Yesterday I was doing my usual 35 mile ride and came upon a youngster at a traffic light. He looked like he was ~20 years old and was wearing his pro team kit. He had huge leg muscles. I said hello and commented about the headwind (tropical storm Jeanne was headed our way). I figured he would take off and leave me in the dust before we'd gone more than a hundred yards. I took off as the light changed waiting for a blur to rush past me. Not so! After I'd gone about 1/4 mile I looked in my mirror and saw he was waaaay back there. Looked like he was struggling more than I was. That sure made me feel good.
I guess he got his huge leg muscles at the gym.
The moral of the story: You have to earn strong leg muscles by riding lots of miles and climbing lots of hills. You can't buy them at the gym.