Kevin D. Tipton

Increased Protein Intake Reduces Lean Body Mass Loss during Weight Loss in Athletes

PURPOSEnTo examine the influence of dietary protein on lean body mass loss and performance during short-term hypoenergetic weight loss in athletes.nnnMETHODSnIn a parallel design, 20 young healthy resistance-trained athletes were examined for energy expenditure for 1 wk and fed a mixed diet (15% protein, 100% energy) in the second week followed by a hypoenergetic diet (60% of the habitual energy intake), containing either 15% (approximately 1.0 g x kg(-1)) protein (control group, n = 10; CP) or 35% (approximately 2.3 g x kg(-1)) protein (high-protein group, n = 10; HP) for 2 wk. Subjects continued their habitual training throughout the study. Total, lean body, and fat mass, performance (squat jump, maximal isometric leg extension, one-repetition maximum (1RM) bench press, muscle endurance bench press, and 30-s Wingate test) and fasting blood samples (glucose, nonesterified fatty acids (NEFA), glycerol, urea, cortisol, free testosterone, free Insulin-like growth factor-1 (IGF-1), and growth hormone), and psychologic measures were examined at the end of each of the 4 wk.nnnRESULTSnTotal (-3.0 +/- 0.4 and -1.5 +/- 0.3 kg for the CP and HP, respectively, P = 0.036) and lean body mass loss (-1.6 +/- 0.3 and -0.3 +/- 0.3 kg, P = 0.006) were significantly larger in the CP compared with those in the HP. Fat loss, performance, and most blood parameters were not influenced by the diet. Urea was higher in HP, and NEFA and urea showed a group x time interaction. Fatigue ratings and worse than normal scores on the Daily Analysis of Life Demands for Athletes were higher in HP.nnnCONCLUSIONSnThese results indicate that approximately 2.3 g x kg(-1) or approximately 35% protein was significantly superior to approximately 1.0 g x kg(-1) or approximately 15% energy protein for maintenance of lean body mass in young healthy athletes during short-term hypoenergetic weight loss.

Improving muscle mass: response of muscle metabolism to exercise, nutrition and anabolic agents

Muscle mass is critical for athletic performance and, perhaps more importantly for most, health and survival. The metabolic basis for a change in muscle mass is an increase in net muscle protein balance (termed NBAL). NBAL is the difference between MPS (muscle protein synthesis) and MPB (muscle protein breakdown). Thus an increase in MPS and/or a decrease in MPB are necessary for NBAL to increase, leading to accretion of muscle proteins. In particular, accretion of myofibrillar proteins is necessary. NBAL responds to exercise, feeding and other factors. In healthy, weight-stable adults, muscle mass remains constant because periods of positive balance following feeding are countered by periods of negative balance during fasting. A combination of resistance exercise and nutrition is a potent anabolic stimulus through stimulation of MPS from amino acids and attenuation of MPB by carbohydrates. Increased muscle mass results from the accumulation of small amounts of protein in response to each bout of exercise combined with nutrient intake. The magnitude of the response may be influenced by factors other than just the amount of a nutrient ingested. Timing of ingestion, co-ingestion of nutrients and the type of protein may all influence protein accretion. Testosterone is a potent anabolic stimulus primarily through improvement in re-utilization of amino acids from MPB. There is a general lack of efficacy in studies assessing the potential for growth hormone, androstenedione and dehydroepiandrostenedione to increase muscle mass. Creatine supplementation is clearly an effective means to increase muscle mass, especially in combination with resistance exercise, however the mechanisms remain unclear. Results from acute metabolic studies provide useful information for estimation of the efficacy of anabolic agents.

Essential Amino Acids for Muscle Protein Accretion

THE STIMULATION OF MUSCLE PROTEIN SYNTHESIS IS RELIANT ON THE ADEQUATE AVAILABILITY OF AMINO ACID (AA) PRECURSORS. THE INCREASE IN CIRCULATING AA CONCENTRATIONS IN THE BLOOD SERVES AS A SIGNAL TO INITIATE SYNTHETIC PROCESSES. A SUFFICIENT INCREASE IN BLOOD AA IS REQUIRED TO OVERCOME A CONCENTRATION GRADIENT THAT NORMALLY FAVORS THE INTRACELLULAR SPACE. WE HAVE DEMONSTRATED THAT THE RATE OF MUSCLE PROTEIN SYNTHESIS IS DIRECTLY RELATED TO THE RATE OF APPEARANCE OF AA IN THE INTRACELLULAR SPACE. MUSCLE PROTEINS COMPRISE VARIOUS ESSENTIAL AND NONESSENTIAL AA; HOWEVER, ONLY INGESTION OF THE ESSENTIAL AMINO ACIDS (EAA) IS REQUIRED TO STIMULATE MUSCLE PROTEIN SYNTHESIS. WHILE EAA ALONE STIMULATE MUSCLE PROTEIN ANABOLISM, THE EFFECT IS MAGNIFIED WHEN COMBINED WITH EXERCISE. FURTHERMORE, THE TIMING OF INGESTION IN RELATION TO EXERCISE IS IMPORTANT IN ACHIEVING A MAXIMAL ANABOLIC RESPONSE. THE BENEFITS OF FREE-FORM EAA AND INTACT PROTEIN ON EXERCISE-INDUCED MUSCLE ANABOLISM ARE DISCUSSED. FINALLY, THE EFFECTS OF AGING MUST BE CONSIDERED IN THE OPTIMAL EAA FORMULATION.

Legal nutritional boosting for cycling.

Several nutritional strategies have been used in cycling to improve performance. Carbohydrate feeding during exercise has been shown to be effective, but recent studies have suggested that recommendations may have to be adjusted to take into account recent findings. Protein co-ingested with carbohydrate during exercise has received a lot of recent interest, but the evidence is equivocal, at best. Thus, in the absence of a plausible mechanism, it is difficult to see how protein would increase endurance performance. There also has been a lot of interest in training with low glycogen to maximize training adaptations, but the longer-term effects upon performance are still unclear. Various supplements have been suggested to improve endurance performance, but most of these nutrition supplements lack the scientific support that would warrant the recommendation.

Measuring synthesis rates of different proteins - clues to training adaptations

Over the past 15–20 years several laboratories have been investigating the regulation of muscle protein synthesis by diet and exercise. It is clear that resistance exercise stimulates muscle protein synthesis. The greatest stimulation comes from resistance exercise plus a source of amino acids (for review see Tipton & Ferrando, 2008). Interestingly, similar increases in muscle protein synthesis are observed following endurance exercise (Tipton et al. 1996); protein ingestion also enhances this response (Howarth et al. 2009). Given the differences in adaptations to these types of exercise, this similarity of response of muscle protein synthesis may seem somewhat paradoxical. The explanation may lie in the methodology. n nThe response of mixed muscle protein synthesis was determined in these studies (Tipton & Ferrando, 2008). Measurement of mixed muscle protein synthesis is essentially a weighted average of the rates of synthesis of all proteins in the muscle, i.e. it does not distinguish the responses of different proteins. Intuitively, given the differences in adaptations to different types of training, it is not difficult to accept that resistance and endurance exercise, for example, should differentially influence different proteins. Recent advances in methodology have allowed us to begin to address these questions. n nThe acute response to exercise and nutritional interventions may be measured and extrapolated to represent the potential for long-term adaptive changes. Adaptations to any exercise training regime result from changes in the type, quantity and activity of proteins in various tissues. For example, muscle growth in response to resistance exercise training is determined by increases in the myofibrillar proteins. Muscle protein synthesis rate has been shown to be predictive of long-term changes in muscle (Tipton, 2008). For example, a recent metabolic study demonstrated that milk ingestion resulted in greater muscle protein synthesis than soy following resistance exercise (Wilkinson et al. 2007). A follow-up longitudinal study by the same research group demonstrated that milk supplementation resulted in greater increases in muscle mass and strength than soy supplements (Hartman et al. 2007). Thus, it is clear that the acute metabolic response to various exercise and nutritional combinations is a useful way to determine optimal training and diet regimes. n nThe results of a study published in this issue of The Journal of Physiology by Moore et al. (2009) offer interesting and important advances toward our understanding of the influence of nutrition and exercise on different types of proteins. This study helps pave the way for future studies that will further our understanding of training adaptations. Moore et al. (2009) used a unilateral exercise model to simultaneously measure protein synthesis rates in response to whey protein ingestion at rest and following resistance exercise. Moreover, the time course of the response to each was determined. The results demonstrate a differential response of the two protein types to feeding. The rate of sarcoplasmic protein synthesis was increased following protein ingestion to the same extent in both the resting and the exercised leg. On the other hand, myofibrillar protein synthesis was increased to a greater extent and the response lasted longer in the exercised leg. These novel findings illustrate that the response of proteins to exercise and nutrition is not uniform. Moreover, and perhaps more importantly, these results underline the value of measuring the response of various protein fractions to nutritional and exercise interventions. n nThe present study examined the response only to resistance exercise (Moore et al. 2009). However, another recent study by this research group provides additional information on differential responsiveness of various protein fractions. Wilkinson et al. (2008) report that myofibrillar protein synthesis and mitochondrial protein synthesis rates both increased in response to resistance exercise. Only mitochondrial protein synthesis increased in response to endurance exercise. Furthermore, exercise training changed these responses (Wilkinson et al. 2008). These data were gathered with a background of hyperaminoacidaemia for all conditions, so the interactive effect of exercise type and nutrition on the different types of protein could not be determined. n nClearly, these types of studies provide us with the ability to investigate the potential for exercise and nutrition to influence training results. Further investigation of the impact of different types of exercise on the synthesis of different protein fractions and the interaction with nutritional interventions must follow. Furthermore, studies should delineate responses in various populations. These studies will provide important information for athletes practicing various types of sports. More importantly, these types of studies will offer information critical to designing optimal nutrition and exercise interventions to diminish muscle wasting and metabolic disease.

Sport and exercise nutrition: from theory to practice

Sport and exercise nutrition has developed as a separate field of research and there have been significant advances in this field in the last 20 40 years. Sport and exercise nutrition is likely to get even more attention in the future considering that a large percentage of modern health issues are related to lack of physical activity or poor nutrition. Nutrition influences nearly every process in the body involved in energy production and recovery from exercise. Our knowledge has increased significantly in the last few years, mainly as a result of laboratorybased studies, most of which had a rather fundamental approach. Often, research that is lab-based is difficult to translate directly into practical recommendations both for elite endurance athletes aiming to improve performance and for the average person on the street who aims to increase his or her physical activity level and improve nutritional intake. Large gaps exist between the science and practice. In July 2007 a conference was organized at the University of Birmingham in the UK to bridge the gap between science and practice. A limited number of participants was invited to join the discussions and help to make the translation. Although some areas have advanced considerably (for example hydration, the role of carbohydrates etc.), other areas are virtually untouched. For example, in this issue Dr Shona Halson discusses the importance of sleep and ways to improve sleep quantity and quality. It is generally recognized by scientists, athletes and coaches that sleep is important for recovery. Yet, there is very little research on the effects of exercise on sleep and how to improve sleep quality by nutritional or other means. This is a fascinating area of research with direct applications that will certainly develop in the next few years. Another example is the interaction between exercise and nutrition on adaptations to training. This is discussed in detail in this issue by Drs Kevin Tipton and Keith Baar. It has been known for some time that regular physical activity will result in adaptations that ultimately result in improved function. Exercise training makes use of this principle by planning and systematically applying exercises with the goal to optimize these adaptations and ultimately performance. There is a multitude of adaptations at all levels including increased capillarization, fastto-slow muscle fibre type conversion, increased mitochondrial mass, muscle hypertrophy etc. The complex process of exercise-induced adaptation in skeletal muscle starts with specific molecular events that trigger an increase in protein synthesis. More specifically, signalling mechanisms triggered by the exercise stress initiate replication of DNA genetic sequences that enable subsequent translation of the genetic code into a series of amino acids to synthesize new proteins. It is the synthesis of these specific proteins that will ultimately result in the adaptations. It appears that the adaptations to training are highly specific to the type of training, suggesting that there may be different signalling events involved. The signalling events, the resulting increases in messenger DNA, as well as the synthesis of proteins is dependent on the intensity and duration of exercise, the type of exercise but also the intake of specific nutrients. Drs Kevin Tipton and Keith Baar discuss the molecular signalling events that underlie the training adaptations to resistance exercise and endurance exercise respectively and discuss the effects that certain nutritional interventions can have on these events as well as on the outcome. Again, this is an area that will receive a lot of attention in the future and that can have a very significant impact on athletes’ performances. Whether the aim is winning medals at the Olympic Games in Beijing 2008 or London 2012, or whether the aim is to set a personal best in a local race, the translation from scientific theory into practical recommendations is crucial.