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Position statement The International Society of Sports Nutrition (ISSN) provides an objective and critical review related to the intake of protein for healthy, exercising individuals. Based on the current available literature, the position of the Society is as follows: An acute exercise stimulus, particularly resistance exercise, and protein ingestion both stimulate muscle protein synthesis (MPS) and are synergistic when protein consumption occurs before or after resistance exercise. For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, an overall daily protein intake in the range of 1.4–2.0 g protein/kg body weight/day (g/kg/d) is sufficient for most exercising individuals, a value that falls in line within the Acceptable Macronutrient Distribution Range published by the Institute of Medicine for protein. There is novel evidence that suggests higher protein intakes (>3.0 g/kg/d) may have positive effects on body composition in resistance-trained individuals (i.e., promote loss of fat mass). Recommendations regarding the optimal protein intake per serving for athletes to maximize MPS are mixed and are dependent upon age and recent resistance exercise stimuli. General recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g. Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs). These protein doses should ideally be evenly distributed, every 3–4 h, across the day. The optimal time period during which to ingest protein is likely a matter of individual tolerance, since benefits are derived from pre- or post-workout ingestion; however, the anabolic effect of exercise is long-lasting (at least 24 h), but likely diminishes with increasing time post-exercise. While it is possible for physically active individuals to obtain their daily protein requirements through the consumption of whole foods, supplementation is a practical way of ensuring intake of adequate protein quality and quantity, while minimizing caloric intake, particularly for athletes who typically complete high volumes of training. Rapidly digested proteins that contain high proportions of essential amino acids (EAAs) and adequate leucine, are most effective in stimulating MPS. Different types and quality of protein can affect amino acid bioavailability following protein supplementation. Athletes should consider focusing on whole food sources of protein that contain all of the EAAs (i.e., it is the EAAs that are required to stimulate MPS). Endurance athletes should focus on achieving adequate carbohydrate intake to promote optimal performance; the addition of protein may help to offset muscle damage and promote recovery. Pre-sleep casein protein intake (30–40 g) provides increases in overnight MPS and metabolic rate without influencing lipolysis.

Sarcopenia, or the age‐related loss of skeletal muscle mass and function, is an increasingly prevalent condition that contributes to reduced quality of life, morbidity, and mortality in older adults. Older adults display blunted anabolic responses to otherwise anabolic stimuli—a phenomenon that has been termed anabolic resistance (AR)—which is likely a casual factor in sarcopenia development. AR is multifaceted, but historically much of the mechanistic focus has been on signalling impairments, and less focus has been placed on the role of the vasculature in postprandial protein kinetics. The vascular endothelium plays an indispensable role in regulating vascular tone and blood flow, and age‐related impairments in vascular health may impede nutrient‐stimulated vasodilation and subsequently the ability to deliver nutrients (e.g. amino acids) to skeletal muscle. Although the majority of data has been obtained studying younger adults, the relatively limited data on the effect of blood flow on protein kinetics in older adults suggest that vasodilatory function, especially of the microvasculature, strongly influences the muscle protein synthetic response to amino acid feedings. In this narrative review, we examine evidence of AR in older adults following amino acid and mixed meal consumption, examine the evidence linking vascular dysfunction and insulin resistance to age‐related AR, review the influence of nitric oxide and endothelin‐1 on age‐related vascular dysfunction as it relates to AR, briefly review the potential causal role of arterial stiffness in promoting skeletal muscle microvascular dysfunction and AR, and provide a brief overview and future considerations for research examining age‐related AR.

Protein supplementation often refers to increasing the intake of this particular macronutrient through dietary supplements in the form of powders, ready-to-drink shakes, and bars. The primary purpose of protein supplementation is to augment dietary protein intake, aiding individuals in meeting their protein requirements, especially when it may be challenging to do so through regular food (i.e. chicken, beef, fish, pork, etc.) sources alone. A large body of evidence shows that protein has an important role in exercising and sedentary individuals. A PubMed search of \"protein and exercise performance\" reveals thousands of publications. Despite the considerable volume of evidence, it is somewhat surprising that several persistent questions and misconceptions about protein exist. The following are addressed: 1) Is protein harmful to your kidneys? 2) Does consuming \"excess\" protein increase fat mass? 3) Can dietary protein have a harmful effect on bone health? 4) Can vegans and vegetarians consume enough protein to support training adaptations? 5) Is cheese or peanut butter a good protein source? 6) Does consuming meat (i.e., animal protein) cause unfavorable health outcomes? 7) Do you need protein if you are not physically active? 8) Do you to consume protein ≤ 1 hour following resistance training sessions to create an anabolic environment in skeletal muscle? 9) Do endurance athletes need additional protein? 10) Does one need protein supplements to meet the daily requirements of exercise-trained individuals? 11) Is there a limit to how much protein one can consume in a single meal? To address these questions, we have conducted a thorough scientific assessment of the literature concerning protein supplementation.

Military personnel may be exposed to circumstances (e.g., large energy deficits, sleep deprivation, cognitive demands, and environmental extremes) of external stressors during training and combat operations (i.e., operational stressors) that combine to degrade muscle protein. The loss of muscle protein is further exacerbated by frequent periods of severe energy deficit. Exposure to these factors results in a hypogonadal state that may contribute to observed decrements in muscle mass. In this review, lessons learned from studying severe clinical stressed states and the interventions designed to mitigate the loss of muscle protein are discussed in the context of military operational stress. For example, restoration of the anabolic hormonal status (e.g., testosterone, insulin, and growth hormone) in stressed physiological states may be necessary to restore the anabolic influence derived from dietary protein on muscle. Based on our clinical experiences, restoration of the normal testosterone status during sustained periods of operational stress may be advantageous. We demonstrated that in severe burn patients, pharmacologic normalization of the anabolic hormonal status restores the anabolic stimulatory effect of nutrition on muscle by improving the protein synthetic efficiency and limiting amino acid loss from skeletal muscle. Furthermore, an optimal protein intake, and in particular essential amino acid delivery, may be an integral ingredient in a restored anabolic response during the stress state. Interventions which improve the muscle net protein balance may positively impact soldier performance in trying conditions.

Background We have determined the acute response of protein kinetics to one or two servings (6.3 g and 12.6 g) of a proprietary composition containing free-form essential amino acids (EAA) (3.2 g EAA per serving) and whey protein (2.4 g per serving), as well as the response to consumption of a popular whey-based protein supplement (Gatorade Recover) (17 g; 12.6 g protein). Methods Whole-body rates of protein synthesis, breakdown and net balance (taken to be the anabolic response) were determined using primed-constant infusions of 2 H 5 -phenylalnine and 2 H 2 -tyrosine. Muscle protein fractional synthetic rate (FSR) was also determined with the 2 H 5 -phenylalanine tracer. Results Plasma EAA levels increased following consumption of all beverages, with the greatest response in the high-dose EAA/protein composition. Similarly, the increase in net balance between whole-body protein synthesis and breakdown was greatest following consumption of the high-dose EAA/protein composition, while the low-dose EAA/protein composition and Gatorade Recover induced similar increases in net balance. When the net balance response was normalized for the total amount of product given, the high- and low-dose EAA/protein beverages were approximately 6- and 3-fold more anabolic than the Gatorade Recover, respectively. The greater anabolic response to the EAA/protein composition was due to greater increases in whole-body protein synthesis with both doses, and a markedly greater suppression of whole-body protein breakdown in the high-dose group. Muscle protein FSR after beverage consumption reflected changes in whole-body protein synthesis, with the larger EAA/protein dose significantly increasing FSR. Conclusion We conclude that a composition of a balanced EAA formulation combined with whey protein is highly anabolic as compared to a whey protein-based recovery product, and that the response is dose-dependent. Trial registration ClinicalTrials.gov Identifier: NCT03502941 . This trial was registered on April 19, 2018.

This position stand aims to provide an evidence-based summary of the energy and nutritional demands of tactical athletes to promote optimal health and performance while keeping in mind the unique challenges faced due to work schedules, job demands, and austere environments. After a critical analysis of the literature, the following nutritional guidelines represent the position of the International Society of Sports Nutrition (ISSN). Nutritional considerations should include the provision and timing of adequate calories, macronutrients, and fluid to meet daily needs as well as strategic nutritional supplementation to improve physical, cognitive, and occupational performance outcomes; reduce risk of injury, obesity, and cardiometabolic disease; reduce the potential for a fatal mistake; and promote occupational readiness. Energy demands should be met by utilizing the Military Dietary Reference Intakes (MDRIs) established and codified in Army Regulation 40-25. Although research is somewhat limited, military personnel may also benefit from caffeine, creatine monohydrate, essential amino acids, protein, omega-3-fatty acids, beta-alanine, and L-tyrosine supplementation, especially during high-stress conditions. Specific energy needs are unknown and may vary depending on occupation-specific tasks. It is likely the general caloric intake and macronutrient guidelines for recreational athletes or the Acceptable Macronutrient Distribution Ranges for the general healthy adult population may benefit first responders. Strategies such as implementing wellness policies, setting up supportive food environments, encouraging healthier food systems, and using community resources to offer evidence-based nutrition classes are inexpensive and potentially meaningful ways to improve physical activity and diet habits. The following provides a more detailed overview of the literature and recommendations for these populations.

The effect of nandrolone decanoate on fatigue was examined during a volume‐overload training stress in 3‐month‐old male C57Bl/6J mice (n = 24). Mice were randomized into two exercising groups and a control group (C). The exercising animals performed a 3‐day per week resistance training program for 3 weeks. Exercising animals were further randomized into an androgen group (RTA) or a sham group (RTS). To exert a volume‐overload, the frequency of training was increased to six consecutive days during week 4. RTA received a supraphysiological dose of nandrolone decanoate (38‐mg·kg−1) before and after the volume‐overload week. RTS and C received sham injections. Four mice in RTS were determined to be fatigued, while no mice in RTA were fatigued. TNF‐α expression in the plantaris was significantly lower for RTA compared to RTS. Significant elevations in oxidative stress were noted in RTS compared to C in the plantaris, but no differences were noted between RTA and C, suggesting a lower oxidative stress response from nandrolone decanoate administration. Glucocorticoid expression was significantly lower in the soleus of RTA compared to RTS, suggesting a lower catabolic response to the volume‐overload stress. In conclusion, nandrolone decanoate intervention attenuated fatigue in animals during a volume‐overload stress. Nandrolone decanoate administrations reduces fatgiue during a volume‐overload stress in mice.

We previously demonstrated that improved net muscle protein balance, via enhanced protein synthetic efficiency, occurs 5 days after testosterone (T) administration. Whether the effects of T on muscle protein kinetics occur immediately upon exposure is not known. We investigated the effects of acute T exposure on leg muscle protein kinetics and selected amino acid (AA) transport using the arteriovenous balance model, and direct calculations of mixed-muscle protein fractional synthesis (FSR) and breakdown (FBR) rates. Four healthy men were studied over a 5 h period with and without T (infusion rate, 0.25 mg·min − 1 ). Muscle protein FSR, FBR, and net protein balance (direct measures and model derived) were not affected by T, despite a significant increases in arterial ( p  = 0.009) and venous ( p  = 0.064) free T area under the curve during T infusion. T infusion had minimal effects on AA transport kinetics, affecting only the outward transport and total intracellular rate of appearance of leucine. These data indicate that exposing skeletal muscle to T does not confer immediate effects on AA kinetics or muscle anabolism. There remains an uncertainty as to the earliest discernable effects of T on skeletal muscle protein kinetics after initial administration.

Nutritional status is a strong predictor of postoperative outcomes and is recognized as an important component of surgical recovery programs. Adequate nutritional consumption is essential for addressing the surgical stress response and mitigating the loss of muscle mass, strength, and functionality. Especially in older patients, inadequate protein can lead to significant muscle atrophy, leading to a loss of independence and increased mortality risk. Current nutritional recommendations for surgery primarily focus on screening and prevention of malnutrition, pre-surgical fasting protocols, and combating post-surgical insulin resistance, while recommendations regarding macronutrient composition and timing around surgery are less established. The goal of this review is to highlight oral nutrition strategies that can be implemented leading up to and following major surgery to minimize atrophy and the resultant loss of functionality. The role of carbohydrate and especially protein/essential amino acids in combating the surgical stress cascade and supporting recovery are discussed. Practical considerations for nutrient timing to maximize oral nutritional intake, especially during the immediate pre- and post- surgical periods, are also be discussed.

Age-related anabolic resistance can lead to reduced muscle mass but can be costly and timely to diagnose. Multi-frequency bioelectrical impedance analysis could potentially be used as a non-invasive tool for the assessment of anabolic resistance as changes in frequency-dependent impedance values may reflect fluid shifts occurring with nutrient uptake. This exploratory pilot study evaluated the effects of acute essential amino acid (EAA) intake on raw bioimpedance and fluid shifts in healthy young adults (YA, n=5) and older adults (OA, n=7). Participants completed a five-hour protocol with multifrequency bioelectrical impedance analysis (MF-BIA) at baseline and every 30 minutes post-consumption of a 10 g EAA beverage. Whole-body and segmental values for impedance (Z), resistance (R), reactance (Xc), phase angle (PhA), and body water compartments were assessed. YA demonstrated significantly higher Z, R, Xc, and PhA values compared to OA (p<0.05), particularly in the leg segments and at 50 kHz. Time effects revealed declines in R (p=0.013) and Xc (p=0.002) following EAA ingestion, consistent with postprandial fluid shifts. Fluid analysis showed significant group differences only for ECW/ICW ratio (p=0.001-0.004) with OA > YA and increases in TBW, ICW, and ECW over time. Raw bioimpedance values distinguished between age groups and reflected acute responses to nutrient intake. These findings suggest MF-BIA may be sensitive to short-term physiological changes and, with further validation, could support assessments of muscle quality and nutritional responsiveness.