We evaluated the muscle quality of lower limbs among four groups: controls, marathon players, powerlifters, and teenagers using q-space imaging. Initially, we confirmed that fast muscle fiber has a larger cell size than slow muscle fiber in cadaveric immunohistology study of the tibialis anterior muscle (TA). In addition, there were many fast muscle fiber in the TA. In q-space imaging study, the cell diameter increased in the process of growing up from teenage to adulthood, which indicates an increase in fast muscle cells according to growth. Furthermore, the powerlifting players had more enlarged fast muscle cells than other groups.