ABSTRACT
In it simplest form, muscular power is defined as the product of force and velocity (Komi, 2003). It has previously been acknowledged that the ability to generate high levels of power is essential for sporting success (Young, 2006), with the ability to produce high velocity at release or impact being the end goal of a given athletic movement sequence (Newton and Kraemer, 1994). The ability to produce high levels of muscular power is salient upon the type of muscular action involved (Cormie et al., 2011), and previous research has demonstrated that when a muscle is stretched prior to shortening, it can produce an enhanced power output as compared to a concentric contraction in isolation (Komi, 2000). This muscular phenomenon is referred to as the stretch-shortening cycle (SSC), and for optimal SSC enhancement, eccentric and concentric contractions need to be rapid, and the transition between the eccentric and concentric contractions (coupling time) minimal. The SSC has been correlated to various measures of human performance, including acceleration (Bret et al., 2002), maximal running velocity (Chelly and Denis, 2001) and running economy (Kerdok et al., 2002; Kram, 2000), and it is the muscle action that is central to successful plyometric performance. Due to its strong association with performance, the development of plyometric ability throughout childhood and adolescence has been a topic of recent interest (Korff et al., 2009; Lloyd et al., 2011b; Oliver and Smith, 2010). Prior to discussing the literature surrounding the potential benefits and concerns associated with youth plyometric training, it is pertinent to define key terminologies used throughout the chapter:
● Stretch-shortening cycle (SSC). Where pre-activated muscle is first stretched (eccentric) and immediately followed by a shortening (concentric) action (Komi, 2000; Nicol et al., 2006).
