I think I was wrong

My last post praised an article in Pez that basically said: Don't do too much L3 (tempo) riding. Try to ride more L2, L4, L5, et cetera.

Although the article was not completely off base - some people, mostly those who don't structure their training, get in a rut and do L3 ALL the time. That can cause problems. First, it might keep you so fatigued and mentally fried that you can't do your higher-intensity workouts properly so you don't get the full benefit. Second, riding L3 all the time, day after day, might put you in the position of not getting enough recovery time and then you can't get the periodization effect working in your favor. So there was some merit in the article.

But then I studied this chart again:

If you take a good look at all the aerobic training zones, L1 through L4, they all impact the same metabolic systems. As you increase intensity from L1 to L4, you get more training effect per minute of workout for every aerobic adaptation (except you get more muscle glycogen storage response at L3 than at L4), but the effects are the same for all of those levels. There are limits to how long you can train at L4 (probably more mental than physical), so you have to throw some lower level (L2 and L3) workouts in your plan to stress your aerobic systems adequately for base training adaptations to occur.

L1 training days are better than taking an off day because they increase blood flow to the legs and accelerate your recovery process without adding additional fatigue. But why is it important to train at L2? Don't we get the same metabolic benefits by training at L3 in a shorter period? Wouldn't that allow us to stay mentally fresher for those dark basement trainer rides? Why not do all aerobic base training at L1, L3, and L4?

I have posed that question on Google Wattage, and so far, no one has really answered the question. I'm beginning to think that there is no specific reason to do L2 work instead of L3 work as long as you carefully track ATL, CTL, and TSS and include proper recovery.

I guess people ride L2 because it's harder to maintain L3 effort for long periods. But unless any of you haven't noticed, bike racing is hard.

I'm still looking for answers. And if I find any, I'll update this post.