Protein requirements and supplementation in strength sports.

Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
Nutrition (Impact Factor: 3.05). 07/2004; 20(7-8):689-95. DOI: 10.1016/j.nut.2004.04.009
Source: PubMed

ABSTRACT Daily requirements for protein are set by the amount of amino acids that is irreversibly lost in a given day. Different agencies have set requirement levels for daily protein intakes for the general population; however, the question of whether strength-trained athletes require more protein than the general population is one that is difficult to answer. At a cellular level, an increased requirement for protein in strength-trained athletes might arise due to the extra protein required to support muscle protein accretion through elevated protein synthesis. Alternatively, an increased requirement for protein may come about in this group of athletes due to increased catabolic loss of amino acids associated with strength-training activities. A review of studies that have examined the protein requirements of strength-trained athletes, using nitrogen balance methodology, has shown a modest increase in requirements in this group. At the same time, several studies have shown that strength training, consistent with the anabolic stimulus for protein synthesis it provides, actually increases the efficiency of use of protein, which reduces dietary protein requirements. Various studies have shown that strength-trained athletes habitually consume protein intakes higher than required. A positive energy balance is required for anabolism, so a requirement for "extra" protein over and above normal values also appears not to be a critical issue for competitive athletes because most would have to be in positive energy balance to compete effectively. At present there is no evidence to suggest that supplements are required for optimal muscle growth or strength gain. Strength-trained athletes should consume protein consistent with general population guidelines, or 12% to 15% of energy from protein.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Interactions between dietary protein and energy balance on the regulation of human skeletal muscle protein turnover are not well described. A dietary protein intake above the recommended dietary allowance during energy balance typically enhances nitrogen retention and up-regulates muscle protein synthesis, which in turn may promote positive protein balance and skeletal muscle accretion. Recent studies show that during energy deficit, muscle protein synthesis is down-regulated with concomitant increases in ubiquitin proteasome-mediated muscle proteolysis and nitrogen excretion, reflecting the loss of skeletal muscle mass. However, consuming high-protein diets (1.6-2.4 g/kg per day), or high-quality, protein-based meals (15-30 g whey) during energy deficit attenuates intracellular proteolysis, restores muscle protein synthesis, and mitigates skeletal muscle loss. These findings are particularly important for physically active, normal-weight individuals because attenuating the extent to which skeletal muscle mass is lost during energy deficit could prevent decrements in performance, reduce injury risk, and facilitate recovery. This article reviews the relationship between energy status, protein intake, and muscle protein turnover, and explores future research directives designed to protect skeletal muscle mass in physically active, normal-weight adults.-Pasiakos, S. M., Margolis, L. M., and Orr, J. S. Optimized dietary strategies to protect skeletal muscle mass during periods of unavoidable energy deficit. © FASEB.
    The FASEB Journal 12/2014; DOI:10.1096/fj.14-266890 · 5.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Thermodynamics dictates that for body weight (i.e. stored substrate) loss to occur a person must ingest less energy than they expend. Athletes, who owing to their oftentimes large daily energy expenditures, may have greater flexibility than non-athletes in this regard; however, they may also have different goals for weight loss. In particular, weight lost may be less important to an athlete than from which compartment the weight is lost: fat or lean. A critical question is thus, what balance of macronutrients might promote a greater fat loss, a relative retention of lean mass, and still allow athletic performance to remain uncompromised? It is the central thesis of this review that dietary protein should be a nutrient around which changes in macronutrient composition should be framed. The requirement for protein to sustain lean mass increases while in negative energy balance and protein, as macronutrient, may have advantages with respect to satiety during energy balance, and it may allow greater fat loss during a negative energy balance. However, athletes should be mindful of the fact that increasing dietary protein intake while in negative energy balance would come at the 'expense' of another macronutrient. Most recently there has been interest in lower carbohydrate diets, which may not allow performance to be sustained given the importance of dietary carbohydrate in high-intensity exercise. The relative merits of higher protein diets for athletes are discussed.
    Sports Medicine 11/2014; 44 Suppl 2:149-53. DOI:10.1007/s40279-014-0254-y · 5.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Canadian men flock to gyms to enlarge, reshape, and sculpt their bodies. Fitness centers, health-food stores, muscle magazines, and Internet sites profit by aggres-sively selling "sports supplements" to a wide range of exercising men. Once associated with only the hardcore factions of male bodybuilders (Klein, 1995), designer protein powders, creatine products, energy bars, ephedrine, amino acids, diuretics, and growth hormones such as androstenedione are generically marketed to men as health and lifestyle-improving aids. This paper explores how a select group of Canadian men connect the consumption of sports supplements to the pursuit of "established" masculinity. I collected ethnographic data from 57 recre-ational athletes in Canada and interpreted the data through the lens of figurational sociology. Analytic attention is thus given to how contemporary discourses and practices of supplementation are underscored by middle-class understandings of masculine bodies in a time of perceived "gender crisis" in Canada. Les hommes canadiens se ruent vers les gymnases pour développer et sculpter leurs corps. Les centres de conditionnement physique, les magasins d'aliments-santé, les revues de musculation et les sites Internet en profitent en leur vendant agressivement des « suppléments sportifs ». Autrefois associés aux factions dures du culturisme masculin (Klein, 1995), les poudres protéinées, les produits de la créatine, les barres énergétiques, l'éphédrine, les acides aminés, les diurétiques et les hormones de croissance sont maintenant vendus aux hommes en tant que produits améliorant la santé et le style de vie. Cet article explore comment un groupe sélect d'hommes lient la consommation de suppléments sportifs à la quête d'une masculinité « établie ». J'ai colligé des données ethnographiques auprès de 57 athlètes de niveau récréatif au Canada et les ai interprétées à la lumière de la sociologie figurative. Analytiquement, je me suis intéressé à la façon dont les discours contemporains et l'utilisation des suppléments sont associés à une compréhension petite bourgeoise des corps masculins au moment d'une « crise des genres » au Canada.

Full-text (2 Sources)

Available from
Jun 2, 2014