This relates to malmo's post about trends in high school times. Those of us in the 30-34 age group went to high school during the slowest period since the early 60's.
Where I live I've noticed that the 30-34 age group isn't very competetive. It seems like people from 25-29 and 35-39 often place better in races and it's not even too uncommon for the 40-44 group to do better.
What about your area? Same trends?