ABSTRACT
Optimal athletic performance depends upon sports-specific body build and body composition (Tittel and Wutscherk 1992). For example, 100 m runners are more muscular than endurance athletes who are typically slender and lean (Weyand and Davis 2005). Athletes use training and diet manipulation to achieve body size and body composition judged optimal for an athletic discipline (Loucks 2004). Noakes (2000) suggests that endurance runners aim to be as light as possible before competition since achieving a lighter body mass for endurance running may improve performance by reducing the energy cost of running per unit distance. In support of this, two studies on elite Kenyan endurance runners (Onywera et al. 2004; Fudge et al. 2006) reported that these athletes were in negative energy balance prior to major competition (National Championships 2003 and Athens Olympic Games 2004 national trials, respectively). Considering the repeated competitive success of east African runners in the last several decades (Pitsiladis et al. 2004), the lifestyle and nutritional practices of these runners may possibly represent an optimal pattern for elite endurance running even though not conforming to current official fluid and nutritional intake guidelines (see Chapter 5 for more on this). These observations raise several interesting questions: what are the limits of gaining advantage from lowering body mass for endurance performance? Are top athletes, who are typically lean, close to this limit? Considering endurance running ability as a key development in human evolution (Bramble and Lieberman 2004), and today’s athletes as the closest equivalent of early Homo in terms of daily physical activity levels (Cordain et al. 1998), it is of interest to compare the bioenergetics and dietary patterns of modern athletes to those thought to be of our early ancestors. Therefore, the aim of the present chapter is to discuss the implications for health and racing performance of a short-term negative energy balance and consequent reduction in body mass as found in elite Kenyan endurance runners prior to major competition. The lifestyle and nutritional practices of elite Kenyan endurance runners are described elsewhere in this book by Christensen (see Chapter 7).
