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Optimizing Nutrition for Exercise and Sport
Abstract
The primary factors that affect exercise performance capacity include an individual’s genetic endowment, the quality of training, and the effectiveness of coaching (see Fig. 1). Beyond these factors, nutrition plays a critical role in optimizing performance capacity. In order for an athlete to perform well, their training and diet must be optimal. If an athlete does not train enough or has an inadequate diet, their performance may be decreased (1). On the other hand, if an athlete trains too much without a sufficient diet, they maybe susceptible to become overtrained (see Fig. 2).
... Among these, diet plays a crucial role in practice and performance (6). Adequate nutrition has not only a leading role to meet the player's optimum sports performance but also has a crucial role in improving their physical, technical, and tactical training (7,8). The joint position statement authored by the Academy of Nutrition and Dietetics (AND), the Dietitians of Canada (DC), and the American College of Sports Medicine (ACSM), stresses the critical role of optimal nutrition in athletic performance and recovery from exercise (5). ...
... The previous study also reported that energy intake was positively associated with handgrip strength (16). The most important component to optimize athletic performance through diet is to ensure that the athlete is consuming enough calories to maintain a positive energy balance (7,19). The large volume of rigorous exercise, meanwhile, may make it difficult to meet the energy requirements of athletes. ...
Background
Optimum dietary intake and adequate nutritional knowledge have been recognized as the key factors that play a critical role in improving the athlete's health and nutrition status. This study aimed to measure the association of nutritional knowledge, practice, supplement use, and nutrient intake with strength performance among Nepalese Taekwondo players.
Methods
Between August 2019 and January 2020, a cross-sectional study was conducted among 293 Taekwondo players in Kathmandu Metropolitan City (mean age, 18 years; 63.1% male, 36.9% female). Face-to-face interviews were conducted using semi-structured questionnaires. Anthropometric measures, nutritional intake, nutrition knowledge, and practice were all recorded. The handgrip strength was measured using a handgrip dynamometer as a proxy for strength performance. Univariate and bivariate analyses were used to find out the association between predictor and outcome variables.
Results
More than half of the participants had poor nutrition knowledge [54.3% (159/293)], and poor nutrition practice [55.3% (162/293)] scores. Daily mean energy, carbohydrate, protein and fat intake were 48.0 kcal.kg⁻¹.d⁻¹, 8.6, 1.6, and 1.5 g.kg⁻¹.d⁻¹, respectively among Taekwondo players. Daily total energy and carbohydrate intake were 48.2 kcal.kg⁻¹.d⁻¹ and 8.7 g.kg⁻¹.d⁻¹, respectively among male players which is higher than female players. However, daily protein and fat intake were higher in female players (1.7 and 1.6 g.kg⁻¹.d⁻¹, respectively). Both calcium (375.3 mg) and iron (9 mg) intake among Taekwondo players were significantly lower than current sports nutrition guidelines. Nutritional knowledge score (r = 0.117), height (r = 0.538), weight (r = 0.651), body mass index (r = 0.347), fat (r = 0.075), and energy (r = 0.127) intake showed significant positive correlation with strength performance of athletes. The strength performance was positively associated with training hours per day (β = 0.41, 95% CI: 0.09–0.91), body mass index (β = 0.35, 95% CI: 0.09–0.61), nutrition knowledge score (β = 0.13, 95% CI: 0.01–0.25), and energy intake (β = 0.13, 95% CI: 0.12–0.14).
Conclusions
The nutritional knowledge and practice both were suboptimal among Taekwondo athletes. Height, weight, body mass index, nutritional knowledge, energy, and fat intake showed a positive correlation with strength performance. Future studies can build on the premise of this study to identify the robust relationship between nutritional knowledge, practice, different supplement use, and nutrient intake among other athletes too.
... TKD is a predominantly anaerobic sport (both alactacide and lactacide) with a signi cant aerobic component too [2]. To meet the optimum sports performance by TKD players, besides physical, technical, and tactical training, a sporting lifestyle during which adequate nourishment has a leading role [2,6]. ...
... The previous study also reported that energy intake was positively associated with handgrip strength [20]. The most important component to optimize athletic performance through diet is to ensure the athlete is consuming enough calories to maintain positive energy balance [6,15]. However, it might be challenging to meet the energy needs of athletes with a high volume of intense training. ...
Introduction: Adequate nutrition knowledge and dietary intake are important for enhancing athletic performance. Athletes are more likely to be tired and perform poorly during sports when they do not get enough diet. To the best of our knowledge, this study is first of its kind to measure the association of nutritional knowledge, practice, supplement use, and nutrient intake with athletic performance among Nepalese Taekwondo (TKD) players.
Methodology:We conducted an analytical cross-sectional study among 293 Taekwondo players of Kathmandu Metropolitan City, between August 2019 and January 2020. A two-stage cluster random sampling technique was used to select the desired number of respondents for the study. Face-to-face interviews were carried out using semi-structured questionnaires. Nutrition knowledge (NK), nutrition practice (NP), supplement use, nutrient intake using 24-hour dietary recall, and anthropometric measurements were taken. A handgrip dynamometer was used to assess the handgrip strength (HGS), as an indirect measure of athletic performance. Univariate and bivariate analyses were employed to find out the association of predictor and outcome variables. Data were analyzed using STATA/MP version 14.1.
Results: Out of 293 participants, more than half (56.31% and 55.63%) had poor nutrition knowledge and nutrition practice scores respectively. Total energy intake (2368 Kcal) and protein (13.28%), fat (15.85%), calcium (416 mg), and iron (7 mg) respectively were significantly lower than corresponding Recommended Dietary Allowances (RDA) except carbohydrates intake (71.41%). Nutritional knowledge (r = 0.117), height (r = 0.538), weight (r = 0.651), BMI (r = 0.347), fat (r = 0.075), and energy (0.127) intake showed significant positive correlation with handgrip strength of athletes. The athletic performance were positively associated with training hours per day (β = 0.41, 95% CI: 0.09–0.91), BMI (β = 0.35, 95% CI: 0.09–0.61), NK score (β = 0.13, 95% CI: 0.01–0.25), and energy intake (β = 0.13, 95% CI: 0.12 = 0.14).
Conclusions: The results suggested that nutritional knowledge and nutrient intake both were poor among TKD athletes. Height, weight, BMI, nutritional knowledge, energy, and fat intake were positive correlation with athletic performance. Further well-constructed longitudinal research is warranted to identify the robust relationship between nutritional knowledge, practice, different supplement use, and nutrient intake among athletes.
... Ingesting carbohydrates and protein within 2 hours following exercise (e.g., 1.5 g/kg carbohydrate and 0.5 g/kg protein) has been reported to increase glycogen resynthesis and protein synthesis, promote a more optimal anabolic hormonal environment, and improve immune function. Theoretically, optimizing availability of carbohydrates prior to and during exercise as well as following exercise can help optimize exercise performance and recovery, which lead to greater training adaptations (5). ...
... Our rationale was based on results of our initial study in this series (3,6), which found that the carbohydrate profile and glycemic index response of honey was nearly identical to that of a popular sports gel. Moreover, contrary to anecdotal myth, we found honey did not promote physical or psychological signs of hypoglycemia in fasted subjects (3,5), during resistance training (1), or following resistance training (1,2). In this study, 9 welltrained male cyclists performed three 40-mile time trials on their own racing bicycle attached to a computerized race simulator. ...
... During performance, honey significantly raised the blood glucose level and heart rate (Kreider et al. 2002). It did not cause physiological or psychological hypoglycaemia in fasting or resistance-exercising athletes (Leutholtz and Kreider 2001;Earnest et al. 2000). Another study tested how low-and high-GI honey and carbohydrate gels affected 64-km cycling performance. ...
The natural highly concentrated sweet solution known as honey is produced by honey bees from plant nectar and honeydew. Since the beginning, it has been one of the most cherished and recognized natural food and medicine. Approximately 300 different varieties of honey exist, and they are divided into groups based on their texture, processing and nectar source. Honey has found more than 180 identifiable molecules, including carbohydrate proteins, minerals, enzymes, aroma compounds, amino acids, vitamins and polyphenols. Carbohydrates contain mostly glucose and fructose and approximately 25 different di- and trisaccharides. Honey is best consumed before going to bed, whether fatigued or sick. The botanical source claims that honey has a lower glycaemic index (32–80) than sugar (60–110). Honey components have antioxidant, anticancer, antibacterial, anti-inflammatory, antidiabetic and wound-healing activities. Moreover, honey has many health-improving effects on general physical fitness; respiratory, cardiovascular, gastroenterology, bone, face, hair, skin and mental health etc. In addition, the excessive consumption of honey can lead to side effects, especially in children and older people. There will be enough evidence to support using honey as a natural medicine in clinical wards for various medical purposes.
... The previous study also reported that energy intake was positively associated with handgrip strength [17]. The most important component to optimize athletic performance through diet is to ensure the athlete is consuming enough calories to maintain positive energy balance [7,19]. However, it might be challenging to meet the energy needs of athletes with a high volume of intense training. ...
Introduction: Adequate knowledge on nutrition and dietary intake are important to enhance the athletic performance. When athletes’ nutrition requirements are not met, they are more likely to be exhausted compromising athletic performance. The main objective of this study was to measure the association of nutritional knowledge, practice, supplement use, and nutrient intake with athletic performance among Nepalese Taekwondo (TKD) players.
Methodology: We conducted an analytical cross-sectional study among 293 Taekwondo players of Kathmandu Metropolitan City, between August 2019 and January 2020. A two-stage cluster random sampling technique was used to select respondents for this study. Face-to-face interviews were carried out using semi-structured questionnaires. Nutrition knowledge (NK), nutrition practice (NP), supplement use, nutrient intake using 24-hour dietary recall, and anthropometric measurements were taken. A handgrip dynamometer was used to assess the handgrip strength (HGS) as an indirect measure of athletic performance. Univariate and bivariate analyses were used to find out the association of predictor and outcome variables. Data were analyzed using Stata/MP version 14.1.
Results: Out of 293 participants, more than half (56.3% and 55.6%) had poor nutrition knowledge and nutrition practice scores, respectively. Total energy (2368 Kcal), carbohydrate (430.5 gm), protein (79.5 gm ), fat (71.2 gm), calcium (416 mg), and iron (7 mg) intake among TKD players were significantly lower than the corresponding Recommended Dietary Allowances (RDA) for athletes. Nutritional knowledge score (r=0.117, p<0.045), height (r=0.538, p<0.001), weight (r=0.651, p<0.001), BMI (r=0.347, p<0.001), fat (r=0.075, p<0.002), and energy (r=0.127, p<0.029) intake showed significant positive correlation with handgrip strength of athletes. The athletic performance were positively associated with training hours per day (β=0.41, 95% CI: 0.09-0.91), BMI (β=0.35, 95% CI: 0.09-0.61), NK score (β=0.13, 95% CI: 0.01-0.25), and energy intake (β=0.13, 95% CI: 0.12=0.14).
Conclusions: The results suggest that nutritional knowledge and nutrient intake both were poor among TKD athletes. Height, weight, BMI, nutritional knowledge, energy, and fat intake showed positive correlation with athletic performance. Future studies can build on the premise of this study to identify the robust relationship between nutritional knowledge, practice, different supplement use, and nutrient intake among athletes.
... The assessment of athletic performance, both from a biological, psychological, educational or end performance point of view, usually is one of the key components of the management process of sports training. According to Viru, A. & Viru, M. (2003) the training load is usually evaluated from the biological point of view through blood or urine analysis, using metabolic and hormonal criteria to get aware of the effect of the training session, therefore the biological conditions are usually extremely valuable and well studied by related scientists such as Fernández, Delgado, B. & Delgado, M. (2003); Kreider, Leutholtz, Katch & Katch (2009), among others. Moreover, the performance conditions based on psychological control value indicators such as competitive stress and the link with biological growth (Stafford, 2011), the willingness to win (Kremer & Moran, 2013) and other aspects of the preparation of the athlete, while the final performance is evaluated primarily on the stage of maximum performance in sports (Calero, 2009) or as part of the competition itself (Weinberg, 2010;Calero, 2011;Lebed & Bar-Eli, 2013). ...
This research project determines the basic indicators used in the sciences of Physical Activity and Sports in order to assess the population characteristics in functional capabilities and the possibilities of athletic performance. A representative sample of 6,902 individuals was used to study the Vertical Jump Power; 3,066 individuals to study the Horizontal Jump Power; 10,211 individuals to study the Local Muscular Power (Abs); 10,213 individuals for Rapid Strength and Agility, 10,285 for Peak Oxygen Uptake and 10,285 individuals studied with the Trunk Flexibility test. This article evaluates the information generally because it totals real data of subjects aged between 5 to 18 years old without strata distinction. It describes the untrained population of Ecuador from the quantitative point of view. It corresponds to a segment of a study that defines national parameters aimed at the development of sports.
... La valoración del rendimiento deportivo, tanto desde el punto de vista biológico, psicológico, pedagógico o del rendimiento final, suele ser uno de los componentes esenciales del proceso de gestión del entrenamiento deportivo. La carga de entrenamiento según Viru, A. y Viru, M. (2003) suele evaluarse desde el punto de vista biológico a través de análisis de sangre u orina, utilizando criterios metabólicos y hormonales para conocer el efecto de la sesión de entrenamiento,por lo cual, las condicionantes biológicas suelen ser sumamente valiosas y bien estudiadas por científicos afines, tales comoFernández, Delgado, B. y Delgado, M. (2003); Kreider, Leutholtz, Katch y Katch (2009) entre otros. Por otra parte, los condicionantes de rendimiento basados en el control psicológico, valoran indicadores tales como el stress competitivo y la relación con el crecimiento biológico (Stafford, 2011), la disposición para la victoria (Kremer y Moran, 2013) entre otros aspectos de la preparación del deportista, mientras que el rendimiento final es valorado básicamente en la etapas de máximo rendimiento deportivo (Calero, 2009) o como parte del proceso de competición propiamente dicho (Weinberg, 2010;Calero, 2011;Lebed y Bar-Eli, 2013). ...
El presente trabajo investigativo determina los indicadores básicos utilizados en la ciencias de la Actividad Física y el Deporte para valorar las características poblacionales en capacidades funcionales y las posibilidades de rendimiento deportivo. Se utilizó una muestra representativa de 6902 individuos para estudiar la Potencia de Salto Vertical, 3066 individuos para estudiar la Potencia de Salto Horizontal, 10211 sujetos para estudiar la Potencia Muscular Local (Abdominales), 10213 para la Fuerza Rápida y Agilidad, 10285 para el Volumen Máximo de Oxigeno y 10285 sujetos estudiados con la prueba de Flexibilidad del Tronco. Este artículo valora la información de forma general, pues totaliza datos reales de sujetos en edades entre 5 y 18 años sin distinción de estratos, por lo cual describe a la población no entrenada del Ecuador desde el punto de vista cuantitativo. Corresponde a un segmento de un estudio que define parámetros nacionales orientados al desarrollo del deporte.
Honey is a naturally occurring food with a very high nutritional value. Nectar content and quality vary widely depending on the botanical origin as well as the surrounding environment and climatic factors. Honey can improve people’s health and dietary conditions, depending on its quality. The current chapter covers the composition, nutritional value, and health advantages of honey in general. According to the research evidence, honey has a variety of advantageous effects on dietary intake and health. Honey is suitable for all ages—older people, children, and adults. Honey has been proven to have anti-inflammatory, antiviral, antiparasitic, antibacterial, antioxidant, and anticancer properties. Honey’s low water activity prevents the growth of microbes. Natural antioxidants found in honey are good at lowering the risk of numerous diseases. In daily life, we typically utilize honey to treat many conditions, such as hearing loss, bad breath, pimples, exhaustion, weight loss, influenza, gastrointestinal issues, toothaches, hairlessness, bladder infections, and infertility. Many natural ingredients, including lemon, milk, cloves, cinnamon, and water, are mixed with honey to treat a variety of illnesses and other health issues.
Honeybee products have recently begun to attract attention with their effects on athlete performance. In the present study, it was aimed to investigate the effects of honeybee products’ mixtures on the performance and some blood biochemical parameters of young trained gymnasts. Twenty-four young gymnasts aged between 6 and 12 years were observed for 4 weeks as they continued their usual daily training schedules. The gymnasts were divided into three groups. Group 1 was administered a mixture of honey and bee pollen at a dose of 50 g/day, whereas Group 2 was provided with a mixture of honey, bee pollen, royal jelly and propolis. Group 3 served as the control group and was administered a placebo of wheat starch at a dose of 50g/day. In the beginning and at the end of the study, performance parameters and biochemical parameters of young gymnasts were determined. After treatment, grip force and muscular strength measurements increased in Group 2 (p<0.05). The muscular endurance tests in the two honeybee product mixtures treatment groups showed improvement after supplementation (p<0.05). The improvement noted in the power test in Group 1 was significantly higher than the other groups (p<0.05). There was no significant difference between treatment and placebo groups in all investigated biochemical parameters except total protein, which was lower in placebo group. Although bee products supplements were administered only for a short period of time, the gymnasts showed higher performance in some investigated parameters. It is recommended to conduct further long-term studies using bee products.
Background:
Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words 'sport nutrition'. Consequently, staying current with the relevant literature is often difficult.
Methods:
This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.
Conclusions:
This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.
Abstract Sport nutrition is a constantly evolving field with literally thousands of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper presents a well-referenced overview of the current state of the science related to how to optimize training through nutrition. More specifically, this article discusses: 1.) how to evaluate the scientific merit of nutritional supplements; 2.) general nutritional strategies to optimize performance and enhance recovery; and, 3.) our current understanding of the available science behind weight gain, weight loss, and performance enhancement supplements. Our hope is that ISSN members find this review useful in their daily practice and consultation with their clients.
A nutrient-dense diet is a critical aspect in attaining optimal exercise training, recovery, and athletic performance outcomes. While including safe and effective nutritional supplements in the dietary design can be extremely helpful in promoting adequate caloric and nutrient ingestion, they are not a complete cure in promoting adequate caloric ingestion based on individualized caloric expenditure needs without the proper diet. Specifically, a strategic and scientifically based nutrient-dense dietary profile should be created by qualified professionals to meet the sport/exercise-specific energy and nutrient demands of any individual involved in select training intensity protocols. Finally, ingesting the right quantity and quality of nutrient-dense calories at precise windows of opportunity becomes vital in attaining desired training and/or competitive performance outcomes. © Springer International Publishing Switzerland 2015. All rights reserved.
Crocus sativus, commonly known as saffron, is a rich source of carotenoids with many health benefits. The muscular strength, pulmonary function, and reaction time are vital to the athlete's performance, and this study aimed to investigate an ergogenic effect of saffron. Twenty-eight nonactive and healthy male university students were randomly assigned into the saffron (n = 14) and control (n = 15) groups. The experimental group received dried saffron stigma (300 mg/day for 10 days) and the control group received a placebo. After one session, familiarization with the tests, anthropometric parameters, visual and audio reaction times, and the maximum isometric and isotonic forces on a leg press machine were measured accordingly, 1 day before and after the supplementation period. This study shows that 10 days of supplementation with saffron significantly increased (10.1%) the isometric force (p < .0001; effect size (EF) = 0.432) and increased 6.1% the isotonic force (p < .0001; effect size = 0.662), as well as effecting faster visual (p < .05; EF = 0.217) and audio (p < .05; EF = 0.214) reaction times. The ergogenic effect of saffron (increase in the forces) may contribute to increase in the muscle mitochondrial biogenesis and positive effect on the motor cortex, both of which may explain faster audio and visual reaction times. Saffron supplementation was also possibly responsible for improvement of muscle blood perfusion and facilitation in the oxygen transport.
The road to a safe, effective, and enjoyable fitness and athletic lifestyle should be considered an ultramarathon and not a 100-meter sprint. The often quoted phrase that Rome was not built in one day really holds credence here because of the number of annual exercisers that initiate an exercise protocol only to quit within a few weeks because they did not attain the desired results in their specified time frame. Because of inappropriate dietary habits and or training protocols that lead to overreaching (short-term) and overtraining (long-term), decrements of physiologic and psychologic outcomes occur in many exercisers (Kreider et al. In: Kreider et al., eds. Overtraining in Sport. Champaign, IL: Human Kinetics Publishers; 1 998:vii-ix). Whereas intense training is necessary to optimize performance, intense training over prolonged periods can hinder performance. The truth of the matter is, although it may take a person 30 or 40 years to display their current physical fitness state, it is human nature to want to immediately become, although unrealistic, the next Mr. or Ms. Olympia overnight. Yes, an effective athletic or fitness lifestyle becomes a journey and not a weekend vacation that involves the development of knowledge, patience, proper nutritional practices, variety, commitment and tenacity, not to mention hard work, in order for a person to reach and maintain their optimal athletic/exercise/fitness goals. Although research supports a plethora of reasons why people abandon exercise protocols (Weinberg and Gould. Foundations of Sport and Exercise Psychology. Champaign, IL: Human Kinetics Publishers; 1999:371-395), the scientific literature has varied on the precise reasons why and how the processes of overreaching/overtraining occur and can be reduced or eliminated. With these elements in mind, the purpose of this chapter is to present the following information: 1) physiologic and psychologic effects of overtraining related to sport and exercise, 2) valid fitness and health assessment guidelines to limit aspects of overtraining, 3) strength and conditioning periodization design to reduce occurrences of overtraining, and 4) scientific-based nutritional strategies to promote and prevent overtraining with exercise and sport populations.
In the last few decades, the use of ergogenic aids has become widespread among professional and amateur athletes. There are several reasons for this, including changes in the way dietary supplements are marketed, the growing body of research, and increased financial rewards for stand-out athletes. It is important for physicians, athletic trainers, and coaches to have a solid working knowledge about the risks, benefits, and efficacy of common supplements in order to ensure effective and honest communication with athletes.
Creatine has become a popular nutritional supplement among athletes. Recent research has also suggested that there may be a number of potential therapeutic uses of creatine. This paper reviews the available research that has examined the potential ergogenic value of creatine supplementation on exercise performance and training adaptations. Review of the literature indicates that over 500 research studies have evaluated the effects of creatine supplementation on muscle physiology and/or exercise capacity in healthy, trained, and various diseased populations. Short-term creatine supplementation (e.g. 20 g/day for 5–7 days) has typically been reported to increase total creatine content by 10–30% and phosphocreatine stores by 10–40%. Of the approximately 300 studies that have evaluated the potential ergogenic value of creatine supplementation, about 70% of these studies report statistically significant results while remaining studies generally report non-significant gains in performance. No study reports a statistically significant ergolytic effect. For example, short-term creatine supplementation has been reported to improve maximal power/strength (5–15%), work performed during sets of maximal effort muscle contractions (5–15%), single-effort sprint performance (1–5%), and work performed during repetitive sprint performance (5–15%). Moreover, creatine supplementation during training has been reported to promote significantly greater gains in strength, fat free mass, and performance primarily of high intensity exercise tasks. Although not all studies report significant results, the preponderance of scientific evidence indicates that creatine supplementation appears to be a generally effective nutritional ergogenic aid for a variety of exercise tasks in a number of athletic and clinical populations.
A nutrient-dense diet is a critical aspect in attaining optimal exercise training and athletic performance outcomes. Although
including safe and effective nutritional supplements in the dietary design can be extremely helpful in promoting adequate
caloric ingestion, they are not sufficient for promoting adequate caloric ingestion based on individualized caloric expenditure
needs without the proper diet. Specifically, a strategic and scientifically based nutrient-dense dietary profile should be
created by qualified professionals to meet the sport/exercise-specific energy demands of any individual involved in select
training intensity protocols. Finally, ingesting the right quantity and quality of nutrient dense calories at precise windows
of opportunity becomes vital in attaining desired training and/or competitive performance outcomes.
Key wordsNutrient dense–Nutritional supplements–Caloric intake–Caloric expenditure–Nutrient timing–Restoration–Macronutrient profiles
We examined the effects of short-term consumption of whey protein isolate on muscle proteins and force recovery after eccentrically-induced muscle damage in healthy individuals.
Seventeen untrained male participants (23 ± 5 yr, 180 ± 6 cm, 80 ± 11 kg) were randomly separated into two supplement groups: i) whey protein isolate (WPH; n = 9); or ii) carbohydrate (CHO; n = 8). Participants consumed 1.5 g/kg.bw/day supplement (~30 g consumed immediately, and then once with breakfast, lunch, in the afternoon and after the evening meal) for a period of 14 days following a unilateral eccentric contraction-based resistance exercise session, consisting of 4 sets of 10 repetitions at 120% of maximum voluntary contraction on the leg press, leg extension and leg flexion exercise machine. Plasma creatine kinase and lactate dehydrogenase (LDH) levels were assessed as blood markers of muscle damage. Muscle strength was examined by voluntary isokinetic knee extension using a Cybex dynamometer. Data were analyzed using repeated measures ANOVA with an alpha of 0.05.
Isometric knee extension strength was significantly higher following WPH supplementation 3 (P < 0.05) and 7 (P < 0.01) days into recovery from exercise-induced muscle damage compared to CHO supplementation. In addition, strong tendencies for higher isokinetic forces (extension and flexion) were observed during the recovery period following WPH supplementation, with knee extension strength being significantly greater (P < 0.05) after 7 days recovery. Plasma LDH levels tended to be lower (P = 0.06) in the WPH supplemented group during recovery.
The major finding of this investigation was that whey protein isolate supplementation attenuated the impairment in isometric and isokinetic muscle forces during recovery from exercise-induced muscle injury.
Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.
In 1988 Segura and Ventura (14) reported that 1.2 g of L-Tryptophan (L-TRY) supplementation increased total exercise time by 49.4% when the subjects were running at 80% of maximal oxygen uptake (VO2max). In human performance research, acute improvements of that category are rather uncommon. Both for this reason and because ingestion of purified L-TRY may have adverse effects, it seemed pertinent to repeat the investigation of Segura and Ventura. Forty-nine well-trained male runners, aged 18-44, with an average maximal aerobic power of 66 (57-78) ml.kg-1.min-1, participated in a randomized double blind placebo (P) study. Each subject underwent four trials on the treadmill. The first two served as learning experience, including measurement of VO2max and anaerobic threshold. During the last two trials the subjects ran until exhaustion at a speed corresponding to 100% of their VO2max-first an initial trial and then after receiving a total of 1.2 g L-TRY or P over a 24 hour period prior to the run. No significant difference between the improvements in the L-TRY and P group could be demonstrated. It is concluded that oral L-TRY supplementation does not enhance running performance.
Total iron losses in feces, urine and sweat in endurance-trained athletes are approximately 1.75 mg/d (compared with the reference value of 1 mg/d) in males and approximately 2.3 mg/d (compared with the reference value of 1.4 mg/d) in females because of the additional iron losses with menses. Therefore, it is not surprising that many investigators report that iron deficiency is a common problem in athletes who do not increase their iron intake above that of the general population. Recently, several observations of iron deficiency associated with mild exercise have been reported. Investigation of the extent of iron loss and utilization in individuals exercising for fitness is needed. Because compromised iron status can affect athletic performance as well as general health, including immune functions, cognitive development and ability to thermoregulate, it is advisable to emphasize meeting the recommended dietary allowances for iron during exercise training.
Five trained, fasted male cyclists rode a cycle ergometer three times at 50% of VO2max for 180 min. Using a balanced order, double-blind procedure, subjects were given either a solution containing polylactate (PL: 80% polylactate, 20% sodium lactate, in 7% solution with water), glucose polymer (GP: multidextrin in 7% solution with water), or control (C: water sweetened with aspartame) 5 min before exercise and at 20-min intervals during exercise. Venous blood samples were taken at rest and at 20-min intervals during exercise. In general, PL and GP rendered similar results except that pH and bicarbonate (HCO3-) were higher in PL. There were no differences between treatments in perceived exertion, sodium, potassium, chloride, lactate, heart rate, oxygen consumption, rectal temperature, or selected skin temperatures. These data show that polylactate may help maintain blood glucose and enhance blood buffering capacity during prolonged exercise and could be a useful component in an athletic fluid replacement beverage.
There is widespread belief among athletes that special nutritional practices--in particular high-protein diets--will enhance their achievements in competition. Supplementation with vitamins, especially vitamin C, is equally popular. But because genetic predisposition, hard physical training and psychological factors play a most important role in determining performance, and because any potential difference in achievement will be small, it is almost impossible to obtain scientific evidence of a beneficial effect of a particular nutrient. There have been many investigations during the past four decades of the potential effect of high-dose vitamin C supplementation on physical performance. The variables used have included maximum oxygen uptake, blood lactic acid levels, and heart rate after exercise, and in some cases performance was assessed in competitive events. The results have been equivocal: Most studies could not demonstrate an effect. On the other hand, a suboptimal vitamin C status results in an impaired working capacity which can be normalized by restoring vitamin C body pools. Athletes, who follow irrational, unhealthy eating patterns often not including vitamin-C-containing fruit and vegetables, are in need of nutrition education.
A double-blind study of combined restriction of thiamin, riboflavin, and vitamins B-6 and C was carried out with 23 healthy males. During 8 wk of low vitamin intake, 12 deficient subjects consumed daily a diet of normal food products, providing maximally 32.5% of the Dutch Recommended Dietary Allowances (RDA) for thiamin, riboflavin, vitamins B-6 and C. Other vitamins were supplemented at twice the RDA. Eleven control subjects consumed the same diet but with a supplementation of twice the RDA of all vitamins. In deficient subjects blood vitamin levels, urinary vitamin excretion, and erythrocytic enzyme activities decreased; in vitro enzyme stimulation increased. Vitamin depletion had no ill effects on health, physical activity, and mental performance. A significant decrease was observed in aerobic power (VO2max) and onset of blood lactate accumulation (p less than 0.001) of 9.8 and 19.6%, respectively. A combined restricted intake of thiamin, riboflavin, and vitamins B-6 and C causes a decrease in physical performance within a few weeks.
To examine the effect of zinc (Zn) supplementation on exercise-induced changes in immune function, five male runners were randomly assigned in a double-blind crossover design to take a supplement (S; 25 mg of Zn and 1.5 mg of copper) or placebo (P) twice daily for 6 days. On morning 4 of each phase, 1 h after taking S or P, subjects ran on a treadmill at 70-75% of maximal oxygen uptake until exhaustion (approximately 2 h). Blood samples were obtained before (Pre), immediately after (Post), and 1 (Rec1) and 2 (Rec2) days after the run. [3H]thymidine incorporation by mitogen-treated mononuclear cell cultures was significantly lower (P < 0.05) Post than Pre, Rec1, or Rec2 for both S and P. Respiratory burst activity of isolated neutrophils was enhanced after exercise with P but not with S (P: Pre 12.0 +/- 1.1 vs. Post 17.6 +/- 2.3 nmol O2-/10(6) cells; S: Pre 11.7 +/- 0.3 vs. Post 12.1 +/- 1.2 nmol O2-/10(6) cells). Thus supplemental Zn blocked the exercise-induced increase in reactive oxygen species. Whether this antioxidant effect of Zn will benefit individuals exposed to chronic physical stress remains to be determined.
Polylactate (PL), a semi-soluble amino acid/lactate salt, is a newly developed carbohydrate supplement purported to increase endurance. Our purpose was to determine if the addition of PL to a glucose polymer solution (GP) extends exercise time relative to a pure GP solution. In a double blind and random crossover design, 5 subjects exercised twice to exhaustion at 70% of VO2max. During the trials, they consumed GP or a GP/PL mixture at the rate of 0.3 g carbohydrate per kg of body wt in a 7% solution every 20 min until exhaustion. The GP/PL mixture contained 6.25 g GP to 0.75 g PL per 100 ml of water. Mixture composition was critical because PL, as supplied by the manufacturer and under our experimental conditions, produced severe gastro-intestinal efflux in concentrations > or = 2.5%; PL was tolerable in concentrations < or = 0.75%. At 20 min intervals, we measured VO2, respiratory exchange ratio, heart rate, and perceived exertion. At 30 min intervals, we measured serum glucose, insulin, free fatty acids, and glycerol as well as whole blood lactate and pH. We found that the addition of PL to a GP solution had no measurable physiological or performance effects.
Several studies have observed an increased risk of respiratory infections in subjects doing heavy physical exercise. Vitamin C has been shown to affect some parts of the immune system, and accordingly it seems biologically conceivable that it could have effects on the increased incidence of respiratory infections caused by heavy physical stress. In this report the results of three placebo-controlled studies that have examined the effect of vitamin C supplementation on common cold incidence in subjects under acute physical stress are analyzed. In one study the subjects were school-children at a skiing camp in the Swiss Alps, in another they were military troops training in Northern Canada, and in the third they were participants in a 90 km running race. In each of the three studies a considerable reduction in common cold incidence in the group supplemented with vitamin C(0.6-1.0 g/day) was found. The pooled rate ratio (RR) of common cold infections in the studies was 0.50 (95% CI: 0.35-0.69) in favour of vitamin C groups. Accordingly, the results of the three studies suggest that vitamin C supplementation may be beneficial for some of the subjects doing heavy exercise who have problems with frequent upper respiratory infections.
On three occasions separated by 10 days, six endurance-trained cyclists rode for 2 h at 60% of peak O2 uptake and then performed a simulated 40-km time trial (T-trial). During the rides, the subjects ingested a total of 2 liters of a [U-14C]glucose-labeled beverage containing a random order of either 10% glucose [carbohydrate (CHO)], 4.3% medium-chain triglycerides (MCTs); or 10% glucose + 4.3% MCTs (CHO+MCT). Although replacing CHO with MCTs slowed the T-trials from 66.8 +/- 0.4 (SE) to 72.1 +/- 0.6 min (P < 0.001), adding MCTs to CHO improved the T-trials from 66.8 +/- 0.4 to 65.1 +/- 0.5 min (P < 0.05). Faster T-trials in the CHO+MCT trial than in the CHO trial were associated with increased final circulating concentrations of free fatty acids (0.58 +/- 0.09 vs. 0.36 +/- 0.06 mmol/l; P < 0.05) and ketones (1.51 +/- 0.25 vs. 0.51 +/- 0.07 mmol/l; P < 0.01) and decreased final circulating concentrations of glucose (5.2 +/- 0.2 vs. 6.3 +/- 0.3 mmol/l; P < 0.01) and lactate (1.9 +/- 0.4 vs. 3.7 +/- 0.5 mmol/l; P < 0.05). Adding MCTs to ingested CHO reduced total CHO oxidation rates from 14 +/- 1 to 10 +/- 1 mmol/min at 2 h and from 17 +/- 1 to 14 +/- 1 mmol/min in the T-trial (P < 0.01), without affecting the corresponding approximately 5 and approximately 7 mmol/min rates of [14C]glucose oxidation. These data suggest that MCT oxidation decreased the direct and/or indirect (via lactate) oxidation of muscle glycogen. A reduced reliance on CHO oxidation at a given O2 uptake is similar to an endurance-training effect, and that may explain the improved T-trial performances.
Recent major advances in pharmacological management have provided asthmatics with a satisfactory range of drugs to control asthma. These include sodium cromoglycate (cromolyn sodium), H1-antagonists, belladonna alkaloids, methyl xanthines, glucocorticoids and β2-adrenoceptor stimulants. Despite the tendency for most asthmatics to develop broncho-constriction after exercise, sport and physical activity are now accepted as valuable in the overall management of patients with asthma. Thus, control of exercise-induced asthma (EIA) is essential, if asthmatics are to participate safely in physical activity and without respiratory disadvantage in competitive sport. Fortunately, inhibition or minimisation of exercise-induced asthma may be achieved in most asthmatics by pre-exercise aerosol β2-agonists supplemented if necessary by sodium cromoglycate and/or theophylline. Regular medication as required to attain and maintain normal ventilatory function throughout each day is the objective in all patients with asthma and appears to be a prerequisiste to control exercise-induced asthma.
The introduction of anti-doping controls into high performance sport has presented added difficulties for the asthmatic athlete. Although not always so, currently all of the classes of drugs previously noted are acceptable for the treatment of asthma and exercise-induced asthma. Anomalies may exist in the banning of 2 β2-adrenoceptor agonists, fenoterol and orciprenaline (metaproterenol). All sympathomimetic amines with α-or predominately β-stimulation are banned. The perpetuation of the need to report the use of β2-agonists prior to competition appears unnecessary.
Although relatively little specific research has been undertaken, there is minimal evidence to suggest that asthmatics can derive any additional ergogenic advantage from medication to control asthma and exercise-induced asthma. β2-agonists, sodium cromoglycate and glucocorticoids administered by the aerosol route are not considered to be ergogenic. Some doubts have been raised concerning theophylline and its enhancement of both cardiac and respiratory muscle function. Investigations as to the validity of the suggestion that theophylline could augment physical performance appear warranted. It is reported that some athletes may be unnecessarily taking oral and perhaps parenteral glucocorticoids to obtain certain side effects. Any decision to ban these agents except for aerosol or local use could be supported.
The aim of this randomized, double-blind, placebo controlled study was to investigate the efficacy and safety of different doses and preparations of Echinacea purpurea in the treatment of common cold. 246 of 559 recruited healthy, adult volunteers caught a common cold and took 3 times daily 2 tablets of either Echinaforce® (Echinacea purpurea-preparation from 95% herba and 5% radix), Echinacea purpurea concentrate (same preparation at 7 times higher concentration), special Echinacea purpurea radix preparation (totally different from that of Echinaforce®) or placebo until they felt healthy again but not longer than 7 days. The primary endpoint was the relative reduction of the complaint index defined by 12 symptoms during common cold according to the doctor's record. Echinaforce® and its concentrated preparation were significantly more effective than the special Echinacea extract or placebo. All treatments were well tolerated. Among the Echinacea groups the frequency of adverse events was not significantly higher than in the placebo group. Therefore, Echinacea concentrate as well as Echinaforce® represent a low-risk and effective alternative to the standard symptomatic medicines in the acute treatment of common cold.
Small decreases in hydration status can result in a dramatic decrement in athletic performance and greatly increase the risk of thermal injury. Because of its osmotic properties, which enable greater fluid retention than the ingestion of water alone, glycerol has been proposed as a hyperhydrating agent. In fact, glycerol is now commercially available and marketed as a sport supplement to be ingested with water or sport drinks; thus, dietitians need to be cognizant of this new addition to the sports nutrition table. The results of glycerol-induced hyperhydration research have been equivocal, most likely because of methodologic differences between studies, such as variations in the intensity of exercise, environmental conditions, and concentration or dose of glycerol administered. Although the suggested dosage of glycerol depends on body size and varies between manufacturers, 1 g/kg body weight with an additional 1.5 L fluid taken 60 to 120minutes before competition is standard. Some test subjects reported feeling bloated or nauseated after ingesting glycerol. This review examines glycerol-induced hyperhydration research and the safety of ingesting glycerol, discusses commercial availability of glycerol, and makes recommendations for glycerol-induced hyperhydration research. J Am Diet Assoc. 1999;99:207–212.
The purpose of this study was to investigate the ergogenic effect of oral inosine (IN) supplementation (6,000 mg.d-1 for 2 d) upon 3-mile run time (3MTIME) and [latin capital V with dot above]o2 peak. Nine highly trained endurance runners participated in a double-blind, placebo (PL), crossover study. Each subject undertook an IN or PL trial, consisting of three exercise tests: a submaximal warm-up run (SUBRUN), a competitive 3-mile treadmill run (3MRUN), and a maximal treadmill run (MAXRUN) to determine [latin capital V with dot above]o2 peak and time to exhaustion (MAXTIME). Additional measurements during the 3MRUN and MAXRUN included oxygen uptake ([latin capital V with dot above]o2), ventilation ([latin capital V with dot above]E), respiratory exchange ratio (R), and ratings of perceived exertion (RPE); blood samples were also taken prior (PRERUN) to the SUBRUN test and following the SUBRUN, 3MRUN, AND MAXRUN tests in order to assess glucose, pyruvate, lactate, phosphorus, 2,3-DPG, hemoglobin, and uric acid. Analyses of the data revealed no significant effect of oral IN supplementation either upon 3MTIME (IN = 18.31 +/- 1.21; PL = 18.33 +/- 1.15 min) or [latin capital V with dot above]o2 peak (IN = 58.6 +/- 5.1; PL = 60.7 +/- 4.5 ml O2.kg-1.min-1) or upon other dependent variables. MAXTIME was significantly longer during the PL trial (P < 0.05), suggestive of a possible impairment effect of oral IN supplementation. Based upon our data, we conclude that IN is not an effective ergogenic aid to enhance athletic performance of an aerobic nature. (C)1990The American College of Sports Medicine
Med. Sci. Sports Exerc., Vol. 30, No. 11, pp. 1584-1591, 1998. Magnesium (Mg) is important for regulating ion transport and cellular metabolism in all body tissues. In skeletal muscle Mg is involved in the neuromuscular activity, excitation, and muscle contraction. Mg deficiency can cause muscle weakness and muscle cramps. Less than 1% of total body Mg is found in serum, yet the serum Mg concentration is used to assess the body's Mg status.
Purpose: The purpose of this study was to determine whether an oral Mg supplementation (500 mg Mg-oxide·d-1 for 3 wk) affects exercise performance, clinical symptoms, and the Mg concentration in various body compartments in athletes with low-normal serum Mg levels (N = 10 in each group).
Methods: In a double-blind, placebo-controlled study, correlation analysis between the Mg concentration in serum, blood cells, and skeletal muscle was performed to establish a measure for muscle cell Mg.
Results: The data indicate that a 3-wk Mg supplementation did not affect exercise performance, neuromuscular activity, or muscle related symptoms. Also, the supplementation did not increase the Mg concentration in serum or any cellular compartment studied. However, in the placebo group the renal Mg clearance decreased, whereas it increased in the subjects receiving Mg supplementation. Correlation analysis revealed that serum Mg only correlated with red cell Mg and that only leukocyte Mg correlated with the nuclear magnetic resonance (NMR)-measured muscle cell Mg concentration.
Conclusions: These results indicate that Mg supplementation in athletes with low-normal serum Mg did not improve performance and failed to increase the body's Mg stores. Serum Mg appears to be a poor indicator for Mg in skeletal muscle or most other cellular compartments, but the concentration of Mg in mononuclear leukocytes might be used as an indicator of skeletal muscle Mg when NMR is not available.
Concomitant losses of skeletal muscle and bone mass along with gradual accretion of adipose tissue typify usual human aging. Recent investigations have attempted to modify these processes with various combinations of dietary and exercise intervention in older adults. Complete nutritional supplements given with weight-lifting exercise have been shown to augment muscle and fat gains in healthy older men, but have merely suppressed habitual dietary intake when administered to frail sedentary elders, and have not altered body composition responses to strength training in this population. Protein supplementation at twice the RDA does not improve skeletal muscle function or increase muscle mass in healthy elderly weight lifters compared to those on a normal diet. Calcium supplementation during one year of aerobic training has an independent beneficial effect on cortical bone density at the femoral neck in postmenopausal women, whereas the exercise is associated with trabecular bone increases in the lumbar vertebrae. Hypocaloric dieting, with or without aerobic exercise, results in losses of weight, fat and lean mass in obese elderly men and women. By contrast, resistance training during hypocaloric dieting augments lean mass while further reducing fat mass. Low protein, isoenergetic diets result in muscle atrophy in older women. Current studies will determine the ability of resistance training to offset these catabolic effects on skeletal muscles of a low-protein (0.6 g/kg/day) diet prescribed for elderly with chronic renal failure. More long-term studies of efficacy and feasibility of diet and exercise combinations are needed in the aged to optimize the potential for healthful shifts in body composition.
Chromium is an essential nutrient involved in the regulation of carbohydrate and lipid metabolism. Normal dietary intake of chromium in humans and farm animals is often suboptimal. In addition to its effects on glucose, insulin, and lipid metabolism, chromium has been reported to increase lean body mass and decrease percentage body fat, which may lead to weight loss in humans. The effects of chromium on body composition are controversial but are supported by animal studies, which increase their validity. A subject's response to chromium depends on his or her chromium status, diet consumed, type and amount of supplemental chromium, and study duration. There have been no confirmed negative effects of chromium in nutritional studies. Chromium is only a small part of the puzzle in the control of weight loss and body composition, and its effects, if present, will be small compared with those of exercise and a well-balanced diet.
As the biologically active component of glucose tolerance factor (GTF), the essential trace mineral chromium is now being marked to athletes. GTF potentiates insulin activity and is responsible for normal insulin function. Thus, insulin's effects on carbohydrate, fat, and protein metabolism are dependent upon the maintenance of adequate chromium stores. Due to excessive chromium loss and marginal chromium intake, athletes may have an increased requirement for chromium. Therefore, in some circumstances the dietary supplementation of a chromium compound may be efficacious. The restoration and maintenance of chromium stores via supplementation would promote optimal insulin efficiency, necessary for high-level athletic performance. However, potential anabolic effects of enhanced insulin function would likely be marginal, and reports of short-term anabolic increases from the supplementation of an organic chromium compound need to be confirmed.
Three patients with AMP deaminase deficiency (AMPD deficiency) performed exercise on a bicycle ergometer with increasing work load without and with administration of ribose (3 g p.o. every 10 min, beginning 1 h before exercise until the end). The patients performed exercise until heart rate was 200 minus age. Maximum capacity was not increased by administration of ribose, but postexertional muscle stiffness and cramps disappeared almost completely in 2 of 3 AMPD-deficient patients. Plasma concentrations of lactate and inosine were increased in AMPD-deficient patients after oral administration of ribose. Our data suggest that ribose may both serve as an energy source and enhance the de novo synthesis of purine nucleotides.
The use of gamma-oryzanol and phytosterols is gaining popularity among various athletic populations. These compounds are being consumed in the belief that they elicit anabolic effects ranging from increased testosterone production and release to stimulating human growth hormone release. However, published scientific studies suggest that these compounds are poorly absorbed. Furthermore, animal studies indicate that when these compounds are injected subcutaneously or intravenously, they induce antianabolic or catabolic activity. Normally, less than 5% of orally consumed phytosterols are absorbed from the intestinal tract, with the majority being excreted in the feces. Intravenous or subcutaneous injections of gamma-oryzanol in rats have been shown to suppress luteinizing hormone release, reduce growth hormone synthesis and release, and increase release of the catecholamines, dopamine and norepinephrine, in the brain. Although it hasn't been directly measured, this metabolic milieu, if accurate, may actually reduce testosterone production.
Nine healthy men and a patient with myoadenylate deaminase deficiency were exercised on a bicycle ergometer (30 minutes, 125 Watts) with and without oral ribose administration at a dose of 2 g every 5 minutes of exercise. Plasma or serum levels of glucose, free fatty acids, lactate, ammonia and hypoxanthine and the urinary hypoxanthine excretion were determined. After 30 minutes of exercise without ribose intake the healthy subjects showed significant increases in plasma lactate (p less than 0.05), ammonia (p less than 0.01) and hypoxanthine (p less than 0.05) concentrations and a decrease in serum glucose concentration (p less than 0.05). When ribose was administered, the plasma lactate concentration increased significantly higher (p less than 0.05) and the increase in plasma hypoxanthine concentration was no longer significant. The patient showed the same pattern of changes in serum or plasma concentrations with exercise with the exception of hypoxanthine in plasma which increased higher when ribose was administered.
To determine if early (4-h) thallium-201 imaging with ribose infusion would enhance detection of thallium redistribution better than late (24-h) imaging without ribose infusion, 15 patients with coronary artery disease underwent thallium stress tests by both methods within 2 weeks. All 15 patients had quantitative coronary angiography. After immediate postexercise planar imaging during the first of two exercise tests, patients were randomized to receive either intravenous ribose (3.3 mg/kg per min) or a control infusion of saline solution for 30 min. Images performed at 4 h for the ribose study were compared with those at 24 h for the saline control study. During the second test, exercise was carried to the same rate-pressure product and each patient received the opposite infusion. Four-hour postexercise images after ribose infusion identified 21 reversible defects not seen in the 24-h saline study. Three reversible defects were seen only in saline studies, but not with ribose at 4 h (p less than 0.01); 15 reversible defects were seen with both tests. When analyzed with respect to the 31 vascular territories supplied by a coronary artery with a greater than 50% stenosis, 8 territories had reversible defects present in the ribose but not the saline study and the saline study did not demonstrate reversible defects in territories that were seen in the ribose study (p less than 0.01). In 14 of these territories, reversible defects were seen with both tests. In 6 of 15 patients, additional vascular territories with reversible defects were identified after ribose infusion. It is concluded that ribose enhances the detection of thallium redistribution at 4 h compared with 24-h control images in patients with coronary artery disease and, therefore, substantially improves the identification of viable ischemic myocardium.
The effects of dietary supplementation of dihydroxyacetone and pyruvate (DHAP) on metabolic responses and endurance capacity during leg exercise were determined in eight untrained males (20-30 yr). During the 7 days before exercise, a high-carbohydrate diet was consumed (70% carbohydrate, 18% protein, 12% fat; 35 kcal/kg body weight). One hundred grams of either Polycose (placebo) or dihydroxyacetone and pyruvate (treatment, 3:1) were substituted for a portion of carbohydrate. Dietary conditions were randomized, and subjects consumed each diet separated by 7-14 days. After each diet, cycle ergometer exercise (70% of peak oxygen consumption) was performed to exhaustion. Biopsy of the vastus lateralis muscle was obtained before and after exercise. Blood samples were drawn through radial artery and femoral vein catheters at rest, after 30 min of exercise, and at exercise termination. Leg endurance was 66 +/- 4 and 79 +/- 2 min after placebo and DHAP, respectively (P less than 0.01). Muscle glycogen at rest and exhaustion did not differ between diets. Whole leg arteriovenous glucose difference was greater (P less than 0.05) for DHAP than for placebo at rest (0.36 +/- 0.05 vs. 0.19 +/- 0.07 mM) and after 30 min of exercise (1.06 +/- 0.14 vs. 0.65 +/- 0.10 mM) but did not differ at exhaustion. Plasma free fatty acids, glycerol, and beta-hydroxybutyrate were similar during rest and exercise for both diets. Estimated total glucose oxidation during exercise was 165 +/- 17 and 203 +/- 15 g after placebo and DHAP, respectively (P less than 0.05). It is concluded that feeding of DHAP for 7 days in conjunction with a high carbohydrate diet enhances leg exercise endurance capacity by increasing glucose extraction by muscle.
The purpose of this study was to investigate the ergogenic effect of oral inosine (IN) supplementation (6,000 mg.d-1 for 2 d) upon 3-mile run time (3MTIME) and VO2 peak. Nine highly trained endurance runners participated in a double-blind, placebo (PL), crossover study. Each subject undertook an IN or PL trial, consisting of three exercise tests: a submaximal warm-up run (SUBRUN), a competitive 3-mile treadmill run (3MRUN), and a maximal treadmill run (MAXRUN) to determine VO2 peak and time to exhaustion (MAXTIME). Additional measurements during the 3MRUN and MAXRUN included oxygen uptake (VO2), ventilation (VE), respiratory exchange ratio (R), and ratings of perceived exertion (RPE); blood samples were also taken prior (PRERUN) to the SUBRUN test and following the SUBRUN, 3MRUN, and MAXRUN tests in order to assess glucose, pyruvate, lactate, phosphorus, 2,3-DPG, hemoglobin, and uric acid. Analyses of the data revealed no significant effect of oral IN supplementation either upon 3MTIME (IN = 18.31 +/- 1.21; PL = 18.33 +/- 1.15 min) or VO2 peak (IN = 58.6 +/- 5.1; PL = 60.7 +/- 4.5 ml O2.kg-1.min-1) or upon other dependent variables. MAXTIME was significantly longer during the PL trial (P less than 0.05), suggestive of a possible impairment effect of oral IN supplementation. Based upon our data, we conclude that IN is not an effective ergogenic aid to enhance athletic performance of an aerobic nature.
Exogenous fructose 1,6-diphosphate (FDP), a glycolytic intermediate, has recently been demonstrated to accelerate ATP production, prevent glycogen breakdown, stimulate glycogen synthesis, and synthesize free fatty acids in animals and humans. To assess the effects of FDP on the hormonal and metabolic response to exercise, ten trained males (34 +/- 7 yr) underwent 1 h of continuous exercise at 70% VO2max followed by 20 W.min-1 increments to exhaustion. Two hundred fifty mg.kg-1 body weight FDP or placebo was infused in randomized, double-blind, crossover fashion. No differences were observed in heart rate, blood pressure, gas exchange data, perceived effort, or glucose, insulin, free fatty acid, lactate, beta-hydroxybutyrate, glycerol, and glucagon concentration at rest, during exercise, or upon exhaustion. In contrast to the previously reported bioenergetic effects of FDP under conditions in which glycolysis is impeded (acidosis, hypoxia, and ischemia), FDP did not affect the gas exchange, hormonal, or substrate response to moderately high intensity exercise in healthy normals.
Vitamins serve primarily as regulators of metabolic functions, many of which are critical to exercise performance. Depending upon the nature of their sport, e.g., strength, speed, power, endurance, or fine motor control, athletes may use megadoses of various vitamins in attempts to increase specific metabolic processes important to improved performance. Surveys have indicated that most elite athletes do take vitamin supplements, often in dosages greater than 50-100 times the United States Recommended Dietary Allowances. The theoretical basis underlying the use of each vitamin depends upon its specific metabolic function in relation to sport. Vitamin A functions to maintain night vision; thiamin, riboflavin, niacin, and pantothenic acid are all involved in muscle cell energy metabolism; niacin may also block free fatty acid release; pyridoxine is involved in the synthesis of hemoglobin and other oxygen transfer protein; folic acid and vitamin B12 are integrally involved in red blood cell (RBC) development; vitamins C and E are antioxidants, possibly preventing the destruction of the red blood cell membrane during exercise; vitamin D may be involved in muscle cell energetics through its influence on calcium. These are but a few of the possible metabolic functions of vitamins which have been suggested to have ergogenic applications to sport. Research has shown that a vitamin deficiency impairs physical performance. If this deficiency is corrected, performance usually improves. In general, vitamin supplementation to an athlete on a well-balanced diet has not been shown to improve performance. However, additional research with certain vitamins appears to be warranted, such as with the vitamin B complex and fine motor control, and with vitamin E and endurance at high altitudes. Moreover, research with megadose supplementation may also be necessary.
Recent major advances in pharmacological management have provided asthmatics with a satisfactory range of drugs to control asthma. These include sodium cromoglycate (cromolyn sodium), H1-antagonists, belladonna alkaloids, methyl xanthines, glucocorticoids and beta 2-adrenoceptor stimulants. Despite the tendency for most asthmatics to develop bronchoconstriction after exercise, sport and physical activity are now accepted as valuable in the overall management of patients with asthma. Thus, control of exercise-induced asthma (EIA) is essential, if asthmatics are to participate safely in physical activity and without respiratory disadvantage in competitive sport. Fortunately, inhibition or minimization of exercise-induced asthma may be achieved in most asthmatics by pre-exercise aerosol beta 2-agonists supplemented if necessary by sodium cromoglycate and/or theophylline. Regular medication as required to attain and maintain normal ventilatory function throughout each day is the objective in all patients with asthma and appears to be a prerequisiste to control exercise-induced asthma. The introduction of anti-doping controls into high performance sport has presented added difficulties for the asthmatic athlete. Although not always so, currently all of the classes of drugs previously noted are acceptable for the treatment of asthma and exercise-induced asthma. Anomalies may exist in the banning of 2 beta 2-adrenoceptor agonists, fenoterol and orciprenaline (metaproterenol). All sympathomimetic amines with alpha- or predominantly beta-stimulation are banned. The perpetuation of the need to report the use of beta 2-agonists prior to competition appears unnecessary. Although relatively little specific research has been undertaken, there is minimal evidence to suggest that asthmatics can derive any additional ergogenic advantage from medication to control asthma and exercise-induced asthma. beta 2-agonists, sodium cromoglycate and glucocorticoids administered by the aerosol route are not considered to be ergogenic. Some doubts have been raised concerning theophylline and its enhancement of both cardiac and respiratory muscle function. Investigations as to the validity of the suggestion that theophylline could augment physical performance appear warranted. It is reported that some athletes may be unnecessarily taking oral and perhaps parenteral glucocorticoids to obtain certain side effects. Any decision to ban these agents except for aerosol or local use could be supported.
The performance of strenuous physical exercise is associated with discomfort and pain, the tolerance forthat being modulated by the activity of the endogenous opioid systems. As 5-hydroxy-tryptamine (5-HT) affects nociception through its effects on the enkephalin-endorphin system, we have analyzed the effects of a moderate supplementation with L-tryptophan, the immediate precursor of 5-HT, on endurance and sensation of effort.
Twelve healthy sportsmen were subjected to a work load corresponding to 80% of their maximal oxygen uptake on two separate trials, after receiving a placebo and after receiving the same amount of L-tryptophan. The subjects ran on a treadmill until exhaustion. Total exercise time, perceived exertion rate, maximum heart rate, peak oxygen consumption, pulse recovery rate, and excess post-exercise oxygen consumption were determined during the two trials.
The total exercise time was 49.4% greater after receiving L-tryptophan than after receiving the placebo. A lower rate of perceived exertion was exhibited by the group while on tryptophan although the differences from the control group were not statistically significant. No differences were observed in the other parameters between the two trials.
The longer exercise time als well at the total work load performed could be due to an increased pain tolerance as a result of L-tryptophan ingestion.
Vitamin E is an important intramembrane antioxidant and membrane stabiliser. Over the past 40 years, vitamin E supplementation has been advocated for athletes in the hope of improving performance, minimising exercise-induced muscle damage and maximising recovery. However, there is currently a lack of conclusive evidence that exercise performance or recovery would benefit in any significant way from dietary vitamin E supplementation. Exceeding current recommended intakes of vitamin E even by several orders of magnitude will result in relatively modest increases in tissue or serum vitamin E concentrations. Most evidence suggests that there is no discernible effect of vitamin E supplementation on performance, training effect or rate of postexercise recovery in either recreational or elite athletes. There is very little evidence, particularly involving humans, that exercise or training will significantly alter tissue or serum vitamin E levels. While there is some evidence that certain indices of tissue peroxidation may be reduced following dietary vitamin E supplementation, the physiological and performance consequences in humans of these relatively minor effects are unknown. Although there appears to be little reason for vitamin E supplementation among athletes, it does not appear that the practice of supplementation is harmful.
Three nutritional products that have very different mechanisms of action are antioxidant vitamins, carnitine, and choline. Antioxidant vitamins do not appear to have a direct effect on physical performance in well-fed people but have been touted for their ability to detoxify potentially damaging free radicals produced during exercise. Carnitine purportedly enhances lipid oxidation, increases VO2max, and decreases plasma lactate accumulation during exercise. However, studies of carnitine do not generally support its use for ergogenic purposes. Choline supplements have been advocated as a means of preventing the decline in acetylcholine production purported to occur during exercise; this decline may reduce the transmission of contraction-generating impulses across the skeletal muscle, an effect that could impair one's ability to perform muscular work. However, there are no definitive studies in humans that justify choline supplementation. Much of the scientific data regarding the aforementioned nutrients are equivocal and contradictory. Their potential efficacy for improving physical performance remains largely theoretical.
Since the 1930s, scientists have attempted to determine if increasing the body's ability to buffer metabolic acids will enhance physical performance. The buffer of major interest has been bicarbonate; to a lesser degree, citrate and phosphate salts have been investigated. In theory, the buffers facilitate performance by decreasing the accumulation of hydrogen ions that would otherwise presumably inhibit glycolysis and interfere with energy production or impair cross-bridge formation between myofilaments and thereby reduce force production. Literature findings indicate variable results, but overall it appears that bicarbonate salts taken at dosages of 0.3 g.kg-1 may improve performance during repeated sprints or at the end of a progressively more intense exercise test. Athletes are advised of potential ill effects of bicarbonate ingestion, such as gastrointestinal distress. Prior to applying the agents in a competitive setting, athletes should test the effects of buffers on performance during training sessions and consider the sport governing body's stand on buffer usage.
The purpose of this study was to assess how selected physiological and performance responses are affected when the normal increase in plasma free fatty acid concentration during exercise is blunted by ingesting nicotinic acid. On four occasions, 10 subjects cycled at 68 +/- 1% VO2peak for 120 min followed by a timed 3.5-mile performance task. Every 15 min during exercise, subjects ingested 3.5 ml.kg LBM-1 of one of four beverages: 1) water placebo (WP), 2) WP + 280 mg nicotinic acid.l-1 (WP + NA), 3) 6% carbohydrate-electrolyte beverage (CE), and 4) CE + NA. Ingestion of nicotinic acid (WP + NA and CE + NA) blunted the rise in FFA associated with WP and CE; in fact, NA ingestion effectively prevented FFA from rising above rest values. The low FFA levels with NA feeding were associated with a 3- to 6-fold increase in concentrations of human growth hormone throughout exercise. The mean performance time for CE (10.7 min) was significantly less than for WP (12.2 min) and WP + NA (12.8 min), but did not differ from CE + NA (11.4 min). The results indicate that blunting the normal rise in FFA alters the hormonal response to exercise and reduces the capacity to perform high-intensity exercise.
The present study examined the effect of diet supplementation of oxaloacetate precursors (aspartate and asparagine) and carnitine on muscle metabolism and exercise endurance. The results suggest that the diet supplementation increased the capacity of the muscle to utilize FFA and spare glycogen. Time to exhaustion was about 40% longer in the experimental group compared to the control, which received commercial diet only. These findings suggest that oxaloacetate may be important to determine the time to exhaustion during a prolonged and moderate exercise.
Changes in blood glutathione antioxidant system in response to exercise and training, and aerobic performance, were investigated. Selenium (Se) supplementation effects on these changes were evaluated. The study was double blind. Both groups selenium (Sel, N = 12) and placebo (Pla, N = 12), followed a 10-wk endurance training program, with a prolonged exhaustive exercise bout performed (Cap Max), before (Pre) and after (Post) training. Blood was sampled before (Bef) and after (Aft) Cap Max. The oxidation of blood glutathione after Cap Max exercise showed a reactive oxygen species production. Training developed maximal aerobic power and capacity, significantly increased (P < 0.001) plasma and erythrocyte glutathione peroxidase (GPx) activity, and decreased (P < 0.001) erythrocyte glutathione reductase activity. The Se supplementation caused an increase in the basal plasma GPx level (P < 0.05). There was also a correlation (r = 0.66, P < 0.05) between the variation in VO2max and that of erythrocyte GPx only in supplemented subjects. Our results confirm that blood glutathione remains a sensitive marker of oxidative stress induced by exhausting submaximal exercise and that the antioxidant potential of GPx can be developed by endurance training. Se supplementation at the dose used had no effect on physical performance.
Ginseng has been used for several thousand years in the Orient as a tonic, prophylactic agent and 'restorative'. However, its efficacy has been established primarily through clinical experience as opposed to scientific verification of its pharmacological effects. Ginseng has been used by athletes as an ergogenic aid for many years, but there is an absence of compelling research evidence in support of its use for this purpose. Indeed, most of the support favouring the use of ginseng to enhance physical performance is of a testimonial nature. While studies with animals show that ginseng or its active components may prolong survival to physical or chemical stress, there is, generally, a lack of controlled research demonstrating the ability of ginseng to improve or prolong performance in fatigued humans.
Electrolytes are essential to normal skeletal muscle contraction and are thought to play a role in muscle fatigue. Excess accumulation of ammonia and hydrogen ions after strenuous bouts of physical activity are thought to slow muscle contractions and decrease muscle tension development. Certain disease states cause abnormal levels of such electrolytes as calcium, magnesium, potassium, or sodium. Excessively high or low levels of these ions in the serum are associated with symptoms such as muscle weakness or cramping. Nurses should know the effects of abnormal electrolyte levels on muscle function in the assessment and treatment of their patients.
Recently, a proliferation of athletic supplements has been marketed touting boron as an ergogenic aid capable of increasing testosterone. The effect of boron supplementation was investigated in male bodybuilders. Ten male bodybuilders (aged 20 to 26) were given a 2.5-mg boron supplement, while nine male bodybuilders (aged 21 to 27) were given a placebo for 7 weeks. Plasma total and free testosterone, plasma boron, lean body mass, and strength measurements were determined on day 1 and day 49 of the study. A microwave digestion procedure followed by inductively coupled argon plasma spectroscopy was used for boron determination. Twelve subjects had boron values at or above the detection limit with median value of 25 ng/ml (16 ng/ml lower quartile and 33 ng/ml upper quartile). Of the ten subjects receiving boron supplements, six had an increase in their plasma boron. Analysis of variance indicated no significant effect of boron supplementation on any of the other dependent variables. Both groups demonstrated significant increases in total testosterone (p < 0.01), lean body mass (p < 0.01), and one repetition maximum (RM) squat (p < 0.001) and one RM bench press (p < 0.01). The findings suggest that 7 weeks of bodybuilding can increase total testosterone, lean body mass, and strength in lesser-trained bodybuilders, but boron supplementation affects these variables not at all.
Yohimbine is an alkaloid derived mainly from the bark of the African tree, Pausinystalia yohimbe. Although many pharmacological properties of yohimbine have been described, at the plasma concentration attained at recommended dosages in man the predominant activity is antagonism of alpha 2-adrenoceptors. For more than 70 years yohimbine has been used as a treatment for male and female sexual difficulties. It has enjoyed a reputation as an aphrodisiac although no effect on sexual drive in humans has been adequately demonstrated. Yohimbine has been evaluated in the management of erectile disorder by means of placebo-controlled but often poorly designed trials. It does appear to have a modest therapeutic benefit over placebo, particularly in essentially psychogenic erectile disorder, and is generally well tolerated. Yohimbine is not licensed in the UK.
We conducted a survey of 624 commercially available supplements targeted towards bodybuilding athletes. Over 800 performance claims were made for these supplements. Supplements include amino acids, boron, carnitine, choline, chromium, dibencozide, ferulic acid, gamma oryzanol, medium chain triglycerides, weight gain powders, Smilax compounds and yohimbine. Many performance claims advertised were not supported by published research studies. In some instances, we found no research to validate the claims; in other cases, research findings were extrapolated to inappropriate applications. For example, biological functions of some non-essential compounds were interpreted as performance claims for the supplements. Claims for others were based on their ability to enhance hormonal release or activity. We suggest that more research be conducted on this group of athletes and their nutritional needs. Furthermore, the effectiveness and safety of supplements merit further investigation.
By means of a 5-week vitamin B-complex supplementation, associations between indices of vitamin B1, B2, and B6 status (activation coefficients [AC] for erythrocyte transketolase, glutathione reductase, and aspartate aminotransferase) and exercise-induced blood lactate concentration were studied. Subjects, 42 physically active college students (18-32 yrs), were randomized into vitamin (n = 22) and placebo (n = 20) groups. Before the supplementation there were no differences in ACs or basal enzyme activities between the groups. The ACs were relatively high, suggesting marginal vitamin status. In the vitamin group, all three ACs were lower (p < 0.0001) after supplementation: transketolase decreased from 1.16 (1.14-1.18) (mean and 95% confidence interval) to 1.08 (1.06-1.10); glutathione reductase decreased from 1.33 (1.28-1.39) to 1.14 (1.11-1.17); and aspartate aminotransferase decreased from 2.04 (1.94-2.14) to 1.73 (1.67-1.80). No changes were found after placebo. Despite improved indices of vitamin status, supplementation did not affect exercise-induced blood lactate concentration. Hence no association was found between ACs and blood lactate. It seems that marginally high ACs do not necessarily predict altered lactate metabolism.
The effect of boron supplementation was investigated in 19 male bodybuilders ages 20-27 years. Ten were given a 2.5-mg boron supplement while 9 were given a placebo every day for 7 weeks. Plasma total and free testosterone, plasma boron, lean body mass, and strength measurements were determined on Days 1 and 49 of the study. Plasma boron values were significantly (p < 0.05) different as the experimental group increased from (+/- SD) 20.1 +/- 7.7 ppb pretest to 32.6 +/- 27.6 ppb posttest, while the control group mean decreased from 15.1 +/- 14.4 ppb pretest to 6.3 +/- 5.5 ppb posttest. Analysis of variance indicated no significant effect of boron supplementation on any of the dependent variables. Both groups demonstrated significant increases in total testosterone, lean body mass, 1-RM squat, and 1-RM bench press. The findings suggest that 7 weeks of bodybuilding can increase total testosterone, lean body mass, and strength in lesser trained bodybuilders, and that boron supplementation had no effect on these measures.
It has been suggested that ubiquinone improves exercise performance and antioxidant capacity. We studied the effects of ubiquinone supplementation (120 mg.day-1 for 6 weeks) on aerobic capacity and lipid peroxidation during exercise in 11 young (aged 22-38 years) and 8 older (aged 60-74 years), trained men. The cross-over study was double-blind and placebo-controlled. Serum ubiquinone concentration increased after supplementation (P < 0.0001 for treatment) in both age groups. The maximal oxygen uptake (VO2max) was measured using a direct incremental ergometer test. In the young subjects, the VO2max after placebo and ubiquinone treatment was 58.5 (95% confidence interval: 53.0-64.0) and 59.0 ml.min-1.kg-1 (52.2-66.8), respectively. The corresponding results in the older subjects were: 37.2 (31.7-42.7) and 33.7 ml.min-1.kg-1 (26.2-41.7) (P < 0.0001 for age group, P > 0.05 for treatment). In a prolonged test (60-min submaximal, then incremental load until exhaustion) time to exhaustion was longer after the placebo [young men: 85.7 (82.4-89.0), older men: 82.9 min (75.8-89.9)] than after ubiquinone [young men: 82.1 (78.5-85.8), older men: 77.2 min (70.1-83.7); P = 0.0003 for treatment]. Neither ubiquinone supplementation nor exercise affected serum malondialdehyde concentration. Oral ubiquinone was ineffective as an ergogenic aid in both the young and older, trained men.
Carnitine plays a central role in fatty acid (FA) metabolism. It transports long-chain fatty acids into mitochondria for β-oxidation. Carnitine also modulates the metabolism of coenzyme-A (CoA). Several rationales have been forwarded in support of the potential ergogenic effects of oral carnitine supplementation. However the following arguments derived from established scientific observations may be forwarded: (i) carnitine supplementation neither enhances FA oxidation in vivo nor spares glycogen or postpones fatigue during exercise. Carnitine supplementation does not unequivocally improve performance of athletes; (ii) carnitine supplementation does not reduce body fat or help to lose weight; (iii) in vivo pyruvate dehydrogenase complex (PDC) is fully active already after a few seconds of intense exercise. Carnitine supplementation induces no further activation of PDC in vivo; (iv) despite an increased acetyl-CoA/free CoA ratio, PDC is not depressed during exercise in vivo and therefore supplementary carnitine has no effect on lactate accumulation; (v) carnitine supplementation per se does not affect the maximal oxygen uptake (V̇O2max); (vi) during exercise there is a redistribution of free carnitine and acylcarnitines in the muscle but there is no loss of total carnitine. Athletes are not at risk for carnitine deficiency and do not have an increased need for carnitine. Although there are some theoretical points favouring potential ergogenic effects of carnitine supplementation, there is currently no scientific basis for healthy individuals or athletes to use carnitine supplementation to improve exercise performance.
Three new steroidal saponins were isolated from the rhizomes of Smilax officinalis. The structures of these saponins were established by extensive spectral data, hydrolysis and chemical correlation as sarsasapogenin 3-O-beta-D-glucopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->6 )-beta- D-glucopyranoside, neotigogenin 3-O-beta-D-glucopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->6 )]-beta- D-glucopyranoside and 25S-spirostan-6 beta-ol 3-O-beta-D-glucopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->6 )]-beta- D-glucopyranoside. Acid hydrolysis of the latter compound gave a sapogenin which has a new orientation of an hydroxyl on the steroidal skeleton. A route is proposed for the biogenesis of the latter sapogenin which is an uncommon steroidal aglycone.
To investigate the efficacy of the 3-carbon compounds pyruvate and dihydroxyacetone (PD) in inhibiting reaccumulation of body weight and fat with refeeding after weight loss.
Longitudinal, in Clinical Research Center. After weight loss induced by hypoenergetic diet (1.3 MJ/d) for 3 weeks, refeeding with hyperenergetic diet (1.5 x resting energy expenditure) for 3 weeks. Refeeding diet randomized to contain PD or placebo (PL, polyglucose) as approximately 20% of energy intake.
17 obese healthy women (n = 8 in PL group, n = 9 in PD group) (age: 22-60 y, weight: 72.5-139.7 kg).
Resting energy expenditure (REE), body composition (by bioelectrical impedance), nitrogen balance, serum proteins, biochemical profile, thyroid hormones, and insulin, before and after refeeding and weight and fat gain.
Refeeding with a hyperenergetic diet, weight gain was significantly less in patients receiving PD compared to placebo (1.8 + 0.2 kg vs 2.9 +/- 0.1 kg, P < 0.01). Body fat regain was also less with feeding of PD (0.8 +/- 0.2 kg vs 1.8 +/- 0.2 kg, P < 0.01). Body protein metabolism, as measured by nitrogen balance, serum protein concentrations and fat free mass, was similar in subjects consuming either PD or PL.
We conclude that 3-carbon compounds decrease weight gain and reaccumulation of body fat, without decreasing body protein gain, in obese subjects with hyperenergetic refeeding subsequent to weight loss.