text: That depends on what you mean by effective. If the "effect" you want is to gain cardiovascular health (heart health) than yes you should be slightly out of breath. You don't want to be gasping though. Especially when you first start working out. After a week or two, depending on many times a week you are exercising, it will not be as pronounced. If you are just focusing on building muscular strength you don't necessarily need to become out of breath.