When I was eight years old, my family relocated briefly to an area that was only serviced by one elementary school--a Roman Catholic elementary school run by nuns.
I was a shy, chubby loner with a fertile imagination. Intimidated by the other kids, I'd spend recess and the lunch hour by myself, inventing solitary games to keep myself occupied.
I'd recently started reading the Black Stallion series, and I was obsessed with horses, so...I invented a game I called "horsey." Basically, I would straddle a bike rack, and gently bounce up and down with the horizontal shaft of the bike rack gently rubbing against my pubic area. I was pretending to ride a horse, you see. But additionally, I discovered that this game made me feel really, really good.
Sadly, my fun came to end one day when I was apprehended by a concerned teacher/nun. She was a kind woman, and she had a very strange expression on her face, as she told me sweetly, but firmly that I was not allowed to play this game ever again, as I may accidentally "hurt" myself.
Honestly, at the time I had no idea what she was so concerned about. It only dawned on me years later, as a young adult. I think it's a good example of how we learn to crave, seek out and enjoy physical pleasure even before we're old enough to experience sexual desire. Pleasure is innocent and as natural as growing up.
And in case you were wondering, yes, I do still derive great pleasure from straddling hard objects (regardless of whether or not bicycles are involved).