ABSTRACT
Speed is a desirable characteristic that has been associated with successful sports performance in children (Reilly et al., 2000). A failure to fully develop sprint speed during childhood may also restrict opportunities in adulthood, as speed is often reported to distinguish between adults of differing competitive standards (Pyne et al., 2005). Both the ability to accelerate and to attain maximal velocity are components of speed and should be considered in the development of speed during childhood. For the purpose of this chapter, speed will be considered with regards to overground running as this is the most common application of speed in competition and training. The term speed will be used as a generic term that ignores the phase of sprinting. It is clear that all aspects of speed develop through childhood and, as with other components of fitness, improvements have been reported to follow a non-linear process (Borms, 1986; Viru et al., 1999). The development of speed throughout childhood is influenced by increases in muscle cross-sectional area and limb length, biological and metabolic changes, morphological alterations to the muscle and tendon, neural and motor development as well as biomechanical and coordination factors (Ford et al., 2011). Given the interaction of so many variables, identifying a single primary mechanism responsible for improvements in speed at different stages of growth and maturation is difficult. However, biomechanical analyses can provide useful information regarding the development of speed, which, in its simplest form, is a function of stride frequency and stride length. Stride frequency at maximal speed changes very little through childhood into adulthood, with gains in maximal speed attributable to gains in stride length (Schepens et al., 1998). Therefore, considering factors that contribute to increased stride length in childhood seems a useful strategy. The developmental changes that underpin natural gains in speed may help to identify the types of training regimes that can be most successful at different stages
of growth and development (Balyi and Hamilton, 2004; Viru et al., 1999). The interaction of different training regimes, different phases of sprinting, different mechanistic adaptations and growth and maturation effects make this a potentially complex topic. This chapter will consider the theory and evidence of the development and trainability of speed during childhood, whether any interaction effects exist with growth and maturation and how different types of training influence chronic adaptations.
