^ I don't think that has to be true. I'm faster at 50 than I was at 30, mostly because I train smarter now.
Also, I race Masters 45, and Cat4. By definition the Masters are 45 and over. Most of the Cat 4's are between 18 and 35. Masters 45 is much harder and faster than the Cat 4's.
Age obviously brings with it a decrease in our maximum potential performance. However, most of us are so far below our potential that even as we age, there is still the potential to be faster and stronger than you've ever been simply by realizing a greater percentage of the potential you have left.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.