Clay, great observation. One of the challenges in writing the 70.3 and IM plans for the masses is that we just don’t know where each athlete will fall for their preferred race intensity. Some will spend 0 hours in Zone X on race day, and some will spend 5 hours in low Zone X: both could be totally appropriate 70.3 or IM intensities for those two individuals. So, each plan does need some adjustment for the athlete.
The other thing is that low Zone 3 is so close to upper Zone 2 that some blurring is permitted. For example, we agree that 80/20 training is better than 60/40 training. But we also instinctively understand that performing the 40 of the 60/40 at the low Zone X is going to less harm than the upper end of Zone X. And, with 70.3 racing in particular, where Zone X is the perfect intensity for advanced or aggressive athletes, it may present more advantages than disadvantages.
This is a long way of saying: it’s OK if you end up at 75/25 training for 70.3 training during the final 8 weeks if that includes a lot of low Zone X. Specificity is just as important as intensity balance, and specificity is king during those last 8 weeks.
So, don’t eliminate the Zone 3, you need it still. Reduce it? Yes. Then, don’t be shy about getting in some serious Zone X time and tipping the 80/20 scales if that is your intended pace for race day.
David