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1.
Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis.
Refalo, MC, Helms, ER, Trexler, ET, Hamilton, DL, Fyfe, JJ
Sports medicine (Auckland, N.Z.). 2023;(3):649-665
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Abstract
BACKGROUND AND OBJECTIVE This systematic review with meta-analysis investigated the influence of resistance training proximity-to-failure on muscle hypertrophy. METHODS Literature searches in the PubMed, SCOPUS and SPORTDiscus databases identified a total of 15 studies that measured muscle hypertrophy (in healthy adults of any age and resistance training experience) and compared resistance training performed to: (A) momentary muscular failure versus non-failure; (B) set failure (defined as anything other than momentary muscular failure) versus non-failure; or (C) different velocity loss thresholds. RESULTS There was a trivial advantage for resistance training performed to set failure versus non-failure for muscle hypertrophy in studies applying any definition of set failure [effect size=0.19 (95% confidence interval 0.00, 0.37), p=0.045], with no moderating effect of volume load (p=0.884) or relative load (p=0.525). Given the variability in set failure definitions applied across studies, sub-group analyses were conducted and found no advantage for either resistance training performed to momentary muscular failure versus non-failure for muscle hypertrophy [effect size=0.12 (95% confidence interval -0.13, 0.37), p=0.343], or for resistance training performed to high (>25%) versus moderate (20-25%) velocity loss thresholds [effect size=0.08 (95% confidence interval -0.16, 0.32), p=0.529]. CONCLUSION Overall, our main findings suggest that (i) there is no evidence to support that resistance training performed to momentary muscular failure is superior to non-failure resistance training for muscle hypertrophy and (ii) higher velocity loss thresholds, and theoretically closer proximities-to-failure do not always elicit greater muscle hypertrophy. As such, these results provide evidence for a potential non-linear relationship between proximity-to-failure and muscle hypertrophy.
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The Effects of Intermittent Diet Breaks during 25% Energy Restriction on Body Composition and Resting Metabolic Rate in Resistance-Trained Females: A Randomized Controlled Trial.
Siedler, MR, Lewis, MH, Trexler, ET, Lamadrid, P, Waddell, BJ, Bishop, SF, SanFilippo, G, Callahan, K, Mathas, D, Mastrofini, GF, et al
Journal of human kinetics. 2023;:117-132
Abstract
The purpose of this study was to examine the effects of intermittent versus continuous energy restriction on body composition, resting metabolic rate, and eating behaviors in resistance-trained females. Thirty-eight resistance-trained females (mean ± standard deviation age: 22.3 ± 4.2 years) were randomized to receive either six weeks of a continuous 25% reduction in energy intake (n = 18), or one week of energy balance after every two weeks of 25% energy restriction (eight weeks total; n = 20). Participants were instructed to ingest 1.8 g protein/kilogram bodyweight per day and completed three weekly supervised resistance training sessions throughout the intervention. There were no differences between groups for changes over time in body composition, resting metabolic rate, or seven of the eight measured eating behavior variables (p > 0.05). However, a significant group-by-time interaction for disinhibition (p < 0.01) from the Three-Factor Eating Questionnaire was observed, with values (± standard error) in the continuous group increasing from 4.91 ± 0.73 to 6.17 ± 0.71, while values in the intermittent group decreased from 6.80 ± 0.68 to 6.05 ± 0.68. Thus, diet breaks do not appear to induce improvements in body composition or metabolic rate in comparison with continuous energy restriction over six weeks of dieting, but may be employed for those who desire a short-term break from an energy-restricted diet without fear of fat regain. While diet breaks may reduce the impact of prolonged energy restriction on measures of disinhibition, they also require a longer time period that may be less appealing for some individuals.
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International society of sports nutrition position stand: caffeine and exercise performance.
Guest, NS, VanDusseldorp, TA, Nelson, MT, Grgic, J, Schoenfeld, BJ, Jenkins, NDM, Arent, SM, Antonio, J, Stout, JR, Trexler, ET, et al
Journal of the International Society of Sports Nutrition. 2021;18(1):1
Abstract
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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Post-Exercise Ingestion of Low or High Molecular Weight Glucose Polymer Solution Does Not Improve Cycle Performance in Female Athletes.
Mock, MG, Hirsch, KR, Blue, MNM, Trexler, ET, Roelofs, EJ, Smith-Ryan, AE
Journal of strength and conditioning research. 2021;(1):124-131
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Abstract
Mock, MG, Hirsch, KR, Blue, MNM, Trexler, ET, Roelofs, EJ, and Smith-Ryan, AE. Postexercise ingestion of low or high molecular weight glucose polymer solution does not improve cycle performance in female athletes. J Strength Cond Res 35(1): 124-131, 2021-The current study sought to evaluate the effects of postexercise ingestion of a high molecular weight (HMW) glucose polymer solution compared with an isocaloric low molecular weight (LMW) solution or placebo (PLA) on subsequent cycling performance in female athletes. In a randomized, double-blind, placebo-controlled, cross-over design, 10 competitive female cyclists (Mean ± SD; Age = 25.7 ± 5.0 years; V̇o2peak = 49.7 ± 4.3 ml·kg-1·min-1) completed 3 testing sessions separated by 7-10 days. Visits consisted of a ride-to-exhaustion (RTE) at 75% V̇o2peak, followed by immediate consumption of 700 ml containing either: 1.2 g·kg-1 LMW (maltodextrin/dextrose/fructose); 1.2 g·kg-1 HMW (Vitargo); or 0.066 g·kg-1 PLA (noncaloric flavoring). After 2 hours of rest, subjects performed a 15-minute time trial (TT). Respiratory exchange ratio (RER) was assessed via indirect calorimetry during exercise. Total body water (TBW) was measured using bioelectrical impedance to assess fluid balance. When covaried for estrogen, there was no treatment effect on distance (km; p = 0.632) or power output (watts; p = 0.974) during the 15-minute TT. Respiratory exchange ratio was not significantly different during the LMW and HWM TTs (p > 0.999), but both were significantly higher than PLA (p = 0.039, p = 0.001, respectively). Changes in total body water pre-exercise to postexercise were not significantly different between trials (p = 0.777). Despite benefits of HMW on cycling performance previously reported in males, current results demonstrate no ergogenic effect of HMW or LMW in females. Sex differences in substrate utilization may account for the discrepancy, and further research involving performance nutrition for female athletes is merited.
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The Acute Effects of a Multi-Ingredient Herbal Supplement on Performance Fatigability: A Double-Blind, Randomized, and Placebo-Controlled Trial.
Ryan, ED, Gerstner, GR, Mota, JA, Trexler, ET, Giuliani, HK, Blue, MNM, Hirsch, KR, Smith-Ryan, AE
Journal of dietary supplements. 2021;(5):507-516
Abstract
The purpose of the present study was to examine the acute effects of an herbal supplement containing a 70:30 blend of Rhaponticum carthamoides extract and Rhodiola rosea extract, respectively, on performance fatigability and the affective responses prior to and following exercise. Thirty men (age = 22.3 ± 4.1 years) volunteered for this randomized, placebo-controlled, double-blind, cross-over study. Following familiarization, participants visited the laboratory on three separate occasions where they consumed one 350 mg dose, a 175 mg dose of the supplement plus 175 mg of maltodextrin, or a placebo. Participants completed feeling, arousal, and mood surveys at supplement ingestion and following testing. Ninety minutes following ingestion, participants performed five sets of 30 maximal, concentric, leg extension muscle actions at 180°/sec, with one minute of rest between sets. Peak torque, average torque, and total work were calculated for each set, and the rating of perceived exertion (RPE) was assessed after each set. Data were analyzed with a repeated measures analysis of variance and intent-to-treat approach. For the performance variables, there was no interaction (p ≥ 0.317) or treatment effect (p ≥ 0.660), however, all torque variables decreased across sets and plateaued at sets 4-5, whereas RPE increased across sets (p < 0.001). For the affective responses, there was no interaction (p ≥ 0.781) or treatment effect (p ≥ 0.314); however, participants felt better, had an improved mood, and felt more aroused following testing (p < 0.047). This combination of herbal extracts likely does not acutely influence performance fatigability during high-intensity, repeated muscle actions.
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Provision of ready-to-drink protein following bariatric surgery: An evaluation of tolerability, body composition, and metabolic rate.
Hirsch, KR, Blue, MNM, Trexler, ET, Ahuja, S, Smith-Ryan, AE
Clinical nutrition (Edinburgh, Scotland). 2021;(4):2319-2327
Abstract
BACKGROUND & AIMS It is recommended that patients consume at least 60 g of dietary protein per day to attenuate loss of fat-free mass (FFM) following bariatric surgery. To date, research on the effectiveness and tolerability of protein supplementation in bariatric patients is limited. The purpose of the current study was to determine if provision of 12-weeks of daily protein supplementation was an effective and tolerable method of facilitating higher protein intakes in bariatric surgery patients. A secondary aim was to evaluate the effects of protein supplementation on body composition, metabolic rate, and functional outcomes. An exploratory aim was to compare body composition estimates from bioelectrical impedance spectroscopy and dual-energy x-ray absorptiometry. METHODS Bariatric surgery patients (n = 49; 88% female) (mean ± standard deviation; Age: 43.7 ± 10.7 yrs; BMI: 51.2 ± 13.7 kg m-2) were provided with either a 12-week supply of ready-to-drink protein shakes (PRO; n = 25) or instructed to follow standard-of-care recommendations (SOC; n = 24) following surgery. Patients completed measures of body composition (fat mass [FM], percent body fat [%BF], FFM; bioelectrical impedance [BIS] and/or dual-energy x-ray absorptiometry [DXA]), resting metabolic rate (RMR; indirect calorimetry), a 30-s chair stand, and 3-day food logs prior to surgery (base), 3-weeks, 12-weeks, and 24-weeks post-surgery. RESULTS About 80% of all patients achieved the recommended intake of 60 g per day, with no significant differences in protein intake between groups (p < 0.05). Patients in PRO were more likely to increase protein consumption over the course of the entire intervention compared to SOC. Both groups experienced significant decreases in weight, BMI, %BF, FM, FFM, and total body water (TBW) (p < 0.05). The percentage of weight lost as FFM was significantly greater when measured by BIS (39.1%) compared to when measured by DXA (17.8%) (p < 0.05). There was a significant decrease in RMR from base-3 weeks for both groups (p = 0.002; 95% confidence interval [-370.6, -90.7]); there were no significant changes after 3 weeks (p > 0.05). The number of sit-to-stand trials increased at each testing session after the first 3 weeks (p < 0.05). CONCLUSIONS Patients were able to achieve the recommended 60 g of protein per day post-surgery, but the provision of ready-to-drink protein shakes may help bariatric patients achieve higher post-surgery protein intakes. Both groups experienced significant decreases in weight, BMI, and body composition; results varied depending on the method of body composition used. Changes in FFM measured by BIS may reflect greater changes in TBW as opposed to actual muscle mass. Registered at ClinicalTrials.gov, ID#NCT02951663.
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Effects of Citrulline Supplementation on Exercise Performance in Humans: A Review of the Current Literature.
Gonzalez, AM, Trexler, ET
Journal of strength and conditioning research. 2020;(5):1480-1495
Abstract
Gonzalez, AM and Trexler, ET. Effects of citrulline supplementation on exercise performance in humans: A review of the current literature. J Strength Cond Res 34(5): 1480-1495, 2020-L-citrulline, a nonessential amino acid found primarily in watermelon, has recently garnered much attention for its potential to augment L-arginine bioavailability, nitric oxide production, and exercise performance. Over the past decade, L-citrulline has received considerable scientific attention examining potentially ergogenic properties for both aerobic and anaerobic exercise performance. Thus, the purpose of this article is to summarize the theoretical rationale behind L-citrulline supplementation and to comprehensively review the available scientific evidence assessing the potential ergogenic value of L-citrulline supplementation on vascular function and exercise performance in humans. In addition, research that has investigated the potential synergistic effects of L-citrulline with other dietary ingredients (e.g., arginine, antioxidants, nitrates, and branched-chain amino acids) is reviewed. Oral L-citrulline and citrulline malate supplementation have shown to increase plasma citrulline and arginine concentrations, along with total nitrate and nitrite concentrations. Although blood flow enhancement is a proposed mechanism for the ergogenic potential of L-citrulline, evidence supporting acute improvements in vasodilation and skeletal muscle tissue perfusion after supplementation is scarce and inconsistent. Nevertheless, several studies have reported that L-citrulline supplementation can enhance exercise performance and recovery. Given the positive effects observed from some investigations, future studies should continue to investigate the effects of both acute and chronic supplementation with L-citrulline and citrulline malate on markers of blood flow and exercise performance and should seek to elucidate the mechanism underlying such effects.
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Effects of Citrulline Malate and Beetroot Juice Supplementation on Energy Metabolism and Blood Flow During Submaximal Resistance Exercise.
Trexler, ET, Keith, DS, Lucero, AA, Stoner, L, Schwartz, TA, Persky, AM, Ryan, ED, Smith-Ryan, AE
Journal of dietary supplements. 2020;(6):698-717
Abstract
The ergogenic effects of citrulline malate (CitMal) and beetroot juice (BEET) have been widely studied, but their effects on physiological outcomes related to resistance exercise are not fully understood. The purpose of this randomized, double-blind, crossover study was to investigate the effects of CitMal (8 g) and BEET (400 mg nitrate) on blood pressure (BP), blood flow, and energy efficiency during submaximal leg extension. Recreationally active males (n = 27; age: 22 ± 4 yrs) completed familiarization, followed by three testing visits. Supine and standing BP were measured upon arrival, followed by supplement ingestion, a 2-h rest period, postsupplement BP measurement, and a bout of repeated submaximal isotonic leg extensions at 25% of maximal voluntary contraction torque. Diameter (aDIAM) and blood flow (aBF) of the superficial femoral artery, and cross-sectional area (CSA) and echo intensity (EI) of the vastus lateralis, were measured before and after exercise via ultrasonography. Muscle blood flow (mBF) and oxygen consumption (mVO2), along with whole-body energy expenditure (EE) and respiratory exchange ratio (RER), were measured before and during exercise via indirect calorimetry and near-infrared spectroscopy. Baseline RER values differed among treatments (p = 0.01); BEET was higher than CitMal (p = 0.01) but not PLA (p = 0.58); CitMal and PLA were not significantly different (p = 0.12). No other measurements were significantly affected by treatment (all p > 0.05). Results suggest that neither CitMal nor BEET significantly influence resting BP, blood flow, or metabolic efficiency during submaximal leg extension in recreationally active males.
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Nutritional Recommendations for Physique Athletes.
Roberts, BM, Helms, ER, Trexler, ET, Fitschen, PJ
Journal of human kinetics. 2020;71:79-108
Abstract
The popularity of physique sports is increasing, yet there are currently few comprehensive nutritional guidelines for these athletes. Physique sport now encompasses more than just a short phase before competition and offseason guidelines have recently been published. Therefore, the goal of this review is to provide an extensive guide for male and female physique athletes in the contest preparation and recovery period. As optimal protein intake is largely related to one's skeletal muscle mass, current evidence supports a range of 1.8-2.7 g/kg. Furthermore, as a benefit from having adequate carbohydrate to fuel performance and activity, low-end fat intake during contest preparation of 10-25% of calories allows for what calories remain in the "energy budget" to come from carbohydrate to mitigate the negative impact of energy restriction and weight loss on training performance. For nutrient timing, we recommend consuming four or five protein boluses per day with one consumed near training and one prior to sleep. During competition periods, slower rates of weight loss (≤0.5% of body mass per week) are preferable for attenuating the loss of fat-free mass with the use of intermittent energy restriction strategies, such as diet breaks and refeeds, being possibly beneficial. Additionally, physiological and psychological factors are covered, and potential best-practice guidelines are provided for disordered eating and body image concerns since physique athletes present with higher incidences of these issues, which may be potentially exacerbated by certain traditional physique practices. We also review common peaking practices, and the critical transition to the post-competition period.
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High-Fat Breakfast Meal Replacement in Overweight and Obesity: Implications on Body Composition, Metabolic Markers, and Satiety.
Smith-Ryan, AE, Hirsch, KR, Blue, MNM, Mock, MG, Trexler, ET
Nutrients. 2019;(4)
Abstract
The purpose of this paper was to determine the effect of replacing breakfast with a high-fat drink on fat mass (FM), lean mass (LM), percent body fat (%BF), visceral fat (VAT), resting metabolic rate (RMR), fuel utilization (RER), blood lipids and satiety in overweight and obese adults. Healthy adults (n = 42; 21 Females; body mass index (BMI): 32.8 ± 4.6 kg·m-2) were randomized to control (CON; n = 21) or meal replacement (MRP; n = 22) groups. Body composition was measured using a four-compartment model; RMR and RER were assessed from indirect calorimetry. The MRP (70% fat) was consumed once daily for eight weeks. For males, there was no change (p > 0.05) in FM (mean difference (MD) = 0.41 ± 1.19 kg], %BF MD = 0.50 ± 1.09%, LM MD = -0.64 ± 1.79 kg, or VAT MD = -0.31 ± 1.36 cm for MRP versus CON. Similarly, no differences for females for FM MD = -0.73 ± 1.37 kg, %BF MD = -0.57 ± 1.26%, LM MD = 0.31 ± 1.37 kg, or VAT MD -0.83 ± 1.2 cm. HDL was significantly reduced in the MRP group for females (adjusted mean change: -6.41 ± 4.44 units, p = 0.018). There was no effect on RMR or RER. Satiety increased in the afternoon for MRP (p = 0.021). Despite high fat, no negative impact on lipids resulted; increased satiety may be beneficial for controlling afternoon cravings, but does not affect body composition.