I like to remind athletes and others involved in Performance or fitness training that gravity forced us to be "ground based" creatures. In essence, while standing we are based on the ground where our base is located, with the kinetic chain working all the way up.
When we perform actions during training such as KB swings, squats, hang cleans etc. the better our base is (foot placement, feet width, etc.) the better the action.
I like to take it a step further and say the better footwear we have, the better the base, the better the athletic action.
When training, if you wear footwear (unlike our barefoot training brethren) select something with a comfortable fit that benefits your training action.
The better base you have, the better you'll training!)