You don't need to carry a load when running. If you need to carry weight, just do weight training. In addition, it is not easy to build muscular legs when running, but it is easier to build large walking muscles when carrying loads. Long-distance running can lose excess fat in the legs. In addition, although long-distance running has no obvious effect on reducing muscles and calves, it will not make the legs muscular. Finally, paying attention to the stretching and massage of legs after running can stretch and soften muscles. The following pictures are some methods of massage stretching, and you can also search for leg stretching online: