ABSTRACT
A consequence of growing participation in sports by children and adolescents has been greater focus on training and competition. In order to manage this emphasis
on youth athletes and to temper an increasingly competitive environment, the Long-Term Athlete Development (LTAD) model has been proposed as a means of combining the cultivation of ‘athletic potential’ with the concerns of ‘biological growth’ (Balyi and Hamilton, 2004; Ford et al., 2011). By identifying ‘windows of opportunity’, or sensitive periods of growth and development (Balyi and Hamilton, 2004), the LTAD model can provide an outline for specific nutritional considerations (Table 13.1). For the purpose of this chapter, we will term the nutritional approach to youth athlete development with the use of the LTAD framework, the LTND model. The LTND model should be considered, at minimum, a companion to the growing and well-deserved attention garnered by the LTAD model or, possibly, a necessary precursor that would allow for the participation of young athletes in their respective activities. The general domains or stages of the proposed LTND model would include: Eat to develop, Learn to eat, Eat to grow, Eat to train and Eat to win. Similar to previous convention and for the sake of convenience, chronological age will be used to describe these stages, but it is important to remember that these windows of opportunity are not simply demarcated by years and that both biological and training age must also be considered. The first two stages of the LTND model coincide with general growth and development as well as a period of increasing physical literacy (Ford et al., 2011). Eat to develop is associated with the time period of 6-9 years of age, while Learn to eat is associated with the age of 9-12 years old, both of which have been related to periods of peak brain maturation (Balyi and Hamilton, 2004; Borms, 1986; Ford et al., 2011; Rabinowicz, 1986). With regard to the Eat to develop stage, it is important that all children, especially those with heightened activity levels, meet the necessary requirements for the macro-and micro-nutrients. Basic nutrition at home and school should be strictly emphasized to meet the demands of the various
TABLE 13.1 Comparison of the LTAD and LTND models
Developmental focus Typical age span Long-term athlete development model
Long-term nutritional development model
Physical literacy Males: 6-9 years old Females: 6-8 years old
FUNdamentals Eat to develop
Males: 9-12 years old Females: 8-11 years old
Learning to train Learn to eat
Physical and mental capacity
Males: 12-16 years old Females: 11-15 years old
Training to train Eat to grow
Males: 16-23 years old Females: 15-21 years old
Training to compete Eat to train
High performance Males: 19 years and older Females: 18 years and older
Training to win Eat to win
development processes tied to this age span. The habit of consuming breakfast to start the day should be highlighted with the benefit of improved cognitive performance and a decreased likelihood for obesity (Hoyland et al., 2009; Rampersaud et al., 2005; Szajewska and Ruszczynski, 2010). The Learn to eat stage typically coincides with pre-pubescence, a period of development previously associated with the development of more complex movement skills and cognitive processes, including motor development (Ford et al., 2011). This stage should include an element of nutritional education and ownership of dietary choices for children (Oliver et al., 2011). Education should be comprised of proper food selection, primarily balance among different types of healthy foods, as well as the concepts of moderation, portion control and proper snacking, which will lead to improved decision-making in future sporting (and life) endeavours. The lessons learned in the Learn to eat stage are crucial to support the numerous physiological changes associated with puberty and sexual maturation during the Eat to grow stage. The Eat to grow stage occurs between the ages of 12 and 16 years old and coincides with accelerated growth (peak height and weight velocity) as well as emotional and cognitive development (Ford et al., 2011). The LTAD model characterizes this period as the Training to train stage (Balyi and Hamilton, 2004) and specific attention should be devoted to meeting or exceeding energy expenditure requirements through nutrient-dense caloric intake in order to support both the increased developmental processes and augmented physical training loads (Oliver et al., 2011; Petrie et al., 2004). An additional 500 kilocalories per day has been recommended during times of rapid growth in adolescents (Hoch et al., 2008). This increase in energy intake should be addressed through the consumption of nutrient-rich food choices as opposed to ‘empty calories’, such as refined sugars or saturated fats. In particular, calcium for bone growth and iron to support hemoglobin production should be attained through the diet during this sensitive period of development (American Academy of Pediatrics, 2000). The LTAD model is characterized by a developmental adjustment with girls approaching this stage prior to boys, however, the daily nutrition and energy recommendations should be similar regardless of sex. During the Eat to train stage, it is helpful to distinguish between energy balance and energy availability. The Eat to train stage encompasses the age span between 16 and 20 years old. Energy balance is the trade-off between energy expenditure and energy intake throughout the day, while energy availability is the difference between energy intake and the energy needed for physical activity in the form of exercise (Loucks et al., 2011). Energy balance should be maintained during this transition period, which is associated with concomitant increases in the rate of muscular development due to changes in the hormonal milieu and physical training loads (Ford et al., 2011; Janssen, 2007; Petrie et al., 2004). Energy availability is of concern due to the benefits of nutrient timing on training and recovery in young athletes. Nutrient timing recommendations may need to be adjusted to support individual training needs and will be discussed in greater detail in this chapter.
