Nutritional strategies to influence adaptations to training

Effect of warm-up protocols using lower and higher loads on multiple-set back squat volume-load

Background

The present study aimed to investigate the effects of post-activation performance enhancement (PAPE) after three warm-up protocols on back squat performance in trained men.

Methods

Fourteen resistance-trained men performed conditioning activity (CA) with high-load (HL-CA), low-load (LL-CA), or usual specific warm-up as a control (CON). HL-CA consisted of one set of three repetitions with 90% of one repetition maximum (RM); LL-CA consisted of one set of six repetitions with 45% of 1 RM performed at maximal velocity; CON involved eight repetitions with 45% of 1 RM at controlled velocity. The participant's performance was measured using the total number of repetitions and volume load (reps × load × sets).

Results

There were no significant differences between warm-up for the total number of repetitions (p = 0.17) or total volume load (p = 0.15). There was no difference between conditions for the number of repetitions (main condition effect; p = 0.17); however, participants achieved a significantly higher volume load after HL-PAPE than after CON for the first set (p = 0.04).

Conclusion

High or low equated-load CA used as warm-up strategies did not potentiate subsequent performance enhancement in multiple-set back squat exercise performed until muscle failure in comparison with usual warm-up.

Sex differences and considerations for female specific nutritional strategies: a narrative review

Although there is a plethora of information available regarding the impact of nutrition on exercise performance, many recommendations are based on male needs due to the dominance of male participation in the nutrition and exercise science literature. Female participation in sport and exercise is prevalent, making it vital for guidelines to address the sex-specific nutritional needs. Female hormonal levels, such as estrogen and progesterone, fluctuate throughout the mensural cycle and lifecycle requiring more attention for effective nutritional considerations. Sex-specific nutritional recommendations and guidelines for the active female and female athlete have been lacking to date and warrant further consideration. This review provides a practical overview of key physiological and nutritional considerations for the active female. Available literature regarding sex-specific nutrition and dietary supplement guidelines for women has been synthesized, offering evidenced-based practical information that can be incorporated into the daily lives of women to improve performance, body composition, and overall health.

Dose-dependent effect of caffeine supplementation on judo-specific performance and training activity: a randomized placebo-controlled crossover trial

Background

Caffeine (CAF) supplementation could have a positive impact on physical performance and sport abilities. Nevertheless, the CAF-induced, dose-dependent influence on discipline-specific performance and combat activity in combat sports have not been sufficiently investigated. The aim of this study was to examine the effect of single ingestion of 3, 6, or 9 mg/kg body weight of CAF and placebo (PLA) on judo-specific performance and sparring combat activities.

Methods

In a randomised double-blind placebo-controlled cross-over design, acute pre-exercise supplementation with CAF (3, 6, or 9 mg/kg body weight) and placebo PLA in 22 male highly-trained judoists was examined. The study protocol involved five separate testing sessions using the Special Judo Fitness Test (SJFT) with heart rate monitoring, three judo sparring combats and evaluation of the rate of perceived exertion (RPE) using the Borg scale.

Results

Six and 9 mg/kg CAF improved SJFT performance, while 9 mg/kg increased combat activity. Three mg/kg CAF lacked any apparent positive ergogenic effect. Among athletes, who include CAF-containing products in their habitual diet (consumers), only 9 mg/kg CAF effectively enhanced SJFT performance, while in those who do not consume CAF-containing products at regular basis (non-consumers), the enhancing effect was achieved even at 6 mg/kg.

Conclusions

Regarding combat sports, higher (6–9 mg/kg) than currently recommended CAF dosages (3–6 mg/kg) are apparently more effective in terms of judo-specific performance. However, the ergogenic CAF effect is not only dose-dependent, but it is also related to customary CAF consumption.

Trial registration

Clinical Trials Gov, NCT03822663. Registered 28 January 2019 - Retrospectively registered

Electronic supplementary material

The online version of this article (10.1186/s12970-019-0305-8) contains supplementary material, which is available to authorized users.

Effects of Transcranial Direct Current Stimulation With Caffeine Intake on Muscular Strength and Perceived Exertion

Lattari, E, Vieira, LAF, Oliveira, BRR, Unal, G, Bikson, M, de Mello Pedreiro, RC, Marques Neto, SR, Machado, S, and Maranhão-Neto, GA. Effects of transcranial direct current stimulation with caffeine intake on muscular strength and perceived exertion. J Strength Cond Res 33(5): 1237-1243, 2019-The aim of this study was to investigate the acute effects of transcranial direct current stimulation (tDCS) associated with caffeine intake on muscular strength and ratings of perceived exertion (RPE). Fifteen healthy young males recreationally trained (age: 25.3 ± 3.2 years, body mass: 78.0 ± 6.9 kg, height: 174.1 ± 6.1 cm) were recruited. The experimental conditions started with the administration of caffeine (Caff) or placebo (Pla) 1 hour before starting the anodal tDCS (a-tDCS or sham). There was an intake of 5 mg·kg of Caff or 5 mg·kg of Pla. After the intake, a-tDCS or sham was applied in the left dorsolateral prefrontal cortex with intensity of 2 mA and 20 minutes of duration. The experimental conditions were defined as Sham + Pla, a-tDCS + Pla, Sham + Caff, and a-tDCS + Caff. After the conditions, muscular strength and RPE were verified. Muscular strength was determined by volume load performed in bench press exercise. Muscular strength in Sham + Pla condition was lower compared with all others conditions (p < 0.05). The RPE in the Sham + Pla was greater compared with a-tDCS + Caff (p < 0.05). Muscular strength was greater in all experimental conditions, and a-tDCS + Caff had lower RPE compared with placebo. When very little gains in muscle strength are expected, both caffeine and tDCS were effective in increasing muscle strength. Besides, the improvement in RPE of the caffeine associated with a-tDCS could prove advantageous in participants experienced in strength training. In fact, coaches and applied sport scientists quantitating the intensity of training based on RPE.

Effects of Caffeine Supplementation on Performance in Ball Games

Although a large body of evidence exists documenting the ergogenic properties of caffeine, most studies have focused on endurance performance. However, findings from endurance sports cannot be generalized to performance in ball games where, apart from having a high level of endurance, successful athletic performances require a combination of physiological, technical and cognitive capabilities. The purpose of this review was to critically evaluate studies that have examined the effect of a single dose of caffeine in isolation on one or more of the following performance measures: total distance, sprint performance, agility, vertical jump performance and accuracy in ball games. Searches of three major databases resulted in 19 studies (invasion games: 13; net-barrier games: 6) that evaluated the acute effects of caffeine on human participants, provided the caffeine dose administered, and included a ball games specific task or simulated match. Improvements in sprint performance were observed in 8 of 10 studies (80%), and vertical jump in 7 of 8 studies (88%). Equivocal results were reported for distance covered, agility and accuracy. Minor side effects were reported in 4 of 19 studies reviewed. Pre-exercise caffeine ingestion between 3.0 and 6.0 mg/kg of body mass appears to be a safe ergogenic aid for athletes in ball games. However, the efficacy of caffeine varies depending on various factors, including, but not limited to, the nature of the game, physical status and caffeine habituation. More research is warranted to clarify the effects of caffeine on performance measures unique to ball games, such as agility and accuracy. It is essential that athletes, coaches and practitioners evaluate the risk-benefit ratio of caffeine ingestion strategies on an individual case-by-case basis.

Combination of nutritional polyphenols supplementation with exercise training counteracts insulin resistance and improves endurance in high-fat diet-induced obese rats

Separately, polyphenols and exercise are known to prevent insulin resistance (IR) but their combined curative effects on established obesity and IR require further investigation. Therefore, we compared the metabolic effects of a combination of exercise and grape polyphenols supplementation in obese IR rats with high-fat diet (EXOPP) to the effect of high-fat diet alone (HF) or with a nutritional supplementation of grape polyphenols (PP) or with endurance exercise (EXO) during 8 wks. We observed an improvement of systemic and skeletal muscle insulin sensitivity in EXO and EXOPP rats. EXOPP rats compared to HF rats presented a lower insulinemia and HOMA-IR with higher liver and muscle glycogen contents. Interestingly, EXOPP rats had a 68% enhanced endurance capacity compared to EXO rats with also a higher activation of AMPK compared to sedentary and EXO rats with increased lipid oxidation. Together, our results suggest that grape polyphenols supplementation combined with exercise has a synergistic effect by increasing muscle lipid oxidation and sparing glycogen utilization which thus enhances endurance capacity. Our data highlight that in cases of established obesity and IR, the combination of nutritional grape polyphenols supplementation and exercise heighten and intensify their individual metabolic effects.

Periodized Nutrition for Athletes

It is becoming increasingly clear that adaptations, initiated by exercise, can be amplified or reduced by nutrition. Various methods have been discussed to optimize training adaptations and some of these methods have been subject to extensive study. To date, most methods have focused on skeletal muscle, but it is important to note that training effects also include adaptations in other tissues (e.g., brain, vasculature), improvements in the absorptive capacity of the intestine, increases in tolerance to dehydration, and other effects that have received less attention in the literature. The purpose of this review is to define the concept of periodized nutrition (also referred to as nutritional training) and summarize the wide variety of methods available to athletes. The reader is referred to several other recent review articles that have discussed aspects of periodized nutrition in much more detail with primarily a focus on adaptations in the muscle. The purpose of this review is not to discuss the literature in great detail but to clearly define the concept and to give a complete overview of the methods available, with an emphasis on adaptations that are not in the muscle. Whilst there is good evidence for some methods, other proposed methods are mere theories that remain to be tested. 'Periodized nutrition' refers to the strategic combined use of exercise training and nutrition, or nutrition only, with the overall aim to obtain adaptations that support exercise performance. The term nutritional training is sometimes used to describe the same methods and these terms can be used interchangeably. In this review, an overview is given of some of the most common methods of periodized nutrition including 'training low' and 'training high', and training with low- and high-carbohydrate availability, respectively. 'Training low' in particular has received considerable attention and several variations of 'train low' have been proposed. 'Training-low' studies have generally shown beneficial effects in terms of signaling and transcription, but to date, few studies have been able to show any effects on performance. In addition to 'train low' and 'train high', methods have been developed to 'train the gut', train hypohydrated (to reduce the negative effects of dehydration), and train with various supplements that may increase the training adaptations longer term. Which of these methods should be used depends on the specific goals of the individual and there is no method (or diet) that will address all needs of an individual in all situations. Therefore, appropriate practical application lies in the optimal combination of different nutritional training methods. Some of these methods have already found their way into training practices of athletes, even though evidence for their efficacy is sometimes scarce at best. Many pragmatic questions remain unanswered and another goal of this review is to identify some of the remaining questions that may have great practical relevance and should be the focus of future research.

Nutra-ergonomics: influence of nutrition on physical employment standards and the health of workers

The importance of ergonomics across several scientific domains, including biomechanics, psychology, sociology, and physiology, have been extensively explored. However, the role of other factors that may influence the health and productivity of workers, such as nutrition, is generally overlooked. Nutra-ergonomics describes the interface between workers, their work environment, and performance in relation to their nutritional status. It considers nutrition to be an integral part of a safe and productive workplace that encompasses physical and mental health as well as the long-term wellbeing of workers. This review explores the knowledge, awareness, and common practices of nutrition, hydration, stimulants, and fortified product use employed prior to physical employment standards testing and within the workplace. The influence of these nutra-ergonomic strategies on physical employment standards, worker safety, and performance will be examined. Further, the roles, responsibilities, and implications for the applicant, worker, and the employer will be discussed within the context of nutra-ergonomics, with reference to the provision and sustainability of an environment conducive to optimize worker health and wellbeing. Beyond physical employment standards, workplace productivity, and performance, the influence of extended or chronic desynchronization (irregular or shift work) in the work schedule on metabolism and long-term health, including risk of developing chronic and complex diseases, is discussed. Finally, practical nutra-ergonomic strategies and recommendations for the applicant, worker, and employer alike will be provided to enhance the short- and long-term safety, performance, health, and wellbeing of workers.

Improvements in skeletal muscle strength and cardiac function induced by resveratrol during exercise training contribute to enhanced exercise performance in rats

Exercise training (ET) improves endurance capacity by increasing both skeletal muscle mitochondrial number and function, as well as contributing to favourable cardiac remodelling.Interestingly, some of the benefits of regular exercise can also be mimicked by the naturally occurring polyphenol, resveratrol (RESV). However, it is not known whether RESV enhances physiological adaptations to ET. To investigate this, male Wistar rats were randomly assigned to a control chow diet or a chow diet that contained RESV (4 g kg⁻¹ of diet) and subsequently subjected to a programme of progressive treadmill running for 12 weeks. ET-induced improvements in exercise performance were enhanced by 21% (P <0.001) by the addition of RESV to the diet. In soleus muscle, ET+RESV increased both the twitch (1.8-fold; P <0.05) and tetanic(1.2-fold; P <0.05) forces generated during isometric contraction, compared to ET alone. In vivo echocardiography demonstrated that ET+RESV also increased the resting left ventricular ejection fraction by 10% (P <0.05), and reduced left ventricular wall stress compared to ET alone.These functional changes were accompanied by increased cardiac fatty acid oxidation (1.2-fold;P <0.05) and favourable changes in cardiac gene expression and signal transduction pathways that optimized the utilization of fatty acids in ET+RESV compared to ET alone. Overall, our findings provide evidence that the capacity for fatty acid oxidation is augmented by the addition of RESV to the diet during ET, and that this may contribute to the improved physical performance of rats following ET.

Sport-specific nutrition: practical strategies for team sports

Implementation of a nutrition programme for team sports involves application of scientific research together with the social skills necessary to work with a sports medicine and coaching staff. Both field and court team sports are characterized by intermittent activity requiring a heavy reliance on dietary carbohydrate sources to maintain and replenish glycogen. Energy and substrate demands are high during pre-season training and matches, and moderate during training in the competitive season. Dietary planning must include enough carbohydrate on a moderate energy budget, while also meeting protein needs. Strength and power team sports require muscle-building programmes that must be accompanied by adequate nutrition, and simple anthropometric measurements can help the nutrition practitioner monitor and assess body composition periodically. Use of a body mass scale and a urine specific gravity refractometer can help identify athletes prone to dehydration. Sports beverages and caffeine are the most common supplements, while opinion on the practical effectiveness of creatine is divided. Late-maturing adolescent athletes become concerned about gaining size and muscle, and assessment of maturity status can be carried out with anthropometric procedures. An overriding consideration is that an individual approach is needed to meet each athlete's nutritional needs.

Carbohydrates for training and competition

An athlete's carbohydrate intake can be judged by whether total daily intake and the timing of consumption in relation to exercise maintain adequate carbohydrate substrate for the muscle and central nervous system ("high carbohydrate availability") or whether carbohydrate fuel sources are limiting for the daily exercise programme ("low carbohydrate availability"). Carbohydrate availability is increased by consuming carbohydrate in the hours or days prior to the session, intake during exercise, and refuelling during recovery between sessions. This is important for the competition setting or for high-intensity training where optimal performance is desired. Carbohydrate intake during exercise should be scaled according to the characteristics of the event. During sustained high-intensity sports lasting ~1 h, small amounts of carbohydrate, including even mouth-rinsing, enhance performance via central nervous system effects. While 30-60 g · h(-1) is an appropriate target for sports of longer duration, events >2.5 h may benefit from higher intakes of up to 90 g · h(-1). Products containing special blends of different carbohydrates may maximize absorption of carbohydrate at such high rates. In real life, athletes undertake training sessions with varying carbohydrate availability. Whether implementing additional "train-low" strategies to increase the training adaptation leads to enhanced performance in well-trained individuals is unclear.

Tea consumption maybe an effective active treatment for adult attention deficit hyperactivity disorder (ADHD)

Adult attention-deficit/hyperactivity disorder (ADHD) is an increasingly recognized Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) psychiatric disorder associated with significant functional impairment in multiple domains. Although stimulant has the most empirical support as treatment for ADHD in adults, because of the poor treatment compliance, many adults with the disorder continue to experience significant residual symptoms. Tea is a kind of stimulant and many adults like to drink it. The caffeine in tea can reduce one's fatigue, increase people's self-confidence, motivation, alertness, vigilance, efficiency, concentration, and cognitive performance. This report proposes that tea consumption maybe an effective active treatment for adult ADHD.

Caffeine enhances upper body strength in resistance-trained women

Background

Research has indicated that low-to-moderate dosages of caffeine supplementation are ergogenic for sustained endurance efforts as well as high-intensity exercise. The effects of caffeine supplementation on strength-power performance are equivocal, with some studies indicating a benefit and others demonstrating no change in performance. The majority of research that has examined the effects of caffeine supplementation on strength-power performance has been carried out in both trained and untrained men. Therefore, the purpose of this study was to determine the acute effects of caffeine supplementation on strength and muscular endurance in resistance-trained women.

Methods

In a randomized manner, 15 women consumed caffeine (6 mg/kg) or placebo (PL) seven days apart. Sixty min following supplementation, participants performed a one-repetition maximum (1RM) barbell bench press test and repetitions to failure at 60% of 1RM. Heart rate (HR) and blood pressure (BP) were assessed at rest, 60 minutes post-consumption, and immediately following completion of repetitions to failure.

Results

Repeated measures ANOVA indicated a significantly greater bench press maximum with caffeine (p ≤ 0.05) (52.9 ± 11.1 kg vs. 52.1 ± 11.7 kg) with no significant differences between conditions in 60% 1RM repetitions (p = 0.81). Systolic blood pressure was significantly greater post-exercise, with caffeine (p < 0.05) (116.8 ± 5.3 mmHg vs. 112.9 ± 4.9 mmHg).

Conclusions

These findings indicate a moderate dose of caffeine may be sufficient for enhancing strength performance in resistance-trained women.

International society of sports nutrition position stand: caffeine and performance

Position Statement: The position of The Society regarding caffeine supplementation and sport performance is summarized by the following seven points: 1.) Caffeine is effective for enhancing sport performance in trained athletes when consumed in low-to-moderate dosages (~3-6 mg/kg) and overall does not result in further enhancement in performance when consumed in higher dosages (≥ 9 mg/kg). 2.) Caffeine exerts a greater ergogenic effect when consumed in an anhydrous state as compared to coffee. 3.) It has been shown that caffeine can enhance vigilance during bouts of extended exhaustive exercise, as well as periods of sustained sleep deprivation. 4.) Caffeine is ergogenic for sustained maximal endurance exercise, and has been shown to be highly effective for time-trial performance. 5.) Caffeine supplementation is beneficial for high-intensity exercise, including team sports such as soccer and rugby, both of which are categorized by intermittent activity within a period of prolonged duration. 6.) The literature is equivocal when considering the effects of caffeine supplementation on strength-power performance, and additional research in this area is warranted. 7.) The scientific literature does not support caffeine-induced diuresis during exercise, or any harmful change in fluid balance that would negatively affect performance.

Suppression of the aging-associated decline in physical performance by a combination of resveratrol intake and habitual exercise in senescence-accelerated mice

The decline in physical performance with increasing age is a crucial problem in our aging society. We examined the effects of resveratrol, a natural polyphenolic compound present in grapes, in combination with habitual exercise on the aging-associated decline in physical performance in senescence-accelerated prone mice (SAMP1). The endurance capacity of SAMP1 mice undergoing an exercise regimen (SAMP1-Ex) decreased over 12 weeks whereas that of SAMP1 mice fed 0.2% (w/w) resveratrol along with exercise (SAMP1-ExRes) remained significantly higher. In the SAMP1-ExRes group, there was a significant increase in oxygen consumption and skeletal muscle mRNA levels of mitochondrial function-related enzymes. These results suggest that the intake of resveratrol, together with habitual exercise, is beneficial for suppressing the aging-related decline in physical performance and that these effects are attributable, at least in part, to improved mitochondrial function in skeletal muscle.

Tea catechin ingestion combined with habitual exercise suppresses the aging-associated decline in physical performance in senescence-accelerated mice

Catechins, which are abundant in green tea, possess a variety of biologic actions, and their clinical application has been extensively investigated. In this study, we examined the effects of tea catechins and regular exercise on the aging-associated decline in physical performance in senescence-accelerated prone mice (SAMP1) and age-matched senescence-accelerated resistant mice (SAMR1). The endurance capacity of SAMR1 mice, measured as the running time to exhaustion, tended to increase over the 8-wk experimental period, whereas that of SAMP1 mice decreased by 17%. On the other hand, the endurance capacity of SAMP1 mice fed 0.35% (wt/wt) catechins remained at the initial level and was significantly higher than that of SAMP1 mice not fed catechins. In SAMP1 mice fed catechins and given exercise, oxygen consumption was significantly increased, and there was an increase in skeletal muscle fatty acid β-oxidation. The mRNA levels of mitochondria-related molecules, such as peroxisome proliferator-activated receptor-γ coactivator-1, cytochrome c oxidase-II, III, and IV in skeletal muscle were also higher in SAMP1 mice given both catechins and exercise. Moreover, oxidative stress measured as thiobarbituric reactive substances was lower in SAMP1 groups fed catechins than in the SAMP1 control group. These results suggest that long-term intake of catechins, together with habitual exercise, is beneficial for suppressing the aging-related decline in physical performance and energy metabolism and that these effects are due, at least in part, to improved mitochondrial function in skeletal muscle.

The continuing story of nutritional supplements and doping infractions

Nutritional supplements can be a source of positive doping cases as some supplements contain prohibited substances without showing this on their label. This problem has existed for some time and has been extensively studied in the past 8 years. The sport of tennis has played a particular role in this problem because of some peculiar doping cases within its community. This article focuses on this particular doping problem, explaining the background and reviewing the available literature. It presents the first 3 years of experience within the Netherlands Security System Nutritional Supplements Elite Sports ("Nederlands Zekerheidssysteem Voedingssupplementen Topsport" or NZVT) and explains the most extensive system established to combat this particular doping problem. The NZVT experience has shown that paper-based quality systems are still prone to possible contaminations, which leads to the conclusion that the best possible solution for athletes who wish to use nutritional supplements must include laboratory-based analysis for doping substances, preferably repeated for every new batch. The most important educational message, however, is to use a nutritional supplement only if it is deemed of benefit by a nutritional expert.

Exercise and the Institute of Medicine Recommendations for Nutrition

The Food and Nutrition Board of the Institutes of Medicine (IOM) recently released energy, macronutrient, and fluid recommendations, which acknowledged for the first time that active individuals have unique nutritional needs. The IOM calculated an acceptable macronutrient distribution range for carbohydrate (45%-65% of energy), protein (10%-35% of energy), and fat (20%-35% of energy; limit saturated and trans fats). These proportions provide a range broad enough to cover the macronutrient needs of most active individuals, but specific carbohydrate and protein recommendations are also typically made based on a g/kg body weight formula. These ranges are 5 to 12 g of carbohydrate/kg body weight and 1.2 to 1.8 g/kg body weight for protein depending on the level of physical activity. The IOM report also gives recommendations for the two essential fatty acids: linoleic acid (men, 14-17 g/d; women, 11-12 g/d) and linolenic acid (men, 1.6 g/d; women, 1.1 g/d). Baseline adequate intakes for fluid (water + other beverages) were set at 3.0 L and 2.2 L for sedentary men and women, respectively, with higher intakes needed to account for physical activity and exposure to extreme environments.

Carbohydrates and fat for training and recovery

An important goal of the athlete's everyday diet is to provide the muscle with substrates to fuel the training programme that will achieve optimal adaptation for performance enhancements. In reviewing the scientific literature on post-exercise glycogen storage since 1991, the following guidelines for the training diet are proposed. Athletes should aim to achieve carbohydrate intakes to meet the fuel requirements of their training programme and to optimize restoration of muscle glycogen stores between workouts. General recommendations can be provided, preferably in terms of grams of carbohydrate per kilogram of the athlete's body mass, but should be fine-tuned with individual consideration of total energy needs, specific training needs and feedback from training performance. It is valuable to choose nutrient-rich carbohydrate foods and to add other foods to recovery meals and snacks to provide a good source of protein and other nutrients. These nutrients may assist in other recovery processes and, in the case of protein, may promote additional glycogen recovery when carbohydrate intake is suboptimal or when frequent snacking is not possible. When the period between exercise sessions is < 8 h, the athlete should begin carbohydrate intake as soon as practical after the first workout to maximize the effective recovery time between sessions. There may be some advantages in meeting carbohydrate intake targets as a series of snacks during the early recovery phase, but during longer recovery periods (24 h) the athlete should organize the pattern and timing of carbohydrate-rich meals and snacks according to what is practical and comfortable for their individual situation. Carbohydrate-rich foods with a moderate to high glycaemic index provide a readily available source of carbohydrate for muscle glycogen synthesis, and should be the major carbohydrate choices in recovery meals. Although there is new interest in the recovery of intramuscular triglyceride stores between training sessions, there is no evidence that diets which are high in fat and restricted in carbohydrate enhance training.

Dietary supplements

For the athlete training hard, nutritional supplements are often seen as promoting adaptations to training, allowing more consistent and intensive training by promoting recovery between training sessions, reducing interruptions to training because of illness or injury, and enhancing competitive performance. Surveys show that the prevalence of supplement use is widespread among sportsmen and women, but the use of few of these products is supported by a sound research base and some may even be harmful to the athlete. Special sports foods, including energy bars and sports drinks, have a real role to play, and some protein supplements and meal replacements may also be useful in some circumstances. Where there is a demonstrated deficiency of an essential nutrient, an increased intake from food or from supplementation may help, but many athletes ignore the need for caution in supplement use and take supplements in doses that are not necessary or may even be harmful. Some supplements do offer the prospect of improved performance; these include creatine, caffeine, bicarbonate and, perhaps, a very few others. There is no evidence that prohormones such as androstenedione are effective in enhancing muscle mass or strength, and these prohormones may result in negative health consequences, as well as positive drug tests. Contamination of supplements that may cause an athlete to fail a doping test is widespread.