Relationship between physical activity and physical fitness, skeletal muscle mass and muscle quality in junior high school students

Abstract

It would be interesting to examine how characterize relationship among physical activity (PA), physical fitness (PF), and skeletal muscle (SM) characteristics in adolescents; however, it is not well understood how those parameters are related each other. The purpose of this study was to elucidate relationship among PA, PF, or SM in adolescents. Fifty-five male and female students (13.1 ± 0.8 years) engaged in this study and PA, PF, and SM characteristics were measured. Muscle thickness (MT) and echo intensity (EI) of the quadriceps femoris were measured based on transverse images of B-mode ultrasonography. PF tests consisted of 9 different tests such as hand grip strength, sit-ups or side-to-side jump, developed by the Ministry of Education, Culture, Sports, Science and Technology, were used to estimate functional properties of the students. Significant correlations were found between moderate and vigorous intensity PA time and the PF test score (r=0.61 to 0.64, p<0.01), and VPA and MT (r=0.47, p<0.05) or EI (r=-0.52, p<0.05) in boys. We also found significant correlations between VPA and hand grip strengt (r=0.36, p<0.05) and MT (r=0.57, p<0.001) in girls. These results suggest that longer moderate and vigorous intensity PA time a day may help development of physical fitness and skeletal muscle size in adolescents, especially, in boys.