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Med J Aust 2000; 173 Suppl 7 August: S6

Children who participate in sport have increased energy needs. However, very little is known about the exact energy requirements of young athletes.¹⁵ If energy needs are not met, chronic negative energy balance during growth can lead to short stature and delayed puberty, menstrual irregularities, reduced bone mineral density, increased incidence of injuries and risk of developing eating disorders.¹⁵ If energy intake is sufficient it is likely that athletic children will obtain adequate nutrients.

Although protein needs are increased during the growing years, there have not been enough studies published to support recommendations for high protein intake for child athletes.¹⁶ We know the recommended intake of protein is higher for adults who exercise to account for gains in lean body mass, to compensate for protein used as a fuel source during physical activity and in muscle regeneration.¹⁷ Therefore, it may be appropriate to suggest that young athletes also have higher protein needs than the other children to help meet these increased demands. Lemon suggests that, if total energy intake from a nutritionally balanced diet meets energy expenditure, protein needs of between 1.2-2 g per kilogram body weight per day should be met.¹⁷ The recommended protein intake for normally active children aged 5-11 years is 1 g per kilogram body weight per day.¹⁸

While the benefits of high carbohydrate diets for enhancing athletic performance are well documented, there is a paucity of data on the carbohydrate requirements of young athletes.¹⁶ Therefore, until more information becomes available, carbohydrate recommendations for young athletes are similar to those recommended for adults (around 55% of total energy).¹⁹ To meet their carbohydrate needs, active children should base their meals on carbohydrate-rich foods as well as including nutritious high-carbohydrate snacks between meals. There are no data on glycogen resynthesis rates in young athletes, but, from a practical perspective, a snack or drink rich in carbohydrate is recommended as soon as possible after sport or strenuous physical activity.¹⁶

Maintaining adequate hydration is crucial for the prevention of heat stress. It has been suggested that children have less developed, and therefore less efficient, thermoregulatory mechanisms than adults. Children produce more body heat per kilogram of body weight than adults, but their ability to transfer heat from the centre of the body to the skin by blood is less effective.²⁰ Children sweat less than adults, and their sweating threshold (the core temperature when sweating starts) appears to be higher. When environmental temperatures exceed core temperature, children may be more exposed to the heat than adults because of their higher body surface area to body mass ratio. Thus, they are more vulnerable to heat gain and a great deal of caution is required. Children most at risk of heat stress are those who are overweight, unfit and unacclimatised.²¹ Children who exercise in the heat should be monitored closely for signs of heat stress.²²

Children rarely drink enough to replenish fluid losses, even when fluid is offered freely. Sports Medicine Australia recommends that active children drink 150-200 mL of fluid 45 minutes prior to exercise, plus an additional 75-100 mL every 20 minutes during exercise.²³ After exercise, a liberal amount of fluid should be consumed as soon as possible.

While water is often described as the best choice of fluid, during periods of vigorous physical activity a sports electrolyte-replacement drink may help children rehydrate more effectively. Studies on voluntary drinking habits and flavour preferences in children also suggest that they drink more fluids when sports drinks are offered instead of water.²⁰

Karen E Inge

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