UEFA expert group statement on nutrition in elite football. Current evidence to inform practical recommendations and guide future research.

Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising, a 'food first' philosophy (ie, food over supplements), is fundamental to ensure effective player support. This requires relevant scientific evidence to be applied according to the constraints of what is practical and feasible in the football setting. The science underpinning sports nutrition is evolving fast, and practitioners must be alert to new developments. In response to these developments, the Union of European Football Associations (UEFA) has gathered experts in applied sports nutrition research as well as practitioners working with elite football clubs and national associations/federations to issue an expert statement on a range of topics relevant to elite football nutrition: (1) match day nutrition, (2) training day nutrition, (3) body composition, (4) stressful environments and travel, (5) cultural diversity and dietary considerations, (6) dietary supplements, (7) rehabilitation, (8) referees and (9) junior high-level players. The expert group provide a narrative synthesis of the scientific background relating to these topics based on their knowledge and experience of the scientific research literature, as well as practical experience of applying knowledge within an elite sports setting. Our intention is to provide readers with content to help drive their own practical recommendations. In addition, to provide guidance to applied researchers where to focus future efforts.

Comparison of anthropometry, upper-body strength, and lower-body power characteristics in different levels of Australian football players.

The aim of this study was to compare the anthropometry, upper-body strength, and lower-body power characteristics in elite junior, sub-elite senior, and elite senior Australian Football (AF) players. Nineteen experienced elite senior (≥4 years Australian Football League [AFL] experience), 27 inexperienced elite senior (<4 years AFL experience), 22 sub-elite senior, and 21 elite junior AF players were assessed for anthropometric profile (fat-free soft tissue mass [FFSTM], fat mass, and bone mineral content) with dual-energy x-ray absorptiometry, upper-body strength (bench press and bench pull), and lower-body power (countermovement jump [CMJ] and squat jump with 20 kg). A 1-way analysis of variance assessed differences between the playing levels in these measures, whereas relationships between anthropometry and performance were assessed with Pearson's correlation. The elite senior and sub-elite senior players were older and heavier than the elite junior players (p ≤ 0.05). Both elite playing groups had greater total FFSTM than both the sub-elite and junior elite players; however, there were only appendicular FFSTM differences between the junior elite and elite senior players (p < 0.001). The elite senior playing groups were stronger and had greater CMJ performance than the lower level players. Both whole-body and regional FFSTM were correlated with bench press (r = 0.43-0.64), bench pull (r = 0.58-0.73), and jump squat performance measures (r = 0.33-0.55). Australian Football players' FFSTM are different between playing levels, which are likely because of training and partly explain the observed differences in performance between playing levels highlighting the importance of optimizing FFSTM in young players.

The accuracy and precision of DXA for assessing body composition in team sport athletes.

This study determined the precision of pencil and fan beam dual-energy X-ray absorptiometry (DXA) devices for assessing body composition in professional Australian Football players. Thirty-six professional Australian Football players, in two groups (fan DXA, N = 22; pencil DXA, N = 25), underwent two consecutive DXA scans. A whole body phantom with known values for fat mass, bone mineral content and fat-free soft tissue mass was also used to validate each DXA device. Additionally, the criterion phantom was scanned 20 times by each DXA to assess reliability. Test-retest reliability of DXA anthropometric measures were derived from repeated fan and pencil DXA scans. Fat-free soft tissue mass and bone mineral content from both DXA units showed strong correlations with, and trivial differences to, the criterion phantom values. Fat mass from both DXA showed moderate correlations with criterion measures (pencil: r = 0.64; fan: r = 0.67) and moderate differences with the criterion value. The limits of agreement were similar for both fan beam DXA and pencil beam DXA (fan: fat-free soft tissue mass = -1650 ± 179 g, fat mass = -357 ± 316 g, bone mineral content = 289 ± 122 g; pencil: fat-free soft tissue mass = -1701 ± 257 g, fat mass = -359 ± 326 g, bone mineral content = 177 ± 117 g). DXA also showed excellent precision for bone mineral content (coefficient of variation (%CV) fan = 0.6%; pencil = 1.5%) and fat-free soft tissue mass (%CV fan = 0.3%; pencil = 0.5%) and acceptable reliability for fat measures (%CV fan: fat mass = 2.5%, percent body fat = 2.5%; pencil: fat mass = 5.9%, percent body fat = 5.7%). Both DXA provide precise measures of fat-free soft tissue mass and bone mineral content in lean Australian Football players. DXA-derived fat-free soft tissue mass and bone mineral content are suitable for assessing body composition in lean team sport athletes.

A Qualitative Study of 11 World-Class Team-Sport Athletes' Experiences Answering Subjective Questionnaires: A Key Ingredient for 'Visible' Health and Performance Monitoring?

BACKGROUND: Athlete monitoring trends appear to be favouring objective over subjective measures. One reason of potentially several is that subjective monitoring affords athletes to give dishonest responses. Indeed, athletes have never been systematically researched to understand why they are honest or not. OBJECTIVE: Because we do not know what motivates professional athletes to be honest or not when responding to subjective monitoring, our objective is to explore the motives for why the athlete may or may not respond honestly. METHODS: A qualitative and phenomenological approach was used, interviewing 11 world-class team-sport athletes (five women, six men) about their experiences when asked to respond to subjective monitoring questionnaires. Interview transcripts were read in full and significant quotations/statements extracted. Meanings were formulated for each interviewees' story and assigned codes. Codes were reflected upon and labelled as categories, with similar categories grouped into an overall theme. Themes were examined, articulated, re-interpreted, re-formulated, and written as a thematic story, drawing on elements reported from different athletes creating a blended story, allowing readers a feel for what it is like to live the experience. RESULTS: Overall, four key themes emerged: (i) pursuit of the ideal-self, (ii) individual barriers to athlete engagement, (iii) social facilitators to athlete engagement; and (iv) feeling compassion from performance staff. CONCLUSIONS: Our main insight is that athletes' emotions play a major role in whether they respond honestly or not, with these emotions being driven at least in part by the performance staff asking the questions.

The Preparation Period in Basketball: Training Load and Neuromuscular Adaptations.

PURPOSE: To investigate the effect of the preparation period on neuromuscular characteristics of 12 professional (PRO) and 16 semiprofessional (SEMIPRO) basketball players and relationships between training-load indices and changes in neuromuscular physical performance. METHODS: Before and after the preparation period, players underwent a countermovement jump (CMJ) test followed by a repeated change-of-direction (COD) test consisting of 4 levels with increasing intensities. The peripheral neuromuscular functions of the knee extensors (peak torque [PT]) were measured using electrical stimulations after each level (PT1, PT2, PT3, and PT4). Furthermore, PT Max (the highest value of PT) and PT Dec (PT decrement from PT Max to PT4) were calculated. RESULTS: Trivial to small (effect size [ES] = -0.17 to 0.46) improvements were found in CMJ variables, regardless of competitive level. After the preparation period, peripheral fatigue induced by a COD test was similarly reduced in both PRO (PT Dec: from 27.8% [21.3%] to 11.4% [13.7%]; ES = -0.71; 90% confidence interval [CI], ±0.30) and SEMIPRO (PT Dec: from 26.1% [21.9%] to 10.2% [8.2%]; ES = -0.69; 90% CI, ±0.32). Moderate to large relationships were found between session rating of perceived exertion training load and changes in peak power output (PPO) measured during the CMJs (rs [90% confidence interval]: PPOabs, -.46 [±.26]; PPOrel, -.53 [±.23]) and in some PTs measured during the COD test (PT1, -.45 [±.26]; PT2, -.44 [±.26]; PT3, -.40 [±.27]; and PT Max, -.38 [±.28]). CONCLUSIONS: The preparation period induced minimal changes in the CMJ, while the ability to sustain repeated COD efforts was improved. Reaching high session rating of perceived exertion training loads might partially and negatively affect the ability to produce strength and power.

Longitudinal Changes and Seasonal Variation in Body Composition in Professional Australian Football Players.

PURPOSE: To compare development and variations in body composition of early-, mid-, and late-career professional Australian Football (AF) players over 3 successive seasons. METHODS: Regional and total-body composition (body mass [BM], fat mass [FM], fat-free soft-tissue mass [FFSTM], and bone mineral content [BMC]) were assessed 4 times, at the same time of each season-start preseason (SP), end preseason (EP), midseason (MS), and end season (ES)-from 22 professional AF players using pencil-beam dual-energy X-ray absorptiometry. Nutritional intake for each player was evaluated concomitantly using 3-d food diaries. Players were classified according to their age at the beginning of the observational period as either early- (<21 y, n = 8), mid- (21 to 25 y, n = 9), or late- (>25 y, n = 5) career athletes. RESULTS: Early-career players had lower FFSTM, BMC, and BM than mid- and late-career throughout. FM and %FM had greatest variability, particularly in the early-career players. FM reduced and FFSTM increased from SP to EP, while FM and FFSTM decreased from EP to MS. FM increased and FFSTM decreased from MS to ES, while FM and FFSTM increased during the off-season. CONCLUSIONS: Early-career players may benefit from greater emphasis on specific nutrition and resistance-training strategies aimed at increasing FFSTM, while all players should balance training and diet toward the end of season to minimize increases in FM.

Changes in Anthropometry, Upper-Body Strength, and Nutrient Intake in Professional Australian Football Players During a Season.

The purpose of this study was to examine the seasonal changes in body composition, nutrition, and upper-body (UB) strength in professional Australian Football (AF) players. The prospective longitudinal study examined changes in anthropometry (body mass, fat-free soft-tissue mass [FFSTM], and fat mass) via dual-energy X-ray absorptiometry 5 times during an AF season (start preseason, midpreseason, start season, midseason, end season) in 45 professional AF players. Dietary intakes and strength (bench press and bench pull) were also assessed at these time points. Players were categorized as experienced (>4 y experience, n = 23) or inexperienced (<4 y experience, n = 22). Fat mass decreased during the preseason but was stable through the in-season for both groups. %FFSTM was increased during the preseason and remained constant thereafter. UB strength increased during the preseason and was maintained during the in-season. Changes in UB FFSTM were related to changes in UB-strength performance (r = .37-.40). Total energy and carbohydrate intakes were similar between the experienced and inexperienced players during the season, but there was a greater ratio of dietary fat intake at the start-preseason point and an increased alcohol, reduced protein, and increased total energy intake at the end of the season. The inexperienced players consumed more fat at the start of season and less total protein during the season than the experienced players. Coaches should also be aware that it can take >1 y to develop the appropriate levels of FFSTM in young players and take a long-term view when developing the physical and performance abilities of inexperienced players.

Metabolic power and energetic costs of professional Australian Football match-play.

OBJECTIVES: To compare the metabolic power demands between positional groups, and examine temporal changes in these parameters during Australian Football match-play. DESIGN: Longitudinal observational study. METHODS: Global positioning system data were collected from 39 Australian Football players from the same club during 19 Australian Football League competition games over two seasons. A total of 342 complete match samples were obtained for analysis. Players were categorised into one of six positional groups: tall backs, mobile backs, midfielders, tall forwards, mobile forwards and rucks. Instantaneous raw velocity data obtained from the global positioning system units was exported to a customised spreadsheet which provided estimations of both speed-based (e.g. total and high-speed running distance) and derived metabolic power and energy expenditure variables (e.g. average metabolic power, high-power distance, total energy expenditure). RESULTS: There were significant differences between positional groups for both speed-based and metabolic power indices, with midfielders covering more total and high-speed distance, as well as greater average and overall energy expenditure compared to other positions (all p<0.001). There were reductions in total, high-speed, and high-power distance, as well as average metabolic power throughout the match (all p<0.001). CONCLUSIONS: Positional differences exist for both metabolic power and traditional running based variables. Generally, midfielders, followed by mobile forwards and mobile backs had greater activity profiles compared to other position groups. We observed that the reductions in most metabolic power variables during the course of the match are comparable to traditional running based metrics. This study demonstrates that metabolic power data may contribute to our understanding of the physical demands of Australian Football.

Match-to-match variation in physical activity and technical skill measures in professional Australian Football.

OBJECTIVES: To determine the match-to-match variability in physical activity and technical performance measures in Australian Football, and examine the influence of playing position, time of season, and different seasons on these measures of variability. DESIGN: Longitudinal observational study. METHODS: Global positioning system, accelerometer and technical performance measures (total kicks, handballs, possessions and Champion Data rank) were collected from 33 players competing in the Australian Football League over 31 matches during 2011-2012 (N=511 observations). The global positioning system data were categorised into total distance, mean speed (mmin(-1)), high-speed running (>14.4 kmh(-1)), very high-speed running (>19.9 kmh(-1)), and sprint (>23.0 kmh(-1)) distance while player load was collected from the accelerometer. The data were log transformed to provide coefficient of variation and the between subject standard deviation (expressed as percentages). RESULTS: Match-to-match variability was increased for higher speed activities (high-speed running, very high-speed running, sprint distance, coefficient of variation %: 13.3-28.6%) compared to global measures (speed, total distance, player load, coefficient of variation %: 5.3-9.2%). The between-match variability was relativity stable for all measures between and within AFL seasons, with only few differences between positions. Higher speed activities (high-speed running, very high-speed running, sprint distance), but excluding mean speed, total distance and player load, were all higher in the final third phase of the season compared to the start of the season. CONCLUSIONS: While global measures of physical performance are relatively stable, higher-speed activities and technical measures exhibit a large degree of between-match variability in Australian Football. However, these measures remain relatively stable between positions, and within and between Australian Football League seasons.

Training periodization of professional Australian football players during an entire Australian Football League season.

PURPOSE: To examine the training periodization of an elite Australian Football team during different phases of the season. METHODS: Training-load data were collected during 22 wk of preseason and 23 wk of in-season training. Training load was measured using the session rating of perceived exertion (session-RPE) for all training sessions and matches from 44 professional Australian Football players from the same team. Training intensity was divided into 3 zones based on session-RPE (low, <4; moderate, >4 AU and <7 AU; and high, >7 AU). Training load and intensity were analyzed according to the type of training session completed. RESULTS: Higher training load and session duration were undertaken for all types of training sessions during the preseason than in-season (P<.05), with the exception of "other" training (ie, re/prehabilitation training, cross-training, and recovery activities). Training load and intensity were higher during the preseason, with the exception of games, where greater load and intensity were observed during the in-season. The overall distribution of training intensity was similar between phases with the majority of training performed at moderate or high intensity. CONCLUSIONS: The current findings may allow coaches and scientists to better understand the characteristics of Australian Football periodization, which in turn may aid in developing optimal training programs. The results also indicate that a polarized training-intensity distribution that has been reported in elite endurance athletes does not occur in professional Australian Football.

Match score affects activity profile and skill performance in professional Australian Football players.

OBJECTIVES: To examine the influence of quarter outcome and the margin of the score differential on both the physical activity profile and skill performance of players during professional Australian Football matches. DESIGN: Prospective, longitudinal. METHODS: Physical activity profiles were assessed via microtechnology (Global Positioning System and accelerometer) from 40 professional AF players from the same team during 15 Australian Football League games. Skill performance measures (involvement and effectiveness) and player rank scores (Champion Data(©) Rank) were provided by a commercial statistical provider. The physical performance variables, skill involvements and individual player performance scores were expressed relative to playing time for each quarter. The influence of the quarter result (i.e. win vs. loss) and score margin (i.e. small: <9 points, moderate: 10-18 points, and large: >19 points) on activity profile and skill involvements and skill efficiency performance of players were examined. RESULTS: Skill involvements (total disposals/min, long kicks/min, marks/min, running bounces/min and player rank/min) were greater in quarters won (all p<0.01). In contrast, the players high speed running distance per minute (>14.5 km h(-1), HSR/min), sprints/min and peak speed were higher in losing quarters (all p<0.01). Smaller score margins were associated with increased physical activity (m/min, HSR/min, and body load/min, all p<0.05) and decreased skill efficiency (handball clangers/min and player rank/min, all p<0.05). CONCLUSIONS: Professional AF players are likely to have an increased physical activity profile and decreased skill involvement and proficiency when their team is less successful.

Factors affecting match performance in professional Australian football.

OBJECTIVES: To determine the physical activity measures and skill-performance characteristics that contribute to coaches' perception of performance and player performance rank in professional Australian Football (AF). DESIGN: Prospective, longitudinal. METHODS: Physical activity profiles were assessed via microtechnology (GPS and accelerometer) from 40 professional AF players from the same team during 15 Australian Football League games. Skill-performance measure and player-rank scores (Champion Data Rank) were provided by a commercial statistical provider. The physical-performance variables, skill involvements, and individual player performance scores were expressed relative to playing time for each quarter. A stepwise multiple regression was used to examine the contribution of physical activity and skill involvements to coaches' perception of performance and player rank in AF. RESULTS: Stepwise multiple-regression analysis revealed that 42.2% of the variance in coaches' perception of a player's performance could be explained by the skill-performance characteristics (player rank/min, effective kicks/min, pressure points/min, handballs/min, and running bounces/ min), with a small contribution from physical activity measures (accelerations/min) (adjusted R2 = .422, F6,282 = 36.054, P < .001). Multiple regression also revealed that 66.4% of the adjusted variance in player rank could be explained by total disposals/min, effective kicks/min, pressure points/min, kick clangers/min, marks/min, speed (m/min), and peak speed (adjusted R2 = .664, F7,281 = 82.289, P < .001). Increased physical activity throughout a match (speed [m/min] ß - 0.097 and peak speed ß - 0.116) negatively affects player rank in AF. CONCLUSIONS: Skill performance rather than increased physical activity is more important to coaches' perception of performance and player rank in professional AF.

Physiological and performance responses to a training camp in the heat in professional Australian football players.

PURPOSE: To examine the physiological and performance responses to a heat-acclimatization camp in highly trained professional team-sport athletes. METHODS: Eighteen male Australian Rules Football players trained for 2 wk in hot ambient conditions (31-33°C, humidity 34-50%). Players performed a laboratory-based heat-response test (24-min walk + 24 min seated; 44°C), a YoYo Intermittent Recovery Level 2 Test (YoYoIR2; indoor, temperate environment, 23°C) and standardized training drills (STD; outdoor, hot environment, 32°C) at the beginning and end of the camp. RESULTS: The heat-response test showed partial heat acclimatization (eg, a decrease in skin temperature, heart rate, and sweat sodium concentration, P < .05). In addition, plasma volume (PV, CO rebreathing, +2.68 [0.83; 4.53] mL/kg) and distance covered during both the YoYoIR2 (+311 [260; 361] m) and the STD (+45.6 [13.9; 77.4] m) increased postcamp (P < .01). None of the performance changes showed clear correlations with PV changes (r < .24), but the improvements in running STD distance in hot environment were correlated with changes in hematocrit during the heat-response test (r = -.52, 90%CI [-.77; -.12]). There was no clear correlation between the performance improvements in temperate and hot ambient conditions (r < .26). CONCLUSION: Running performance in both hot and temperate environments was improved after a football training camp in hot ambient conditions that stimulated heat acclimatization. However, physiological and performance responses were highly individual, and the absence of correlations between physical-performance improvements in hot and temperate environments suggests that their physiological basis might differ.