[tobym]

Possibly a question for Serpico, or anyone else with an interest in sports physiology;

The anaerobic threshold, if I understand correctly, depends on the capillary density in one's muscles, and their ability to deliver oxygenated blood to the muscles, and remove excreted products of respiration.
 According to texts such as PRC and SCC(and Fluxus' posts on RC.com), the only effective way of increasing capillary density in the forearms, in an applicable way to climbing, is with ARC-type training.

If someone were to have relatively sparse capillarity in their forearms, and so get quickly pumped on the easiest of sequences, would the presence of all that lactate and blood, not mean that a certain amount of extra capillarisation occur, in the muscles, to aid recovery of those tissues?

Apologies for my basic level of understanding, it is years since my physiology lectures (I'm a GP!)

I only ask, as I am climbing again, after a layoff of several years(don't ask!), and I can't seem to even traverse, for long, on jugs on a vertical wall, without getting very pumped.

[Serpico]

A quick answer because I'm in a rush.
There are other factors which affect the local anaerobic threshold, such as: Mitochondrial density, levels of various enzymes, hypertrophy and it's effects on occlusion.
Routes where you get pumped will build/widen capillaries but the time spent with a high pressure of blood is less than what you'd achieve while ARCing because for a large part of the time the vessels are occluded, and the acidity makes it harder to complete the same volume of work.
Routes build capillaries and mitochondria, but ARCing is more efficient because you work at a level below significant occlusion and the subsequent increase in acidity but with a reasonable level of blood flow/pressure in the forearms. Routes probably increase capilarisation and mitochondrial density around fast twitch fibres and increase the enzymatic activity to a greater degree than ARCing.
When you've got a spare hour or so read this:
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=586354;page=1;sb=post_latest_reply;so=ASC;mh=25;

[tobym]

A quick answer because I'm in a rush.
There are other factors which affect the local anaerobic threshold, such as: Mitochondrial density, levels of various enzymes, hypertrophy and it's effects on occlusion.
Routes where you get pumped will build/widen capillaries but the time spent with a high pressure of blood is less than what you'd achieve while ARCing because for a large part of the time the vessels are occluded, and the acidity makes it harder to complete the same volume of work.
Routes build capillaries and mitochondria, but ARCing is more efficient because you work at a level below significant occlusion and the subsequent increase in acidity but with a reasonable level of blood flow/pressure in the forearms. Routes probably increase capilarisation and mitochondrial density around fast twitch fibres and increase the enzymatic activity to a greater degree than ARCing.

thanks, that quick summary was the kind of thing my smple brain was after!

When you've got a spare hour or so read this:
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=586354;page=1;sb=post_latest_reply;so=ASC;mh=25;

I have read that thread, and I think I posted on it, a few years ago.