ABSTRACT
Human Performance Laboratory, Ball State University, Muncie, USA 32.1 INTRODUCTION The study of exercise responses in children can be accomplished using any one of a number of well-established exercise testing protocols in the laboratory. For example, threshold responses and peak aerobic exercise capacity can be assessed using a graded exercise test (Mahon et al., 2003). Anaerobic power is often assessed using the Wingate Anaerobic Test (Van Praagh and Doré, 2002). Constant work, submaximal exercise, is used to examine locomotion economy (Morgan et al., 2004) or fuel use patterns (Stephens et al., 2006). The assessment of oxygen uptake kinetic responses at the onset of submaximal exercise has been shown to be a viable non-invasive determinant of muscle oxidative capacity (Armstrong and Barker, 2009). Finally, repeated bouts of intense exercise performed for a fixed duration and rest interval have been used to assess characteristics of fatigue (Ratel et al., 2006). Variable-intensity exercise (VIE) is another form of exercise that can be performed in the laboratory setting. This type of exercise is characterized by frequent changes in a wide range of exercise intensities usually performed for relatively short periods of time and then repeated for a fixed amount of time. Recent examples of the use of a VIE protocol are the soccer-specific exercise protocol developed by Oliver et al. (2007) and the Loughborough Intermittent Shuttle Test (Nicholas et al., 2000). Given the limited amount of research on exercise responses during VIE, especially in children, this study sought to evaluate the physiological and perceptual responses in children during VIE with particular regard to the day-to-day consistency in these responses. The specific aim of the study was to determine the suitability of a standard VIE protocol that could be used in future studies assessing fatigue, exercise performance, energy metabolism and supplementation.
