I'm 34, and the only thing that slows me down is that my knees are shot to pieces from all the heavy leg workouts over the years. Sometimes, on a bad day, it hurts to walk.
The rest of me is fine - still got the same motivation for training as I've ever had and I can still recover from workouts just as quickly. My strength levels are the same too, if not better - I'm as strong as I've ever been as a natural.
In other words, I don't feel 34 - feel like I'm in my mid twenties or thereabouts.