[J.R.]

Yeah, you pretty much got it.

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This jives with what I anecdotally knew of pro cycling training, which is basically that they try very hard to stay under lactate threshold, and will just do a little interval once in a while. In fact they think that training above lactate is harmful to endurance (I have yet to find the science behind why that might be true).

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Intense interval training *is not* harmful to endurance. In and of itself it will help a person's endurance.

The issue is recovery. Training above the lactate level, as occurs with intense intervals, results in amongst other things, lots of lactic acid. Its harder to recover from, and that presents an issues for *elite endurance athletes* who are looking to train every day.

Basically their is a trade-off they have to make and the preference is to focus on lactate threshold.

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Basically, VO2Max adapts very quickly, and almost any kind of exercise can boost it (even weight lifting), and in fact intervals are great for it. If you're a fit person who just took a break for a while, VO2Max will come back up very quickly.

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Steady state will boost VO2 max, more so the higher the intensity. Intense intervals will boost VO2 max max much better, but the issue is it is easier to get to your VO2 max ceiling than your max lactate threshold, so diminishing marginal returns are abrupt as one approaches the ceiling of their Vo2 max.

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Lactate Threshold is much harder to change and takes years of steady state training, and is the limiting factor for endurance athletes. The way that pros train is mainly for LT, not VO2max.

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This is why they try to limit intense intervals, because they get more return out of focusing their training on their lactate levels. Intense intervals limit the ability to do lactate training by presenting greater recovery issues.

That all said, it still speaks volumes that elite endurance athletes who have been training for years are still incorporating intense interval training, albeit at a lesser frequency than steady state.

I would think anyone looking to improve their aerobic capacity would incorporate intense intervals, especially those well below elite levels.