This is because you can only get out of it what you put into it. For simplicity's sake, I will put recreational cyclists in three groups. These will be the casual cyclist who does less than 20 miles per ride, the intermediate cyclist who does from 20 to 50 miles per ride, and the serious cyclist who does from 50 to over 100 miles in one ride. The latter group will include riders who do multiple day rides. I will state things in the earlier classifications that all of you should pay attention to such as spinning which will be discussed in the casual group.
Most casual cyclists go out for very short and relatively slow pleasure rides, often with a spouse.
Some only ride on weekends while others may ride every day. The two most important things which I wish to state here is that for minimum basic fitness, you should ride at least two to three times per week for at least half an hour to one hour. The minimum should be something like Sunday, Tuesday, and Thursday. You can move these days around to fit your life style such as Saturday, Monday, and Thursday or Sunday, Wednesday, and Friday. Any three days spread out during the week are fine and the minimum.