Publications by authors named "Jozo Grgic"

78 Publications

International Society of Sports Nutrition position stand: sodium bicarbonate and exercise performance.

J Int Soc Sports Nutr 2021 Sep 9;18(1):61. Epub 2021 Sep 9.

Performance & Physique Enhancement Laboratory, University of South Florida, Tampa, FL, 33612, USA.

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. Supplementation with sodium bicarbonate (doses from 0.2 to 0.5 g/kg) improves performance in muscular endurance activities, various combat sports, including boxing, judo, karate, taekwondo, and wrestling, and in high-intensity cycling, running, swimming, and rowing. The ergogenic effects of sodium bicarbonate are mostly established for exercise tasks of high-intensity that last between 30 s and 12 min. 2. Sodium bicarbonate improves performance in single- and multiple-bout exercise. 3. Sodium bicarbonate improves exercise performance in both men and women. 4. For single-dose supplementation protocols, 0.2 g/kg of sodium bicarbonate seems to be the minimum dose required to experience improvements in exercise performance. The optimal dose of sodium bicarbonate dose for ergogenic effects seems to be 0.3 g/kg. Higher doses (e.g., 0.4 or 0.5 g/kg) may not be required in single-dose supplementation protocols, because they do not provide additional benefits (compared with 0.3 g/kg) and are associated with a higher incidence and severity of adverse side-effects. 5. For single-dose supplementation protocols, the recommended timing of sodium bicarbonate ingestion is between 60 and 180 min before exercise or competition. 6. Multiple-day protocols of sodium bicarbonate supplementation can be effective in improving exercise performance. The duration of these protocols is generally between 3 and 7 days before the exercise test, and a total sodium bicarbonate dose of 0.4 or 0.5 g/kg per day produces ergogenic effects. The total daily dose is commonly divided into smaller doses, ingested at multiple points throughout the day (e.g., 0.1 to 0.2 g/kg of sodium bicarbonate consumed at breakfast, lunch, and dinner). The benefit of multiple-day protocols is that they could help reduce the risk of sodium bicarbonate-induced side-effects on the day of competition. 7. Long-term use of sodium bicarbonate (e.g., before every exercise training session) may enhance training adaptations, such as increased time to fatigue and power output. 8. The most common side-effects of sodium bicarbonate supplementation are bloating, nausea, vomiting, and abdominal pain. The incidence and severity of side-effects vary between and within individuals, but it is generally low. Nonetheless, these side-effects following sodium bicarbonate supplementation may negatively impact exercise performance. Ingesting sodium bicarbonate (i) in smaller doses (e.g., 0.2 g/kg or 0.3 g/kg), (ii) around 180 min before exercise or adjusting the timing according to individual responses to side-effects, (iii) alongside a high-carbohydrate meal, and (iv) in enteric-coated capsules are possible strategies to minimize the likelihood and severity of these side-effects. 9. Combining sodium bicarbonate with creatine or beta-alanine may produce additive effects on exercise performance. It is unclear whether combining sodium bicarbonate with caffeine or nitrates produces additive benefits. 10. Sodium bicarbonate improves exercise performance primarily due to a range of its physiological effects. Still, a portion of the ergogenic effect of sodium bicarbonate seems to be placebo-driven.
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http://dx.doi.org/10.1186/s12970-021-00458-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8427947PMC
September 2021

Effects of Caffeine on Resistance Exercise: A Review of Recent Research.

Authors:
Jozo Grgic

Sports Med 2021 Jul 22. Epub 2021 Jul 22.

Institute for Health and Sport, Victoria University, Melbourne, Australia.

In the last few years, a plethora of studies have explored the effects of caffeine on resistance exercise, demonstrating that this field of research is growing fast. This review evaluates and summarizes the most recent findings. Given that toxic doses of caffeine are needed to increase skeletal muscle contractility, the binding of caffeine to adenosine receptors is likely the primary mechanism for caffeine's ergogenic effects on resistance exercise. There is convincing evidence that caffeine ingestion is ergogenic for (i) one-repetition maximum, isometric, and isokinetic strength; and (ii) muscular endurance, velocity, and power in different resistance exercises, loads, and set protocols. Furthermore, there is some evidence that caffeine supplementation also may enhance adaptations to resistance training, such as gains in strength and power. Caffeine ingestion is ergogenic for resistance exercise performance in females, and the magnitude of these effects seems to be similar to that observed in men. Habitual caffeine intake and polymorphisms within CYP1A2 and ADORA2A do not seem to modulate caffeine's ergogenic effects on resistance exercise. Consuming lower doses of caffeine (e.g., 2-3 mg/kg) appears to be comparably ergogenic to consuming high doses of caffeine (e.g., 6 mg/kg). Minimal effective doses of caffeine seem to be around 1.5 mg/kg. Alternate caffeine sources such as caffeinated chewing gum, gel, and coffee are also ergogenic for resistance exercise performance. With caffeine capsules, the optimal timing of ingestion seems to be 30-60 min before exercise. Caffeinated chewing gums and gels may enhance resistance exercise performance even when consumed 10 min before exercise. It appears that caffeine improves performance in resistance exercise primarily due to its physiological effects. Nevertheless, a small portion of the ergogenic effect of caffeine seems to be placebo-driven.
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http://dx.doi.org/10.1007/s40279-021-01521-xDOI Listing
July 2021

Ergogenic Effects of Sodium Bicarbonate Supplementation on Middle-, But Not Short-Distance Swimming Tests: A Meta-Analysis.

J Diet Suppl 2021 Jun 21:1-12. Epub 2021 Jun 21.

Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.

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 placebo and sodium bicarbonate when considering data from all included studies (SMD: -0.10;  = 0.208) or in the subgroup analysis for 91.4-m and 100-m swimming tests (SMD: 0.11;  = 0.261). In the subgroup analysis for 200-m and 400-m swimming tests, there was a significant ergogenic effect of sodium bicarbonate (SMD: -0.22;  < 0.001; -1.3%). Overall, these results suggest that sodium bicarbonate ingestion improves performance in 200-m and 400-m swimming events. The ergogenic effects of this supplement were small, but they may also be of substantial practical importance given that placings in swimming competitions are commonly determined by narrow margins.
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http://dx.doi.org/10.1080/19390211.2021.1942381DOI Listing
June 2021

Ergogenic Effects of Acute Caffeine Intake on Muscular Endurance and Muscular Strength in Women: A Meta-Analysis.

Int J Environ Res Public Health 2021 05 27;18(11). Epub 2021 May 27.

Centre for Sport Studies, Rey Juan Carlos University, 43959 Fuenlabrada, Spain.

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-body and lower-body muscular endurance and muscular strength. Eight crossover placebo-controlled studies were included in the review. In the main meta-analysis that considered data from all included studies, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.25; = 0.027) and muscular strength (SMD = 0.18; < 0.001). In a subgroup analysis that considered only upper-body exercises, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.20; = 0.007) and muscular strength (SMD = 0.17; < 0.001). In a subgroup analysis that considered only lower-body exercises, there was no significant difference between caffeine and placebo for muscular endurance (SMD = 0.43; = 0.092) or muscular strength (SMD = 0.16; = 0.109). The main finding of this meta-analysis is that caffeine ingestion has a significant ergogenic effect on muscular endurance and muscular strength in women. The effects reported in this analysis are similar to those previously observed in men and suggest that women may use caffeine supplementation as an ergogenic aid for muscular performance. Future research is needed to explore the effects of caffeine on lower-body muscular endurance and muscular strength in this population.
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http://dx.doi.org/10.3390/ijerph18115773DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8199301PMC
May 2021

Effects of beta-alanine supplementation on Yo-Yo test performance: A meta-analysis.

Authors:
Jozo Grgic

Clin Nutr ESPEN 2021 06 20;43:158-162. Epub 2021 Apr 20.

Institute for Health and Sport, Victoria University, Melbourne, Australia. Electronic address:

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 effects of beta-alanine supplementation duration on Yo-Yo test performance, and the effects of beta-alanine supplementation on performance only in Yo-Yo level 2 test variants.

Results: Ten study groups were included in the meta-analysis. All studies included athletes as study participants. When considering all available studies, there was no significant difference between the placebo/control and beta-alanine groups (SMD: 0.68; 95% confidence interval [CI]: -0.30, 1.67). When considering only the studies that used supplementation protocols lasting between 6 and 12 weeks, there was a significant ergogenic effect of beta-alanine (SMD: 1.02; 95% CI: 0.01, 2.05). When considering only the studies that used the level 2 variants of the Yo-Yo test, there was a significant ergogenic effect of beta-alanine (SMD: 1.41; 95% CI: 0.35, 2.48).

Conclusions: This meta-analysis found that beta-alanine is ergogenic for Yo-Yo test performance in athletes when the supplementation protocol lasts between 6 and 12 weeks and when using the level 2 variants of the Yo-Yo test.
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http://dx.doi.org/10.1016/j.clnesp.2021.03.027DOI Listing
June 2021

Effects of Plyometric Jump Training on Repeated Sprint Ability in Athletes: A Systematic Review and Meta-Analysis.

Sports Med 2021 Oct 28;51(10):2165-2179. Epub 2021 Apr 28.

School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Crawley, WA, Australia.

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 explore the effects of PJT on RSA in athletes.

Methods: Searches for this review were conducted in four databases. We included studies that satisfied the following criteria: (1) examined the effects of a PJT exercise intervention on measures of RSA; (2) included athletes as study participants, with no restriction for sport practiced, age or sex; and (3) included a control group. The random-effects model was used for the meta-analyses. The methodological quality of the included studies was assessed using the PEDro checklist.

Results: From 6367 search records initially identified, 13 studies with a total of 16 training groups (n = 198) and 13 control groups (n = 158) were eligible for meta-analysis. There was a significant effect of PJT on RSA best sprint (ES = 0.75; p = 0.002) and RSA mean sprint (ES = 0.36; p = 0.045) performance. We did not find a significant difference between control and PJT for RSA fatigue resistance (ES = 0.16; p = 0.401). The included studies were classified as being of "moderate" or "high" methodological quality. Among the 13 included studies, none reported injury or any other adverse events.

Conclusion: PJT improves RSA best and mean performance in athletes, while there were no significant differences between control and PJT for RSA fatigue resistance. Improvements in RSA in response to PJT are likely due to neuro-mechanical factors (e.g., strength, muscle activation and coordination) that affect actual sprint performance rather than the ability to recover between sprinting efforts.
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http://dx.doi.org/10.1007/s40279-021-01479-wDOI Listing
October 2021

Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum.

Sports (Basel) 2021 Feb 22;9(2). Epub 2021 Feb 22.

Department of Health Sciences, CUNY Lehman College, Bronx, NY 10468, USA.

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 strength, moderate load training optimizes increases muscle hypertrophy, and low-load training optimizes increases local muscular endurance. However, despite the widespread acceptance of this theory, current research fails to support some of its underlying presumptions. Based on the emerging evidence, we propose a new paradigm whereby muscular adaptations can be obtained, and in some cases optimized, across a wide spectrum of loading zones. The nuances and implications of this paradigm are discussed herein.
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http://dx.doi.org/10.3390/sports9020032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7927075PMC
February 2021

Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis.

J Sport Health Sci 2021 Jan 23. Epub 2021 Jan 23.

Fitness Academy, Zagreb 10000, Croatia; Faculty of Kinesiology, University of Zagreb, Zagreb 10000, Croatia.

Purpose: 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 moderating effects of variables such as training status (trained vs. untrained), training volume (volume equated vs. volume non-equated), body region (upper vs. lower), exercise selection (multi- vs. single-joint exercises (only for strength)), and study design (independent vs. dependent groups).

Results: Fifteen studies were included in the review. All studies included young adults as participants. Meta-analysis indicated no significant difference between the training conditions for muscular strength (ES = -0.09; 95% confidence interval (95%CI): -0.22 to 0.05) and for hypertrophy (ES = 0.22; 95%CI: -0.11 to 0.55). Subgroup analyses that stratified the studies according to body region, exercise selection, or study design showed no significant differences between training conditions. In studies that did not equate training volume between the groups, the analysis showed significant favoring of non-failure training on strength gains (ES = -0.32; 95%CI: -0.57 to -0.07). In the subgroup analysis for resistance-trained individuals, the analysis showed a significant effect of training to failure for muscle hypertrophy (ES = 0.15; 95%CI: 0.03-0.26).

Conclusion: Training to muscle failure does not seem to be required for gains in strength and muscle size. However, training in this manner does not seem to have detrimental effects on these adaptations, either. More studies should be conducted among older adults and highly trained individuals to improve the generalizability of these findings.
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http://dx.doi.org/10.1016/j.jshs.2021.01.007DOI Listing
January 2021

International society of sports nutrition position stand: caffeine and exercise performance.

J Int Soc Sports Nutr 2021 Jan 2;18(1). Epub 2021 Jan 2.

Performance & Physique Enhancement Laboratory, University of South Florida, Tampa, FL, 33612, USA.

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 include, but are not limited to: muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions. 2. Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use, although the magnitude of its effects differs between individuals. 3. Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3-6 mg/kg body mass. Minimal effective doses of caffeine currently remain unclear but they may be as low as 2 mg/kg body mass. Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. 4. The most commonly used timing of caffeine supplementation is 60 min pre-exercise. Optimal timing of caffeine ingestion likely depends on the source of caffeine. For example, as compared to caffeine capsules, caffeine chewing gums may require a shorter waiting time from consumption to the start of the exercise session. 5. Caffeine appears to improve physical performance in both trained and untrained individuals. 6. Inter-individual differences in sport and exercise performance as well as adverse effects on sleep or feelings of anxiety following caffeine ingestion may be attributed to genetic variation associated with caffeine metabolism, and physical and psychological response. Other factors such as habitual caffeine intake also may play a role in between-individual response variation. 7. Caffeine has been shown to be ergogenic for cognitive function, including attention and vigilance, in most individuals. 8. Caffeine may improve cognitive and physical performance in some individuals under conditions of sleep deprivation. 9. The use of caffeine in conjunction with endurance exercise in the heat and at altitude is well supported when dosages range from 3 to 6 mg/kg and 4-6 mg/kg, respectively. 10. Alternative sources of caffeine such as caffeinated chewing gum, mouth rinses, energy gels and chews have been shown to improve performance, primarily in aerobic exercise. 11. Energy drinks and pre-workout supplements containing caffeine have been demonstrated to enhance both anaerobic and aerobic performance.
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http://dx.doi.org/10.1186/s12970-020-00383-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7777221PMC
January 2021

Effects of Sodium Bicarbonate Ingestion on Measures of Wingate Test Performance: A Meta-Analysis.

Authors:
Jozo Grgic

J Am Coll Nutr 2020 Dec 14:1-10. Epub 2020 Dec 14.

Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia.

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 in the review. There was no significant difference between the sodium bicarbonate and placebo trials for mean power in Wingate test 1 (standardized mean difference [SMD] = 0.02; 95% confidence interval [CI]: -0.07, 0.11) and test 3 (SMD = 0.21; 95% CI: -0.16, 0.58). There was a significant effect of sodium bicarbonate on mean power in Wingate test 2 (SMD = 0.09; 95% CI: 0.03, 0.16), and test 4 (SMD = 0.62; 95% CI: 0.15, 1.08). When considering studies that used shorter rest intervals between repeated Wingate tests, a significant effect of sodium bicarbonate was found on mean power in Wingate test 3 (SMD = 0.40; 95% CI: 0.01, 0.80). There was no significant difference between the sodium bicarbonate and placebo trials for peak power in Wingate test 1 (SMD = -0.01; 95% CI: -0.06, 0.04), test 2 (SMD = 0.02; 95% CI: -0.10, 0.13), or test 4 (SMD = 0.29; 95% CI: -0.13, 0.71). There was a significant effect of sodium bicarbonate on peak power in test 3 (SMD = 0.09; 95% CI: 0.00, 0.17). The results of this review suggest that sodium bicarbonate may provide an ergogenic effect on measures of repeated Wingate test performance.Key Teaching PointsSodium bicarbonate is a popular ergogenic aid. The Wingate test is commonly used to evaluate high-intensity exercise performance. While several studies explored the effects of sodium bicarbonate ingestion on Wingate test performance, the findings are conflicting.In this meta-analysis, 10 studies that examined the acute effects of sodium bicarbonate on single and/or repeated Wingate test performance were included.There was no significant difference between sodium bicarbonate and placebo trials for mean or peak power in a single Wingate test.However, sodium bicarbonate was ergogenic for mean power in repeated Wingate tests. Specifically, an ergogenic effect was found in test 2 and test 4 (standardized mean difference: 0.09 to 0.62). When considering only studies that used shorter rest intervals between repeated Wingate tests, an ergogenic effect was found in test 3 (standardized mean difference: 0.40).Sodium bicarbonate was also ergogenic for peak power in Wingate test 3, but with small effects (standardized mean difference: 0.09).
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http://dx.doi.org/10.1080/07315724.2020.1850370DOI Listing
December 2020

Caffeine Ingestion Enhances Repetition Velocity in Resistance Exercise: A Randomized, Crossover, Double-Blind Study Involving Control and Placebo Conditions.

J Hum Kinet 2020 Aug 31;74:177-183. Epub 2020 Aug 31.

Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.

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 supplementation (i.e., control), and after ingesting caffeine (6 mg/kg), and placebo (6 mg/kg of dextrose). At 50% 1RM, there was a significant effect of caffeine on mean velocity compared to control (effect size [ES] = 0.29; p = 0.003), but not when compared to placebo (ES = 0.09; p = 0.478). At 75% 1RM, there was a significant effect of caffeine on mean velocity compared to placebo (ES = 0.34; p = 0.001), and compared to control (ES = 0.32; p < 0.001). At 90% 1RM, there was a significant effect of caffeine on mean velocity compared to placebo (ES = 0.36; p < 0.001), and compared to control (ES = 0.46; p < 0.001). There was no significant difference between placebo and control in any of the analyzed outcomes. When evaluated pre-exercise and post-exercise, 20% to 44% and 28% to 52% of all participants identified caffeine and placebo trials beyond random chance, respectively. Given that the blinding of the participants was generally effective, and that there were no significant ergogenic effects of placebo ingestion, the improvements in performance following caffeine ingestion can be mainly attributed to caffeine's physiological mechanisms of action.
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http://dx.doi.org/10.2478/hukin-2020-0023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7706645PMC
August 2020

The Effects of Low-Load Vs. High-Load Resistance Training on Muscle Fiber Hypertrophy: A Meta-Analysis.

Authors:
Jozo Grgic

J Hum Kinet 2020 Aug 31;74:51-58. Epub 2020 Aug 31.

Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia.

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 failure); and, (b) assessed muscle fiber hypertrophy. A random-effects meta-analysis was performed to analyze the data. Ten study groups were included in the analysis. In the meta-analysis for the effects of low-load vs. high-load resistance training on type I muscle fiber hypertrophy, there was no significant difference between the training conditions (standardized mean difference: 0.28; 95% confidence interval: -0.27, 0.82; p = 0.316; I = 18%; 95% prediction interval: -0.71, 1.28). In the meta-analysis for the effects of low-load vs. high-load resistance training on type II muscle fiber hypertrophy, there was no significant difference between the training conditions (standardized mean difference: 0.30; 95% confidence interval: -0.05, 0.66; p = 0.089; I = 0%; 95% prediction interval: -0.28, 0.88). In this meta-analysis, there were no significant differences between low-load and high-load resistance training on hypertrophy of type I or type II muscle fibers. The 95% confidence and prediction intervals were very wide, suggesting that the true effect in the population and the effect reported in a future study conducted on this topic could be in different directions and anywhere from trivial to very large. Therefore, there is a clear need for future research on this topic.
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http://dx.doi.org/10.2478/hukin-2020-0013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7706639PMC
August 2020

A time and a place: A framework for caffeine periodization throughout the sporting year.

Nutrition 2021 02 5;82:111046. Epub 2020 Nov 5.

Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia.

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 these ergogenic properties, caffeine is widely used by athletes at all levels around both competition and training. Caffeine exerts its performance benefits through a variety of mechanisms, each of which may be of increased importance at a given stage of training or competition. Additionally, regular caffeine use may diminish the performance-enhancing effects of a subsequent dose of caffeine. Recently, interest in the concept of nutritional periodization has grown. Here we propose a framework for the periodization of caffeine through the sporting year, balancing its training and competition performance-enhancing effects, along with the need to mitigate any negative effects of habituation. Furthermore, the regular use of caffeine within training may support the development of positive beliefs toward caffeine by athletes-potentially serving to enhance future performance through placebo and expectancy mechanisms-as well as allowing for the optimization of individual athlete caffeine strategies. Although future work is required to validate some of the suggestions made, the framework proposed here represents a starting point for athletes to maximize caffeine's performance benefits across the sporting year.
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http://dx.doi.org/10.1016/j.nut.2020.111046DOI Listing
February 2021

CYP1A2 genotype and acute ergogenic effects of caffeine intake on exercise performance: a systematic review.

Eur J Nutr 2021 Apr 2;60(3):1181-1195. Epub 2020 Nov 2.

Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.

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 through nine databases.

Results: Seventeen studies were included in the review. Based on the included studies, it seems that individuals with the AA or AC/CC genotype may experience an increase in performance following caffeine ingestion. Significant differences between genotypes were found in four studies, and all four reported a more favorable response in the AA vs. AC/CC genotype. These results suggest that if there is an actual genotype-related effect of acute caffeine supplementation, it might be in that direction. In the studies that reported such data for aerobic endurance, the findings are specific to male participants performing cycling time trials (distances of ≥ 10 km) and ingesting caffeine 60 min before exercise. For high-intensity exercise, two studies reported that genotype variations determined the response to caffeine ingestion, even though the differences were either small (~ 1 additional repetition in high-load resistance exercise set performed to muscular failure) or inconsistent (i.e., observed only in one out of eight performance tests).

Conclusions: CYP1A2 genotype variations may modulate caffeine's ergogenic effects, but the differences between genotypes were small, inconsistent, or limited to specific exercise scenarios. Future studies with larger sample sizes are needed to fully elucidate this research area.
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http://dx.doi.org/10.1007/s00394-020-02427-6DOI Listing
April 2021

Alterations in Body Composition, Resting Metabolic Rate, Muscular Strength, and Eating Behavior in Response to Natural Bodybuilding Competition Preparation: A Case Study.

J Strength Cond Res 2020 Nov;34(11):3124-3138

Trexler Fitness LLC, Raleigh, North Carolina.

Schoenfeld, BJ, Alto, A, Grgic, J, Tinsley, G, Haun, CT, Campbell, BI, Escalante, G, Sonmez, GT, Cote, G, Francis, A, and Trexler, ET. Alterations in body composition, resting metabolic rate, muscular strength, and eating behavior in response to natural bodybuilding competition preparation: A case study. J Strength Cond Res 34(11): 3124-3138, 2020-We carried out a prospective case study in a high-level amateur natural male bodybuilder throughout preparation for 4 competitions and during the ensuing postcontest 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), multifrequency bioelectrical impedance analysis, blood pressure and heart rate assessment, resting metabolic rate via indirect calorimetry, skinfold testing, vertical jump height, isometric lower-body strength testing, and a 3-factor eating questionnaire. Blood work (including testosterone, thyroid hormone, sex hormone binding globulin, glomerular filtration rate, blood urea nitrogen, aspartate aminotransferase, alanine aminotransferase, white blood count, albumin to globulin ratio, and lipoprotein A) was obtained separately from an outside laboratory at 4 time points. We also assessed the effectiveness of a carbohydrate (carb) deplete and carb load peaking strategy employed immediately before competition. The subject employed a high-volume, high-frequency, whole-body training program throughout the study period. Average daily nutritional intakes ranged from 1,953 to 3,415 kcal: 104-386 g carb; 253-263 g protein, and; 57-95 g lipid. Body fat was reduced to very low levels (∼5%) immediately before competition, but this corresponded with a loss of lean mass. Alterations in metabolism, hormonal status, explosive strength, and psychological aspects of eating were observed during precontest preparation; however, all of these variables recovered quickly postcompetition. The implementation of a carb depleteand carb load peaking strategy acutely increased MT and thus may be a viable precontest approach to maximize muscular aesthetics.
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http://dx.doi.org/10.1519/JSC.0000000000003816DOI Listing
November 2020

Test-Retest Reliability of Velocity and Power in the Deadlift and Squat Exercises Assessed by the GymAware PowerTool System.

Front Physiol 2020 9;11:561682. Epub 2020 Sep 9.

Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.

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 the deadlift and squat exercises with loads of 30, 45, 60, 75, and 90% of one-repetition maximum. The consistency of test results between the first session and the second session was considered to represent the reliability with no familiarization session. The consistency of test results between the second session and the third session was considered to represent the reliability with one familiarization session because the first session simulates a familiarization session. Intraclass correlation coefficients (ICCs) ranged 0.63-0.99 in the deadlift, and 0.78-0.99 in the squat. ICCs were higher than 0.75 for 93 and 100% of all deadlift and squat tests, respectively. For velocity and power, standard error of measurement ranged 0.03-0.08 m/s and 20-176 W, respectively. The coefficient of variation ranged 2.2-10.6% for the deadlift and 2.6-6.9% for the squat tests. Except for peak and mean velocity at 30% of 1RM in the squat, we found no significant improvements in reliability with a familiarization session. The test-retest reliability of velocity and power assessed by the GYM system was moderate-to-excellent for the deadlift and good-to-excellent for the squat. Reliability of velocity and power did not seem to improve with a familiarization session.
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http://dx.doi.org/10.3389/fphys.2020.561682DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7510176PMC
September 2020

Acute effects of caffeine supplementation on resistance exercise, jumping, and Wingate performance: no influence of habitual caffeine intake.

Eur J Sport Sci 2021 Aug 2;21(8):1165-1175. Epub 2020 Oct 2.

Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia.

This study explored the influence of habitual caffeine intake on the acute effects of caffeine ingestion on resistance exercise, jumping, and Wingate performance. 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 ( = 13; habitual caffeine intake: 65 ± 46 mg/day) and as moderate-to-high caffeine users ( = 11; habitual caffeine intake: 235 ± 82 mg/day). Exercise performance was evaluated by measuring: (a) movement velocity, power, and muscular endurance in the bench press; (b) countermovement jump; and, (c) a Wingate test, performed in that order. Two-way repeated-measures ANOVA revealed a significant main effect ( < 0.05) for condition in the majority of analyzed exercise outcomes. In all cases, effect sizes for condition favoured caffeine and ranged from 0.14 to 0.97. Mean increases in velocity and power in resistance exercise ranged from 0.02 to 0.08 m/s and 42 to 156 W, respectively. The number of performed repetitions increased by 1.2 and jump height by 0.9 cm. Increases in power in the Wingate test ranged from 31 to 75 W. We did not find significant group × condition interaction effect ( > 0.05) in any of the analyzed exercise outcomes. Additionally, there were no significant correlations ( > 0.05; ranged from -0.29 to 0.32) between habitual caffeine intake and the absolute change in exercise performance. These results suggest that habitual caffeine intake might not moderate the ergogenic effects of acute caffeine supplementation on resistance exercise, jumping, and Wingate performance.
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http://dx.doi.org/10.1080/17461391.2020.1817155DOI Listing
August 2021

Effects of Resistance Training on Muscle Size and Strength in Very Elderly Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Sports Med 2020 Nov;50(11):1983-1999

Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia.

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.

Methods: Randomized controlled studies that explored the effects of resistance training in very elderly on muscle strength, handgrip strength, whole-muscle hypertrophy, and/or muscle fiber hypertrophy were included in the review. Meta-analyses of effect sizes (ESs) were used to analyze the data.

Results: Twenty-two studies were included in the review. The meta-analysis found a significant effect of resistance training on muscle strength in the very elderly [difference in ES = 0.97; 95% confidence interval (CI) 0.50, 1.44; p = 0.001]. In a subgroup analysis that included only the oldest-old participants (80 + years of age), there was a significant effect of resistance training on muscle strength (difference in ES = 1.28; 95% CI 0.28, 2.29; p = 0.020). For handgrip strength, we found no significant difference between resistance training and control groups (difference in ES = 0.26; 95% CI - 0.02, 0.54; p = 0.064). For whole-muscle hypertrophy, there was a significant effect of resistance training in the very elderly (difference in ES = 0 30; 95% CI 0.10, 0.50; p = 0.013). We found no significant difference in muscle fiber hypertrophy between resistance training and control groups (difference in ES = 0.33; 95% CI - 0.67, 1.33; p = 0.266). There were minimal reports of adverse events associated with the training programs in the included studies.

Conclusions: We found that very elderly can increase muscle strength and muscle size by participating in resistance training programs. Resistance training was found to be an effective way to improve muscle strength even among the oldest-old.
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http://dx.doi.org/10.1007/s40279-020-01331-7DOI Listing
November 2020

Both Caffeine and Placebo Improve Vertical Jump Performance Compared With a Nonsupplemented Control Condition.

Int J Sports Physiol Perform 2020 Jul 24;16(3):448-451. Epub 2020 Jul 24.

Purpose: To compare the acute effects of caffeine and placebo ingestion with a control condition (ie, no supplementation) on vertical jump performance.

Methods: The sample for this study consisted of 26 recreationally trained men. Following the familiarization visit, the subjects were randomized in a double-blind manner to 3 main conditions: placebo, caffeine, and control. Caffeine was administered in the form of a gelatin capsule in the dose of 6 mg·kg body weight-1. Placebo was also administered in the form of a gelatin capsule containing 6 mg·kg-1 of dextrose. Vertical jump performance was assessed using a countermovement jump performed on a force platform. Analyzed outcomes were vertical jump height and maximal power output.

Results: For vertical jump height, significant differences were observed between placebo and control conditions (g = 0.13; 95% confidence interval [CI], 0.03-0.24; +2.5%), caffeine and control conditions (g = 0.31; 95% CI, 0.17-0.50; +6.6%), and caffeine and placebo conditions (g = 0.19; 95% CI, 0.06-0.34; +4.0%). For maximal power output, no significant main effect of condition (P = .638) was found.

Conclusions: Ingesting a placebo or caffeine may enhance countermovement jump performance compared with the control condition, with the effects of caffeine versus control appearing to be greater than the effects of placebo versus control. In addition, caffeine was ergogenic for countermovement jump height compared with placebo. Even though caffeine and placebo ingestion improved vertical jump height, no significant effects of condition were found on maximal power output generated during takeoff.
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http://dx.doi.org/10.1123/ijspp.2019-1028DOI Listing
July 2020

Test-Retest Reliability of the One-Repetition Maximum (1RM) Strength Assessment: a Systematic Review.

Sports Med Open 2020 Jul 17;6(1):31. Epub 2020 Jul 17.

Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia.

Background: The test-retest reliability of the one-repetition maximum (1RM) test varies 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 and resistance training experience.

Objectives: The aim of this paper was to review studies that investigated the reliability of the 1RM test of muscular strength and summarize their findings.

Methods: The PRISMA guidelines were followed for this systematic review. Searches for studies were conducted through eight databases. Studies that investigated test-retest reliability of the 1RM test and presented intra-class correlation coefficient (ICC) and/or coefficient of variation (CV) were included. The COSMIN checklist was used for the assessment of the methodological quality of the included studies.

Results: After reviewing 1024 search records, 32 studies (pooled n = 1595) on test-retest reliability of 1RM assessment were found. All the studies were of moderate or excellent methodological quality. Test-retest ICCs ranged from 0.64 to 0.99 (median ICC = 0.97), where 92% of ICCs were ≥ 0.90, and 97% of ICCs were ≥ 0.80. The CVs ranged from 0.5 to 12.1% (median CV = 4.2%). ICCs were generally high (≥ 0.90), and most CVs were low (< 10%) for 1RM tests: (1) among those without and for those with some resistance training experience, (2) conducted with or without familiarization sessions, (3) with single-joint or multi-joint exercises, (4) for upper- and lower-body strength assessment, (5) among females and males, and (6) among young to middle-aged adults and among older adults. Most studies did not find systematic changes in test results between the trials.

Conclusions: Based on the results of this review, it can be concluded that the 1RM test generally has good to excellent test-retest reliability, regardless of resistance training experience, number of familiarization sessions, exercise selection, part of the body assessed (upper vs. lower body), and sex or age of participants. Researchers and practitioners, therefore, can use the 1RM test as a reliable test of muscular strength.
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http://dx.doi.org/10.1186/s40798-020-00260-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7367986PMC
July 2020

Effects of Combining Caffeine and Sodium Bicarbonate on Exercise Performance: A Review with Suggestions for Future Research.

Authors:
Jozo Grgic

J Diet Suppl 2021 25;18(4):444-460. Epub 2020 Jun 25.

Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia.

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 one study found that the combined ingestion of both supplements provided additive effects. In other studies, the following findings were observed: (a) only caffeine was ergogenic; (b) isolated and combined ingestion of both supplements was comparably ergogenic; (c) neither isolated nor combined ingestion of caffeine and sodium bicarbonate provided a performance-enhancing effect; and, (d) caffeine and caffeine plus sodium bicarbonate improved performance compared to sodium bicarbonate (but not as compared to placebo). Even though studies used currently recommended protocols of caffeine supplementation and exercise tasks for which the isolated ergogenic effects of caffeine and sodium bicarbonate are already established, the response to sodium bicarbonate supplementation was very variable, which might largely explain the discrepancies in the findings. The protocols of sodium bicarbonate ingestion generally resulted in high incidence and severity of side-effects, which might have had a negative effect on exercise performance. Future studies that optimize protocols of sodium bicarbonate supplementation are needed to fully explore if combining caffeine and sodium bicarbonate indeed provides any additive effects on exercise performance.
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http://dx.doi.org/10.1080/19390211.2020.1783422DOI Listing
September 2021

Effects of plyometric vs. resistance training on skeletal muscle hypertrophy: A review.

J Sport Health Sci 2020 Jun 21. Epub 2020 Jun 21.

Faculty of Kinesiology, University of Zagreb, Zagreb 10000, Croatia.

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 hypertrophy.

Results: Eight relevant studies were included in the review. Six studies compared the effects of plyometric vs. resistance training on muscle hypertrophy, while 2 studies explored the effects of combining plyometric and resistance training vs. isolated resistance training on acute anabolic signaling or muscle hypertrophy. Based on the results of these studies, we conclude that plyometric and resistance training may produce similar effects on whole muscle hypertrophy for the muscle groups of the lower extremities. Therefore, it seems that plyometric training has a greater potential for inducing increases in muscle size than previously thought. Despite the findings observed at the whole muscle level, the evidence for the effects of plyometric training on hypertrophy on the muscle fiber level is currently limited for drawing inferences. Compared to isolated resistance training, combining plyometric and resistance exercise does not seem to produce additive effects on anabolic signaling or muscle growth; however, this area requires future study. The limitations of the current body of evidence are that the findings are specific to (a) musculature of the lower extremities, (b) short-term training interventions that lasted up to 12 weeks, and (c) previously untrained or recreationally active participants.

Conclusion: This review highlights that plyometric and resistance training interventions may produce similar effects on whole muscle hypertrophy, at least for the muscle groups of the lower extremities, in untrained and recreationally trained individuals, and over short-term (i.e., ≤12 weeks) intervention periods.
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http://dx.doi.org/10.1016/j.jshs.2020.06.010DOI Listing
June 2020

Test-retest reliability of the 30-15 Intermittent Fitness Test: A systematic review.

J Sport Health Sci 2021 07 15;10(4):413-418. Epub 2020 May 15.

Institute for Health and Sport (IHES), Victoria University, Melbourne, VIC 3011, Australia.

Purpose: This review aimed to synthesize previous findings on the test-retest reliability of the 30-15 Intermittent Fitness Test (IFT).

Methods: The literature searches were performed in 8 databases. Studies that examined the test-retest reliability of the 30-15 IFT and presented the intraclass correlation coefficient (ICC) and/or the coefficient of variation (CV) for maximal velocity and/or peak heart rate were included. The consensus-based standards for the selection of health measurement instruments (COSMIN) checklist was used for the assessment of the methodological quality of the included studies.

Results: Seven studies, with a total of 10 study groups, explored reliability of maximal velocity assessed by the 30-15 IFT. ICCs ranged from 0.80 to 0.99, where 70% of ICCs were ≥0.90. CVs for maximal velocity ranged from 1.5% to 6.0%. Six studies, with a total of 7 study groups, explored reliability of peak heart rate as assessed by the 30-15 IFT. ICCs ranged from 0.90 to 0.97 (i.e., all ICCs were ≥0.90). CVs ranged from 0.6% to 4.8%. All included studies were of excellent methodological quality.

Conclusion: From the results of this systematic review, it can be concluded that the 30-15 IFT has excellent test-retest reliability for both maximal velocity and peak heart rate. The test may, therefore, be used as a reliable measure of fitness in research and sports practice.
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http://dx.doi.org/10.1016/j.jshs.2020.04.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8343059PMC
July 2021

Do the anatomical and physiological properties of a muscle determine its adaptive response to different loading protocols?

Physiol Rep 2020 05;8(9):e14427

Department of Health Sciences, CUNY Lehman College, Bronx, NY, USA.

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 (muscle with a similar composition of slow and fast-twitch fibers) when subjected to light (20-30 repetition maximum) and heavy (6-10 repetition maximum) load plantarflexion exercise.

Methods: The study employed a within-subject design whereby 26 untrained young men had their lower limbs randomized to perform plantarflexion with a low-load (LIGHT) and a high-load (HEAVY) for 8 weeks. Muscle thickness was estimated via B-mode ultrasound and maximal strength was determined by isometric dynamometry.

Results: Results showed that changes in muscle thickness were similar for the soleus and the gastrocnemius regardless of the magnitude of load used in training. Furthermore, each of the calf muscles demonstrated robust hypertrophy, with the lateral gastrocnemius showing greater gains compared to the medial gastrocnemius and soleus. Both HEAVY and LIGHT training programs elicited similar hypertrophic increases in the triceps surae. Finally, isometric strength increases were similar between loading conditions.

Conclusions: The triceps surae muscles respond robustly to regimented exercise and measures of muscle hypertrophy and isometric strength appear independent of muscle fiber type composition. Moreover, the study provides further evidence that low-load training is a viable strategy to increase hypertrophy in different human muscles, with hypertrophic increases similar to that observed using heavy loads.
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http://dx.doi.org/10.14814/phy2.14427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7186566PMC
May 2020

CYP1A2 genotype and acute effects of caffeine on resistance exercise, jumping, and sprinting performance.

J Int Soc Sports Nutr 2020 Apr 15;17(1):21. Epub 2020 Apr 15.

Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia.

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 of CYP1A2 (rs762551) on the individual variation in responses to caffeine ingestion.

Methods: Twenty-two men were included as participants (AA homozygotes n = 13; C-allele carriers n = 9) and were tested after the ingestion of caffeine (3 mg/kg of body mass) and a placebo. Exercise performance was assessed with the following outcomes: (a) movement velocity and power output in the bench press exercise with loads of 25, 50, 75, and 90% of one-repetition maximum (1RM); (b) quality and quantity of performed repetitions in the bench press exercise performed to muscular failure with 85% 1RM; (c) vertical jump height in a countermovement jump test; and (d) power output in a Wingate test.

Results: Compared to placebo, caffeine ingestion enhanced: (a) movement velocity and power output across all loads (effect size [ES]: 0.20-0.61; p <  0.05 for all); (b) the quality and quantity of performed repetitions with 85% of 1RM (ES: 0.27-0.85; p <  0.001 for all); (c) vertical jump height (ES: 0.15; p = 0.017); and (d) power output in the Wingate test (ES: 0.33-0.44; p <  0.05 for all). We did not find a significant genotype × caffeine interaction effect (p-values ranged from 0.094 to 0.994) in any of the analyzed performance outcomes.

Conclusions: Resistance-trained men may experience acute improvements in resistance exercise, jumping, and sprinting performance following the ingestion of caffeine. The comparisons of the effects of caffeine on exercise performance between individuals with the AA genotype and AC/CC genotypes found no significant differences.

Trial Registration: Australian New Zealand Clinical Trials Registry. ID: ACTRN12619000885190.
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http://dx.doi.org/10.1186/s12970-020-00349-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7161272PMC
April 2020

ADOR2A C Allele Carriers Exhibit Ergogenic Responses to Caffeine Supplementation.

Nutrients 2020 Mar 11;12(3). Epub 2020 Mar 11.

Institute for Health and Sport (IHES), Victoria University, Melbourne 3011, Australia.

Caffeine's ergogenic effects on exercise performance are generally explained by its ability to bind to adenosine receptors. is the gene that encodes A subtypes of adenosine receptors. It has been suggested that gene polymorphisms may be responsible for the inter-individual variations in the effects of caffeine on exercise performance. In the only study that explored the influence of variation in -in this case, a common polymorphism (rs5751876)-on the ergogenic effects of caffeine on exercise performance, C allele carriers were identified as "non-responders" to caffeine. To explore if C allele carriers are true "non-responders" to the ergogenic effects of caffeine, in this randomized, double-blind study, we examined the acute effects of caffeine ingestion among a sample consisting exclusively of C allele carriers. Twenty resistance-trained men identified as C allele carriers (CC/CT genotype) were tested on two occasions, following the ingestion of caffeine (3 mg/kg) and a placebo. Exercise performance was evaluated with movement velocity, power output, and muscle endurance during the bench press exercise, countermovement jump height, and power output during a Wingate test. Out of the 25 analyzed variables, caffeine was ergogenic in 21 (effect size range: 0.14 to 0.96). In conclusion, (rs5751876) C allele carriers exhibited ergogenic responses to caffeine ingestion, with the magnitude of improvements similar to what was previously reported in the literature among samples that were not genotype-specific. Therefore, individuals with the CT/CC genotype may still consider supplementing with caffeine for acute improvements in performance.
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http://dx.doi.org/10.3390/nu12030741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7146260PMC
March 2020

Authors' Reply to Painelli et al.: Comment on "Caffeine and Exercise: What Next?"

Sports Med 2020 06;50(6):1219-1221

Institute for Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia.

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http://dx.doi.org/10.1007/s40279-020-01279-8DOI Listing
June 2020

Effects of Sodium Bicarbonate Supplementation on Muscular Strength and Endurance: A Systematic Review and Meta-analysis.

Sports Med 2020 Jul;50(7):1361-1375

Institute for Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia.

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.

Methods: A search for studies was performed using five databases. Meta-analyses of standardized mean differences (SMDs) were performed using a random-effects model to determine the effects of sodium bicarbonate supplementation on muscular strength (assessed by changes in peak force [N], peak torque [N m], or maximum load lifted [kg]) and muscular endurance (assessed by changes in the number of repetitions performed, isokinetic total work, or time to maintain isometric force production). Subgroup meta-analyses were conducted for the muscular endurance of small vs. large muscle groups and muscular strength tested in a rested vs. fatigued state. A random-effects meta-regression analysis was used to explore possible trends in the effects of: (a) timing of sodium bicarbonate ingestion; and (b) acute increase in blood bicarbonate concentration (from baseline to pre-exercise), on muscular endurance and muscular strength.

Results: Thirteen studies explored the effects of sodium bicarbonate on muscular endurance and 11 on muscular strength. Sodium bicarbonate supplementation was found to be ergogenic for muscular endurance (SMD = 0.37; 95% confidence interval [CI]: 0.15, 0.59; p = 0.001). The performance-enhancing effects of sodium bicarbonate were significant for both small (SMD = 0.31; 95% CI: 0.04, 0.59; p = 0.025) and large muscle groups (SMD = 0.40; 95% CI: 0.13, 0.66; p = 0.003). Sodium bicarbonate ingestion was not found to enhance muscular strength (SMD = - 0.03; 95% CI: - 0.18, 0.12; p = 0.725). No significant effects were found regardless of whether the testing was carried out in a rested (SMD = 0.02; 95% CI: - 0.09, 0.13; p = 0.694) or fatigued (SMD = - 0.16; 95% CI: - 0.59, 0.28; p = 0.483) state. No significant linear trends in the effects of timing of sodium bicarbonate ingestion or acute increase in blood bicarbonate concentrations on muscular endurance or muscular strength were found.

Conclusions: Overall, sodium bicarbonate supplementation acutely improves muscular endurance of small and large muscle groups, but no significant ergogenic effect on muscular strength was found.
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http://dx.doi.org/10.1007/s40279-020-01275-yDOI Listing
July 2020

What influence does resistance exercise order have on muscular strength gains and muscle hypertrophy? A systematic review and meta-analysis.

Eur J Sport Sci 2021 Feb 28;21(2):149-157. Epub 2020 Feb 28.

Metabolism, Nutrition, and Exercise Laboratory, Physical Education and Sport Center, Londrina State University, Londrina, Brazil.

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 databases. Studies were included if they explored the effects of EO on dynamic muscular strength and/or muscle hypertrophy. The meta-analysis was performed using a random-effects model with Hedges' g effect size (ES). The methodological quality of studies was appraised using the TESTEX checklist. Eleven good-to-excellent methodological quality studies were included in the review. When all strength tests, that is, both in multi-joint (MJ) and single-joint (SJ) exercises were considered, there was no difference between the EOs (ES = -0.11;   0.306). However, there was a difference between the MJ-to-SJ and SJ-to-MJ orders for strength gains in the MJ exercises, favouring starting the exercise session with MJ exercises (ES = 0.32;   0.034), and the strength gains in the SJ exercises, favouring starting the exercise session with SJ exercises (ES = -0.58;   0.032). No significant effect of EO was observed for hypertrophy combining site-specific and indirect measures (ES = 0.03;   0.862). In conclusion, increases in muscular strength are the largest in the exercises performed at the beginning of an exercise session. For muscle hypertrophy, our meta-analysis indicated that both MJ-to-SJ and SJ-to-MJ EOs may produce similar results.
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http://dx.doi.org/10.1080/17461391.2020.1733672DOI Listing
February 2021

The Effects of Caffeine Ingestion on Measures of Rowing Performance: A Systematic Review and Meta-Analysis.

Nutrients 2020 Feb 8;12(2). Epub 2020 Feb 8.

Faculty of Kinesiology, University of Zagreb, Zagreb 10000, Croatia.

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 used to assess the methodological quality of the included studies. Seven studies of good and excellent methodological quality were included. None of the included studies examined on-water rowing. The majority of studies that were included in the meta-analysis used a 2000m rowing distance with only one using 1000m distance. Results of the main meta-analysis indicated that caffeine enhances performance on a rowing ergometer compared to placebo with a mean difference of -4.1 s (95% confidence interval (CI): -6.4, -1.8 s). These values remained consistent in the analysis in which the study that used a 1000m distance was excluded (mean difference: -4.3 s; 95% CI: -6.9, -1.8 s). We also found a significant increase in mean power (mean difference: 5.7 W; 95% CI: 2.1, 9.3 W) and minute ventilation (mean difference: 3.4 L/min; 95% CI: 1.7, 5.1 L/min) following caffeine ingestion. No significant differences between caffeine and placebo were found for the rating of perceived exertion, oxygen consumption, respiratory exchange ratio, and heart rate. This meta-analysis found that acute caffeine ingestion improves 2000m rowing ergometer performance by ~4 s. Our results support the use of caffeine pre-exercise as an ergogenic aid for rowing performance.
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http://dx.doi.org/10.3390/nu12020434DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7071243PMC
February 2020
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