Almost all forms of exercise are cardiovascular training. Your heart responds to any change in activity. The intensity of that change in activity makes a difference in the reponse of the heart. Untrained individuals should start small and make small changes to the variables of exercise. The heart responds to each exercise bout. The recovery outcomes depend on many things. But in answer to your question. Cardiovascular training is only necessary if you want to remain fit for life and must be continued throughout your life to get a benefit that lasts. You don’t necessarily have to spend hours sweating and huffing puffing like crazy. But you do need to do enough to get to and maintain a good level of fitness. If someone doesn’t like traditional cardio training (ie. running, swimming, biking, etc.) , you can still get adequate cardiovascular response from maintaining effort levels doing almost anything that elevates heart rate. And short intervals are also effective when done properly and with sufficient repetition of the interval bouts in a workout. Like the sayings go. You get out what you put into anything. Do nothing, get nothing. Gargage in, gargabe out. And Too much or too little are counter productive.