Nonsugar Sweeteners-Time for Transparency and Caution.

This Viewpoint discusses the growing presence of nonsugar sweeteners (NSSs) in the food supply and mounting concerns about their use, which suggest that disclosure of the amounts of NSS in food and beverages and restrictions on their use in products marketed to children are warranted.

Costs, Reach, and Benefits of COVID-19 Pandemic Electronic Benefit Transfer and Grab-and-Go School Meals for Ensuring Youths' Access to Food During School Closures.

Importance: School meals are associated with improved nutrition and health for millions of US children, but school closures due to the COVID-19 pandemic disrupted children's access to school meals. Two policy approaches, the Pandemic Electronic Benefit Transfer (P-EBT) program, which provided the cash value of missed meals directly to families on debit-like cards to use for making food purchases, and the grab-and-go meals program, which offered prepared meals from school kitchens at community distribution points, were activated to replace missed meals for children from low-income families; however, the extent to which these programs reached those who needed them and the programs' costs were unknown. Objective: To assess the proportion of eligible youths who were reached by P-EBT and grab-and-go meals, the amount of meals or benefits received, and the cost to implement each program. Design, Setting, and Participants: This cross-sectional study was conducted from March to June 2020. The study population was all US youths younger than 19 years, including US youths aged 6 to 18 years who were eligible to receive free or reduced-price meals (primary analysis sample). Exposures: Receipt of P-EBT or grab-and-go school meals. Main Outcomes and Measures: The main outcomes were the percentage of youths reached by P-EBT and grab-and-go school meals, mean benefit received per recipient, and mean cost, including implementation costs and time costs to families per meal distributed. Results: Among 30 million youths eligible for free or reduced-price meals, grab-and-go meals reached an estimated 8.0 million (27%) and P-EBT reached 26.9 million (89%). The grab-and-go school meals program distributed 429 million meals per month in spring 2020, and the P-EBT program distributed $3.2 billion in monthly cash benefits, equivalent to 1.1 billion meals. Among those receiving benefits, the mean monthly benefit was larger for grab-and-go school meals ($148; range across states, $44-$176) compared with P-EBT ($110; range across states, $55-$114). Costs per meal delivered were lower for P-EBT ($6.46; range across states, $6.41-$6.79) compared with grab-and-go school meals ($8.07; range across states, $2.97-$15.27). The P-EBT program had lower public sector implementation costs but higher uncompensated time costs to families (eg, preparation time for meals) compared with grab-and-go school meals. Conclusions and Relevance: In this economic evaluation, both the P-EBT and grab-and-go school meal programs supported youths' access to food in complementary ways when US schools were closed during the COVID-19 pandemic from March to June 2020.

Does HMB Enhance Body Composition in Athletes? A Systematic Review and Meta-analysis.

ABSTRACT: 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 36(2): 585-592, 2022-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. Studies were deemed eligible for inclusion if they met the following criteria: (a) were an experimental design published in a peer-reviewed, English-language journal; (b) included human athletic populations; (c) assessed body mass (BM), fat mass (FM), or fat-free mass (FFM) using a validated measure; (d) and had a minimum supplementation period of 4 weeks. Separate analyses were performed for BM, FM, and FFM using robust variance random-effects meta-regression for multilevel data structures, with adjustments for small samples. The final analysis of BM comprised a total of 208 subjects from 7 studies. Analysis of FFM and FM encompassed 5 studies comprising 161 subjects and 5 studies comprising 128 subjects, respectively. The principal finding of this analysis suggests HMB may have a small, positive impact on FFM in athletes (0.30 ± 0.13; 95% confidence interval [CI]: -0.07 to 0.68; p = 0.08), although this seems specific to when protein intake is suboptimal (<1.6 g·kg-1·d-1). Consistent with previous research on athletes, HMB demonstrated no significant effect on BM (-0.02 ± 0.04; 95% CI: -0.14 to 0.10; p = 0.70) and a small, nonsignificant effect on FM (-0.33 ± 0.23; 95% CI: -0.96 to 0.31; p = 0.22). More research is required to establish HMB's influence on FFM in athletes. It is also important to consider the dosage of HMB and training parameters of athletes because these will likely influence the efficacy of supplementation.

Messages Promoting Healthy Kids' Meals: An Online RCT.

INTRODUCTION: Calorie labeling is now required on all large U.S. chain restaurant menus, but its influence on consumer behavior is mixed. This study examines whether different parent-targeted messages encourage parents to order lower-calorie meals for their children in a hypothetical online setting. METHODS: An online RCT was conducted with sociodemographically diverse primary caregivers of children aged 6-12 years (data collected and analyzed in 2017-2019). Participants (N=2,373) were randomized to see 1 of 4 messages: (1) nonfood control, (2) kids' meals are the right size for children, (3) doctors recommend a 600 kcal per meal limit for kids, or (4) 600 kcal per meal is a generally recommended limit for kids. Participants ordered hypothetical meals for their children and themselves and rated meal and message perceptions. RESULTS: There were no significant differences between conditions in calories ordered for children at either restaurant, although all 3 food message conditions ordered fewer calories for their children than the control (full service: 27-68 fewer kcal, fast food: 18-64 fewer kcal). The general 600 kcal/meal limit message consistently performed best across outcomes, encouraging parents to order the fewest calories for their children at both restaurants (5%-7% fewer) and significantly increasing their understanding of calorie recommendations for kids' meals. It also significantly reduced fast-food calories parents ordered for themselves compared with the control (-106 kcal, p=0.042). CONCLUSIONS: Although no statistically significant differences were detected, messages with specific calorie recommendations for kids led parents to order lower-calorie restaurant meals for their children, suggesting that additional real-world studies with larger sample sizes are warranted.

A Qualitative Study of Parents With Children 6 to 12 Years Old: Use of Restaurant Calorie Labels to Inform the Development of a Messaging Campaign.

BACKGROUND: US law mandates that chain restaurants with 20 or more locations post calorie information on their menus to inform consumers and encourage healthy choices. Few qualitative studies have assessed how parents perceive and use this information when ordering for their children and what types of accompanying messages might increase use of calorie labels when ordering food. OBJECTIVE: We aimed to better understand parents' perceptions and use of calorie labeling and the types of messages that might increase use. DESIGN: We conducted 10 focus groups (n = 58) and 20 shop-along interviews (n = 20). Focus group participants discussed their hypothetical orders and restaurant experiences when dining with their children, and shop-along participants verbalized their decision processes while ordering at a restaurant. Both groups gave feedback on 4 public service messages aimed to increase healthier ordering for children. All interviews were voice-recorded and transcribed. PARTICIPANTS/SETTING: Participants were primary caregivers of at least 1 child between 6 and 12 years who reported having less than a college education at the time of screening and who commonly ate at chain restaurants. Focus groups were conducted in a conference room, and shop-alongs were conducted in quick-serve and full-service chain restaurants around Philadelphia between August 2016 and May 2017. ANALYSES: A modified grounded theory approach was used to extract themes from transcripts. RESULTS: Thematic analysis of transcripts revealed 5 key themes: (1) parents' use of calorie labels; (2) differences across restaurant settings; (3) nonjudgmental information; (4) financial value and enjoyment of food; and (5) message preferences. These themes suggested that nonjudgmental, fact-based messages that highlight financial value, feelings of fullness, and easy meal component swaps without giving up the treatlike aspect of eating out may be particularly helpful for consumers. CONCLUSIONS: These findings can inform current US Food and Drug Administration campaign efforts to support consumer use of calorie labels on menus.

A systematic review of the effectiveness of promoting water intake to reduce sugar-sweetened beverage consumption.

OBJECTIVE: To examine whether the promotion of water intake could reduce sugar-sweetened beverage (SSB) consumption or purchases independent of interventions that target SSBs. METHODS: Seven databases were systematically searched. Included studies used water promotion as the primary intervention; used a controlled trial, single group pre-post, or prospective cohort study design; included a measure of SSB consumption or purchase; enrolled human participants of any age who lived in high-income or middle-income countries; contained original data; and appeared in a peer-reviewed English-language article published from 1 January 2000 to January 4, 2019. The search yielded 7068 publications, from which 108 were chosen for full-text review. Seventeen were included in this review. RESULTS: Nine of the 17 studies were randomized controlled trials, six were nonrandomized controlled trials, and 2 were single-group pre-post studies. Participants were primarily children and adolescents. Interventions included water provision, education or promotion activities. Ten of 17 studies were at low or some/moderate risk of bias. Seven studies showed a statistically significant decrease in SSB consumption of which only 2 were at low or some/moderate risk of bias. CONCLUSIONS: This review found limited evidence that interventions aimed solely at increasing water consumption reduce SSB intake. Further research is needed to investigate whether interventions that combine water promotion and SSB reduction strategies could be synergistic for reducing SSB intake.

Sex Differences in Resistance Training: A Systematic Review and Meta-Analysis.

Roberts, BM, Nuckols, G, and Krieger, JW. Sex differences in resistance training: A systematic review and meta-analysis. J Strength Cond Res 34(5): 1448-1460, 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 resistance training protocol. The protocol was pre-registered with PROSPERO (CRD42018094276). Meta-analyses were performed using robust variance random effects modeling for multilevel data structures, with adjustments for small samples using package robumeta in R. Statistical significance was set at P < 0.05. The analysis of hypertrophy comprised 12 outcomes from 10 studies with no significant difference between males and females (effect size [ES] = 0.07 ± 0.06; P = 0.31; I = 0). The analysis of upper-body strength comprised 19 outcomes from 17 studies with a significant effect favoring females (ES = -0.60 ± 0.16; P = 0.002; I = 72.1). The analysis of lower-body strength comprised 23 outcomes from 23 studies with no significant difference between sexes (ES = -0.21 ± 0.16; P = 0.20; I = 74.7). We found that males and females adapted to resistance training with similar effect sizes for hypertrophy and lower-body strength, but females had a larger effect for relative upper-body strength. Given the moderate effect size favoring females in the upper-body strength analysis, it is possible that untrained females display a higher capacity to increase upper-body strength than males. Further research is required to clarify why this difference occurs only in the upper body and whether the differences are due to neural, muscular, motor learning, or are an artifact of the short duration of studies included.

Resistance Training Frequencies of 3 and 6 Times Per Week Produce Similar Muscular Adaptations in Resistance-Trained Men.

Saric, J, Lisica, D, Orlic, I, Grgic, J, Krieger, JW, Vuk, S, and Schoenfeld, BJ. Resistance training frequencies of 3 and 6 times per week produce similar muscular adaptations in resistance-trained men. J Strength Cond Res 33(7S): S122-S129, 2019-We examined the effects of resistance training (RT) frequency performed 3 times per week (RT3) vs. 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 strength were assessed using the 1 repetition maximum test. Also, muscular endurance (60% 1 repetition maximum performed to momentary failure) and muscle thickness (elbow flexors, elbow extensors, rectus femoris, and vastus intermedius) were measured before and after intervention. Pre-to-post intervention, both groups increased upper-body strength (RT3: +4%; RT6: +6%) and lower-body strength (RT3: +22%; RT6: +18%) with no significant between-group differences. No significant pre-to-post intervention increases in muscular endurance were seen in either of the training groups. Both groups increased elbow extensor thickness (RT3: +14%; RT6: +11%), rectus femoris thickness (RT3: +5%; RT6: +6%), and vastus intermedius thickness (RT3: +10%; RT6: +11%) with no significant between-group differences. Only the RT3 group significantly increased elbow flexor thickness from pre-to-post intervention (+7%). When training volume is equated, it seems that RT performed either 3 or 6 times per week can result in similar strength gains over a 6-week training period. Furthermore, under volume-equated conditions, comparable hypertrophy results may also be expected with both RT frequencies. Finally, no changes were seen in muscular endurance possibly because of the considerable interindividual variability in responses. The findings presented herein might be of interest to coaches, exercise practitioners, athletes, and recreational trainees.

Effect of Resistance Training Frequency on Gains in Muscular Strength: A Systematic Review and Meta-Analysis.

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 muscular strength outcomes with different RT frequencies. METHODS: To carry out this review, English-language literature searches of the PubMed/MEDLINE, Scopus, and SPORTDiscus databases were conducted. The meta-analysis was performed using a random-effects model. The meta-analysis models were generated with RT frequencies classified as a categorical variable as either 1, 2, 3, or 4+ times/week, or, if there were insufficient data in subgroup analyses, the training frequencies were categorized as 1, 2, or 3 times/week. Subgroup analyses were performed for potential moderators, including (1) training volume; (2) exercise selection for the 1 repetition maximum (RM) test (for both multi-joint and single-joint exercises); (3) upper and lower body strength gains; (4) training to muscular failure (for studies involving and not involving training to muscular failure); (5) age (for both middle-aged/older adults and young adults); and (6) sex (for men and for women). The methodological quality of studies was appraised using the modified Downs and Black checklist. RESULTS: A total of 22 studies were found to meet the inclusion criteria. The average score on the Downs and Black checklist was 18 (range 13-22 points). Four studies were classified as being of good methodological quality, while the rest were classified as being of moderate methodological quality. Results of the meta-analysis showed a significant effect (p = 0.003) of RT frequency on muscular strength gains. Effect sizes increased in magnitude from 0.74, 0.82, 0.93, and 1.08 for training 1, 2, 3, and 4+ times per week, respectively. A subgroup analysis of volume-equated studies showed no significant effect (p = 0.421) of RT frequency on muscular strength gains. The subgroup analysis for exercise selection for the 1RM test suggested a significant effect of RT frequency on multi-joint (p < 0.001), but not single-joint, 1RM test results (p = 0.324). The subgroup analysis for upper and lower body showed a significant effect of frequency (p = 0.004) for upper body, but not lower body, strength gains (p = 0.070). In the subgroup analysis for studies in which the training was and was not carried out to muscular failure, no significant effect of RT frequency was found. The subgroup analysis for the age groups suggested a significant effect of training frequency among young adults (p = 0.024), but not among middle-aged and older adults (p = 0.093). Finally, the subgroup analysis for sex indicated a significant effect of RT frequency on strength gains in women (p = 0.030), but not men (p = 0.190). CONCLUSIONS: The results of the present systematic review and meta-analysis suggest a significant effect of RT frequency as higher training frequencies are translated into greater muscular strength gains. However, these effects seem to be primarily driven by training volume because when the volume is equated, there was no significant effect of RT frequency on muscular strength gains. Thus, from a practical standpoint, greater training frequencies can be used for additional RT volume, which is then likely to result in greater muscular strength gains. However, it remains unclear whether RT frequency on its own has significant effects on strength gain. It seems that higher RT frequencies result in greater gains in muscular strength on multi-joint exercises in the upper body and in women, and, finally, in contrast to older adults, young individuals seem to respond more positively to greater RT frequencies. More evidence among resistance-trained individuals is needed as most of the current studies were performed in untrained participants.

Strength, body composition, and functional outcomes in the squat versus leg press exercises.

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 solely performed squats for the lower body; a leg press-only group (LP) that solely performed leg presses for the lower body, or a combined squat and leg press group (SQ-LP) that performed both squats and leg presses for the lower body. All other RT variables were held constant. The study period lasted 10 weeks with subjects performing 2 lower body workouts per week comprising 6 sets per session at loads corresponding to 8-12 RM with 90- to 120-second rest intervals. RESULTS: Results showed that SQ had greater transfer to maximal squat strength compared to the leg press. Effect sizes favored SQ and SQ-LP versus LP with respect to countermovement jump while greater effect sizes for dynamic balance were noted for SQ-LP and LP compared to SQ, although no statistical differences were noted between conditions. CONCLUSIONS: These findings suggest that both free weights and machines can improve functional outcomes, and that the extent of transfer may be specific to the given task.

A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.

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 with RET ≥6 weeks in duration and dietary protein supplementation. DESIGN: Random-effects meta-analyses and meta-regressions with four a priori determined covariates. Two-phase break point analysis was used to determine the relationship between total protein intake and changes in fat-free mass (FFM). RESULTS: Data from 49 studies with 1863 participants showed that dietary protein supplementation significantly (all p<0.05) increased changes (means (95% CI)) in: strength-one-repetition-maximum (2.49 kg (0.64, 4.33)), FFM (0.30 kg (0.09, 0.52)) and muscle size-muscle fibre cross-sectional area (CSA; 310 µm2 (51, 570)) and mid-femur CSA (7.2 mm2 (0.20, 14.30)) during periods of prolonged RET. The impact of protein supplementation on gains in FFM was reduced with increasing age (-0.01 kg (-0.02,-0.00), p=0.002) and was more effective in resistance-trained individuals (0.75 kg (0.09, 1.40), p=0.03). Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM. SUMMARY/CONCLUSION: Dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults. Increasing age reduces and training experience increases the efficacy of protein supplementation during RET. With protein supplementation, protein intakes at amounts greater than ~1.6 g/kg/day do not further contribute RET-induced gains in FFM.

Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis.

Schoenfeld, BJ, Grgic, J, Ogborn, D, and Krieger, JW. Strength and hypertrophy adaptations between low- vs. high-load resistance training: a systematic review and meta-analysis. J Strength Cond Res 31(12): 3508-3523, 2017-The purpose of this article 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- vs. high-load resistance training protocols. Searches of PubMed/MEDLINE, Cochrane Library, and Scopus were conducted for studies that met the following criteria: (a) an experimental trial involving both low-load training [≤60% 1 repetition maximum (1RM)] and high-load training (>60% 1RM); (b) with all sets in the training protocols being performed to momentary muscular failure; (c) at least one method of estimating changes in muscle mass or dynamic, isometric, or isokinetic strength was used; (d) the training protocol lasted for a minimum of 6 weeks; (e) 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- vs. low-load training, whereas 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.

The effects of short versus long inter-set rest intervals in resistance training on measures of muscle hypertrophy: A systematic review.

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, Scopus, Web of Science, Cochrane Library, and Physiotherapy Evidence Database (PEDro) electronic databases. Six studies were found to have met the inclusion criteria: (a) an experimental trial published in an English-language peer-reviewed journal; (b) the study compared the use of short (≤60 s) to long (>60 s) inter-set rest intervals in a traditional dynamic resistance exercise using both concentric and eccentric muscle actions, with the only difference in resistance training among groups being the inter-set rest interval duration; (c) at least one method of measuring changes in muscle mass was used in the study; (d) the study lasted for a minimum of four weeks, employed a training frequency of ≥2 resistance training days per week, and (e) used human participants without known chronic disease or injury. Current evidence indicates that both short and long inter-set rest intervals may be useful when training for achieving gains in muscle hypertrophy. Novel findings involving trained participants using measures sensitive to detect changes in muscle hypertrophy suggest a possible advantage for the use of long rest intervals to elicit hypertrophic effects. However, due to the paucity of studies with similar designs, further research is needed to provide a clear differentiation between these two approaches.

Hypertrophic Effects of Concentric vs. Eccentric Muscle Actions: A Systematic Review and Meta-analysis.

Schoenfeld, BJ, Ogborn, DI, Vigotsky, AD, Franchi, MV, and Krieger, JW. Hypertrophic effects of concentric vs. eccentric muscle actions: A systematic review and meta-analysis. J Strength Cond Res 31(9): 2599-2608, 2017-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 vs. eccentric training in healthy adults after regimented resistance training (RT). Studies were deemed eligible for inclusion if they met the following criteria: (a) were an experimental trial published in an English-language refereed journal; (b) directly compared concentric and eccentric actions without the use of external implements (i.e., blood pressure cuffs) and all other RT variables equivalent; (c) measured morphologic changes using biopsy, imaging (magnetic resonance imaging, computerized tomography, or ultrasound), bioelectrical impedance, and/or densitometry; (d) had a minimum duration of 6 weeks; and (e) used human participants without musculoskeletal injury or any health condition that could directly, or through the medications associated with the management of said condition, be expected to impact the hypertrophic response to resistance exercise. A systematic literature search determined that 15 studies met inclusion criteria. Results showed that eccentric muscle actions resulted in a greater effect size (ES) compared with concentric actions, but results did not reach statistical significance (ES difference = 0.25 ± 0.13; 95% confidence interval: -0.03 to 0.52; p = 0.076). The mean percent change in muscle growth across studies favored eccentric compared with concentric actions (10.0% vs. 6.8, respectively). The findings indicate the importance of including eccentric and concentric actions in a hypertrophy-oriented RT program, as both have shown to be effective in increasing muscle hypertrophy.

Comparison of amplitude-mode ultrasound versus air displacement plethysmography for assessing body composition changes following participation in a structured weight-loss programme in women.

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 the length of the study intended to facilitate a 500 calorie-a-day deficit. Subjects also performed 3 h a week of supervised aerobic exercise. Per cent fat mass and lean body mass were obtained via ADP and US both pre- and postintervention. Pretesting, post-testing and delta data for %fat resulted in no significant differences in mean values along with a slope of the regression line no different than one and a y-intercept no different than zero (P<0·05). Similar to %fat values, pretesting, post-testing and delta data for fat-free mass resulted in no significant differences in mean values along with a slope of the regression line no different than one and a y-intercept no different than zero (P<0·05) with the exception of the delta for slope (0·39, P = 0·04). The current findings indicate that US can provide a similar degree of accuracy for tracking group-based fat loss in women compared to ADP. Given the low-cost relative to DXA and ADP, researchers and practitioners therefore can consider US as a viable option for monitoring group-based changes in body fat over time.

Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis.

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 effect of volume on changes in muscle size (P = 0.002). Each additional set was associated with an increase in effect size (ES) of 0.023 corresponding to an increase in the percentage gain by 0.37%. Outcomes for weekly sets categorised as lower or higher within each study showed a significant effect of volume on changes in muscle size (P = 0.03); the ES difference between higher and lower volumes was 0.241, which equated to a percentage gain difference of 3.9%. Outcomes for weekly sets as a three-level categorical variable (<5, 5-9 and 10+ per muscle) showed a trend for an effect of weekly sets (P = 0.074). The findings indicate a graded dose-response relationship whereby increases in RT volume produce greater gains in muscle hypertrophy.