Kids Nutrition & Hydration during Training
Nutrition for children and adolescent athletes are very different to those of adults. There are limited studies and information on this topic largely due to ethical considerations. There are however a lot of facts on how the young body works and from that conclusions and guidelines have been made for reference to nutrition during training or competing for young athletes.
Glycogen depletion is a major cause of fatigue in both endurance and high-intensity exercise or sports for young athletes. Endogenous glycogen stores are lower in young athletes especially pre-pubertal athletes as they do not have the same capacity to store glycogen as adults. Kids have a higher metabolic cost of movement per body mass than adults, i.e. they have lower gross efficiency.
In young athletes, Activity Energy Expenditure is the greatest contributor to Total Energy Expenditure, and it is the most variable component as it is influenced by body size and locomotion (type, duration and intensity of exercise). The results are large variability in Energy Expenditure between young athletes and the requirements of Total Energy Expenditure can vary day-to-day.
The energy intake of each young athlete should be dictated by their Total Energy Expenditure.
TEE = BMR (Basal Metabolic Rate) +
TEF (Thermic Effect of Food) +
Activity EE (Energy Expenditure)
Children oxidise relatively more fat than CHO when compared to adults during exercise at a similar intensity.
Hormonal responses to exercise can contribute to maturity-related differences in fuel metabolism between adults and children. When exogenous carbohydrate is consumed during exercise, the oxidation rate of exogenous carbohydrate, relative to body mass, is higher in children and adolescents compared to adults. Young athletes will benefit from ingestion of CHO during exercise. There are no specific rates recommended for young athletes so we must rely on the recommendations of adults. For young athletes the recommendation will be anything from 30-60g CHO/h. But not more than 1g CHO/min.
It is also recommended that children take CHO after training to restore the glycogen stores. Post exercise protein will also replenish, repair, remodel and help with growth and development. Studies have shown that protein doesn’t help performance but will assist in short term inflammatory response as there is an increase in the anti-inflammatory marker IL-10.
Hydration status during sport is important to performance in young athletes.
Electrolyte losses through sweating is different in young athletes compared to adults. Children sweat less than adults but depend more on skin blood flow to cool down. Children are also more susceptible to dehydration. Dehydration can also be more detrimental in children than adults. Due to their increased susceptibility to succumb to heat illness, hydration is a more important consideration in young athletes than in adults. In addition to an increased body surface area to body mass ratio children have been shown to have diminished sweat rates as compared to adults. Diminished sweat rates are advantageous as a result of the protection of body water, but disadvantageous due to the reduced ability to dissipate heat. Added importance of hydration is the fact that, in addition to performance reduction, hypohydration has been shown to lead to increased physiological strain, increased risk of heat illness, and increased perceived exertion at similar workloads. As a result of hypohydration, the body experiences fluid shifts resulting in increased cardiovascular strain as plasma volume declines. Additionally, the impaired cardiovascular function also leads to diminished skin blood flow resulting in a decline in the ability to dissipate heat.
What then is the recommended fluid intake for children. Anything from 5-11ml/kg/h but the sport and environment will also dictate how much they should be drinking.
Coaches and parents should be involved in the decision making as common sense will be needed for every individual child to make sure that the best feeding and hydration plan is in place for the young athlete.
Source: Marcus Hannon, Graeme Close, James P Morton
Flavia Meyer, Helen O’Connor
John Eric W. Smith, Megan E. Holmes, and Matthew J. McAllister.
