Version classiqueVersion mobile

Nutrition and Performance in Sport

 | 
Christophe Hausswirth

Chapter 5. Nutrition and physical composition

Topic 3. Protein requirements and recommendations for athletes: arguments for practical recommendations

Lindsay S Macnaughton et Kevin D Tipton

Résumé

Protein plays an integral role in the growth and repair of tissues, making it an important part of the human diet. Protein requirements are designed to prevent deficiencies; however, athletes look to use protein as a tool for increasing adaptations to training. Therefore, we suggest that protein recommendations are more useful than proteins requirements for athletes and coaches. Challenges exist in making protein recommendations for large groups of athletes due to differences in athlete type, sport, position, goals and training. Ideally, protein recommendations should be made on an individual basis. A number of general strategies can be employed to maximize the impact of protein on training adaptations. These considerations include the amount of protein to consume, timing of protein ingestion (both throughout the day and in relation to exercise), the type of protein consumed and the impact of co-ingestion of other nutrients.

Texte intégral

1. Introduction

1Protein is a critical component of the diet of athletes and exercisers. Humans require protein in their diet for the growth and repair of tissues and cells within the body and to supply amino acids for production of nitrogen-containing compounds, e.g. DNA, neurotransmitters, etc. A sufficient intake of protein is necessary to supply amino acids to support exercise-stimulated muscle growth and to repair damage to cells and tissues from exercise. Thus, athletes and coaches are particularly interested in protein guidelines, arguably perhaps even more than the general population.

2In this chapter, we aim to address the issue of protein intake for athletes from a practical standpoint. Many comprehensive reviews covering the background information of the studies that exist on this issue are available (Rennie & Tipton, 2000; Phillips, 2004; Tarnopolsky, 2004; Tipton & Witard, 2007; Phillips & van Loon, 2011; Phillips, 2014), so detailed information on protein intake for athletes will be presented only briefly here. Instead, we present the argument that protein requirements for athletes hold little practical application and that protein recommendations are far more practically relevant and valuable. We attempt to demonstrate that producing protein intake guidelines for athletes has to be considered on an individual basis for a number of reasons. Finally, we provide some general protein intake guidelines that aim to serve as a starting point for more individualized and periodized recommendations that maximize muscle protein synthesis (MPS) to support and supplement adaptations to training.

2. Requirements or recommendations

3Our first consideration is to differentiate between requirements and recommendations for protein intake. Athletes and coaches almost certainly will define the word requirement differently than scientists. A physiological requirement for a nutrient, including protein, is the amount necessary in the diet to sustain health. That amount may be very different from the amount necessary to optimize performance. Protein requirements are based on measurement of nitrogen (N) balance defined as the minimum amount of protein that must be consumed to ensure N equilibrium in the body. N loss occurs through various processes, including breakdown of body proteins and amino acid oxidation, leading to the production and excretion of urea. A minimum amount of protein must be consumed to maintain N balance, leading to the generation of protein requirements. In contrast, the basis for protein recommendations for athletes is determined by the amount of protein necessary to optimize training adaptations and, ultimately, performance. These recommendations will come from studies aiming to measure physical adaptations in response to exercise and nutrition. Thus, recommendations often differ from requirements for most athletes and exercisers.

4Protein requirements, as defined by the dietary protein necessary to maintain N balance, for the general population differ from those given for athletes. The US RDA for protein intake is 0.8 g•kg body mass (BM)-1•d-1 of protein. A number of experts in the field of nutrition agree that athletes should consume more protein than non-exercisers to maintain N balance (Rennie & Tipton, 2000; Phillips, 2004; Tarnopolsky, 2004; Tipton & Witard, 2007; Phillips & van Loon, 2011; Phillips, 2014). Based on carefully performed, well-controlled N balance studies, the amount of protein necessary for endurance athletes to maintain N balance is ˜1.2 g•kg BM-1•d-1 (summarized in Tarnopolsky, 2004). The amount of protein necessary for resistance-trained athletes to meet N balance is higher, ˜1.6-1.7 g•kg BM-1•d-1 (Phillips, 2004). However, despite these well-documented requirement estimates, there exists disagreement within the scientific community about protein requirements for athletes.

5There is some controversy over the necessity for higher protein intakes by athletes. The argument for greater protein requirements for athletes stems from increased requirement for greater tissue growth and repair and increased oxidation of amino acids, both of which occur under conditions of frequent exercise training (Phillips et al. 1993; McKenzie et al. 2000; Hartman et al. 2006). Contrary to this argument, increased utilization of amino acids from ingested protein occurs with regular exercise (Todd et al. 1984; Hartman et al. 2006; Moore et al. 2007), potentially reducing protein requirements. Part of the confusion likely stems from the reliance on N balance measurements to determine protein requirements for those involved in heavy exercise. There often is a troubling disconnect between N balance measurements and more direct, phenotypic measurements, such as changes in muscle mass and strength, particularly at higher levels of protein intake in athletes (Tipton & Witard, 2007). Critiques of N balance studies argue that this methodology both underestimates and overestimates protein requirements (Tarnopolsky, 2004; Phillips, 2006; Tipton & Witard, 2007). Thus, there is uncertainty regarding the necessity of higher protein intakes for those individuals participating in intense exercise training programmes.

6Despite the differing opinions regarding protein requirements for athletes, it is clear that the vast majority of athletes consume sufficient protein. Protein requirements exist to prevent deficiencies that potentially lead to health problems, but this delineation may be moot for most athletes. Protein deficiency rarely occurs in the Western diet as the general population, including athletes, far exceed the national protein requirements by consuming on average at least ˜1.2 g□kg BM-1•d-1 (Tarnopolsky, 2004; Phillips, 2006; Tipton & Witard, 2007). However, athletes aim to achieve more from their diet than simply to avoid deficiency. Thus, the diet of athletes should aim to maximize adaptations to training stimuli. For athletes, we contend that protein recommendations aimed at achieving optimal adaptations and performance are more useful than requirements, which do not necessarily reflect the goals of the athlete and which, moreover, many, if not most, athletes habitually exceed.

7If we consider protein intake for athletes in terms of recommendations, rather than strictly requirements, more information useful to athletes and coaches is likely to be ascertained. Recommendations for protein intake should cover, not just the total amount of protein athletes might consume, but other important considerations that will influence adaptations to training. Moreover, at this point, information on protein requirements for athletes is typically categorized for two broad characterizations: endurance and resistance, male athletes (Phillips, 2004; Tarnopolsky, 2004; Rodriguez et al. 2009). To our knowledge, no direct information on requirements is available for athletes involved in a mixture of training types or outside of those two categories, nor is there any information on protein requirements for female athletes (Rodriguez et al. 2009). As should now be clear, a blanket set of recommendations for all athletes could not be made with ease nor would it be of maximum benefit to all athletes for a number of reasons. Considering protein intake for athletes from the standpoint of recommendations based on all available data, rather than restricting recommendations on protein intake to requirements based on N balance for limited athletic populations, would allow athletes, coaches and practitioners much greater flexibility.

8The varied demands of training and competition for various types of athletes contribute to the inability to provide specific protein intake recommendations for all athletes. The type of athlete will determine to some extent the recommendations necessary. Endurance athletes, team sport athletes and strength or power athletes all have a different optimal body shape, rely on different energy systems and train in different ways making it hard to recommend a nutritional strategy to suit all athlete types. Even within a particular sport, demands placed on the body vary. For example, players of different positions within the same sport may differ in the amount of lean mass they wish to carry depending on the particular requirements of that position. Thus, athletes within the same sport will have different protein recommendations that apply depending on the goals and training demands of that particular athlete. Any nutrition plan must work to best allow the athlete to achieve their short-term and long-term goals. The time of season also impacts the protein recommendations given. At different points in the season athletes train less or more or have different outcomes to achieve. So, protein recommendations must support the phase of training or competition of the athlete (Mujika et al. 2014). Clearly, protein recommendations have to be made on an individual basis to be as effective as possible due to these and many other factors involving individual physical characteristics of athletes, their sports and training demands. However, a number of strategies can be utilized by all athletes, at least as a starting point, to maximize their training response and induce increased adaptations above that of training alone.

3. General protein recommendations

9Protein recommendations are typically made on the basis of the total amount of protein consumed in the diet. Those recommendations may be made on the basis of percentage of the diet, but more often are made on the basis of g protein•kg BM-1•d-1 (Phillips, 2004; Tarnopolsky, 2004; Rodriguez et al. 2009). However, determination of the recommended amount of protein is very difficult, even for any individual athlete taking into account all the above limitations. A recommendation for a particular amount of protein may be considered to be too restrictive. Over the last few years, it has become clear that there are a number of nutritional factors that influence the acute response of the body, in particular skeletal muscle, to the ingestion of protein. Thus, even if two individuals consumed an equivalent amount of dietary protein over a month, week or day the adaptive response engendered would not necessarily be the same. The basis for these adaptive responses is the maximal stimulation of MPS, the metabolic determinant for changes in muscle proteins in response to exercise and nutrition (Tipton & Phillips, 2013; Phillips, 2014). Exercise and amino acid ingestion increase overall MPS (Biolo et al. 1997). The particular proteins that are stimulated depend primarily on the type of exercise performed (Wilkinson et al. 2008; Moore et al. 2009). However, the magnitude and duration of the response is influenced by the amount, timing and quality of the protein ingested in association with an exercise bout (Tipton & Witard, 2007; Phillips & van Loon, 2011; Tipton & Phillips, 2013; Phillips, 2014). Thus, whereas the total amount of protein ingested in a day is an important consideration, these other nutritional factors will help determine the phenotypic adaptations and, ultimately, performance. Therefore, it is overly simplistic to make a recommendation based solely on the total amount of protein to ingest without consideration of other factors for each athlete.

10The amount of protein ingested in any single episode of feeding is one nutritional consideration that may impact the adaptive response to protein ingestion. The response of MPS to each individual episode of protein ingestion is determined by the amount of protein ingested at that time. Data from studies that provided protein following resistance exercise and at rest, including one from our laboratory, show that ˜20 to 25 g of high quality protein maximally stimulates MPS in young, men (Moore et al. 2008; Witard et al. 2014). However, in older adults the maximal response of MPS occurs with ingestion of up to 40 g of protein. Taken together, the results from the experimental studies by Moore et al. (2009) and Witard et al. (2014) have been analysed to estimate the amount of protein necessary to stimulate maximal MPS per kg of body mass (Moore et al. 2014). This analysis demonstrated that ingestion of ˜0.25 g•kg BM-1•d-1 for young males and ˜0.45 g•kg BM-1•d-1 for older males (>60 y) maximally stimulates MPS. Thus, even if an equivalent amount of protein is ingested on a daily basis, variation in the amount ingested at any given time may influence the overall adaptive response to protein ingestion. Recommendations for protein intake should take this factor into consideration.

11Another factor that may influence the adaptive response to protein ingestion is the timing of the ingestion relative to an exercise bout. As briefly mentioned above, investigators examining the effects of protein ingestion often provide protein following exercise. There exists a near obsession within certain exercise communities that protein must be ingested immediately after resistance exercise – in fact several books have been written on this topic (Ivy & Portman, 2009). The importance of this timing is reflected by the term often applied to this time period, i.e. “the anabolic window of opportunity”. What is clear is that exercise sensitizes the muscle to the anabolic impact of amino acids, i.e. the response to amino acids is greater in association with exercise (Witard et al. 2014). However, the “anabolic window” is greater than many claim – MPS can be stimulated with amino acid or protein provision for up to 24 h following resistance exercise (Burd et al. 2011). Clearly, the anabolic window is not limited to the immediate time period following exercise. However, it is possible, if not likely, that the maximal response might occur in this time period – no study to date has directly compared the response to protein ingestion immediately following exercise (e.g. <1 h) with ingestion at a longer time following exercise (e.g. 24 h). Thus, taking a no harm approach, athletes should ingest protein as near to the end of their training session as they can without causing inconvenience. Regardless, it is clear that timing of protein intake in relation to exercise will influence the adaptive response to training.

12Given the influence of the amount of protein consumed and the timing, athletes also should place importance on the pattern of the subsequent protein feeds during exercise recovery in addition to the immediate post exercise feed. The combination of the amount of protein ingested and the timing, i.e. the distribution of the protein ingested over a particular period of time, influences the response of MPS. Over a 12-h period of recovery from resistance exercise ingesting 20 g of protein every 3 h stimulated MPS to a greater extent than 40 g every 6 h or 10 g every 1.5 h (Areta et al. 2013). Similar results in healthy young adults at rest are reported in a recent study (Mamerow et al. 2014). These studies suggest that an even distribution of protein should be consumed throughout the day, even on rest days. Thus, in addition to the acute amount of protein ingested, the timing and pattern of distribution of protein ingestion will influence the adaptive response to protein ingestion.

13The type of protein consumed also is important to consider when making protein recommendations for athletes. A particular amount of protein consumed in a day may, of course, come from a variety of foods. Whey protein, which is found in milk and other dairy products, stimulates MPS to a greater extent than either soy protein or casein protein (also found in dairy) while soy protein stimulates MPS to a greater extent than casein (Tang et al. 2009). We can attribute the observed difference in stimulation of MPS between the protein sources to both the speed of appearance of amino acids into the blood (West et al. 2011) and the amino acid content (Tang et al. 2009; Tipton & Phillips, 2013; Phillips, 2014). The amino acids appear in the blood faster from ingestion of whey and soy protein than casein protein making them available to the muscle more quickly. The amino acid content of the protein sources also differs – whey protein contains more leucine than the other most other amino acid sources. It is clear that the essential amino acid content of a protein is the main driver of MPS (Tipton et al. 1999). Moreover, many scientists consider leucine to be a particularly important amino acid for stimulation of MPS (Churchward-Venne et al. 2012; Churchward-Venne et al. 2014). Thus, proteins with high leucine content, like whey, stimulate MPS to a greater extent than those with lower leucine content (Tang et al. 2009). The type of protein consumed will influence the overall response and thus must be considered when making protein recommendations.

14Concomitant ingestion of the other macronutrients with protein is another factor to consider when making protein recommendations. Within a meal the co-ingestion of all three macronutrients – protein, carbohydrate and fat – typically occurs. Whereas following resistance exercise carbohydrate co-ingestion with protein does not increase MPS compared to protein ingestion alone (Koopman et al. 2007; Staples et al. 2011), it does increase net muscle protein balance – presumably by decreasing protein breakdown (Miller et al. 2003; Borsheim et al. 2004). Moreover, concomitant lipid ingestion increases amino acid utilization of milk proteins following resistance exercise (Elliot et al. 2006). However, this effect has been demonstrated in only one study to date and the mechanism for increased muscle anabolism with concomitant lipid ingestion is not clear. Certainly, further investigation into the effects of lipid and protein co-ingestion is merited. Thus, even within the context of a specific amount of total protein ingested a number of strategies can be employed by athletes and practitioners to maximally stimulate MPS. Therefore, recommendation based solely on the total amount of protein ingested is insufficient and inadequate. Any recommendation for protein intake must take into account these other important nutritional considerations.

4. Conclusion

15Protein requirements are designed to help prevent the development of deficiencies within populations. However, requirements for protein intake are not appropriate for athletic populations. First, almost all athletes consume far more protein than general requirements. Perhaps more importantly, athletes almost certainly seek more from their diet than merely avoiding deficiency and obtaining an “adequate” amount of any nutrient, including protein. The interests of athletes lie far more with protein recommendations than protein requirements. Development of protein recommendations can allow athletes to maximize their training adaptations through optimum protein nutrition. However, a single specific recommended amount of protein is difficult to make for all athletes due to differences in athlete type, sport, position within a sport, training demands on the athlete and individual goals. The most effective recommendations should be made on an individual basis. Moreover, for any given athlete or exerciser protein recommendations should not be based solely on the total amount of protein consumed. Recommendations for protein intake aimed at optimizing training adaptations and improving performance should take into account the type of protein ingested, timing and pattern of protein ingestion, as well as concurrent ingestion of other macronutrients with the protein. The challenge for nutrition practitioners, coaches and athletes is to develop the protein recommendations suited to any particular athlete at a specific time of the season. We have tried to offer some information to consider when making these decisions, but acknowledge that there is much still to learn before definitive recommendations may be offered for all athletes. As always, we recommend a risk/benefit approach. The first consideration should be to avoid harm while attempting to optimize gain.

Bibliographie

5. Bibliographic references

Areta JL, Burke LM, Ross ML, Camera DM, West DW, Broad EM, Jeacocke NA, Moore DR, Stellingwerff T, Phillips SM, Hawley JA, Coffey VG. 2013. “Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis.” In J Physiol. 591, 2319-2331.

Biolo G, Tipton KD, Klein S, Wolfe RR. 1997. “An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein.” In Am J Physiol. 273, E122-129.

Borsheim E, Cree MG, Tipton KD, Elliott TA, Aarsland A, Wolfe RR. 2004. “Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise.” In J Appl Physiol. 96, 674-678.

Burd NA, West DW, Moore DR, Atherton PJ, Staples AW, Prior T, Tang JE, Rennie MJ, Baker SK, Phillips SM. 2011. “Enhanced amino acid sensitivity of myofibrillar protein synthesis persists for up to 24 h after resistance exercise in young men.” In J Nutr. 141, 568-573.

Churchward-Venne TA, Breen L, Di Donato DM, Hector AJ, Mitchell CJ, Moore DR, Stellingwerff T, Breuille D, Offord EA, Baker SK, Phillips SM. 2014. “Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial.” In Am J Clin Nutr. 99, 276-286.

Churchward-Venne TA, Burd NA, Mitchell CJ, West DW, Philp A, Marcotte GR, Baker SK, Baar K, Phillips SM. 2012. “Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men.” In J Physiol. 590, 2751-2765.

Elliot TA, Cree MG, Sanford AP, Wolfe RR, Tipton KD. 2006. “Milk ingestion stimulates net muscle protein synthesis following resistance exercise.” In Med Sci Sports Exerc. 38, 667-674.

Hartman JW, Moore DR, Phillips SM. 2006. “Resistance training reduces whole-body protein turnover and improves net protein retention in untrained young males.” In Appl Physiol Nutr Metab. 31, 557-564.

Ivy JL, Portman R. 2009. Nutrient Timing: The future of sports nutrition. Basic Health Publications, Inc, East Bergen, NJ, USA.

Koopman R, Beelen M, Stellingwerff T, Pennings B, Saris WH, Kies AK, Kuipers H, van Loon LJ. 2007. Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. In Am J Physiol Endocrinol Metab. 293, E833-842.

Mamerow MM, Mettler JA, English KL, Casperson SL, Arentson-Lantz E, Sheffield-Moore M, Layman DK, Paddon-Jones D. 2014. “Dietary Protein Distribution Positively Influences 24-h Muscle Protein Synthesis in Healthy Adults.” In J Nutr.

McKenzie S, Phillips SM, Carter SL, Lowther S, Gibala MJ, Tarnopolsky MA. 2000. “Endurance exercise training attenuates leucine oxidation and BCOAD activation during exercise in humans.” In Am J Physiol Endocrinol Metab. 278, E580-587.

Miller SL, Tipton KD, Chinkes DL, Wolf SE, Wolfe RR. 2003. “Independent and combined effects of amino acids and glucose after resistance exercise.” In Med Sci Sports Exerc. 35, 449-455.

Moore DR, Churchward-Venne TA, Witard O, Breen L, Burd NA, Tipton KD, Phillips SM. 2014. “Protein Ingestion to Stimulate Myofibrillar Protein Synthesis Requires Greater Relative Protein Intakes in Healthy Older Versus Younger Men.” In J Gerontol A Biol Sci Med Sci.

Moore DR, Del Bel NC, Nizi KI, Hartman JW, Tang JE, Armstrong D, Phillips SM. 2007. “Resistance training reduces fastedand fed-state leucine turnover and increases dietary nitrogen retention in previously untrained young men.” In J Nutr. 137, 985-991.

Moore DR, Robinson MJ, Fry JL, Tang JE, Glover EI, Wilkinson SB, Prior T, Tarnopolsky MA, Phillips SM. 2008. “Ingested protein dose–response of muscle and albumin protein synthesis after resistance exercise in young men.” In American Journal of Clinical Nutrition. 89, 161-168.

Moore DR, Tang JE, Burd NA, Rerecich T, Tarnopolsky MA, Phillips SM. 2009. “Differential stimulation of myofibrillar and sarcoplasmic protein synthesis with protein ingestion at rest and after resistance exercise.” In J Physiol. 587, 897-904.

Mujika I, Stellingwerff T, Tipton K. 2014. “Nutrition and training adaptations in aquatic sports.” In Int J Sport Nutr Exerc Metab. 24, 414-424.

Phillips S. 2004. “Protein requirements and supplementation in strength sports1.” In Nutrition. 20, 689-695.

Phillips SM. 2006. “Dietary protein for athletes: from requirements to metabolic advantage” In Appl Physiol Nutr Metab. 31, 647-654.

Phillips SM. 2014. “A brief review of critical processes in exercise-induced muscular hypertrophy.” In Sports Med. 44 Suppl 1, S71-77.

Phillips SM, Atkinson SA, Tarnopolsky MA, MacDougall JD. 1993. “Gender differences in leucine kinetics and nitrogen balance in endurance athletes.” In J Appl Physiol. 75, 2134-2141.

Phillips SM, van Loon LJ. 2011. “Dietary protein for athletes: from requirements to optimum adaptation.” In J Sports Sci. 29 Suppl 1, S29-38.

Rennie MJ, Tipton KD. 2000. “Protein and amino acid metabolism during and after exercise and the effects of nutrition.” In Annu Rev Nutr. 20, 457-483.

Rodriguez NR, DiMarco NM, Langley S. 2009. “Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance.” J Am Diet Assoc. 109, 509-527.

Staples AW, Burd NA, West DW, Currie KD, Atherton PJ, Moore DR, Rennie MJ, Macdonald MJ, Baker SK, Phillips SM. 2011. “Carbohydrate does not augment exercise-induced protein accretion versus protein alone.” Med Sci Sports Exerc. 43, 1154-1161.

Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. 2009. “Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men.” In J Appl Physiol. 107, 987-992.

Tarnopolsky M. 2004. “Protein requirements for endurance athletes.” In Nutrition. 20, 662-668.

Tipton KD, Ferrando AA, Phillips SM, Doyle D, Jr, Wolfe RR. 1999. “Postexercise net protein synthesis in human muscle from orally administered amino acids.” In Am J Physiol. 276, E628-634.

Tipton KD, Phillips SM. 2013. “Dietary protein for muscle hypertrophy.” In Nestle Nutr Inst Workshop Ser. 76, 73-84.

Tipton KD, Witard OC. 2007. “Protein requirements and recommendations for athletes: relevance of ivory tower arguments for practical recommendations.” In Clin Sports Med. 26, 17-36.

Todd KS, Butterfield GE, Calloway DH. 1984. “Nitrogen balance in men with adequate and deficient energy intake at three levels of work.” In J Nutr. 114, 2107-2118.

West DW, Burd NA, Coffey VG, Baker SK, Burke LM, Hawley JA, Moore DR, Stellingwerff T, Phillips SM. 2011. “Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise.” In Am J Clin Nutr. 94, 795-803.

Wilkinson SB, Phillips SM, Atherton PJ, Patel R, Yarasheski KE, Tarnopolsky MA, Rennie MJ. 2008. “Differential effects of resistance and endurance exercise in the fed state on signalling molecule phosphorylation and protein synthesis in human muscle.” In J Physiol. 586, 3701-3717.

Witard OC, Jackman SR, Breen L, Smith K, Selby A, Tipton KD. 2014. “Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise.” In Am J Clin Nutr. 99, 86-95.

Auteurs

PhD. Health and Exercise Sciences Research Group University of Stirling. Stirling FK9 4LA. Scotland

PhD. Health and Exercise Sciences Research Group University of Stirling. Stirling FK9 4LA. Scotland

© INSEP-Éditions, 2015

Conditions d’utilisation : http://www.openedition.org/6540

Rechercher dans OpenEdition Search

Vous allez être redirigé vers OpenEdition Search