Oh wow our 6 month old female does the same thing. She chases down our 3 year old since he is more her size, but often she'll attack my feet when I'm going upstairs or walking through the living room.. sometimes it's a surprise attack.. little grey paws darting out from underneath the couch!
In the mornings she is a complete pyscho, she runs the entire length of the house several times, jumping on anything and everything. Her tail flicks and she just looks evil. Afterwards she is completely calm and um.. approachable, except when she is in her cat tree, at which time, any head that strays near becomes her personal play toy.
I suspect this is absolutely normal behavior depending on your cats personality. You might want to engage in more playtime with him since he obviously likes to play. Maybe tie a toy to the end of a string and use that so that the focus is not on your feet. Cats need a fair amount of play time each day, especially when they are young to burn off all that excess energy (and they have a lot of it). Older cats seem to want to sleep more than play which is fine in my books -). You could also tell him NO when he is attacking your feet and stand still until the cat moves away. Stopping any kind of play time is a powerful reprimand to a cat and they'll get the message.
Hope that helps