Girls running legs will become thicker because the running program carried out is sprinting. If long-distance running, each running time is greater than 30 minutes, between 1-2 hours, the legs will not become thick, and long-distance running can also consume excessive fat, so that the legs become more slim, for the body’s shaping has many benefits. Girls running, personally, I recommend doing more aerobic exercise, in addition to running, but also swimming, brisk walking, but in any case, the exercise time should be greater than 45 minutes, rather than doing short distance strength training. Sprinting, and some muscle exercises, these will make the leg muscles as well as other muscles become very thick, become very strong, not conducive to thin legs.