The explanation is as follows:
1, it is generally understood that running makes legs thicker because legs increase muscles. In fact, most girls' legs become thicker, not because they have increased muscles, but because they have increased fat. Therefore, the leg thickening is not necessarily due to running, and generally running will not make the runner's leg thicker. Because 90% of marathoners have thinner calves, girls don't have to worry that running will make their legs thicker. On the contrary, not running or exercising leads to the accumulation and thickening of leg fat.
2. Of course, it is not excluded that running will make legs thicker, because most sprinters have thicker legs, regardless of gender. However, these sprinters' running exercises are not the same as what normal people say. Sprinters' running belongs to high-intensity anaerobic exercise, which is easy to develop leg muscles, thus increasing leg muscles and increasing leg circumference.
Generally, the running we adopt belongs to long-term aerobic exercise. The main energy supply system of this kind of running is aerobic energy supply system, and the main energy supply is body fat. Therefore, running for such a long time consumes a lot of body fat, and it is difficult to achieve the effect of developing leg muscles. Secondly, this long-term running can also consume leg fat, increase the elasticity and endurance of leg muscles, and have a better shaping effect on legs.