There's pictures of him in the booking where he's hitting a body bag while stationed somewhere when he joined the army or something as a kid. Not hard to figure that was somewhat of a hobby for him. He also prides himself as somewhat of a health nut in the book, saying he never smoked cigarettes and became a vegetarian.

With that said, yes he was short in size, but a health nuts usually tend to be more agile and have more stamina than most, it's possible Al used that to his advantage.

Anyway, Al's book is okay, I like the parts where he speaks about the old timers like Davie Petillo and how crazy he was.