Abstract

It has been reported that the physical fitness of adolescents has been decreasing gradually over the past twenty years in Japan. The reasons for this decrement were a decrease in physical activity and an increase in the prevalence of obesity. However, there is no clear evidence on the relationships between physical activity and physical fitness or body composition for adolescents. The purpose of this study was to measure the total energy expenditure (TEE), physical activity level (PAL) and times spent in light, moderate and vigorous physical activity and to ascertain relationships between physical activity and physical fitness, and body composition for adolescents. Twenty four male adolescents (age: 17.3 +/- 1.3) volunteered for participation. Subjects assigned as trained adolescents group (n=16) and untrained group (n=8). TEE was measured by doubly labeled water method and times spent in physical activity were assessed by accelerometer method. VO2max was indirectly measured by breath-by-breath method with stepwise incremental cycle ergometer exercise test. Measurement of physical fitness tests was conducted according to the Ministry of Education, Culture, Sports, Science and Technology. TEE and PAL were significantly higher in trained adolescents (4813 +/- 439 kcal/day and 2.64 +/- 0.14) than untrained (2859 +/- 147 kcal/day and 1.84 +/- 0.16), respectively. Times spent in light, moderate and vigorous activities measured from accelerometer were significantly higher in trained adolescents than untrained, while times in sedentary activity were significantly higher in untrained adolescents than trained. PAL and times spent in physical activity (light, moderate, vigorous) were significantly correlated with physical fitness ( O2max, sit-ups and sitting trunk flexion). Additionally, times spent in moderate related to 20-meter shuttle run. However, PAL and times spent in physical activity were not significantly related to %body fat. These results indicated that daily sport activity results in significant difference of activity energy expenditure between trained and untrained adolescents, and that increase in PAL and times spent in physical activity while engaging in daily sport activity would contribute to improvement of health-related fitness in adolescents. Verf.-Referat