It is often said that it takes years of cycling to build the endurance required for road racing. Very few sports make the same demands; hours of effort. Medium level effort sustained for hours interspersed with extreme (often anaerobic) effort.
I've never had athletic ability and my recent 'health check' confirmed one reason why; a lung volume only 74% that predicted by my height and weight (no, I'm not a smoker, I just have small lungs).
When I was young and tried my hand at kayak racing, I had no endurance. I trained hard (too hard actually). I could run 10miles in an hour, bench 90kgx20 reps, lat pull down 1.5 times my body weight. Still, I had no endurance and in any race I rapidly tired. I'd start strong and end with muscles like jelly, crawling along.
Thirty years later and I'm training with a kayak squad again. I'm the slow old man in the group. Muscles are weak, can only barely manage to chin myself 10 times. However, something has changed. As the training session progresses, I get faster.
Initially I thought I was imagining it. Last night, in a hard intervals session, after we'd covered about 9km and were down to 3min intervals, someone remarked on it "You get faster on the way back". On the way out, they were pulling away from me. Part way through, I was level-pegging them. Now, I was pulling away from them, and feeling like I could do more sessions. They were exhausted.
Has it been all those years of commuting on a bike, notching up 150-250miles a week?