistance training is a commonly used strategy for improving both athletic performance and general health. While the contribution of resistance training intensity and volume to muscle strength and hypertrophy have been extensively investigated, training frequency only recently received sufficient attention, especially in older adults. A meta-regre...

We describe improbable data patterns in the work of Barbalho et al.

Roberts, BM, Nuckols, G, and Krieger, JW. Sex differences in resistance training: A systematic review and meta-analysis. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this study was to determine whether there are different responses to resistance training for strength or hypertrophy in young to middle-aged males and females using the same...

Holland, BM, Roberts, BM, Krieger, JW, and Schoenfeld, BJ. Does HMB enhance body composition in athletes? A systematic review and meta-analysis. J Strength Cond Res XX(X): 000-000, 2019-The purpose of this article was to systematically review and meta-analyze the current literature to determine the effects of HMB on body composition in athletes. St...

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...

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 P...

We examined the effects of resistance training (RT) frequency performed 3 times per week (RT3) versus RT performed 6 times per week (RT6) under volume-equated conditions in resistance-trained men. Twenty-seven men were randomly allocated to RT3 (n = 14) or RT6 (n = 13). The supervised training intervention lasted for 6-weeks. Upper and lower-body s...

Purpose: The purpose of this study was to evaluate muscular adaptations between low-, moderate-, and high-volume resistance training (RT) protocols in resistance-trained men. Methods: Thirty-four healthy resistance-trained men were randomly assigned to 1 of 3 experimental groups: a low-volume group (1SET) performing 1 set per exercise per traini...

Schoenfeld, BJ, Nickerson, BS, Wilborn, CD, Urbina, SL, Hayward, SB, Krieger, J, Aragon, AA, and Tinsley, G. Comparison of multifrequency bioelectrical impedance vs. dual-energy x-ray absorptiometry for assessing body composition changes after participation in a 10-week resistance training program. J Strength Cond Res XX(X): 000-000, 2018-The purpo...

Background Current recommendations on resistance training (RT) frequency for gains in muscular strength are based on extrapolations from limited evidence on the topic, and thus their practical applicability remains questionable. Objective To elucidate this issue, we conducted a systematic review and meta-analysis of the studies that compared musc...

The purpose of this study was to determine the effects of resistance training only (RT n=10), dietary intervention only (DIET n=10), resistance training plus diet (RT+DIET n=10) and control (CON n=10) on body composition and resting metabolic rate (RMR) in a cohort of 40 premenopausal female volunteers. Subjects in DIET and RT+DIET were provided wi...

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...

[This corrects the article DOI: 10.7717/peerj.2825.].

Objective We performed a systematic review, meta-analysis and meta-regression to determine if dietary protein supplementation augments resistance exercise training (RET)-induced gains in muscle mass and strength. Data sources A systematic search of Medline, Embase, CINAHL and SportDiscus. Eligibility criteria Only randomised controlled trials wit...

Although the effects of short versus long inter-set rest intervals in resistance training on measures of muscle hypertrophy have been investigated in several studies, the findings are equivocal and the practical implications remain unclear. In an attempt to provide clarity on the topic, we performed a systematic literature search of PubMed/MEDLINE,...

Controversy exists as to whether different dynamic muscle actions produce divergent hypertrophic responses. The purpose of this paper was to conduct a systematic review and meta-analysis of randomized controlled trials comparing the hypertrophic effects of concentric versus eccentric training in healthy adults following regimented resistance traini...

The purpose of this study was to test the anabolic window theory by investigating muscle strength, hypertrophy, and body composition changes in response to an equal dose of protein consumed either immediately pre- versus post-resistance training (RT) in trained men. Subjects were 21 resistance-trained men (>1 year RT experience) recruited from a un...

Data file for all individual outcomes

Background A number of resistance training (RT) program variables can be manipulated to maximize muscular hypertrophy. One variable of primary interest in this regard is RT frequency. Frequency can refer to the number of resistance training sessions performed in a given period of time, as well as to the number of times a specific muscle group is tr...

Background: The purpose of this study was to compare strength, body composition, and functional outcome measures following performance of the back squat, leg press, or a combination of the two exercises. Methods: Subjects were pair-matched based on initial strength levels and then randomly assigned to 1 of 3 groups: A squat-only group (SQ) that...

The purpose of this paper was to systematically review the current literature and elucidate the effects of total weekly resistance training (RT) volume on changes in measures of muscle mass via meta-regression. The final analysis comprised 34 treatment groups from 15 studies. Outcomes for weekly sets as a continuous variable showed a significant ef...

The purpose of this study was to compare the effects of a protocol employing a combination of loading zones vs. one employing a constant medium-repetition loading zone on muscular adaptations in resistance-trained men. 19 trained men (height=176.9±7.0 cm; body mass=83.1±11.8 kg; age=23.3±2.9 years) were randomly assigned to 1 of 2 experimental grou...

The purpose of this study was to compare body composition changes as measured by A-mode ultrasound (US) versus a criterion densitometry-based measure, air displacement plethysmography (ADP), over a 4-week weight-loss protocol in healthy, non-obese young women. Twenty healthy, young female volunteers were provided with customized dietary plans for t...

The purpose of this study was to investigate the effects of short rest intervals normally associated with hypertrophy-type training versus long rest intervals traditionally used in strength-type training on muscular adaptations in a cohort of young, experienced lifters. Twenty-one young resistance-trained men were randomly assigned to either a grou...

Maximizing the hypertrophic response to resistance training (RT) is thought to be best achieved by proper manipulation of exercise program variables including exercise selection, exercise order, length of rest intervals, intensity of maximal load, and training volume. An often overlooked variable that also may impact muscle growth is repetition dur...

It has been hypothesized that eating small, frequent meals enhances fat loss and helps to achieve better weight maintenance. Several observational studies lend support to this hypothesis, with an inverse relationship noted between the frequency of eating and adiposity. The purpose of this narrative review is to present and discuss a meta-analysis w...

Abstract There has been much debate as to optimal loading strategies for maximising the adaptive response to resistance exercise. The purpose of this paper therefore was to conduct a meta-analysis of randomised controlled trials to compare the effects of low-load (≤60% 1 repetition maximum [RM]) versus high-load (≥65% 1 RM) training in enhancing po...

It has been hypothesized that performing aerobic exercise after an overnight fast accelerates the loss of body fat. The purpose of this study was to investigate changes in fat mass and fat-free mass following four weeks of volume-equated fasted versus fed aerobic exercise in young women adhering to a hypocaloric diet. Twenty healthy young female vo...

Protein timing is a popular dietary strategy designed to optimize the adaptive response to exercise. The strategy involves consuming protein in and around a training session in an effort to facilitate muscular repair and remodeling, and thereby enhance post-exercise strength- and hypertrophy-related adaptations. Despite the apparent biological plau...

DETERMINING THE APPROPRIATE NUMBER OF SETS PER EXERCISE IS AN IMPORTANT PART OF DESIGNING A RESISTANCE TRAINING PROGRAM. EVIDENCE FROM A RECENTLY PUBLISHED META-ANALYSIS INDICATES THAT 2-3 SETS PER EXERCISE PRODUCE 46% GREATER STRENGTH GAINS THAN A SINGLE SET. LITTLE BENEFIT IS OBSERVED FOR MORE THAN 3 SETS. FOR CLIENTS INTERESTED IN GENERAL FITNES...

Previous meta-analyses have compared the effects of single to multiple sets on strength, but analyses on muscle hypertrophy are lacking. The purpose of this study was to use multilevel meta-regression to compare the effects of single and multiple sets per exercise on muscle hypertrophy. The analysis comprised 55 effect sizes (ESs), nested within 19...

There has been considerable debate over the optimal number of sets per exercise to improve musculoskeletal strength during a resistance exercise program. The purpose of this study was to use hierarchical, random-effects meta-regression to compare the effects of single and multiple sets per exercise on dynamic strength. English-language studies comp...