BITD when I was young and dumb, I loved taking my fixed wheel bike out to Northern NJ or the Poconos for a century in the hills. IMO, nothing improve your short to mid size hill climbing ability as riding fixed. But it does take a toll after a while, especially the fast descents,, so I don't suggest it as a long term steady diet.
But in rolling terrain with reasonable small climbs, the joys of riding fixed offset the added effort when climbing.
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