I'm racing as 48 and am 47. I can't wait to age up to the 50-54 AG in 2 years (cyclocross I age up next year), never thought I'd be saying that I can't wait to turn 50 but tri'ing changes perspectives.
Turned 56 last month. Had open heart surgery eight years ago at age 48. Did my first sprint tri at age 50 and completed my first half-marathon this past February. Slow as mud, and need to lose 20 pounds, but still out there.