I took the morning off my regular routine to read the Rivendell Reader no.40. Grant, with some apologies and warnings, prints Mark Sisson's article about the dangers of endurance training. I summarize his main points:
1) Our reproductive imperatives (i.e. evolution) designed us to be great slow-movers (foraging for food and stalking prey), with the ability for occasional bursts of strength/speed (run away! run away!).
2) We have two energy systems. The fat-based one allows for long duration at low intensity; the ATP-based one gives us about 20 seconds of burst to get away from the tiger.
3) We can develop the ability for high revs for long periods of time (i.e. endurance training) because we are highly adaptable, but it runs counter to our genetic blueprint and is achieved at high cost.
4) There is medical evidence that suggests that the physiological effects of endurance training may shorten life (i.e. kill you sooner).
5) Direct quote: Readjust your training to fit your DNA blueprint. If you're training hard and long for grueling enduance competitions, back off. On the bike, sprint more and rest more. Break it up and have fun. Lift weights, do yoga and there's a good chance you'll be healthier and look better.
I think this means longer duration rides at lower intensity with sprints (running away from the tiger) to maximize health and enjoyment. Based on the article (and other contemplations/conversations with stoker Malkin), I'm going to see what happens if we reduce our cadence and ave speed slightly, decrease our distance, and increase our time.
p.s. you can see a version (not exactly what's printed in the RR) of the article here: Primal Blueprint.