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SPORTS NUTRITION & THE MODERN ATHLETE
SPORT AND
PERFORMANCE NUTRITION
FOR THE COMPETITIVE
ADOLESCENT ATHLETE
– Written by Marcus Hannon, United Kingdom and Nelda Nader, Qatar
competitive1 biological age have been well documented
INTRODUCTION . The competitive adolescent
Adolescence generally refers to a period of athlete “demonstrate gifts talents in the in the same age groups across different
2
sports
life in young adults between 12 and 18 years. physical, physiological, or movement . Due to the challenges in obtaining
Recent interest in young athletes has domains which may indicate future potential accurate energy intake and expenditure in
led to more research efforts in this field. in high performance sport”. They are set this population, monitoring rate of growth
However, sports nutrition research in apart from the wider ‘active’ population, (e.g. stature and body mass) and maturation
adolescent athletes remains in its infancy. who, may be engaged in formal competition (such as somatic maturation, e.g. maturity
Despite the limited scientific literature, key and regular training, however are unlikely offset, i.e. time from PHV) regularly to track
principles are well established as general to have the same physical demands as their an individual’s progress remains key.
best practice. Adopting a food first approach, “competitive” peers. Modern-day pressures have a significant
structuring good nutrition support around This article considers the latest
impact on young athletes’ eating behaviours.
the physiological demands of the sport and nutritional recommendations and research Peers, team mates, professional athletes,
consideration of sport specific nuances are in the context of competitive adolescent coaches and the media all have significant
principles valid for both adults and junior athletes including how nutrition can effects which can cause vulnerability,
athletes. However, direct application of change during periods of injury and the spectrum of which is wide from poor
certain adult practices to the adolescent rehabilitation. oral health, restrictive eating, unhealthy
athlete is generally not appropriate. This is eating practices to disordered eating. The
due to younger athletes undergoing many focus when working with adolescent
WORKING WITH COMPETITIVE
anatomical, physiological and metabolic ADOLESCENT ATHLETES athletes should be on achieving nutritional
changes during growth that require specific Physiologically, growth and maturation requirements for optimal growth,
considerations. are complex processes influenced by the maturation and physical development as
A recent position statement defined interaction of genes, hormones, nutrients well as making sure adequate energy and
two categories of adolescent athletes in and the environment in which an individual macronutrient intake can support training
the context of sports nutrition: active and lives. Differences between chronological and loads.
18
ENERGY AND THE ADOLESCENT ATHLETE: energy required for tissue growth (~5 kcal have greater relative energy demands than
HOW MUCH IS ENOUGH? per gram of weight increase)6 adults5
. , ≥45 kcal·kg FFM-1·day-1 is likely
The energy intake of each adolescent to be the minimum energy availability
athlete should be based on their total AVOIDING LOW ENERGY AVAILABILITY an adolescent athlete would require.
daily energy expenditure (TEE) (i.e. their (LEA) Difficulties in accurately quantifying energy
energy requirements) to optimise not only Energy availability is the amount of availability have resulted in few studies
growth and maturation but also stimulate energy left for homeostatic physiological reporting this in adolescent athletes. Studies
training adaptations, promote recovery functions, thermoregulation and growth. have reported mean energy availabilities
and sport performance. Before giving Low energy availability can increase the of ~ 29 kcal·kg FFM-1·day-1 in young male
specific macronutrient recommendations 7 and female athletes (11-25 years old), that
risk of overreaching and is associated with
it is first essential to understand the energy iron deficiency which may exacerbate some competed in a range of sports at national
expenditures of adolescent athletes. of the outcomes of low-energy availability or international level8
to 69 ± 10 kcal·kg
The highly variable rates of growth such as fatigue8 FFM-1·day-1, 51 ± 9 kcal·kg FFM-1·day-1 and
. Not only is low-energy
amongst adolescent athletes, particularly availability likely to have a negative 41 ± 15 kcal·kg FFM-1·day-1 in U12/13, U15 and
around peak height velocity (the maximum effect on an adolescent athlete’s sporting U18 respectively in English Premier League
rate of growth in stature during adolescence), 5
performance and development it may also academy soccer players .
influence an individual’s energy
affect their long-term health. Whilst under-reporting of energy
requirements, particularly their resting intake does occur in adolescent athletes,
metabolic rate (RMR). These increases in Energy Availability = (energy intake – available data would still suggest that low
RMR are coincided with increases in stature, physical activity energy expenditure) / FFM). EA is common particularly in adolescent
body mass (BM), fat-free mass (FFM) and basketball players11 12
and swimmers .
maturity status3,4 Due to day to day variation in contributing
.
Activity energy expenditure is the most factors, it is difficult to prescribe exact energy MACRONUTRIENT AND HYDRATION
variable contributor to TEE and in adolescent requirements for adolescent athletes10
. REQUIREMENTS
athletes often the greatest contributor to TEE. Instead, it is strongly recommended to avoid Owing to the limited data on the typical total
Exercise type, duration and intensity as well low energy availability and ensure adequate energy expenditures (Table 1), it is currently
as an athlete’s anthropometric profile will energy availability (EA) for growth. difficult to accurately recommend specific
all influence activity energy expenditure Chronic low-energy availability (defined macronutrient requirements for adolescent
(and thus total energy expenditure), leading as <30 kcal·kg FFM-1·day-1 in adults) may athletes training and competing in different
to a large inter-individual variability in TEE lead to relative energy deficit in sport sports. This is reflected in recent position
between adolescent athletes. Even within (RED-S)9 statements on adolescent athletes, where
. Considering adolescent athletes
the same sport, differences in training and
competition loads and anthropometric
profiles amongst different age-groups COMPONENTS OF TOTAL ENERGY EXPENDITURE
can lead to differences in total energy
expenditure and subsequent energy TEE comprises of three main
requirements. components:
For example, the TEE of academy soccer 1. Resting metabolic rate (RMR);
players was recently established in three the energy required to
different age-groups. U18 players presented maintain homeostatic
with a TEE (3586 ± 487 kcal·day-1; range: Activity enegry expenditure physiology at rest);
2542-5172 kcal·day-1) that was approximately 2. Thermic effect of food / diet
600 and 700 kcal·day-1 higher than both the induced thermogenesis (the
U15 (3029 ± 262 kcal·day-1; range: 2738-3726 energy costs of digestion,
kcal·day-1) and U12/13 (2859 ± 265 kcal·day-1; (N.B. highly variable!) absorption, transport,
range: 2275-3903 kcal·day-1) age-groups metabolism and storage of
Thermic effect of food food and drink), and
respectively5
. There was also large individual 3. Energy expenditure from
variation in TEE within each age-group with planned physical activity and
individual variation of approximately 1600, non-exercise activity
1000 and 2600 kcal·day-1 in the U12/13, U15 thermogenesis.
and U18 squads, respectively within the Resting metabolic rate (RMR)
same week. This highlights the importance
of adopting an individualised and sport-
specific approach to energy intake based on
energy expenditure.
In addition to the standard components
making up TEE, adolescent athletes also Figure 1: Components of total energy expenditure.
have a small but important amount of
SPORTS NUTRITION: SUPPORTING A CHANGING GENERATION TARGETED TOPIC 19
SPORTS NUTRITION & THE MODERN ATHLETE
Table 1
Sport Sex Age Stature Body Mass (kg) Training & Study TEE
(years) (cm) Competition Load Duration (kcal.day-1)
Basketball M & F M: 17.0 ± 0.7 M: 192.5 ± 6.4 M: 80.9 ± 7.7 >10 hours per 7 7 days M: 4626 ± 682
(9) F: 16.9 ± 0.7 F: 173.1 ± 3.3 F: 64.0 ± 5.4 days F: 3497 ± 242
Rugby U16: 15.2 ± 0.8 U16: 180.8 ± 7.0 U16: 79.3 ± 17.1 U16: 4186 ± 946
League M U20: 17.6 ± 1.1 U20: 176.8 ± 3.8 U20: 87.6 ± 8.8 - 14 days U20: 4475 ± 748
(11)
Rugby U16: 15.6 ± 0.5 U16: 182.1 ± 7.5 U16: 85.4 ± 17.3 U16: 3834 ± 521
Union M U20: 18.3 ± 0.5 U20: 178.1 ± 3.5 U20: 85.1 ± 8.3 - 14 days U20: 4338 ± 709
(11)
(Per 14 days) U12: 2859 ± 265
U12: 12.2 ± 0.4 U12: 157.1 ± 4.1 U12: 43.0 ± 4.8 U12: 659 ± 81 min (range: 2738 – 3726)
Soccer U15: 869 ± 72 min U15: 3029 ± 262
(4) M U15: 15.0 ± 0.2 U15: 173.9 ± 5.6 U15: 56.8 ± 6.2 U18: 846 ± 39 min 14 days (range: 2275 – 3903)
U18: 17.5 ± 0.4 U18: 181.2 ± 5.2 U18: 73.1 ± 8.1 U12: 38.3 ± 5.1 km U18: 3586 ± 488
U15: 53.7 ± 4.5 km (range: 2806 – 5172)
U18: 54.4 ± 7.1 km
Speed 918 ± 42 min 4013 ± 908
Skating M 18.2 ± 1.3 179.0 ± 3.0 75.7 ± 7.0 per 10 days 10 days (range: 3057 – 5971)
(12)
Gymnastics M & F 7.6 ± 0.7 116.3 ± 2.4 20.0 ± 1.7 4 hours per day 10 days 2004 ± 258
(13)
Swimmers F 19 ± 1 178.3 ± 2.2 65.4 ± 1.6 ~5-6 hours per day 5 days 5589 ± 502
(10)
Table Tennis M 20 ± 1 168.7 ± 4.1 58.9 ± 7.9 ~3 hours per day 14 days 3695 ± 449
(14)
M=males. F=females. TEE=total energy expenditure.
Table 1: Total energy expenditures of adolescent athletes from different sports (assessed via the doubly labelled water technique).
little evidence exists to suggest that replacement for adolescent athletes can be CALCIUM AND VITAMIN D
carbohydrates, protein and fat needs differ similar to the ones for adults. As a key regulator of calcium homeostasis,
from adults athletes. However, these needs Young athletes under consume fluids Vitamin D is required in adequate levels
should enable a young athlete to “fuel for required during prolonged exercise. Simple for calcium absorption. Sufficient vitamin
the work required” for carbohydrate and/ strategies especially in hot and humid D levels and calcium are therefore
or heightened protein needs during periods conditions should be used. These can crucial to ensure maximal bone mineral
of increased strength training or unique include, the addition of flavourings water, accumulation in developing adolescent
periods of activity reduction such as injury use of ice slushies and planned fluid breaks athletes. Around 95% of adult bone
or off-season. during training/competition. The use of mineral content is achieved by the end of
Despite the importance of hydration to sports drinks should be avoided for shorter adolescence, with ~26% of this accruing
human health (and performance), there exercise periods, and when they are used, during peak bone mineral content
remains a noticeable lack of any current good oral health practices after 30 minutes velocity (~12.5 and ~14 years old in girls
guidelines specific to adolescents on fluid of finishing exercise should be encouraged and boys respectively)13. During peak bone
guidelines and replacement. Heat loss to reduce the risk of dental decay. mineral content velocity skeletal calcium
through sweat will result in fluid and accretion is ~300mg per day14
. Ensuring
electrolyte loss in adolescents just as adults. MICRONUTRIENTS maximal bone mineral content accrual is
However, there are differences in sweat Whilst it is essential that adolescent of paramount importance for adolescent
rates between adults and adolescents, but it athletes consume adequate amounts athletes, to maximise peak bone mass and
appears reduced sweat rate does not impair of all micronutrients, iron, calcium and help reduce the risk of skeletal injuries
heat loss during exercise in the young. vitamin D continue to receive the greatest (e.g. stress fractures) and osteoporosis in
Therefore, the recommendations on fluid attention. adulthood.
20
Historically, adolescent athletes across growth in tissues. The onset of menstruation protein powders being the most prevalent
26
multiple sports fail to meet their daily in females results in iron losses, increasing (54%) .
15 22
calcium requirements . Various strategies their requirements further . Exercise can Recommended sports nutrition
are proposed as triggers to mitigate result in iron loss through haemolysis, principles of using a food first approach i.e.
issues. For youth athletes, this includes as well as in urine, stool and sweat. Iron eating the right amounts of the right types
consumption of a calcium rich snack/ deficiency is highly prevalent amongst of food at the right times remains, in many
meal prior to exercise to attenuate bone adolescent athletes (up to 50% in females), cases, enough for the competitive adolescent
16 athlete to meet their needs. This approach is
resorption (i.e. bone breakdown) . with inadequate dietary iron intake (often
In addition to its involvement in calcium concomitant with inadequate energy intake supported by the latest expert consensus
homeostasis, vitamin D is also involved in and/or a vegetarian diet) often the main groups respective statements on nutrition
23 in sport1,28,29,30
supporting immune function and skeletal cause of iron deficiency . . Sports drinks, sports foods
muscle regeneration17 Symptoms such as fatigue sensation and and in some instances, carbohydrate gels
. Although a blanket
approach to vitamin D3 supplementation decreased performance can be associated to remain the only supplements of potential
is not advised, a common approach is to iron deficiency with or without anaemia. value for competitive adolescents together
supplement athletes with during winter Improving iron status in deficient individuals with supplementation based on clinical
24
months when sun exposure is limited can improve exercise efficiency and needs. These can include iron, vitamin D and
even without testing vitamin D status18 reduce fatigue25 omega 3.
. . Thus, testing of adolescent
Particular attention should be given to athletes who present symptoms associated Certain supplements e.g. creatine, beta
adolescent athletes that train and compete with iron deficiency (e.g. during regular alanine, beetroot juice, caffeine may have
indoors all year round19 medical check-up) will inform appropriate an ergogenic effect in specific sporting
.There is limited
evidence for vitamin D3 supplementation treatment strategies. Iron supplementation situations in adult athletes as part of a
having an ergogenic effect on athletic should only be taken following advice from well-planned approach. However, these
performance. Conversely, deficiency impairs a qualified professional. supplements should be sparingly used with
musculoskeletal health and increases the adolescent athletes. The use of creatine is
risk of injury in adolescent athletes20 PERFORMANCE NUTRITION AND THE common in the latter years of academy
. This
may also extend to reduced power and force COMPETITIVE ADOLESCENT development programs (17-18 years)
output in adolescent females 21. Supplement use in competitive adolescent despite the lack of data on its safe use in
athletes is wide spread. Recent surveys young athletes. However, use amongst this
IRON highlight 82.2% of athletes aged 15-18 years, population appears to be well-tolerated and
During childhood and adolescence, iron competing at international level, in different holds ergogenic effects, including improved
requirements are increased as a result of sports are taking sports supplements, with sprinting capacity, and lower body power
Table 2
U13
Type of Session Description (number U14 U15 U16 U18
of
sessions)
Technical and tactical soccer specific training
Pitch-based 60-90 minutes 5 5 5 5 6
Age adapted volume & intensities
U13: BM movement
30 minutes
Gym-based 4-6 exercices x 3 sets x 8-10 repe-titions 3 3 3 3 4
U14-U18 : external load inclusion
45 minutes
6-8 exercices x 2-4 sets x 5-10 re-petitions
Active recovery and regeneration
Yoga-based Stretching and movement competency 1 1 1 1 1
30 minutes
Competitive 1 1 1 1 1
match-play
U: under- Adapted from Hannon, Carney, et al., 2020
Table 2: Typical week in-season schedule for Premier League male Category 1 adolescent players.
SPORTS NUTRITION: SUPPORTING A CHANGING GENERATION TARGETED TOPIC 21
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