Thebigturtle wrote:
Every training session has a recovery cost. Running interval workouts have a very high recovery cost. You are sacrificing energy that could be spent doing more aerobic running. Most age group triathletes are VERY underdeveloped in terms of their aerobic running base. Building a strong aerobic engine for running takes years of training. If you go to letsrun.com most people agree that speedwork is icing on the cake, and that aerobic development should be the primary focus for developing endurance athletes. I was a cross country runner in college. One summer I ran a 10 mile race in 53 minutes off of 8 weeks of 90-100 miles of aerobic running and strides. No track work, no hills etc. In fact, no triathlete has ever run an ironman marathon at 5:15-5:20 per mile pace. The point is that
ironman running is not about speed, it is about aerobic efficiency, sometimes referred to as "strength". This is developed by going out and running a lot. The sweet spot for this training in my opinion is high end zone 2 heart rate.
For men under age 45, I think only once your running pace for the top of your zone 2 heart rate is below 7:15-7:30 should you start to think about doing tempo runs and or track work.
As far as cycling goes, the recovery cost for hard workouts is much lower, and the aerobic stimulus from "just going out and riding" is lower than running. I think doing some threshold work once a week ie 3-4x10 minutes at threshold power is a good idea.
Swimming is a different beast altogether, but I do think long aerobic swim sets do have a role in swim training.
good point about the stress factor from physical point of view, you are right on the single intense session but you should put together a TSS over the week and consider the whole stress because if I go for 5x1miles on track best pace, I doubt i will put my body under more stress than going for a 15miles "aerobic" run. especially if we talk about athletes who have a bad posture or wrong shoes...
track teaches you also how to run properly with short fast sets, don't see it only as improvement of your speed. and run better means reducing your chances of injury in other "aerobic" long runs.
In red above: ironman is mostly about "your mind". how many times I had my bike power under target and my run was a disaster simply because my mind decided to stop? this is a common issue and it should be tackled from another angle.