Caffeine and exercise performance. An update

Metabolic Insights into Caffeine's Anti-Adipogenic Effects: An Exploration through Intestinal Microbiota Modulation in Obesity

Obesity, a chronic condition marked by the excessive accumulation of adipose tissue, not only affects individual well-being but also significantly inflates healthcare costs. The physiological excess of fat manifests as triglyceride (TG) deposition within adipose tissue, with white adipose tissue (WAT) expansion via adipocyte hyperplasia being a key adipogenesis mechanism. As efforts intensify to address this global health crisis, understanding the complex interplay of contributing factors becomes critical for effective public health interventions and improved patient outcomes. In this context, gut microbiota-derived metabolites play an important role in orchestrating obesity modulation. Microbial lipopolysaccharides (LPS), secondary bile acids (BA), short-chain fatty acids (SCFAs), and trimethylamine (TMA) are the main intestinal metabolites in dyslipidemic states. Emerging evidence highlights the microbiota's substantial role in influencing host metabolism and subsequent health outcomes, presenting new avenues for therapeutic strategies, including polyphenol-based manipulations of these microbial populations. Among various agents, caffeine emerges as a potent modulator of metabolic pathways, exhibiting anti-inflammatory, antioxidant, and obesity-mitigating properties. Notably, caffeine's anti-adipogenic potential, attributed to the downregulation of key adipogenesis regulators, has been established. Recent findings further indicate that caffeine's influence on obesity may be mediated through alterations in the gut microbiota and its metabolic byproducts. Therefore, the present review summarizes the anti-adipogenic effect of caffeine in modulating obesity through the intestinal microbiota and its metabolites.

The New Challenge of Green Cosmetics: Natural Food Ingredients for Cosmetic Formulations

Nowadays, much attention is paid to issues such as ecology and sustainability. Many consumers choose “green cosmetics”, which are environmentally friendly creams, makeup, and beauty products, hoping that they are not harmful to health and reduce pollution. Moreover, the repeated mini-lock downs during the COVID-19 pandemic have fueled the awareness that body beauty is linked to well-being, both external and internal. As a result, consumer preferences for makeup have declined, while those for skincare products have increased. Nutricosmetics, which combines the benefits derived from food supplementation with the advantages of cosmetic treatments to improve the beauty of our body, respond to the new market demands. Food chemistry and cosmetic chemistry come together to promote both inside and outside well-being. A nutricosmetic optimizes the intake of nutritional microelements to meet the needs of the skin and skin appendages, improving their conditions and delaying aging, thus helping to protect the skin from the aging action of environmental factors. Numerous studies in the literature show a significant correlation between the adequate intake of these supplements, improved skin quality (both aesthetic and histological), and the acceleration of wound-healing. This review revised the main foods and bioactive molecules used in nutricosmetic formulations, their cosmetic effects, and the analytical techniques that allow the dosage of the active ingredients in the food.

An Abductive Inference Approach to Assess the Performance-Enhancing Effects of Drugs Included on the World Anti-Doping Agency Prohibited List

Some have questioned the evidence for performance-enhancing effects of several substances included on the World Anti-Doping Agency's Prohibited List due to the divergent or inconclusive findings in randomized controlled trials (RCTs). However, inductive statistical inference based on RCTs-only may result in biased conclusions because of the scarcity of studies, inter-study heterogeneity, too few outcome events, or insufficient power. An abductive inference approach, where the body of evidence is evaluated beyond considerations of statistical significance, may serve as a tool to assess the plausibility of performance-enhancing effects of substances by also considering observations and facts not solely obtained from RCTs. Herein, we explored the applicability of an abductive inference approach as a tool to assess the performance-enhancing effects of substances included on the Prohibited List. We applied an abductive inference approach to make inferences on debated issues pertaining to the ergogenic effects of recombinant human erythropoietin (rHuEPO), beta₂-agonists and anabolic androgenic steroids (AAS), and extended the approach to more controversial drug classes where RCTs are limited. We report that an abductive inference approach is a useful tool to assess the ergogenic effect of substances included on the Prohibited List-particularly for substances where inductive inference is inconclusive. Specifically, a systematic abductive inference approach can aid researchers in assessing the effects of doping substances, either by leading to suggestions of causal relationships or identifying the need for additional research.

Chitosan Nanocarrier Entrapping Hydrophilic Drugs as Advanced Polymeric System for Dual Pharmaceutical and Cosmeceutical Application: A Comprehensive Analysis Using Box-Behnken Design

The objective of the present research is to propose chitosan as a nanocarrier for caffeine—a commonly used drug in combating cellulite. Being a hydrophilic drug, caffeine suffers from insufficient topical penetration upon application on the skin. Chitosan nanoparticles loaded with caffeine were prepared via the ionic gelation technique and optimized according to a Box–Behnken design. The effect of (A) chitosan concentration, (B) chitosan solution pH, and (C) chitosan to sodium tripolyphosphate mass ratio on (Y1) entrapment efficiency percent, (Y2) particle size, (Y3) polydispersity index, and (Y4) zeta potential were studied. Subsequently, the desired constraints on responses were applied, and validation of the optimization procedure was confirmed by the parameters exhibited by the optimal formulation. A caffeine entrapment efficiency percent of 17.25 ± 1.48%, a particle size of 173.03 ± 4.32 nm, a polydispersity index of 0.278 ± 0.01, and a surface charge of 41.7 ± 3.0 mV were attained. Microscopical evaluation using transmission electron microscope revealed a typical spherical nature of the nanoparticles arranged in a network with a further confirmation of the formation of particles in the nano range. The results proved the successful implementation of the Box–Behnken design for optimization of chitosan-based nanoparticles in the field of advanced polymeric systems for pharmaceutical and cosmeceutical applications.

Effects of a topical lotion containing aminophylline, caffeine, yohimbe, l-carnitine, and gotu kola on thigh circumference, skinfold thickness, and fat mass in sedentary females

Background and objective

Topical aminophylline, caffeine, yohimbe, l‐carnitine, and gotu kola (Centella asiatica) may aid in reducing body fat. Lipoxyderm™ contains these ingredients and was used to test if fat loss of the thigh, in conjunction with a low intensity exercise program and restricted calorie intake, was enhanced via the topical application of this lotion.

Methods

This was a double‐blind, placebo‐controlled, within‐group study that investigated the effects of Lipoxyderm™ on thigh fat mass, circumference, and skinfold thickness. Seven participants underwent pre/post‐exercise testing for weight, bilateral thigh circumference/skinfold thickness, and body composition/thigh fat mass assessment via dual‐energy X‐ray absorptiometry. Participants followed a hypocaloric diet, walked 150 minutes/wk, and were randomly assigned to apply a placebo to one leg and Lipoxyderm™ to their other leg for 28 days. Separate two‐way mixed factorial repeated measures ANOVAs were used to compare the effects of Lipoxyderm™ to the placebo on thigh circumference, skinfold thickness, and fat mass.

Results

A significant time x group interaction was found for thigh circumference (F_1,6 = 18.2, P = 0.005), skinfold thickness (F_1,6 = 14.6, P = 0.009), and fat mass (F_1,6 = 37.1, P = 0.001).

Conclusions

A twice‐daily topical application of Lipoxyderm™ for 28 days compared to a placebo combined with a walking program and a restricted caloric intake is more effective at reducing thigh circumference (1.2 vs 0.8 cm), thigh skinfold thickness (3.7 vs 2.0 mm), and thigh fat mass (100.0 g vs 57.3 g).

The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis

BACKGROUND

Caffeine is a widely used ergogenic aid with most research suggesting it confers the greatest effects during endurance activities. Despite the growing body of literature around the use of caffeine as an ergogenic aid, there are few recent meta-analyses that quantitatively assess the effect of caffeine on endurance exercise.

OBJECTIVES

To summarise studies that have investigated the ergogenic effects of caffeine on endurance time-trial performance and to quantitatively analyse the results of these studies to gain a better understanding of the magnitude of the ergogenic effect of caffeine on endurance time-trial performance.

METHODS

A systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance.

RESULTS

Forty-six studies met the inclusion criteria and were included in the meta-analysis. Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3-6 mg/kg) as well as an overall improvement following caffeine compared to placebo in mean power output (3.03 ± 3.07%; effect size = 0.23 ± 0.15) and time-trial completion time (2.22 ± 2.59%; effect size = 0.41 ± 0.2). However, differences in responses to caffeine ingestion have been shown, with two studies reporting slower time-trial performance, while five studies reported lower mean power output during the time-trial.

CONCLUSION

Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.

Exercise and neurologic disease

PURPOSE OF REVIEW

This article provides a practical clinical approach for the role of exercise in the treatment and management of neurologic disorders.

RECENT FINDINGS

A number of clinical studies have reported positive benefits from exercise in various neurologic disease states, suggesting that this mode of intervention should be considered as another option in clinical management.

SUMMARY

Significant evidence-based data exists confirming the positive effects of exercise in otherwise healthy populations. Good evidence also exists that physical activity may benefit people with long-term neurologic conditions. Despite this evidence, exercise is often neglected in patients with normal aging or neurologic disease progression. Neurologists should counsel patients on this therapeutic adjunct and provide specific recommendations when possible.

No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population

It is often suggested that coffee causes dehydration and its consumption should be avoided or significantly reduced to maintain fluid balance. The aim of this study was to directly compare the effects of coffee consumption against water ingestion across a range of validated hydration assessment techniques. In a counterbalanced cross-over design, 50 male coffee drinkers (habitually consuming 3–6 cups per day) participated in two trials, each lasting three consecutive days. In addition to controlled physical activity, food and fluid intake, participants consumed either 4×200 mL of coffee containing 4 mg/kg caffeine (C) or water (W). Total body water (TBW) was calculated pre- and post-trial via ingestion of Deuterium Oxide. Urinary and haematological hydration markers were recorded daily in addition to nude body mass measurement (BM). Plasma was analysed for caffeine to confirm compliance. There were no significant changes in TBW from beginning to end of either trial and no differences between trials (51.5±1.4 vs. 51.4±1.3 kg, for C and W, respectively). No differences were observed between trials across any haematological markers or in 24 h urine volume (2409±660 vs. 2428±669 mL, for C and W, respectively), USG, osmolality or creatinine. Mean urinary Na⁺ excretion was higher in C than W (p = 0.02). No significant differences in BM were found between conditions, although a small progressive daily fall was observed within both trials (0.4±0.5 kg; p<0.05). Our data show that there were no significant differences across a wide range of haematological and urinary markers of hydration status between trials. These data suggest that coffee, when consumed in moderation by caffeine habituated males provides similar hydrating qualities to water.

The effects of caffeine on ventilation and pulmonary function during exercise: an often-overlooked response

The effects of caffeine on exercise performance have been well documented, with most reviews focusing on the metabolic, hormonal, and/or central nervous system effects. However, caffeine's effects on ventilation and pulmonary function are often overlooked. Studies have shown that caffeine is a strong ventilatory stimulant, increasing the sensitivity of the peripheral chemoreceptors in untrained subjects and increasing exercise ventilation at all workloads in highly trained endurance athletes. The consequences of increased exercise ventilation could hold either positive or negative effects for exercise performance. Anti-inflammatory and bronchoprotective effects of caffeine are great enough to consider its efficacy as a possible prophylactic antiasthma treatment. Although an upper urinary concentration limit exists for caffeine with international sports doping control agencies, caffeine's universal accessibility in the marketplace has resulted in its daily use being increasingly more socially acceptable as an ergogenic substance for sport and exercise.

Nutritional ergogenic aids and exercise performance

The use of nutritional supplements in sport is widespread and few serious athletes do not, at some stage in their career, succumb to the temptation to experiment with one or more nutritional supplements. Nutritional ergogenic aids are aimed primarily at enhancing performance (either by affecting energy metabolism or by an effect on the central nervous system), at increasing lean body mass or muscle mass by stimulation of protein synthesis and at reducing body fat content. Although not strictly ergogenic (i.e. capable of enhancing work performance), supplements aimed at increasing resistance to infection and improving general health are seen by athletes as important in reducing the interruptions to training that minor illness and infection can cause. Creatine is perhaps the most widely used supplement in sport at the moment. Supplementation can increase muscle creatine phosphate levels and, although not all published studies show positive results, there is much evidence that performance of short-term high-intensity exercise can be improved by supplementation. Ingestion of large doses of bicarbonate can enhance performance of exercise where metabolic acidosis may be a limiting factor, but there is a significant risk of adverse gastrointestinal side effects. Caffeine can also improve performance, in part by a stimulation of fatty acid mobilization and sparing of the body's limited carbohydrate stores, but also via direct effects on muscle and possibly by central nervous system effects on the perception of effort and fatigue. Carnitine plays an essential role in fatty acid oxidation in muscle but, although supplements are used by athletes, there is no good evidence of a beneficial effect of supplementation. None of these products contravenes the International Olympic Committee regulations on doping in sports, although caffeine is not permitted above a urine concentration of 12 mg/l. Supplementation is particularly prevalent among strength and power athletes, where an increase in muscle mass can benefit performance. Protein supplements have not been shown to be effective except in those rare cases where the dietary protein intake is otherwise inadequate. Individual amino acids, especially ornithine, arginine and glutamine, are also commonly used, but their benefit is not supported by documented evidence. Cr and hydroxymethylbutyrate are also used by strength athletes, but again there are no well-controlled studies to provide evidence of a beneficial effect. Athletes use a wide variety of supplements aimed at improving or maintaining general health and vitamin and mineral supplementation is widespread. There is a theoretical basis, and limited evidence, to support the use of antioxidant vitamins and glutamine during periods of intensive training, but further evidence is required before the use of these supplements can be recommended.

A combination of caffeine, arginine, soy isoflavones, and L-carnitine enhances both lipolysis and fatty acid oxidation in 3T3-L1 and HepG2 cells in vitro and in KK mice in vivo

To develop an anti-obesity agent containing dietary components, we focused on the mechanisms that enhance both lipolysis and fatty acid oxidation. Caffeine and arginine (CA), a nonselective adenosine-receptor antagonist and an inducer of lipolytic hormone, respectively, were used to stimulate lipolysis. Soy isoflavones and L-carnitine (SL), stimulators of carnitine palmitoyl transferase 1A and a cofactor for beta-oxidation of fatty acids, respectively, were used to enhance fatty acid oxidation. Effects of a combination of CA and SL (CASL) on lipid metabolism were studied in vitro and in vivo. During 3T3-L1 differentiation, lipid accumulation was significantly lower in cells treated with CASL (50 micromol/L, 1 mmol/L, 1 micromol/L, and 1 mmol/L, respectively) compared with each alone. Lipolysis was also significantly greater in 3T3-L1 adipocytes treated with CASL (50 micromol/L, 1 mmol/L, 10 micromol/L and 0.5 mmol/L, respectively) compared with each alone. In addition, treatment with higher concentrations of CASL (2 mmol/L, 1 mmol/L, 10 micromol/L, and 1 mmol/L, respectively) significantly enhanced beta-oxidation in HepG2 cells. The effects of CASL-containing diets (250 mg, 6 g, 200 mg, and 1.5 g/kg diet, respectively) were studied in vivo. When KK mice were food deprived for 48 h and subsequently refed a fat-free diet for 72 h, hepatic triglyceride (TG) accumulation was significantly lower in mice fed CASL compared with the control mice. In addition, after obese KK mice were fed a low-fat diet for 2 wk, adipose tissue weights were significantly lower in those fed CASL, but not CA or SL alone, compared with the control mice. Plasma and liver TG levels were also lower in mice fed CASL than in the control mice. These results suggest that CASL is effective for controlling obesity.

Disorders of Fuel Metabolism: Medical Complications Associated with Starvation, Eating Disorders, Dietary Fads, and Supplements

Disorders of fuel metabolism as they relate to abnormal fuel intake,abnormal fuel expenditure, and dietary supplements are the focus of this article. The emergency physician should be aware of the medical complications that can occur as a result of starvation states,eating disorders, fad diets, hypermetabolic states, and ergogenic aids. Knowledge and understanding of the complications associated with these disorders will facilitate the diagnosis and management of patients who present to the emergency department with any of the disorders reviewed.

Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis

The purpose of this study was to use the meta-analytic approach to examine the effects of caffeine ingestion on ratings of perceived exertion (RPE). Twenty-one studies with 109 effect sizes (ESs) met the inclusion criteria. Coding incorporated RPE scores obtained both during constant load exercise (n=89) and upon termination of exhausting exercise (n=20). In addition, when reported, the exercise performance ES was also computed (n=16). In comparison to placebo, caffeine reduced RPE during exercise by 5.6% (95% CI (confidence interval), -4.5% to -6.7%), with an equivalent RPE ES of -0.47 (95% CI, -0.35 to -0.59). These values were significantly greater (P<0.05) than RPE obtained at the end of exercise (RPE % change, 0.01%; 95% CI, -1.9 to 2.0%; RPE ES, 0.00, 95% CI, -0.17 to 0.17). In addition, caffeine improved exercise performance by 11.2% (95% CI; 4.6-17.8%). Regression analysis revealed that RPE obtained during exercise could account for approximately 29% of the variance in the improvement in exercise performance. The results demonstrate that caffeine reduces RPE during exercise and this may partly explain the subsequent ergogenic effects of caffeine on performance.

Hypothalamic–Pituitary–Adrenal and Autonomic Nervous System Functioning in Fibromyalgia

In general, there seems to be a reduction in some neuroendocrine and autonomic nervous system (ANS) responses to applied stresses in individuals who have fibromyalgia. This article presents an overview and discussion of these findings with respect to the role of the ANS and the neuroendocrine system in the response to stress, with emphasis on the hypothalamic-pituitary-adrenal axis and the possible implication to fibromyalgia.

Effect of repeated caffeine ingestion on repeated exhaustive exercise endurance

PURPOSE

The purpose of this study was to examine the effect of repeated doses of caffeine on repeated exercise endurance. METHODS Nine male caffeine users performed exercise rides (ER) to exhaustion at 80% VO(2max) after ingesting a placebo, 5 mg x kg-1 of caffeine, or 2.5 mg x kg-1 of caffeine 1 h before the ER. Two ER were performed weekly on the same day once in the morning (AM) and 5 h later in the afternoon (PM). There were four treatments containing either caffeine or placebo, i.e., trial A representing 5-mg x kg-1 caffeine in the AM and 2.5-mg x kg-1 caffeine in the PM; trial B, which was placebo in both AM and PM; trial C representing 5-mg x kg-1 caffeine in the AM and placebo in the PM; and trial D representing a placebo in the AM and 5-mg x kg-1 caffeine in the PM. The order of the treatment trials was double blind and randomized.

RESULTS

Caffeine ingestion significantly increased exercise time to exhaustion in the AM (trial A 24.9 +/- 10.2 min and trial C 21.8 +/- 4.9 vs trial B 18.0 +/- 6.4 min and D 17.7 +/- 4.3 min). This effect was maintained in the PM and greater than placebo (B 18.3 +/- 4.8 min) regardless of whether redosing (trial A 21.5 +/- 8.6 min) or placebo (trial C 21.0 +/- 6.8) followed the initial morning dose. Caffeine dosing in the PM (trial D 22.4 +/- 7.2 min) also increased ER after placebo trial D in the AM.

CONCLUSIONS

It was concluded that redosing with caffeine after exhaustive exercise in the AM was not necessary to maintain the ergogenic effect of the drug during subsequent exercise 6 h later.

Nutritional aspects in ultra-endurance exercise

PURPOSE OF REVIEW

Despite much current debate regarding central and peripheral neural mechanisms which may be responsible for the onset of fatigue during prolonged exercise, maintenance of nutritional and hydration status remains critical for successful participation in ultra-endurance exercise. This review focuses on substrate and fluid homeostasis during ultra-endurance exercise and the use of nutritional supplementation both as ergogenic aid and to attenuate exercise-induced immunosuppression.

RECENT FINDINGS

Current evidence continues to support mandatory high carbohydrate intakes (1). before the event to maximize muscle glycogen stores, (2). during the event to prevent hypoglycaemia and (3). after the event to optimize post-event repletion of endogenous carbohydrate stores. No consistent performance benefit has yet been shown following a high-fat diet. Greater utilization of intrafascicular triglyceride stores appears to account for additional fat utilization in females. Recent trends towards excessive fluid intake have resulted in frequent reports of hyponatraemic hyperhydration in ultra-distance athletes, with greater incidence in women than in men. Carbohydrate supplementation during the event attenuates immunosuppressive hormonal and cytokine responses to ultra-endurance exercise, but may impair vitamin C absorption, while the ergogenic value of caffeine supplementation in ultra-endurance performance is currently being questioned.

SUMMARY

Meeting macronutrient and fluid intake demands remains an important priority for ultra-endurance athletes. Yet these athletes are reported to present with a high incidence of disordered eating patterns during periods of training, and excessive fluid replacement strategies have resulted in an increased incidence of water intoxication with resultant central nervous system dysfunction.

Exercise endurance 1, 3, and 6 h after caffeine ingestion in caffeine users and nonusers

The purpose of the present study was to examine the duration of caffeine's ergogenic effect and whether it differs between users and nonusers of the drug. Twenty-one subjects (13 caffeine users and 8 nonusers) completed six randomized exercise rides to exhaustion at 80% of maximal oxygen consumption after ingesting either a placebo or 5 mg/kg of caffeine. Exercise to exhaustion was completed once per week at either 1, 3, or 6 h after placebo or drug ingestion. Exercise time to exhaustion differed between users and nonusers with the ergogenic effect being greater and lasting longer in nonusers. For the nonusers, exercise times 1, 3, and 6 h after caffeine ingestion were 32.7 +/- 8.4, 32.1 +/- 8.6, and 31.7 +/- 12.0 min, respectively, and these values were each significantly greater than the corresponding placebo values of 24.2 +/- 6.4, 25.8 +/- 9.0, and 23.2 +/- 7.1 min. For caffeine users, exercise times 1, 3, and 6 h after caffeine ingestion were 27.4 +/- 7.2, 28.1 +/- 7.8, and 24.5 +/- 7.6 min, respectively. Only exercise times 1 and 3 h after drug ingestion were significantly greater than the respective placebo trials of 23.3 +/- 6.5, 23.2 +/- 7.1, and 23.5 +/- 5.7 min. In conclusion, both the duration and magnitude of the ergogenic effect that followed a 5 mg/kg dose of caffeine were greater in the nonusers compared with the users.

Effect of ingesting caffeine and ephedrine on 10-km run performance

BACKGROUND

The ingestion of either caffeine (C) or ephedrine (E) has been shown to improve performance during high-intensity aerobic activity lasting 10-20 min, with an additive effect being found when the combination (C + E) was ingested. It was the purpose of this study to determine if the addition of E to C would improve performance in activity lasting longer than 20 min.

METHODS

One and one half hours after ingesting a placebo (P), C (4 mg/kg), E (0.8 mg/kg), or C + E, 12 subjects performed a 10-km run while wearing a helmet and backpack weighing 11 kg. The trials were performed in a climatic suite at 12-13 degrees C, on a treadmill where the speed was regulated by the subject. VO(2), VCO(2), V(E), heart rate (HR), and rating of perceived exertion (RPE) were measured during the run at 15 and 30 min, and again when the individual reached 9 km. Blood was sampled at 15 and 30 min and again at the end of the run and assayed for lactate, glucose, and catecholamines.

RESULTS

Run times (mean +/- SD), in minutes, were for C (46.0 +/- 2.8), E (45.5 +/- 2.9), C + E (45.7 +/- 3.3), and P (46.8 +/- 3.2). The run times for the E trials (E and C + E) were significantly reduced compared with the non-E trials (C and P). Pace was increased for the E trials compared with the non-E trials over the last 5 km of the run. VO(2) was not affected by drug ingestion. HR was elevated for the ephedrine trials (E and C + E). RPE remained similar for all trails. Caffeine increased the epinephrine and norepinephrine response associated with exercise and also increased blood lactate, glucose, and glycerol levels. Ephedrine reduced the epinephrine response but increased dopamine and FFA levels.

CONCLUSION

The previously seen additive nature of E and C was not evident in this study, with the primary ergogenic effect being attributed to E.

Selected herbals and human exercise performance

Herbs have been used throughout history to enhance physical performance, but scientific scrutiny with controlled clinical trials has only recently been used to study such effects. The following herbs are currently used to enhance physical performance regardless of scientific evidence of effect: Chinese, Korean, and American ginsengs; Siberian ginseng, mahuang or Chinese ephedra; ashwagandha; rhodiola; yohimbe; CORDYCEPS: fungus, shilajit or mummio; smilax; wild oats; Muira puama; suma (ecdysterone); Tribulus terrestris; saw palmetto berries; beta-sitosterol and other related sterols; and wild yams (diosgenin). Controlled studies of Asian ginsengs found improvements in exercise performance when most of the following conditions were true: use of standardized root extracts, study duration (>8 wk, daily dose >1 g dried root or equivalent, large number of subjects, and older subjects. Improvements in muscular strength, maximal oxygen uptake, work capacity, fuel homeostasis, serum lactate, heart rate, visual and auditory reaction times, alertness, and psychomotor skills have also been repeatedly documented. Siberian ginseng has shown mixed results. Mahuang, ephedrine, and related alkaloids have not benefited physical performance except when combined with caffeine. Other herbs remain virtually untested. Future research on ergogenic effects of herbs should consider identity and amount of substance or presumed active ingredients administered, dose response, duration of test period, proper experimental controls, measurement of psychological and physiologic parameters (including antioxidant actions), and measurements of performance pertinent to intended uses.

Central nervous system stimulants

Three major types of CNS stimulant are currently abused in sport: amphetamine, cocaine and caffeine. Each drug type has its own characteristic mechanism of action on CNS neurones and their associated receptors and nerve terminals. Amphetamine is widely abused in sports requiring intense anaerobic exercise where it prolongs the tolerance to anaerobic metabolism. It is addictive, and chronic abuse causes marked behavioural change and sometimes psychosis. Major sports abusing amphetamine are cycling, American football, ice-hockey and baseball. Cocaine increases tolerance to intense exercise, yet most of its chronic effects on energy metabolism are negative. Its greatest effects seem to be as a central stimulant and the enhancement of short-term anaerobic exercise. It is highly addictive and can cause cerebral and cardiovascular fatalities. Caffeine enhances fatty acid metabolism leading to glucose conservation, which appears to benefit long-distance endurance events such as skiing. Caffeine is also addictive, and chronic abuse can lead to cardiac damage. Social abuse of each of the three drugs is often difficult to distinguish from their abuse in sport.

The effectiveness of popular, non-prescription weight loss supplements

OBJECTIVES

To review the evidence for the effectiveness of popular, non-prescription weight loss supplements.

DATA SOURCES

A detailed literature search including all relevant medical and supplementary medicine databases and evidence submitted from manufacturers.

DATA SYNTHESIS

The theoretical basis and rationale for the use of each substance is considered along with available research in the published literature on effectiveness and potential risks. We classified the level of evidence represented by the main research studies on each substance.

CONCLUSIONS

There is no good evidence for any weight loss benefits from most of the substances reviewed here. There is some support for mild effects of capsaicin, caffeine and fibre, but only in whole foods. In some cases (e.g., chitosan), there is a plausible theoretical basis for the product, but no supporting proof of effect in humans in the absence of a calorie-controlled diet. Possible synergistic effects of different ingredients cannot be dismissed, but cannot be assessed from current data. There is an absence of good quality research on many substances, which means that advertising claims may be misleading.

Effects of caffeine ingestion on endurance racing in heat and humidity

A hot and humid environment can be detrimental to race performance. Caffeine, on the other hand, has been shown to be an ergogenic aid for improving endurance performance. To examine the influence of caffeine ingestion on race performance during high heat stress, seven endurance trained competitive road racers aged between 23 and 51 years (five men, two women) performed three maximal effort 21-km road races outdoors in hot and humid conditions. The caffeine dose, randomly assigned in a double-blind fashion, consisted of either 0, 5, or 9 mg.kg-1 body mass. During each run, the subjects were allowed to drink water ad libitum at each 5-km point. Blood samples were obtained immediately before and after each run and analysed for changes in concentrations of Na+, K+, glucose, lactate, and hematocrit. Pre and postrun data were also collected for body mass and tympanic membrane temperature. Race times were not significantly different among the races or caffeine doses, with the average times within 1.1% of each other. In addition, none of the other variables measured varied significantly among the races or caffeine doses. In summary, caffeine intake did not affect race performance. Therefore it was concluded from our study that caffeine is not of ergogenic benefit in endurance races during high heat stress.