What are their differences and similarities and what is their function? So let's begin with type one skeletal muscle, also known as slow oxidative or slow twitch muscle. Now, slow simply means the breakdown rate of ATP is slow. So these types of muscles break down ATP very slowly and that means the contraction speed of these muscles, the velocity at which these muscles contract is low. So these muscles basically contract relatively slowly. Now, the oxidative portion of slow oxidative simply means they use oxygen to basically form ATP.