Smoking weed and cardio question?

i do bjj and muay thai kickboxing and im wondering if i smoke a joint once a week would it effect my cardio at all? because ufc commentator joe rogan smokes weed and does bjj and also ufc fighters like bj penn and nick diaz and his brother smokes weed too and there in good shape and if it would effect my cardio at all how do you explain ufc the ufc fighters smoking weed and still being in good shape