ABSTRACT
Kaunas, Lithuania 41.1 INTRODUCTION The beneficial effects of physical activity (PA) to health in adults are well established(Katzmarzyk and Craig, 2006). The influence varies and depends on PA dose and health components. Daily PA is important for children’s health, their physical and cognitive development as well as for their physically active behaviour and health in adulthood (Dencker et al., 2006). Low PA in childhood is a risk factor for particular diseases. Physically active children are more physically fit than their physically inactive counterparts. Insufficient physical fitness of adolescents is one of the risk factors for chronic diseases and has a tendency to be carried over into adulthood (Malina, 1996; Renson and Beunen, 2000). Our previous study of 5-11th grade Lithuanian schoolchildren has shown that only 14.2% of boys and girls are meeting the World Health Organisation’s guidelines for health-enhancing PA, i.e. 60 min of daily moderate-to-vigorous PA (Volbekien0 et al., 2007). We suggest that there is a cause-effect relationship between total volume of PA and health-related physical fitness outcomes in schoolchildren. Nevertheless, further research is needed to identify the most effective dose of PA. The aim of the study was to determine the relationships between total volume of daily PA and health-related physical fitness of adolescent boys. 41.2 METHODS 41.2.1 Experimental design This cross-sectional study initially recruited 151 healthy, non-obese boys of which 135 have completed all of the required measurements. The participants were all students of a 9th grade (aged 15.2 ± 0.4 years) at randomly selected secondary
schools of Lithuania. A full description of the nature of the study has been provided to the boys before obtaining their informed consent. Measurements of PA and health-related physical fitness composed the study protocol. 41.2.2 Physical activity The total volume of PA was obtained by the modified Short Form of the International Physical Activity Questionnaire (IPAQ) (Ainsworth and Levy, 2004). During the interview, boys were asked to recall the numbers of days per week and time periods (minutes) per day spent in vigorous, moderate, and walking activities. The data of sedentary activities were not included in the study protocol. The total volume of PA, defined as metabolic equivalents (METs) per week, consisted of the amount of energy expended on vigorous, moderate, and walking activities over the last seven days. According to the guidelines (IPAQ, 2005) the boys were divided in three groups: high PA ("3001 METs/week; n=42), moderate PA (1387-3000 METs/week; n=52); and low PA (!1386 METs/week; n=41). 41.2.3 Health-related physical fitness The four components of health-related physical fitness (i.e. cardiorespiratory endurance, muscle strength and endurance, flexibility, and body composition) were measured. Body height was measured on a stadiometer. Body mass, body mass index (BMI), body fat (kg), fat mass %, and lean body mass (kg) were measured using bioelectrical impedance analysis (Tanita BC-418MA). The boys were dressed in light clothing and wearing no shoes.
