Originally Posted by DannoXYZ

I think the definition of "reasonable shape" varies. Each person's definition will be different and the "shape" required will depend upon the type of event you're participating in. Personally, I think just about anyone can get out there and do a century without much training at all. You just go slow enough to prevent bonking and sore-muscles. Eat and drink sufficient amounts and you'll be able to do it. It's really a matter of how fast you want to go and just about anyone and everyone can do a century in 8-10 hours if they go slow.

Being in "top fitness" shape then is a different criteria that might be defined using:

- VO2 max
- power-generated at LT
- resting HR
- HR-recovery time
- average-speed at LT
- climbing-rate in ft/hr
- calories burned/hr
- etc. etc. etc.

Personally, I think if you're able to put out 200-250w and burn 750-calories+/hr continuously, you're in "reasonably good physically shape".