Energy requirements of male academy soccer players from the English Premier League

The goal of professional soccer academies is to develop players who can progress and represent their first team or that can be sold for financial gain. As an academy player transitions through the academy pathway (i.e. from under, U9 to U23), they undergo distinct phases of growth and maturation that result in anatomical (e.g. an increase in stature and body mass), physiological (e.g. an increase in growth hormone, insulin-like growth factor 1, testosterone and thyroid hormones) and metabolic changes (e.g. increased glycolytic capabilities). The collective result of such changes are likely to influence such daily energy requirements. However, unlike professional adult players, the body composition, physical loading patterns and associated daily energy expenditure have not yet been quantified in academy soccer players. A detailed understanding of such parameters is fundamental in order to promote growth and maturation whilst also maximising each players physical and technical development. With this in mind, the aim of this thesis was to determine the energy requirements of male academy soccer players from the English Premier League of different chronological and biological ages. The aim of Study 1 (Chapter 4) was to assess body composition and resting metabolic rate in a cohort of academy soccer players. In a cross-sectional design, ninety-nine males from a Category One English Premier League academy (U12-U23 age-groups) underwent assessments of body composition (dual-energy X-ray absorptiometry, DXA) and resting metabolic rate (indirect calorimetry). Fat-free mass increased between the U12 (31.6 ± 4.2 kg) and U16 (56.3 ± 5.3 kg) age-groups after which no further increases occurred. Resting metabolic rate in the U12 (1655 ± 195 kcalday-1), U13 (1720 ± 205 kcalday-1) and U14 (1846 ± 218 kcalday-1) age-groups was significantly lower than the U15 (1957 ± 128 kcalday-1), U16 (2042 ± 155 kcalday-1), U18 (1875 ± 180 kcalday-1) and U23 (1941 ± 197 kcalday-1) age-groups. These data provide the first report of differences in body composition and resting metabolic rate in academy soccer players (as assessed via DXA and indirect calorimetry, respectively) and demonstrate that the growth and maturation occurring between U12-U16 significantly increases resting energy requirements. Having quantified body composition and resting metabolic rate in Study 1 (Chapter 4), the aim of Study 2 (Chapter 5) was to determine the typical weekly training and match loading patterns of academy soccer players. Over the course of an entire competitive season, weekly training and match load was quantified using global positioning system technology in 76 soccer players from a Category One English Premier League academy (U12-U18 age-groups). Weekly training and match volume (i.e. duration and total distance) was similar in the U12 (329 ± 29 min; 19.9 ± 2.2 km), U13 (323 ± 29 min; 20.0 ± 2.0 km) and U14 (339 ± 25 min; 21.7 ± 2.0 km) age-groups, but was lower than the U15 (421 ± 15 min; 26.2 ± 2.1 km), U16 (427 ± 20 min; 25.9 ± 2.5 km) and U18 (398 ± 30 min; 26.1 ± 2.6 km) age-groups. Weekly high-speed running and sprint distance (i.e. intensity) were comparable in the U12 (220 ± 95 m and 6 ± 9 m respectively), U13 (331 ± 212 m and 6 ± 27 m) and U14 (448 ± 193 m and 21 ± 29 m) age-groups was similar, but less than the U15 (657 ± 242 m and 49 ± 98 m), U16 (749 ± 152 m and 95 ± 55 m) and U18 (979 ± 254 m and 123 ± 56 m) age-groups. These data provide the first 4 report to objectively assess accumulative training and match loads in academy soccer players and demonstrate that the absolute loads are progressive in nature throughout the academy pathway. Given the progressive changes in body composition (Study 1, Chapter 4), resting metabolic rate (Study 1, Chapter 4) and physical loading patterns (Study 2, Chapter 5), the aim of Study 3 (Chapter 6) was to quantify the total daily energy expenditure of academy soccer players with different chronological and biological ages. Energy expenditure (doubly labelled water) and energy intake (remote food photographic method) was assessed over a 14-day in-season period in 24 soccer players from a Category One English Premier League academy (U12/13, n=8; U15, n=8; U18, n=8). U18 players presented with greater total energy expenditure (3586 ± 487 kcalday-1) than both the U15 (3029 ± 262 kcalday-1) and U12/13 players (2859 ± 265 kcalday-1), though no differences were evident between the U12/13 and U15 age-groups. Within age-groups, no differences were apparent between energy intake and total energy expenditure, whilst U18 players (3180 ± 279 kcalday-1) reported a higher energy intake than both the U15 (2821 ± 338 kcalday-1) and U12/13 (2659 ± 187 kcalday-1) players. In some individuals (evident in all age-groups) total energy expenditure was greater than that previously observed in adult English Premier League soccer players (3566 ± 585 kcalday-1). In summary, the data presented in this thesis provides the first report to simultaneously quantify body composition, resting metabolic rate, physical loading patterns and total daily energy expenditure of academy soccer players. Importantly, these data demonstrate that players’ absolute daily energy expenditure progressively increase as they become more biologically mature, likely a reflection of increased fat-free mass and physical loading patterns. From a practical perspective, these data will assist in developing population specific sport nutrition guidelines

Energy and Macronutrient Considerations for Young Athletes

Young athletes undergo many anatomical and physiological changes during the first 2 decades of life as a result of growth and maturation. Such changes influence a young athlete's nutritional requirements and it is therefore inappropriate to apply nutritional guidelines for adult athletes to this population. Nutritional recommendations for young athletes should not only focus on sporting performance but should also meet the requirements to ensure optimal growth, maturation, and physical development. This review article provides an overview of the nutritional recommendations for young athletes based on the best available literature from a range of sports

Where do you go when your periods go?: A case-study examining secondary amenorrhea in a professional internationally-capped female soccer player through the lens of the sport nutritionist.

This case study follows a professional internationally capped female soccer player's two-year journey from eumenorrhea, through injury, to amenorrhea, and the challenges faced by the player and nutritionist. The two years are split into three sections: (1) longitudinal profiling of the player, (2) nutrition to support her return from injury, and (3) investigation into the observed secondary amenorrhea. The cause of amenorrhea was investigated through the assessment of energy availability via doubly labelled water, remote food photography, blood biomarkers and resting metabolic rate. Despite having secondary amenorrhea and anovulatory cycles, the player did not have low energy availability. This study shows the importance for practitioner's, particularly nutritionists, to not assume that all menstrual irregularities are caused by low energy availability and could be caused by a combination of factors (e.g. clinical, physiological, and psychological), which requires a multi-disciplinary investigation and intervention team. This study also showed that education needs to be provided about menstrual health to elite female soccer players as the player (i) believed that not having a period was beneficial for performance and unsure of possible health implications; (ii) was convinced that a one-day bleed indicated a regular menstrual cycle; and (iii) was reluctant to waste the practitioners time discussing menstrual issues and was nervous of finding out if she had an actual health issue. It is therefore crucial that players feel comfortable in discussing their menstrual status with practitioners to support their performance and long-term health

An audit of performance nutrition services in English soccer academies: implications for optimising player development

To audit the current provision of performance nutrition services provided to male adolescent players within academies from the English soccer leagues. Practitioners from all 89 academies (status categorised as one-four according to the Elite Player Performance Plan, EPPP) completed an online survey to audit: a) job role/professional accreditation status of persons delivering nutrition support, b) activities inherent to service provision, c) topics of education, d) on-site food, fluid and supplement provision and e) nutritional related data collected for objective monitoring. More full-time accredited nutritionists are employed within category one (14/26) versus category two (0/18), three (1/41) and four (0/4). Respondents from category one clubs report more hours of monthly service delivery (62 ± 57 h) than category two (12 ± 9 h), three (14 ± 26 h) and four (12 ± 14 h), inclusive of one-to-one player support and stakeholder education programmes. Category one practitioners reported a greater prevalence of on-site food, fluid and supplement provision on training and match days. Across all categories, players from the professional development phase receive more frequent support than players from the youth development phase, despite the latter corresponding to the most rapid phase of growth and maturation. We report distinct differences in the extent of service provision provided between categories. Additionally, players from all categories receive nutrition support from non-specialist staff. Data demonstrate that performance nutrition appears an under-resourced component of academy sport science and medicine programmes in England, despite being an integral component of player development

Acute fuelling and recovery practices of academy soccer players: implications for growth, maturation, and physical performance

Academy soccer players frequently train in the evening (i.e. 1700-2000 h), hence limited time to nutritionally prepare and recover due to schooling, travel and sleep schedules. Accordingly, we assessed timing and quantity of energy intake in the pre-training and post-training period. Over a 3-day in-season training period, male players (n=48; n=8 from under (U) 12, 13, 14, 15/16, 18 and 23 players) from an English Premier League academy self-reported dietary intake and physical activity levels (via the remote food photography method and activity diary, respectively) in the four hours pre- and post-training. Timing of pre-training energy intake ranged from 40 ± 28 mins (U15/U16 players) to 114 ± 71 mins (U18) before training and mean carbohydrate (CHO) intake ranged from 0.8±0.4 g.kg-1 (U23) to 1.5±0.9 g.kg-1 (U12). Timing of post-training energy intake ranged from 39 ± 27 mins (U14) to 70 ± 84 mins (U23) and mean CHO intake ranged from 1.6±0.8 g.kg-1 (U12) to 0.9±0.5 g.kg-1 (U14). In contrast to CHO, all age groups consumed sufficient protein intake in the post-training period (i.e. > 0.3 g.kg-1). We conclude academy soccer players habitually practice sub-optimal fuelling and recovery strategies, the consequence of which could impair growth, maturation and physical performance

Seasonal training and match load and micro-cycle periodization in male Premier League academy soccer players

We quantified on pitch external loading of English Premier League (EPL) academy soccer players (n=76; U12-U18 age groups) over an entire competitive season. Mean accumulative weekly duration and total distance, respectively, was similar in the U12 (329±29 min; 19.9±2.2 km), U13 (323±29 min; 20.0±2.0 km) and U14 (339±25 min; 21.7±2.0 km; P>0.05 for all comparisons) age-groups, though all teams were less than U15 (421±15 min; 26.2±2.1 km), U16 (427±20 min; 25.9±2.5 km) and U18 (398±30 min; 26.1±2.6 km) players (P0.05 for all pairwise comparisons) though all squads were less than U15 (657±242 m and 49±98 m), U16 (749±152 m and 95±55 m) and U18 (979±254 m and 123±56 m) age-groups (P<0.05 for all pairwise comparisons). Data demonstrate that absolute weekly training volume in EPL academy soccer players increases throughout the academy pathway. Furthermore, although U16-U18 players are capable of achieving similar training and match volumes as previously reported in adult EPL players, they do not yet achieve the absolute intensities of adult EPL players

Acute fuelling and recovery practices of academy soccer players: implications for growth, maturation, and physical performance.

Considering that academy soccer players frequently train in the evening (i.e. 17:00-20:00 h), there is often limited time to nutritionally prepare and recover due to schooling, travel and sleep schedules. Accordingly, we assessed the timing and quantity of dietary intake of academy soccer players in the pre-training and post-training period. Over a 3-day in-season training period, male adolescent players (n=48; n=8 from under (U) 12, 13, 14, 15/16, 18 and 23 players) from an English Premier League academy self-reported their dietary intake and physical activity levels (via the remote food photography method and activity diary, respectively) in the four hours before and after training. External training load was also quantified via GPS. Timing of pre-training energy intake ranged from 40 ± 28 mins (U15/U16 players) to 114 ± 71 mins (U18) before training and mean carbohydrate (CHO) intake ranged from 0.8±0.4 g.kg-1 (U23) to 1.5±0.9 g.kg-1 (U12). Timing of post-training energy intake ranged from 39 ± 27 mins (U14) to 70 ± 84 mins (U23) and mean CHO intake ranged from 1.6±0.8 g.kg-1 (U12) to 0.9±0.5 g.kg-1 (U14). In contrast to sub-optimal CHO intakes, all age groups consumed sufficient protein intake in the post-training period (i.e. > 0.3 g.kg-1). We conclude academy soccer players habitually practice sub-optimal acute fuelling and recovery strategies, the consequence of which could impair growth, maturation and physical performance. Player and stakeholder education and behaviour change interventions should therefore target specific behaviours that lead to increased CHO intake before, during and after training

Cross-sectional comparison of body composition and resting metabolic rate in Premier League academy soccer players: Implications for growth and maturation

For the first time we aimed to: (1) assess fat-free mass (FFM) and RMR in youth soccer players, (2) compare measured RMR to estimated RMR using previously published prediction equations, and (3) develop a novel population-specific prediction equation. In a cross-sectional design, 99 males from a Premier League academy underwent assessments of body composition (DXA) and RMR (indirect-calorimetry). Measured RMR was compared to estimated values from five prediction equations. A novel RMR prediction equation was developed using stepwise multiple regression. FFM increased (P0.05). RMR in the U12s (1655±195 kcal.day−1), U13s (1720±205 kcal.day−1) and U14s (1846±218kcal.day−1) was significantly lower than the U15s (1957±128 kcal.day−1), U16s (2042±155 kcal.day−1), U18s (1875±180 kcal.day−1) and U23s (1941±197 kcal.day−1) squads (P>0.05). FFM was the single best predictor of RMR (r2=0.43; P<0.01) and was subsequently included in the novel prediction equation: RMR (kcal.day−1) = 1315 + (11.1 x FFM in kg). Both FFM and RMR increase from 12-16 years old, thus highlighting the requirement to adjust daily energy intake to support growth and maturation. The novel prediction RMR equation developed may help to inform daily energy requirements

Energy Requirements of Male Academy Soccer Players from the English Premier League.

PURPOSE: To inform the energy requirements of highly trained adolescent soccer players, total energy expenditure (TEE) was quantified in academy soccer players from the English Premier League (EPL). METHODS: Twenty-four male adolescent soccer players from an EPL academy (n=8 U12/13; n=8 U15; n=8 U18) were assessed for baseline maturity (maturity offset), body composition (DXA) and resting metabolic rate (RMR; indirect calorimetry). Subsequently, TEE, energy intake (EI) and physical loading patterns were assessed over a 14-day in-season period using doubly labelled water, the remote food photographic method and global positioning system technology, respectively. RESULTS: Under-18 players presented with greater RMR (2236±93 kcal⋅day) and TEE (3586±487 kcal⋅day; range: 2542-5172 kcal⋅day) than both U15 (2023±162 and 3029±262 kcal⋅day, respectively; TEE range: 2738-3726 kcal⋅day) and U12/13 players (1892±211 and 2859±265 kcal⋅day, respectively; TEE range: 2275-3903 kcal⋅day) (all P U15: 42.9±5.8 kg > U12/13: 31.1±3.5 kg; all P<0.01). Within age-groups, no differences were apparent between EI and TEE (U12/13: -29±277 kcal⋅day, P=0.78; U15: -134±327 kcal⋅day, P=0.28; U18: -243±724 kcal⋅day, P=0.37), whilst U18 players (3180±279 kcal⋅day) reported higher EI than both U15 (2821±338 kcal⋅day; P=0.05) and U12/13 players (2659±187 kcal⋅day; P<0.01). CONCLUSION: The TEE of male academy soccer players progressively increase as players progress through the academy age-groups. In some individuals (evident in all age-groups), TEE was greater than that previously observed in adult EPL soccer players

Daily energy requirements of male academy soccer players are greater than age-matched non-academy soccer players: A doubly labelled water investigation

This study aimed to test the hypothesis that the total daily energy expenditure (TDEE) of male academy soccer players is greater than players not enrolled on a formalised academy programme. English Premier League academy (ACAD: n = 8, 13 years, 50 ± 6 kg, 88 ± 3% predicted adult stature, PAS) and non-academy players (NON-ACAD: n = 6, 13 years, 53 ± 12 kg, 89 ± 3% PAS) were assessed for TDEE (via doubly labelled water) during a 14-day in-season period. External loading was evaluated during training (ACAD: 8 sessions, NON-ACAD: 2 sessions) and games (2 games for both ACAD and NON-ACAD) via GPS, and daily physical activity was evaluated using triaxial accelerometry. Accumulative duration of soccer activity (ACAD: 975 ± 23 min, NON-ACAD: 397 ± 2 min; p < 0.01), distance covered (ACAD: 54.2 ± 8.3 km, NON-ACAD: 21.6 ± 4.7 km; p < 0.05) and time engaged in daily moderate-to-vigorous (ACAD: 124 ± 17 min, NON-ACAD: 79 ± 18 min; p < 0.01) activity was greater in academy players. Academy players displayed greater absolute (ACAD: 3380 ± 517 kcal · d−1, NON-ACAD: 2641 ± 308 kcal · d−1; p < 0.05) and relative TDEE (ACAD: 66 ± 6 kcal · kg · d−1, NON-ACAD: 52 ± 10 kcal · kg · d−1; p < 0.05) versus non-academy players. Given the injury risk associated with high training volumes during growth and maturation, data demonstrate the requirement for academy players to consume sufficient energy (and carbohydrate) intake to support the enhanced energy cost of academy programmes