Effects of beta-alanine on muscle carnosine and exercise performance: a review of the current literature

Muscle carnosine has been reported to serve as a physiological buffer, possess antioxidant properties, influence enzyme regulation, and affect sarcoplasmic reticulum calcium regulation. Beta-alanine (β-ALA) is a non-essential amino acid. β-ALA supplementation (e.g., 2-6 grams/day) has been shown to increase carnosine concentrations in skeletal muscle by 20-80%. Several studies have reported that β-ALA supplementation can increase high-intensity intermittent exercise performance and/or training adaptations. Although the specific mechanism remains to be determined, the ergogenicity of β-ALA has been most commonly attributed to an increased muscle buffering capacity. More recently, researchers have investigated the effects of co-ingesting β-ALA with creatine monohydrate to determine whether there may be synergistic and/or additive benefits. This paper overviews the theoretical rationale and potential ergogenic value of β-ALA supplementation with or without creatine as well as provides future research recommendations.     

Caffeine Intake May Modulate Inflammation Markers in Trained Rats

Caffeine is presented in many commercial products and has been proven to induce ergogenic effects in exercise, mainly related to redox status homeostasis, inflammation and oxidative stress-related adaptation mechanisms. However, most studies have mainly focused on muscle adaptations, and the role of caffeine in different tissues during exercise training has not been fully described. The aim of this study was therefore, to analyze the effects of chronic caffeine intake and exercise training on liver mitochondria functioning and plasma inflammation markers. Rats were divided into control, control/caffeine, exercise, and exercise/caffeine groups. Exercise groups underwent four weeks of swimming training and caffeine groups were supplemented with 6 mg/kg/day. Liver mitochondrial swelling and complex I activity, and plasma myeloperoxidase (MPO) and acetylcholinesterase (AChE) activities were measured. An anti-inflammatory effect of exercise was evidenced by reduced plasma MPO activity. Additionally, caffeine intake alone and combined with exercise decreased the plasma AChE and MPO activities. The per se anti-inflammatory effect of caffeine intake should be highlighted considering its widespread use as an ergogenic aid. Therefore, caffeine seems to interfere on exercise-induced adaptations and could also be used in different exercise-related health treatments.     

Energy Drinks and Sports Performance,Cardiovascular Risk,and Genetic Associations; Future Prospects

The consumption of energy drinks (e.g., containing caffeine and taurine) has increased over the last decade among adolescents and athletes to enhance their cognitive level and improve intellectual and athletic performance. Numerous studies have shown that drinking moderate doses of such drinks produces beneficial effects, as they considerably boost the sporting performance of elite athletes in various sports, including both endurance and explosive events. However, apart from their ergogenic effects, the regular consumption of energy drinks also increases blood pressure and consequently incites problems such as hypertension, tachycardia, and nervousness, all of which can lead to cardiovascular disorders. A potential positive correlation between genetics and the moderate consumption of energy drinks and athletic performance has recently been reported; notwithstanding, a better understanding of the genetic variants involved in metabolism is a key area for future research to optimize the dose of energy drink consumed and obtain the maximal ergogenic effect in elite sports. The aim of this literature review, therefore, is to present the results of recent studies, classifying them according to the differences in the associations between energy drinks and: (i) Athletic performance; (ii) cardiovascular risk factors while practicing sports; and (iii) genetic associations and future prospects between the consumption of energy drinks and performance.     

Acute Effects of Caffeine Supplementation on Physical Performance,Physiological Responses,Perceived Exertion,and Technical-Tactical Skills in Combat Sports: A Systematic Review and Meta-Analysis

Although the effects of caffeine supplementation on combat sports performance have been extensively investigated, there is currently no consensus regarding its ergogenic benefits.This systematic review with meta-analysis aimed to summarize the studies investigating the effects of caffeine supplementation on different aspects of performance in combat sports and to quantitatively analyze the results of these studies to better understand the ergogenic effect of caffeine on combat sports outcomes. A systematic search for randomized placebo-controlled studies investigating the effects of caffeine supplementation on combat sports’ performance was performed through Scopus, Pubmed, Web of Science and Cochrane Library databases up to 18 April 2022. Random-effects meta-analyses of standardized mean differences (Hedge’s g) were performed to analyze the data. Twenty-six studies of good and excellent methodological quality (based on the Pedro scale) fulfilled the inclusion criteria. The meta-analysis results revealed caffeine has a small but evident effect size (ES) on handgrip strength (ES = 0.28; 95% CI: 0.04 to 0.52; p = 0.02), and total number of throws during the special judo fitness test (SJFT) (ES = 0.42; 95% CI: 0.06 to 0.78; p = 0.02). Regarding the physiological responses, caffeine increased blood lactate concentration ([La]) in anaerobic exercise (ES = 1.23; 95% CI: 0.29 to 2.18; p = 0.01) and simulated combat (ES = 0.91; 95% CI: 0.34 to 1.47; p = 0.002). For Heart Rate (HR), caffeine increased HR final (ES = 0.31; 95% CI: 0.11 to 0.52; p = 0.003), and HR 1min (ES = 0.20; 95% CI 0.004 to 0.40; p = 0.045). However, caffeine had no impact on the countermovement jump height, the SJFT index, the judogi strength-endurance test, the number and duration of offensive actions, HR at the end of the fight, and the rating of perceived exertion. Caffeine supplementation may be ergogenic for a range of combat sports aspects involving isometric strength, anaerobic power, reaction time, and anaerobic metabolism. However, supplementation effects might be ineffective under certain circumstances, indicating supplementation needs to take into account the performance metric in question prior to creating a dosing protocol.     

Ergogenic effects of low doses of caffeine on cycling performance

The purpose of this experiment was to learn whether low doses of caffeine have ergogenic, perceptual, and metabolic effects during cycling. To determine the effects of 1, 2, and 3 mg/kg caffeine on cycling performance, differentiated ratings of perceived exertion (D-RPE), quadriceps pain intensity, and metabolic responses to cycling exercise, 13 cyclists exercised on a stationary ergometer for 15 min at 80% VO, then, after 4 min of active recovery, completed a 15-min VO2peak performance ride 60 min after ingesting caffeine or placebo. Work done (kJ/kg) during the performance ride was used as a measure of performance. D-RPE, pain ratings, and expired-gas data were obtained every 3 min, and blood lactate concentrations were obtained at 15 and 30 min. Compared with placebo, caffeine doses of 2 and 3 mg/kg increased performance by 4% (95% CI: 1.0-6.8%, p = .02) and 3% (95% CI: -0.4% to 6.8%, p = .077), respectively. These effects were ergogenic, on average, but varied considerably in magnitude among individual cyclists. There were no effects of caffeine on D-RPE or pain throughout the cycling task. Selected metabolic variables were affected by caffeine, consistent with its known actions. The authors conclude that caffeine preparations of 2 and 3 mg/kg enhanced performance, but future work should aim to explain the considerable interindividual variability of the drug's ergogenic properties.     

(-)-Hydroxycitrate ingestion and endurance exercise performance

We have been interested in the ergogenic aid effects of food components and supplements for enhancing endurance exercise performance. For this purpose, acute or chronic (-)-hydroxycitrate (HCA) ingestion might be effective because it promotes utilization of fatty acid as an energy source. HCA is a competitive inhibitor of the enzyme ATP: citrate lyase, thereby increasing inhibition of lipogenesis in the body. Many researchers have reported that less body fat accumulation and sustained satiety cause less food intake. After focusing on exercise performance with HCA ingestion, we came up with different results that show positive effects or not. However, our previously reported data showed increased use of fatty acids during moderate intensity exercise. For future research, HCA and co-ingestion of other supplements, such as carnitine or caffeine, might have greater effect on glycogen-sparing than HCA alone.     

Effective nutritional ergogenic aids.

Athletes use a variety of nutritional ergogenic aids to enhance performance. Most nutritional aids can be categorized as a potential energy source, an anabolic enhancer, a cellular component, or a recovery aid. Studies have consistently shown that carbohydrates consumed immediately before or after exercise enhance performance by increasing glycogen stores and delaying fatigue. Protein and amino acid supplementation may serve an anabolic role by optimizing body composition crucial in strength-related sports. Dietary antioxidants, such as vitamins C and E and carotenes, may prevent oxidative stress that occurs with intense exercise. Performance during high-intensity exercise, such as sprinting, may be improved with short-term creatine loading, and high effort exercise lasting 1-7 min may be improved through bicarbonate loading immediately prior to activity. Caffeine dosing before exercise delays fatigue and may enhance performance of high-intensity exercise.     

Acute and chronic caffeine administration increases physical activity in sedentary adults

Caffeine is a commonly used stimulant thought to have ergogenic properties. Most studies on the ergogenic effects of caffeine have been conducted in athletes. The purpose of this study was to test the hypothesis that caffeine reduces ratings of perceived exertion and increases liking of physical activity in sedentary adults. Participants completed treadmill walking at 60% to 70% of their maximal heart rate at baseline and for 6 subsequent visits, during which half of the participants were given caffeine (3 mg/kg) and half given placebo in a sports drink vehicle. To investigate the potential synergistic effects of acute and chronic caffeine on self-determined exercise duration, participants were rerandomized to either the same or different condition for the last visit, creating 4 chronic/acute treatment groups (placebo/placebo, placebo/caffeine, caffeine/placebo, caffeine/caffeine). Participants rated how much they liked the activity and perceived exertion at each visit. There was a main effect of time on liking of physical activity, with liking increasing over time and an interaction of sex and caffeine treatment on liking, with liking of activity increasing in female participants treated with caffeine, but not with placebo. There was no effect of caffeine on ratings of perceived exertion. Individuals who received caffeine on the final test day exercised for significantly longer than those who received placebo. These data suggest that repeated exposure to physical activity significantly increases liking of exercise and reduces ratings of perceived exertion and that caffeine does little to further modify these effects.     

Physiological and cognitive responses to caffeine during repeated, high-intensity exercise

This study investigated the effects of caffeine on repeated, anaerobic exercise using a double-blind, randomized, crossover design. Seventeen subjects (five female) underwent cognitive (reaction time, number recall) and blood (glucose, potassium, catecholamines, lactate) testing before and after consuming caffeine (6 mg/kg), placebo, or nothing (control). An exercise test (two 60 s maximal cycling bouts) was conducted 90 min after caffeine/placebo consumption. Plasma caffeine concentrations significantly increased after caffeine ingestion, however, there were no positive effects on cognitive or blood parameters except a significant decrease in plasma potassium concentrations at rest. Potentially negative effects of caffeine included significantly higher blood lactate compared to control and significantly slower time to peak power in exercise bout 2 compared to control and placebo. Caffeine had no significant effect on peak power, work output, RPE, or peak heart rate. In conclusion, caffeine had no ergogenic effect on repeated, maximal cycling bouts and may be detrimental to anaerobic performance.     

Effect of caffeine on leg-muscle pain during intense cycling exercise: possible role of anxiety sensitivity

This experiment examined the effect of a moderate dose of caffeine on perceptions of leg-muscle pain during a bout of high-intensity cycling exercise and the role of anxiety sensitivity in the hypoalgesic effect of caffeine on muscle pain during exercise. Sixteen college-age women ingested caffeine (5 mg/kg body weight) or a placebo and 1 hr later completed 30 min of cycling on an ergometer at 80% of peak aerobic capacity. The conditions were completed in a counterbalanced order, and perceptions of leg-muscle pain were recorded during the bouts of exercise. Caffeine resulted in a large reduction in leg-muscle pain-intensity ratings compared with placebo (d = -0.95), and the reduction in leg-muscle pain-intensity ratings was larger in those with lower anxiety-sensitivity scores than those with higher anxiety-sensitivity scores (d = -1.28 based on a difference in difference scores). The results support that caffeine ingestion has a large effect on reducing leg-muscle pain during high-intensity exercise, and the effect is moderated by anxiety sensitivity.     

Caffeine as a lipolytic food component increases endurance performance in rats and athletes

Caffeine is one of the famous ergogenic aids in the athletic field. Caffeine has been known to stimulate lipolysis that spares stored glycogen utilization during moderate intensity exercise. Therefore, we investigated the effects of caffeine ingestion on exercise performance in rats and athletes. Rats were administered the caffeine (6 mg/kg) 1 h prior to the exercise then were run on a treadmill at a speed of 20 m/min. They were decapitated at 0 min, 30 min, 60 min of exercise, and exhausted time point. Human subjects ingested the caffeine (5 mg/kg) 1 h prior to the exercise. They exercised on a cycle ergometer at 60% of their VO2max for 45 min, and then the exercise intensity was increased to 80% of their VO2max until exhaustion. Blood and breathing gas samples were collected and calculated every 10 min during exercise. Respiratory exchange ratio of the caffeine trial was significantly lower than that of the placebo trial in the athletes' study (p<0.05). Blood free fatty acid (FFA) levels in studies of both rats and athletes were increased by caffeine ingestion during exercise (p<0.05). Blood lactate levels were also increased during exercise in both rats and athletes (p<0.05). Increased FFA and glycerol concentrations reduced glycogen utilization during exercise compared with placebo group in rats. In addition, endurance time to exhaustion was significantly increased by the caffeine ingestion in both rats and athletes (p<0.05). These results suggest that the caffeine ingestion enhanced endurance performance resulting from spare stored glycogen with increasing lipolysis from adipose tissues and fat oxidation during exercise both in rats and in athletes.     

Effects of a herbal ergogenic drink on cycling performance in young cyclists

It is essential to replace fluids lost so as to remain well hydrated during exercise. The intake of fluids is considered a physiological ergogenic aid to enhance exercise performance. There are currently several products in the market that are believed to have ergogenic properties which act as fluid replacement drinks during exercise. One such drink available in the Malaysian market is 'AgroMas?' herbal drink whose efficacy is yet to be proven. The purpose of this study was, therefore, to evaluate the effects of acute ingestion of this herbal drink (H) or a coloured water placebo (P) on cycling performance. Nine healthy and trained young male cyclists (age: 16.2 ± 0.5 years) exercised on a cycle ergometer at 71.9 ± 0.7% of maximal oxygen consumption (VO2max) until exhaustion on two occasions at 1-week intervals. During each exercise bout, subjects received 3ml kg-1 body weight of H or P every 20 min in a double-blind randomised study design. There was no significant difference between H and P trials in the total work time to exhaustion (83.7 ± 4.6 and 81.5 ± 5.0 min respectively). Changes in oxygen consumption, heart rate and perceived rate of exertion were similar for both types of drinks. These results demonstrate that the herbal drink and the placebo elicited similar physiological responses and exercise performance during endurance cycling. It is therefore concluded that AgroMas? herbal drink and water ingestion resulted in a similar ergogenic response on cycling performance in young cyclists.     

Increases in cycling performance in response to caffeine ingestion are repeatable

The primary aim of this study was to determine the repeatability of caffeine's ergogenic effects on cycling performance. It was hypothesized that improvements in performance would be similar when caffeine was ingested on 2 separate days. Nine endurance-trained men and women (mean age and maximal oxygen uptake, 27.4 ± 5.9 years and 57.5 ± 3.9 mL kg⁻¹ min⁻¹) initially completed 2 familiarization trials. During 3 subsequent sessions separated by at least 48 hours, the subjects completed a 10-km cycling time trial preceded by ingestion of a drink containing caffeine (5 mg/kg) or placebo. Treatments were ingested using a randomized, single-blind, crossover design, and the subjects were deceived as to the specific content of all drinks. During exercise, heart rate, rating of perceived exertion, and time were recorded every 1.6 km. Repeated-measures analysis of variance was used to compare the differences in variables across distance and treatment. In both caffeine trials, caffeine increased (P = .02) cycling performance by 1.6% and 1.9% vs placebo (16.98 ± 0.96 and 16.92 ± 0.97 minutes with caffeine vs 17.25 ± 0.96 minutes in placebo), and 7 of 9 subjects revealed improved performance. The mean performance improvement in the caffeine trials was similar (P = .35; −0.27 and −0.32 minutes, respectively) across days. Heart rate during exercise was higher (P < .001) with caffeine vs placebo, although the rating of perceived exertion was similar (P = .65). Data reveal that caffeine's ergogenic effects on cycling performance are repeatable across days, yet some individuals did not exhibit improved performance with caffeine.     

Acute Effects of Carbohydrate Supplementation on Intermittent Sports Performance

Intermittent sports (e.g., team sports) are diverse in their rules and regulations but similar in the pattern of play; that is, intermittent high-intensity movements and the execution of sport-specific skills over a prolonged period of time (~1–2 h). Performance during intermittent sports is dependent upon a combination of anaerobic and aerobic energy systems, both of which rely on muscle glycogen and/or blood glucose as an important substrate for energy production. The aims of this paper are to review: (1) potential biological mechanisms by which carbohydrate may impact intermittent sport performance; (2) the acute effects of carbohydrate ingestion on intermittent sport performance, including intermittent high-intensity exercise capacity, sprinting, jumping, skill, change of direction speed, and cognition; and (3) what recommendations can be derived for carbohydrate intake before/during exercise in intermittent sports based on the available evidence. The most researched intermittent sport is soccer but some sport-specific studies have also been conducted in other sports (e.g., rugby, field hockey, basketball, American football, and racquet sports). Carbohydrate ingestion before/during exercise has been shown in most studies to enhance intermittent high-intensity exercise capacity. However, studies have shown mixed results with regards to the acute effects of carbohydrate intake on sprinting, jumping, skill, change of direction speed, and cognition. In most of these studies the amount of carbohydrate consumed was ~30–60 g/h in the form of a 6%–7% carbohydrate solution comprised of sucrose, glucose, and/or maltodextrin. The magnitude of the impact that carbohydrate ingestion has on intermittent sport performance is likely dependent on the carbohydrate status of the individual; that is, carbohydrate ingestion has the greatest impact on performance under circumstances eliciting fatigue and/or hypoglycemia. Accordingly, carbohydrate ingestion before and during a game seems to have the greatest impact on intermittent sports performance towards the end of the game.     

Caffeine does not alter RPE or pain perception during intense exercise in active women

Attenuated perceptions of exertion and leg pain are typically reported during exercise with caffeine ingestion, yet these responses are relatively unexplored in women. The primary aim of this study was to assess the effect of caffeine on rating of perceived exertion (RPE) and pain perception during a simulated time trial. Ten active women (age=22.1±1.9yr) completed an 8.2km "all out" time trial on each of 3days separated by at least 48h. Initially, a practice trial was completed, and participants refrained from products containing caffeine and lower-body exercise for 24h prior to subsequent trials. During exercise, heart rate (HR), RPE, and leg pain were recorded. Using a double-blind, randomized crossover design, participants ingested anhydrous caffeine and glucose (each 6mg/kg bw+each 6mg/kg bw glucose) or placebo (each 6mg/kg bw of glucose) 1h pre-exercise. Despite not altering (P>0.05) RPE, HR, or leg pain, caffeine improved (P<0.05) cycling performance (17.7±1.0min versus 18.2±1.1min) and power output (121.6±17.5W versus 114.9±17.9W) versus placebo. Caffeine's ergogenic effects may be independent of changes in RPE or leg pain in active women performing a simulated time trial.     

Effect of Carbohydrates and Caffeine on Plasma Amino Acids,Neuroendocrine Responses and Performance in Tennis

Effects of carbohydrate (CHO) and caffeine (CAF) in amounts typically found in sports-drinks on plasma metabolites, neuroendocrine responses and performance in tennis were investigated in 8 skilled players during a 4 h tennis match. In 3 trials players ingested a placebo (T I), a CAF (T II) or a CHO (T III) drink during court changeover. Total intake consisted of 2.81 of fluid, supplemented with 243 g CHO or with 364 mg CAF, respectively. Self-perceived “drive/motivation” and post-exercise hitting accuracy were evaluated. Plasma free fatty acids increments were lower after CHO while CAF administration had no effect. In all trials, plasma branched-chain amino acids (BCAA) concentrations decreased as a result of exercise; however, no differences were observed between trials. Plasma free tryptophan (TRP) to BCAA ratio was augmented in T I and T II while no change from basal level was found in T III. Plasma prolactin (PRL) and growth hormone (HGH) concentrations after cessation of exercise were lower in T III compared with T I and T II. No main effect for treatment was found for plasma ACTH, COR and β-endorphin. Neither supplement affected number of won games. We conclude that CAF ingestion did not affect the plasma large neutral amino acids concentrations, neuroendocrine system responses or tennis performance. Lower plasma free TRP/BCAA ratio induced by CHO occurred concomitant with reduced plasma PRL and HGH concentrations, suggesting that the brain monoaminergic system might be affected if CHO-containing drinks are consumed during tennis match play. However, the data do not point towards an ergogenic value of reduced plasma free TRP/BCAA ratio.     

Nitrate supplementation's improvement of 10-km time-trial performance in trained cyclists

Six days of dietary nitrate supplementation in the form of beetroot juice (~0.5 L/d) has been reported to reduce pulmonary oxygen uptake (VO?) during submaximal exercise and increase tolerance of high-intensity work rates, suggesting that nitrate can be a potent ergogenic aid. Limited data are available regarding the effect of nitrate ingestion on athletic performance, and no study has investigated the potential ergogenic effects of a small-volume, concentrated dose of beetroot juice. The authors tested the hypothesis that 6 d of nitrate ingestion would improve time-trial performance in trained cyclists. Using a double-blind, repeated-measures crossover design, 12 male cyclists (31±3 yr, VO2peak=58±2 ml·kg?1·min?1, maximal power [Wmax]=342±10 W) ingested 140 ml/d of concentrated beetroot (~8 mmol/d nitrate) juice (BEET) or a placebo (nitrate-depleted beetroot juice; PLAC) for 6 d, separated by a 14-d washout. After supplementation on Day 6, subjects performed 60 min of submaximal cycling (2×30 min at 45% and 65% Wmax, respectively), followed by a 10-km time trial. Time-trial performance (953±18 vs. 965±18 s, p<.005) and power output (294±12 vs. 288±12 W, p<.05) improved after BEET compared with PLAC supplementation. Submaximal VO? was lower after BEET (45% Wmax=1.92±0.06 vs. 2.02±0.09 L/min, 65% Wmax 2.94±0.12 vs. 3.11±0.12 L/min) than with PLAC (main effect, p<.05). Whole-body fuel selection and plasma lactate, glucose, and insulin concentrations did not differ between treatments. Six days of nitrate supplementation reduced VO? during submaximal exercise and improved time-trial performance in trained cyclists.     

Selected health and behavioral effects related to the use of caffeine

This paper reviews the research literature concerning health and selected behavioral effects of caffeine. Epidemiological and laboratory findings are reviewed to determine the health risks associated with both acute and chronic caffeine exposure. Common sources of caffeine, its properties, and physiological effects are considered. The relationships between caffeine and various health conditions are examined including caffeine's association with heart disease, cancer, and benign breast disease. Caffeine's possible contribution to enhanced exercise performance is discussed along with a brief overview of caffeine's effects on mental and emotional health.Over 100 references cited in this review were part of a more extensive literature base obtained from several on-line services including MEDLINE and LEXIS/NEXIS medical data bases. Other sources of relevant literature included manual searches of research journals and the use of selected references from appropriate articles.The relationship between caffeine consumption and various illnesses such as cardiovascular disease and cancer remains equivocal. Prudence might dictate that pregnant women and chronically ill individuals exercise restraint in their use of caffeine, although research suggests relatively low or nonexistent levels of risk associated with moderate caffeine consumption.     

Effects of caffeine ingestion on exercise testing: a meta-analysis

This study used the meta-analytic approach to examine the effects of caffeine ingestion on exercise testing. Forty double-blind studies with 76 effect sizes (ES) met the inclusion criteria. The type of exercise test was classified as endurance, graded, or short-term. In comparison with placebo, caffeine improved test outcome by 12.3 % (95 % CI, 9.1 to 15.4), which was equivalent to an overall ES of 0.41 (95 % CI, 0.31 to 0.51). Endurance exercise significantly improved test outcome (P < 0.05) more than either graded or short-term exercise. When exercise protocol was examined, time-to-exhaustion (Tlim) protocols had a significantly greater (P < 0.05) ES than either the graded or the non-Tlim protocol(s). The results from this meta-analysis confirm the ergogenic effects of caffeine, particularly for endurance testing that use Tlim protocols.     

β-hydroxy-β-methylbutyrate free acid supplementation may improve recovery and muscle adaptations after resistance training: a systematic review

β-Hydroxy-β-methylbutyrate free acid (HMB-FA) has been suggested to accelerate the regenerative capacity of skeletal muscle after high-intensity exercise and attenuate markers of skeletal muscle damage. Herein a systematic review on the use of HMB-FA supplementation as an ergogenic aid to improve measures of muscle recovery, performance, and hypertrophy after resistance training was conducted. This review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. We included randomized, double-blinded, placebo-controlled trials investigating the effects of HMB-FA supplementation in conjunction with resistance exercise in humans. The search was conducted using Medline and Google Scholar databases for the terms beta-hydroxy-beta-methylbutyrate, HMB free acid, exercise, resistance exercise, strength training, and HMB supplementation. Only research articles published from 1996 to 2016 in English language were considered for the analysis. Nine studies met the criteria for inclusion in the analyses. Most studies included resistance-trained men, and the primary intervention strategy involved administration of 3 g of HMB-FA per day. In conjunction with resistance training, HMB-FA supplementation may attenuate markers of muscle damage, augment acute immune and endocrine responses, and enhance training-induced muscle mass and strength. HMB-FA supplementation may also improve markers of aerobic fitness when combined with high-intensity interval training. Nevertheless, more studies are needed to determine the overall efficacy of HMB-FA supplementation as an ergogenic aid.