re: I quit doing cardio

That's what I've enjoyed the most about the zone 2 training is that there are so many ways to get it: weighted stadiums at the local high school (walking, not running), slide board, jumping rope, jogging, swimming, cycling, etc, etc. It's low intensity so most of those nagging injuries that I've had in the past have mostly gone away.

When Attia interviewed the San Milan guy (the expert on training cyclists), he stated that 3 hrs of zone 2 was necessary to maintain fitness and that anything above that was adding to fitness levels. 180 mins/ 12 min miles = 15 miles per week. That's not very much.