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Optimized body composition provides a competitive advantage in a variety of sports. Weight reduction is common among athletes aiming to improve their strength-to-mass ratio, locomotive efficiency, or aesthetic appearance. Energy restriction is accompanied by changes in circulating hormones, mitochondrial efficiency, and energy expenditure that serve to minimize the energy deficit, attenuate weight loss, and promote weight regain. The current article reviews the metabolic adaptations observed with weight reduction and provides recommendations for successful weight reduction and long term reduced-weight maintenance in athletes.

Background Leucine (Leu) regulates muscle protein synthesis (MPS) producing dose-dependent plasma Leu and MPS responses from free amino acid solutions. This study examined the role of Leu content from dietary proteins in regulation of MPS after complete meals. Methods Experiment 1 examined 4 protein sources (wheat, soy, egg, and whey) with different Leu concentrations (6.8, 8.0, 8.8, and 10.9% (w/w), respectively) on the potential to increase plasma Leu, activate translation factors, and stimulate MPS. Male rats (~250 g) were trained for 14 day to eat 3 meals/day consisting of 16/54/30% of energy from protein, carbohydrates and fats. Rats were killed on d14 either before or 90 min after consuming a 4 g breakfast meal. Experiment 2 compared feeding wheat, whey, and wheat + Leu to determine if supplementing the Leu content of the wheat meal would yield similar anabolic responses as whey. Results In Experiment 1, only whey and egg groups increased post-prandial plasma Leu and stimulated MPS above food-deprived controls. Likewise, greater phosphorylation of p70 S6 kinase 1 (S6K1) and 4E binding protein-1 (4E-BP1) occurred in whey and egg groups versus wheat and soy groups. Experiment 2 demonstrated that supplementing wheat with Leu to equalize the Leu content of the meal also equalized the rates of MPS. Conclusion These findings demonstrate that Leu content is a critical factor for evaluating the quantity and quality of proteins necessary at a meal for stimulation of MPS.

Athletes utilise numerous strategies to reduce body weight or body fat prior to competition. The traditional approach requires continuous energy restriction (CER) for the entire weight loss phase (typically days to weeks). However, there is some suggestion that intermittent energy restriction (IER), which involves alternating periods of energy restriction with periods of greater energy intake (referred to as ‘refeeds’ or ‘diet breaks’) may result in superior weight loss outcomes than CER. This may be due to refeed periods causing transitory restoration of energy balance. Some studies indicate that intermittent periods of energy balance during energy restriction attenuate some of the adaptive responses that resist the continuation of weight and fat loss. While IER—like CER—is known to effectively reduce body fat in non-athletes, evidence for effectiveness of IER in athletic populations is lacking. This review provides theoretical considerations for successful body composition adjustment using IER, with discussion of how the limited existing evidence can be cautiously applied in athlete practice.

The purpose of the present study was to determine the effects of short-term supplementation with the free acid form of β-hydroxy-β-methylbutyrate (HMB-FA) on indices of muscle damage, protein breakdown, recovery and hormone status following a high-volume resistance training session in trained athletes. A total of twenty resistance-trained males were recruited to participate in a high-volume resistance training session centred on full squats, bench presses and dead lifts. Subjects were randomly assigned to receive either 3 g/d of HMB-FA or a placebo. Immediately before the exercise session and 48 h post-exercise, serum creatine kinase (CK), urinary 3-methylhistadine (3-MH), testosterone, cortisol and perceived recovery status (PRS) scale measurements were taken. The results showed that CK increased to a greater extent in the placebo (329 %) than in the HMB-FA group (104 %) ( P = 0·004, d = 1·6). There was also a significant change for PRS, which decreased to a greater extent in the placebo (9·1 ( sem 0·4) to 4·6 ( sem 0·5)) than in the HMB-FA group (9·1 ( sem 0·3) to 6·3 ( sem 0·3)) ( P = 0·005, d = − 0·48). Muscle protein breakdown, measured by 3-MH analysis, numerically decreased with HMB-FA supplementation and approached significance ( P = 0·08, d = 0·12). There were no acute changes in plasma total or free testosterone, cortisol or C-reactive protein. In conclusion, these results suggest that an HMB-FA supplement given to trained athletes before exercise can blunt increases in muscle damage and prevent declines in perceived readiness to train following a high-volume, muscle-damaging resistance-training session.

INTENTIONALLY REACHING FAILURE DURING RESISTANCE EXERCISE SETS IS A COMMON PRACTICE THAT MIGHT BE MOST BENEFICIAL FOR STIMULATING HYPERTROPHY. HOWEVER, FAILURE TRAINING PERFORMED TOO FREQUENTLY CAN RESULT IN REDUCTIONS IN THE RESTING CONCENTRATION OF TESTOSTERONE AND CONTRIBUTE TO THE OVERTRAINING SYNDROME. THE RESEARCH SUGGESTS THE GREATEST EFFECTIVENESS WHEN FAILURE TRAINING IS PRACTICED CONSISTENTLY OVER 6-WEEK CYCLES, INTERSPERSED WITH EXCLUSIVE NONFAILURE TRAINING CYCLES OVER EQUAL PERIODS. COACHES SHOULD CONSIDER ATHLETES' TRAINING STATUS AND GOALS AND THE POINT IN A YEARLY TRAINING CYCLE TO DETERMINE WHETHER SETS ARE TO BE PERFORMED TO FAILURE OR ENDED SHORT OF REACHING FAILURE. [PUBLICATION ABSTRACT]

This study investigated the effects of a sport nutrition education intervention (SNEI) on dietary intake, knowledge, body composition, and performance in NCAA Division I baseball players. Resistance trained NCAA Division I baseball players (82.4 ± 8.2 kg; 1.83 ± 0.06 m; 13.7 ± 5 % body fat) participated in the study during 12 weeks of off-season training. Fifteen players volunteered for SNEI while 15 players matched for position served as controls (C) for body composition and performance. The nutrition intervention group (NI) received a 90 min SNEI encompassing energy intake (Kcal), carbohydrate (CHO), protein (PRO), fat, food sources, and hydration. Sport nutrition knowledge questionnaires were administered to NI pre and post. Nutritional status was determined by three-day dietary logs administered to NI pre and post. Body composition and performance (5-10-5 shuttle test, vertical jump, broad jump, 1 RM squat) were measured pre and post for C and NI. Knowledge increased in NI. Pro and fat, but not CHO intake increased in NI. FM decreased pre to post in NI (11.5 ± 4.8 vs. 10.5 ± 5.4 kg) but not C (11.3 ± 4.7 vs. 11.9 ± 4.5 kg). FFM increased pre to post with no differences between groups. The 5-10-5 shuttle times decreased significantly more in NI (4.58 ± 0.15 vs. 4.43 ± 0.13 sec) compared to C (4.56 ± 0.18 vs. 4.50 ± 0.16 sec). Jump and squat performance increased pre to post with no differences between groups. Our findings indicate that an off season SNEI is effective at improving sport nutrition knowledge and some, but not all, nutrient intakes and performance measures in Division I baseball players. (Autor).

Doc number: P23

The purpose of the present study was to determine the effects of short-term supplementation with the free acid form of [beta]-hydroxy-[beta]-methylbutyrate (HMB-FA) on indices of muscle damage, protein breakdown, recovery and hormone status following a high-volume resistance training session in trained athletes. A total of twenty resistance-trained males were recruited to participate in a high-volume resistance training session centred on full squats, bench presses and dead lifts. Subjects were randomly assigned to receive either 3 g/d of HMB-FA or a placebo. Immediately before the exercise session and 48 h post-exercise, serum creatine kinase (CK), urinary 3-methylhistadine (3-MH), testosterone, cortisol and perceived recovery status (PRS) scale measurements were taken. The results showed that CK increased to a greater extent in the placebo (329 %) than in the HMB-FA group (104 %) (P= 0·004, d= 1·6). There was also a significant change for PRS, which decreased to a greater extent in the placebo (9·1 (sem 0·4) to 4·6 (sem 0·5)) than in the HMB-FA group (9·1 (sem 0·3) to 6·3 (sem 0·3)) (P= 0·005, d= - 0·48). Muscle protein breakdown, measured by 3-MH analysis, numerically decreased with HMB-FA supplementation and approached significance (P= 0·08, d= 0·12). There were no acute changes in plasma total or free testosterone, cortisol or C-reactive protein. In conclusion, these results suggest that an HMB-FA supplement given to trained athletes before exercise can blunt increases in muscle damage and prevent declines in perceived readiness to train following a high-volume, muscle-damaging resistance-training session. [PUBLICATION ABSTRACT]

The goal of this research was to elucidate the physiological role that leu plays in complete meals and to determine if the meal distribution of protein or leu is important for optimization of muscle mass. My hypothesis was that optimum MPS would equate to maximum signaling response of the kinase known as mammalian target of rapamycin (mTOR) and directly related to post-prandial plasma leu concentration. Ultimately, the leu content of individual meals and the number of meal per day with sufficient leu to increase MPS will influence muscle mass, lean body mass and long term body composition. In vivo work with purified solutions established that leu has a regulatory role for initiating MPS by activating mTOR and there is a clear threshold of leu required to increase plasma leu and stimulate MPS. In order to test the role of leu in complete meals we examined the duration and peak activation of MPS and mTOR signaling in response to complete test meals containing 10, 20, and 30% of total energy from wheat and whey protein (6.8 and 10.9% leu) respectively. We determined that whey increased plasma leu, mTOR signaling, and MPS more than wheat at all protein intakes. Stimulation of MPS after meals last for 3 hours with a peak at 90 minutes, however plasma leu and mTOR signaling remained at a plateau for 3 hours before decreasing. Meal leu content and the increases in post-prandial plasma leu were closely associated with peak activation of mTOR signaling and MPS but did not determine the duration of protein synthesis which demonstrated a refractory response to the constant elevations in plasma leu. Experiment 2 examined the potential to use leu to predict the quality of individual proteins to stimulate mTOR signaling and MPS. Adult rats were adapted for 2 weeks to a meal-feeding protocol with complete diets containing 16% protein but with different leu contents using wheat, soy, egg, or whey proteins (6.8, 8.0, 8.8, and 10.9% leu). Animals fed egg and whey significantly increased plasma leu and MPS whereas animals fed wheat and soy did not. The leu content of the meals predicted mTOR signaling and peak MPS responses and were closely related to changes in plasma leu. These findings support the hypothesis that there is a meal leu threshold for increasing plasma leu. While experiment 2 provided proof of concept that there is a meal threshold for leu stimulation of MPS, the critical outcomes are changes in muscle mass or body composition. This study tested the hypothesis that long-term meal-feeding of isonitrogenous/isocaloric diets with 16/54/30% of energy from protein/carbohydrates/lipids, respectively, using protein sources (wheat, soy, egg, whey) with different leu contents could produce body composition and muscle weight outcomes in relation to the changes in post-prandial MPS and plasma leu observed in the previous experiments. Based on the leu threshold observed in the previous experiment, the diets were designed such that animals fed egg and whey proteins would receive sufficient leu during each of the three meals to achieve three stimulations of MPS per day as opposed to animals fed wheat and soy proteins with lower leu contents that would achieve the leu threshold only at the larger dinner meal. After 11 weeks of meal-feeding, body composition, lean body mass, and gastrocnemius muscle weights were positively related to the leu content of the diet and reflected the ability of the respective diets to increase post-prandial plasma leu and MPS. Finally, we tested the hypothesis that long-term distribution of protein/leu could make a difference in body composition by feeding isocaloric/isonitrogenous meals containing whey protein evenly distributed to achieve the leu thresholds at each of 3 meals (ED-Whey) daily or unevenly distributed over 3 meals (UD-Whey) with only the dinner meal exceeding the leu threshold. The ED-Whey treatment with evenly distributed leu produced multiple stimulations of MPS throughout the day and larger gastrocnemius muscle weights compared to the UD-Whey that only achieved stimulation of MPS at a single meal. While muscle mass was larger in the ED-Whey treatment, total lean body mass was not different between groups. This may have been due to the large protein (i.e. nitrogen) content of the dinner meal in the UD-Whey group producing a shift in lean body mass deposition to the liver and visceral tissues, which were larger in the UD-Whey group. (Abstract shortened by UMI.)

References ... 33Tissue proteins are constantly being broken down and synthesized simultaneously. Taken together this process is called protein turnover. In muscle, the relative rates of protein synthesis and protein breakdown determine the relative anabolism or catabolism of the tissue. This is commonly referred to as protein balance. Protein balance is equal to the rate of protein synthesis minus the rate of protein breakdown. If the rate of protein synthesis exceeds the rate of protein degradation, the muscle is in a state of positive protein balance and is anabolic. If the rate of protein breakdown exceeds the rate of protein synthesis, then muscle is in a negative protein balance and is catabolic. If the rate of protein synthesis equals the rate of protein breakdown, then the net result is protein balance in which no net growth has occurred. It is important to note that both protein synthesis and protein breakdown are always occurring simultaneously, and it is the relative rates of each that determine the net anabolic or catabolic state of the muscle. In order to maximize muscle mass, athletes will want to increase protein synthesis, limit protein breakdown, or preferably do both. This chapter will describe how protein turnover is regulated and how nutrition, hormones, and exercise affect this metabolic process.