how do you keep your toes pointed while sprinting?

[FF h]

im a high school sprinter i got shin splints my coach said that it was cuz i run with my toes pointed down i try to fix it but i never can i keep my dorsal flexion muscle flexed when running and that just makes it worse i also stay really relaxed when running and it doesnt seem to work either and bringing my knees up higher but when i look at my feet when running i see them stabbing the ground we always do A and B skips in practice i do fine in them and point my toes up but when it comes to running thats when it happen any tips or drills will help