sports nutrition for football · al., 2016). the association between body . composition and health...

SPORTS NUTRITION FOR FOOTBALLAn evidence-based guide for nutrition practice at FC BarcelonaGatorade Sports Science InstituteIan Rollo James CarterAsker Jeukendrup

FC Barcelona Medical DepartmentMª Antonia Lizarraga Franchek Drobnic C. Daniel Medina

SPORTS NUTRITION FOR FOOTBALL: AN EVIDENCE-BASED GUIDE FOR NUTRITION PRACTICE AT FC BARCELONA

AUTHORS

CONTRIBUTORS AND EDITORS

Ian Rollo Asker Jeukendrup

Ian Rollo and James Carter are employees of the Gatorade Sports Science Institute, a division of PepsiCo Inc. The views expressed in this manuscript are those of the authors and do not necessarily reflect the position or policy of PepsiCo Inc.

FC BARCELONA, 2018©. BARÇA INNOVATION HUB

PEPSICO INC, 2018©.

James CarterMa Antonia LizarragaFranchek DrobnicC.Daniel Media Leal


Sports nutrition for football: An evidence-based guide for nutrition practice at FC Barcelona

Gatorade Sports Science InstituteIan Rollo James Carter Asker Jeukendrup

FC Barcelona Medical DepartmentMª Antonia Lizarraga Franchek Drobnic C. Daniel Medina


“If you want to get better you must train hard every day, but without the right nutrition, it will not be possible.”

Lionel MessiFC Barcelona#10

6 Summary

7

SUMMARY


E. Editor’s biographies

0. Introduction tothe Guide

2. MicronutrientRequirements for Football

3. Protein Requirementsfor Football

4. Carbohydrate

5. Fluid Requirementsfor Football

6. DietarySupplementation for Football

7. Nutrition forFootball Injuries

1. Player Energy Balanceand Body Composition P 8

8 Player Energy Balance and Body Composition

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PLAYER ENERGY BALANCE AND BODY COMPOSITIONIn football, league competition does not require players to “peak” for an individual match. Instead, players are required to sustain a high level of performance over periods of weeks, if not months.

Thus, an objective of the professional football player is to maintain a body mass throughout the competitive season that is “realistic” from both a health and performance perspective. The energy intake and macronutrient content of the diet should be adjusted depending on the demands of training or match day performance as well as the specific goals of the player. Therefore, there is no “one size fits all” approach; rather the dietary requirements are specific to the individual player and should be modified depending on the work required (Jeukendrup 2014; Impey et al., 2016).

The association between body composition and health is well established. At the extremes, and for those that are sedentary, excess body fat (obesity) is a significant risk factor for both metabolic (Way et al., 2016) and cardiac disease (Koene et al., 2016). Conversely, individuals with an intense fear of gaining weight and distorted cognitions regarding weight, shape, and drive for thinness may suffer from eating disorders and extremely low body fat (Gorwood et al., 2016). In football, “optimal” values of body fat and muscle tissue required for health and football specific performance are less clear. This is because of the difficulty in measuring performance per se and the variability in player somatotype, which, depending on the tactics of the team, may differ by playing position.

Elite male professional players have been reported to be characterised by a lower body fat percentage, in

comparison to junior counterparts. Interestingly this difference was not a result of lower absolute body fat but higher values in muscle mass (Milsom et al., 2015). Indeed, compared to body composition, lean mass and leg strength have been reported to have greater associations with sprint and jump performance in sub-elite male footballers (Nikolaidis et al., 2016). Having too low or too high body fat is an important consideration in football as both have been reported to increase the risk of injury (Richmond et al., 2013; Kemper et al., 2015). It is intuitive that a player’s physical performance would be hindered by an excess of body fat. Equally, sustaining very low values of body fat during periods of intensified training or competition may compromise immune function and ultimately performance (Nieman 2000; Moreira et al., 2014).

The assessment and monitoring of both a player’s fat and muscle are important considerations with regard to football performance. Consistent messaging throughout academy, development and professional squads is an important process to educate players how to eat for health, performance and body composition management. Thus, the aim of this chapter is to understand best practice with regard to body composition assessment and how applying the basic concepts of energy balance may be applied to body composition development and weight management in football.

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Energy balance in football is a dynamic process (Galgani & Ravussin 2008). Energy is provided to the player via all foods and some beverages in their diet. This energy is used by the player in several fundamental processes including cellular maintenance, thermoregulation, growth, reproduction, immunity and locomotion (Loucks et al., 2011). When players train or compete, energy expenditure is increased significantly, which increases the need for additional energy to be ingested through the diet. However, changing one element of energy intake may unintentionally influence energy expenditure. Thus, numerous factors operate in concert on each side of the energy balance equation, which will ultimately determine body mass and composition (Manore 2015).

If the total energy expenditure of the player, including exercise-related expenditure and the energy required to support daily physiological function, exceeds that of energy intake, the player is said to be in negative energy balance. Alternatively, if energy intake exceeds total energy expenditure, the player will be in positive energy balance. The maintenance of body mass over time is an indication that the player is in a state of energy balance where energy intake (total calories consumed) equals energy expenditure (total calories expended).

The composition of the player’s body and their metabolism will influence energy expenditure. For example, players with more muscle expend more energy, even when at rest. It is important to note that away from football, most professional players, on the whole, lead a sedentary lifestyle. For example, a study of Premier League football players reported that 79% of post-training time is spent engaged in sedentary behaviour (Weiler et al., 2015). Thus, the major occasions of energy expenditure are training and matches. There are various methods which can be used to assess energy expenditure in football. From a clinical research perspective, studies have used measurements of body temperature (Saltin & Hermansen 1966; Edwards & Clark 2006), continuous heart rate monitoring (Esposito et al., 2004; Eniseler 2005) and light weight portable oxygen analysers (Kawakami et al., 1992). These methods consistently report the mean metabolic load of a football match to be approximately 70% of a player’s maximal oxygen uptake. However, many of these methods do not provide information on the high intensity exercise component of football, which significantly increases the energy expenditure (Bangsbo 1994; Bangsbo 2014). Furthermore, the practicality of these systems to be included during matches or day-to-day training sessions is not realistic.

PRINCIPLES OF ENERGY BALANCE

ENERGY EXPENDITUREThus, daily or weekly monitoring of player body mass can provide a gross assessment of a player’s energy balance over the season. So that meaningful differences in body mass can be assessed, the players’ weight should be recorded at the same time of day and when players are euhydrated (Chapter 6).

It is important to recognise that when training is modified to expend more or less energy, players should also modify their diet to increase or reduce energy availability in the management of body composition (Loucks et al., 2011). The main factors governing the energy expended during exercise are the intensity and duration of training/matches. Conversely, in the event of immobilisation, such as if a player is injured, energy expenditure can be substantially reduced and therefore energy intake should also be adjusted accordingly (Chapter 8). To this end, the energy requirements will vary depending on the individual player and the phase of competition / training / recovery / rehabilitation they are involved. The diet (energy intake) and training programs (energy expenditure) need to be carefully managed to modify body composition, achieve performance goals, optimise recovery and avoid ill health.

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MATCHESOver the last four decades the development of video filming during matches and subsequent computer-aided analysis has led to the accurate assessment of individual physical performance and is commonly used in professional teams (Reilly 1983; Carling et al., 2008; Carling 2010; Castellano et al., 2014; Carling et al., 2016). Advanced techniques in video match analysis permit the detailed observation and capture of players’ movement, team positioning as well as ball tracking throughout a 90 min match. The data allows an estimation of energy expenditure of players using distances covered, relative speeds and technical performance (football control). Video analysis also provides valuable insight into the number of ball interactions, passing (number, precision, distance and pitch location), the percentage possession of the ball and areas of the pitch where the greatest activity has occurred (Carling et al., 2012; Schuth et al., 2016).

Data provided by global positioning statelite (GPS) also provides a valuable resource for clubs to monitor match (and training) activities and may be used to identify the different energy requirements between players (Figure 2.1) (FIFA match approval: July 2015). GPS units are light weight, safe, easily worn and are unobstructive to the players natural movements. Data gathered from GPS systems can be processed “live” or downloaded rapidly following exercise. This data can be used to classify the time spent at different exercise intensifies. The greater time spent at high intensity the

greater the energy expenditure. Energy expenditure is typically calculated by speed, acceleration and total distance data. At present the current GPS systems and video analysis are unable to account for the energy expenditure associated with activities such as tackling, heading, kicking, dribbling or backwards running (Bangsbo 1994; Bangsbo 2014). As such, it is likely that common methods significantly underestimate total energy expenditure during football specific play (Murakami et al., 2016).

Tabulating the results of research investigating professional football reveals that the total distance covered in a match ranges from 10 to 13 km, with differences related to standard of play, position of the player and tactics of the team (Bangsbo 1994; Mohr et al., 2003; Bangsbo et al., 2006; Bangsbo 2014). High energy demanding sprints only account for 2-3% of total match time (Figure 2.1), but are associated with the critical moments during a match (Gregson et al., 2010; Faude et al., 2012).

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Figure 2.1 Example of match analysis of two FCB midfield players during a UEFA champions league game v

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The corresponding average energy expenditure during matches has been estimated to range between 1000-1500 Kilocalories (kcal) (Ekblom 1986; Bangsbo 1994; Stolen et al., 2005; Bangsbo et al., 2006).

It is important to note that greater energy expenditures (i.e. distance covered and high intensity running) do not necessarily translate to superior “performance” in football (Bradley et al., 2013; Di Mascio & Bradley 2013; Fernandez-Navarro et al., 2016). For example, analysis of La Liga professional teams revealed that the top-class players performed less high-intensity activity (>19.1 km/h) during a game which they were winning in comparison to when they were losing (Lago et al., 2010).

Therefore, it is important to note that the factors which influence the energy expended during matches are highly complex and are affected by, amongst many others, physical and mental fatigue, the phase of play, team tactics and individual pacing strategy (Paul et al., 2015).

To date, few studies have reported the daily energy expenditure of professional players using the gold standard of doubly labelled water which would capture energy expenditure non-invasively under “free living” conditions (Westerterp et al., 1986). Those studies which have used doubly labelled water have measured both energy expenditure and energy intake during a two-game week playing schedule where consecutive games were separated by two days. Interestingly, the mean values

of daily energy expenditure (3566 ± 585 kcal) and energy intake (3186 ± 367 kcal) of six premier league footballers are remarkably similar to those reported previously in seven professional Japanese players (3532 ± 432 and 3113 ± 581 kcal, respectively) (Ebine et al., 2002; Anderson et al., 2017).

Players at all levels of the game can experience fatigue as the duration of the match nears 90 min. This is evident through either a decrease in maximal sprint speed or a reduction in distance covered (5%–10%) in the second half (Bangsbo et al., 2006; Krustrup et al., 2006; Osgnach et al., 2010; Bendiksen et al., 2012). Fatigue is likely a consequence of the depletion of muscle glycogen; analyses of single muscle fibres after a game have revealed that a significant number of fibres are depleted or partly depleted (Krustrup et al., 2006; Bendiksen et al., 2012). This observation highlights the importance of modifying energy intake, specifically with regard to carbohydrate ingestion on match day, to sustain performance for the duration of the match (Chapter 5).

To date, few studies have reported the daily energy expenditure of professional players using the gold standard of doubly labelled water which would capture energy expenditure non-invasively under “free living” conditions (Westerterp et al., 1986). Those studies which have used doubly labelled water have measured both energy expenditure and energy intake during a two-game week playing schedule where consecutive games were separated by two days. Interestingly, the mean values

of daily energy expenditure (3566 ± 585 kcal) and energy intake (3186 ± 367 kcal) of six premier league footballers are remarkably similar to those reported previously in seven professional Japanese players (3532 ± 432 and 3113 ± 581 kcal, respectively) (Ebine et al., 2002; Anderson et al., 2017).

Players at all levels of the game can experience fatigue as the duration of the match nears 90 min. This is evident through either a decrease in maximal sprint speed or a reduction in distance covered (5%–10%) in the second half (Bangsbo et al., 2006; Krustrup et al., 2006; Osgnach et al., 2010; Bendiksen et al., 2012). Fatigue is likely a consequence of the depletion of muscle glycogen; analyses of single muscle fibres after a game have revealed that a significant number of fibres are depleted or partly depleted (Krustrup et al., 2006; Bendiksen et al., 2012). This observation highlights the importance of modifying energy intake, specifically with regard to carbohydrate ingestion on match day, to sustain performance for the duration of the match (Chapter 5).

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During a competitive season, professional players have been reported to complete up to 120 individual training sessions (Gaudino et al., 2015). This equates to approximately 3 training sessions a week during a 38 week season. Therefore, the time spent engaged in training exceeds that of competition. The energy expended during training will vary depending on the intensity and duration of exercise as well as the body composition of the player. Training will also vary depending on the phase of the season and managerial regime. It is common practice for professional clubs to monitor the external training load by GPS systems as well as heart rate and other measures such as player rating of perceived exertion (RPE) scores (Scott et al., 2013; Rampinini et al., 2015). Total distances covered at high speed running (>14.4 km/h), number of impacts and accelerations (>3 m/s2) are representative of higher training loads which can be reflected in the players subjective response to training i.e. via the 1-10 point RPE scale (Gaudino et al., 2015). Thus, as training intensity is likely to fluctuate, it is important for the player to recognise the increase or decrease in energy requirements (Impey et al., 2016). Paradoxically, football specific activity, i.e. high intensity exercise, may blunt appetite-regulating hormones, which may consequently result in reduced energy intake and disrupt recovery strategies (Stensel 2010; Deighton et al., 2013; Bailey et al., 2015; Briggs et al., 2015).

TRAINING

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All foods and several beverages in a player’s diet are characterised by their composition of macro and micro nutrients. Macronutrients are carbohydrate, proteins and fats, whilst micronutrients include vitamins and minerals (Chapter 3). The energy content of carbohydrate and protein is approximately 4 kcal/g, whereas the energy value of fat is 9 kcal/g. The role and appropriate intake of protein and carbohydrate in the players diet are discussed in Chapters 4 and 5, respectively.

Fat is an essential component of the players’ diet, providing energy, facilitating the absorption of fat-soluble vitamins (Chapter 3) and also providing an essential structural component of cell membranes. The recommended daily intake of fat is 1.2 - 1.4 g/kg body mass (Institute of Medicine (IOM) Food and Nutrition Board 2005). Diets abundant in high fat foods are discouraged as they can replace those foods which contain the other macronutrients essential for football performance, recovery and adaptation.

Furthermore, because high fat foods are often energy dense, they also carry a risk of delivering excess calories. It is important to note that although not a nutrient, water is the other essential component to a player’s dietary intake (Chapter 6). Players are encouraged to work together with the club’s professional sports nutritionist or dietician for meal planning based on energy requirements and individual

ENERGY INTAKE goals, translating nutrient guidelines into food equivalents. Part of the players’ nutritional education is to understand those foods which contain more or less of the macronutrients, as well as those foods which are rich in vitamins and minerals. Thus, the player should understand how to piece together meals on a daily basis which provide the appropriate quantity of macro and micro nutrients for health, body composition and performance.

Energy intake remains one of the most difficult measures to record accurately in sports nutrition. This is because the measures of energy intake are usually reliant on self-reporting or recall of those people completing them. This process frequently results in an under-reporting of dietary energy intake (Poslusna et al., 2009). Developing expertise in the assessment of energy intake requires an appreciation that there are different reasons for undertaking an assessment, different approaches to completing it and different tools that can be used (Burke 2015).

The gold standard of energy intake assessment would require the players to weigh and record all the food and beverages in their diet. This information is then entered into dietary assessment computer programmes for energy intake and breakdown of macro / micro nutrient content. Nevertheless, even accurate assessments only provide brief insights into the players’ energy intake over the duration of the assessment.

Technological advances, through web

based or mobile tablet applications, have provided novel ways to collect and process energy intake information. Many of these systems provide electronic versions of paper and pen questionnaires, such as 24 h recall (Rangan et al., 2016). Key advantages of the technology are that applications can provide a huge data base of food pictures, be updated real time and provide rapid feedback. In the coming years we expect to see these new methods being used to gather information on food practices of athletic populations, including footballers (Stumbo 2013; Burke 2015).

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Research studies have reported that the typical body fat percentage of elite male football players can range between 7 and 19% (Wittich et al., 2001; Reilly et al., 2009) (Figure 2.2). Less data is available on elite female football players (Mala et al., 2015). Based on available research and our own data (FCB, unpublished observations) female body fat percentage ranges from 16-24% (Sedano et al., 2009; Delextrat et al., 2013). It is discouraged to establish rigid

BODY COMPOSITION IN FOOTBALLERS

Stature (cm)170.0 - 194.8

Stature (cm)151.0 - 187.2

Analysed by GE Luna iDXA, Medical Systems Lunar Software

Body Mass (kg): 43.6 - 87.6Fat Free Mass (g): 33.4 - 49.8

Fat Mass (g): 7.8 - 18.9Body Fat Percentage: 14.6 - 29.7

Body Mass (kg): 66.4 - 87.2Fat Free Mass (g): 54.2 - 73.2

Fat Mass (g): 6.0 - 14.0Body Fat Percentage: 10.1 - 16.9

prescriptions for individuals. Instead, it is advised to propose a range of acceptable values for body fat and body mass for players within a team. Historically, it is typical for football players to accumulate body fat in the off season. Indeed, seasonal trends reflect an increase in body fat levels during the off season, which are then reduced during the preseason, where training volume is highest (Carling & Orhant 2010). It can also be common for lean muscle mass to be reduced during heavy training volumes in some players if adequate energy is not ingested. Simple routine monitoring of body mass provides

a quick and non-invasive method to monitor the player’s energy balance. Beyond physical appearance, significant deviation in body mass provides the first indication of changes in fat or lean tissue composition. This early indicator may then provide stimulus for further body composition analysis and consultation if required.

Figure 2.2 Range in anthropome-trical and body compo-sition of elite male and female football players at FCB (2016). v

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BODY MASS MANAGEMENT

A common objective for many players is to lose body fat while gaining or maintaining muscle mass, although the time periods for such gains and losses are infrequent and often short. There are several options available to lose body fat and the general recommendation is for weight loss not to exceed 1 kg per week (Burke & Deakin 2015). Given the previously discussed principle of energy balance, one option is to reduce energy intake by up to 1000 kcal a day for a week, the other to increase energy expenditure by up to 1000 kcal/day per week (whilst keeping energy intake constant) or finally a combination of the two. For players already engaged in football training or in-season competition, a moderate approach to energy intake reduction i.e. 500–700 kcal/day may be a more appropriate approach (Garthe et al., 2011).

Although this method may take longer to achieve weight loss goals (Donnelly et al., 2009; Garthe et al., 2011), it may reduce the risk of the diet negatively impacting on daily performance and feelings of mood/motivation of the player (Achten et al., 2004). One strategy which is effective in decreasing energy intake, without affecting hunger or the enjoyment of food, is to reduce the energy dense foods in the diet. This method is considered more effective than reducing the portion size of meal servings because players are able to eat similar quantities of food. Increasing the intake of foods with a high water and fibre content promotes satiation and may increase the adherence to the dietary modification (Manore 2015).

When energy intake is restricted, it is important to acknowledge the corresponding decrease in protein ingestion. Therefore, particular attention should be placed on increasing or maintaining protein ingestion during periods of energy restriction to help preserve skeletal muscle integrity, in both physically active or inactive (injured) players (Carbone et al., 2012; Phillips 2014).

In general, the protein needs of football players may be higher (1.4–1.7 g/protein/kg) than that recommended (0.8 g/protein/kg) for non-active individuals (Chapter 4). In addition, during periods of energy restriction, increasing dietary protein can help maintain muscle mass, when combined with strength training (Mettler et al., 2010). The quantity and

type of protein required may depend on volume and type of exercise and the level of energy restriction (Phillips et al., 2007; Carbone et al., 2012; Philips 2013). It is recommended that the appropriate quantity of protein is ingested at routine meals spaced throughout the day (Moore et al., 2009).

As well as providing precursors for muscle growth and repair, diets rich in protein may also increase ratings of satiety and therefore can be effective in managing ad libitum energy intake (Weigle et al., 2005). Conversely, this may hinder those players attempting to gain lean body mass. In this circumstance similar quantities and timing of protein intake is advised whilst increasing energy intake to promote a positive energy balance (Chapter 4).

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Many football clubs routinely monitor the body composition of their players. Often, body fat is expressed as a percentage of total body mass. The purposes of body composition analysis are to assess a player’s physical development over time, monitor energy availability status and also assess the impact of specific training or nutrition regimes. It is important to note that a player’s physique is heavily determined by inherited characteristics, for example the height of a player will be determined through genetic predisposition (Davenport 1917). However, the players’ body composition is determined through the influence of their training program and diet.Thus, importantly with regard to physical performance, changing body composition and specifically controlling the amount of body fat, is one variable that a player can directly control.

Finally, a common consequence of a favoured foot for kicking the ball can result in asymmetry in the lower extremities in footballers (Rahnama et al., 2005). Muscle imbalances of 3% in the lower limbs have been reported to correspond to an 8% difference in strength between legs in Australian rules footballers. This imbalance was found to lead to inaccurate kicking, whereas greater levels of symmetry, relative lower-body strength and muscle mass were associated with improved kicking accuracy (Hart et al., 2014). As such, body composition analysis can also help identify significant muscular imbalances which are generally regarded to increase the risk of injury.

An extensive range of methods to assess body composition currently exist. High precision technologies considered as reference values for body composition include X-ray computed tomography (Ashwell et al., 1985), magnetic resonance imaging (Ross et al., 1992), hydrostatic weighing (Donnelly et al., 1988) and DXA (Nana et al., 2013). However, the widespread use of most of these technologies is prevented due to their limited availability, expense and practicalities within a football club. Thus, to our knowledge, the three main methods used to assess body composition in football players are skin folds, bioelectrical impedance analysis (BIA) and DXA.

BODY COMPOSITION ANALYSIS

METHODS TO ANALYSE PLAYER BODY COMPOSTION

In professional footballers body composition is usually measured at the beginning of the preseason period and then monitored at regular intervals during the season, typically every 1-2 months. In addition, assessment of body composition is appropriate before and after specific training/nutrition programmes or immediately following an injury which alters daily energy expenditure (Chapter 8).

The methods and frequency of body composition assessment will differ depending on the resources at the team’s disposal, as well as their preferences.

Nevertheless, independent of the method, it is imperative for appropriate standardisation prior to and in completion of the assessments to ensure meaningful changes can be tracked over time.

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The BIA technique offers a method to non-invasively assess the fluid distribution and body composition of football players (Gatterer et al., 2011; Mascherini et al., 2015; Fassini et al., 2016). BIA works by passing by passing an electrical current through the player’s body.

The resistance to that current, as a result of the specific resistivity and volume of fat free mass, which acts a conductor, is measured. Total body water is also calculated and the value can be used to estimate percentage body fatness (Kushner & Schoeller 1986; Davies et al., 1990; Beertema et al., 2000). The BIA machines vary in size and mobility. Advances in the technique have resulted in devices using both single and multiple frequencies of electrical current, with multiple frequencies reported to improve accuracy (Cornish et al., 1993; Shafer et al., 2009).

BIA has been reported to have a strong absolute agreement with DXA for measurement of body fat percentage (ICC=0.87, 95% CI 0.46, 0.95) (Carter et al., 2013). Body mass scales with electrodes positioned on hand held paddles and on the foot plates are a typical method of applying the electrical current to the extremities of a player’s body. The advantages of BIA are that the assessment can be “self-led” by the player, the duration of analysis is quick, 1-2 minutes, and the results are available instantly.

DXA is a clinical method with the primary purpose to assess bone mineral density (Ryan et al., 1993; Barry & Kohrt 2008). An additional function of a DXA machine is to assess body composition. This technology has become a commonly used method within elite football clubs, providing a relatively precise estimate of fat mass, bone mineral content and lean mass.

Full details of DXA technology and standardisation procedures have been reported previously (Clarys et al., 2010; Nana et al., 2016). In brief, players are positioned in a standardised position on the DXA bed.

BIOELECTRICAL IMPEDANCE

DUAL-ENERGY X-RAY ABSORPTIOMETRY

It is noteworthy to mention that BIA has recently been investigated as a diagnostic tool for the assessment of soft tissue injuries in professional football players.

Specifically, a single frequency phase-sensitive analyser at 50 kHz was used to obtain baseline measures and compared against post-traumatic types of injuries (Nescolarde et al., 2014; Nescolarde et al., 2015). In addition, BIA has been used to successfully assess changes in body water acutely during major football championships, with total distances covered significantly correlated to the percentage drop in fluid at the end of games (Gatterer et al., 2011). With a diverse range of functionality, BIA may become an ever increasing popular choice within football clubs.

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An X-ray beam passes in a posterior to anterior direction through the bone and soft tissue upward to a detector. Fat mass and fat free mass are differentiated by the ratio of X-ray beam attenuation at the lower energy relative to that at the higher energy. Consideration for using DXA in players should include the history of high levels of ionising radiation exposure (i.e. medical treatment following injury). In female players, it is recommended that a pregnancy test be completed prior to assessment to avoid any risk of unnecessary exposure to ionising radiation.

The popularity of DXA is most likely due to scans being relatively quick and easy to perform, whilst providing precise and attractive data to feedback to the players. It is important to note

that DXA also has limitations and strict standardization procedures should be adhered to if meaningful changes are to be identified (Clarys et al., 2010; Nana et al., 2014).

Recent reviews have concluded that when using DXA as a method details of the machine and software, subject positioning protocols, and analysis protocols should be reported and adhered to. This is because the error in DXA measurement of fat mass and muscle mass is approximately 1 kg. Although this may be better than most other techiques, small differences of interest to the practitioner and player during routine monitoring may still be difficult to detect (Clarys et al., 2010; Nana et al., 2014). Therefore, Table 2.1 summarises the recommended procedures for any small changes in

body composition to be confidently detected and correctly interpreted (Nana et al., 2015; Nana et al., 2016).

Novel methods of body composition assessment continue to be developed, of these ultrasound shows some promise. Although ultrasound research is in its infancy, the method may offer a valid and more accurate alternative to skinfolds and more expensive measures of assessment (Pfeiffer et al., 2010; Meyer et al., 2013). Nevertheless, despite adhering to strict standardization procedures, errors will be present independent of the method. Therefore, all body composition results need to be interpreted under the scrutiny of the limitation of the method used. Care is recommended when comparing results from the same methodology used by different research groups or teachers.

BODY COMPOSITION STANDARDISATION ISAK BIA DXA

Completed by same qualified experienced professional X XNo activity or exercisebefore assessment X X XPlayers are assessed Euhydrated (*) X XPlayers should complete the assessment fasted X XStandardised positioning XUse the same equipment/technology for each subsequent measure (for comparision purposes)

X X X

< Figure 2.3 Standardisation of Body Composition Assessment

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Research suggests that a player’s key influencer is their coach. With that regard, implementing nutritional strategies should not be isolated to the “club nutritionist”. Instead, behaviour modification will be most effective when all staff surrounding the player in a team understands the importance of energy balance and nutritional strategies. This can be achieved by small-group nutrition workshops, specifically designed handbooks and more recently, digital materials. Furthermore, involving the coach or having coaching staff present at routine player weight / body composition assessment can have a large impact on a player’s adherence to a nutrition program.

A huge thank you to Edu Pons for his expert insight and sharing of the player match data in this Chapter.

SUMMARY

ACKNOWLEDGEMENT

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sports nutrition for football · al., 2016). the association between body . composition and health...

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