Originally Posted by 531Aussie
I've got one of the Carmichael books (The Lance Armstrong Performanc Program; 7 Weeks to the Perfect Ride), but it doesn't go into enough detail -- it only briefly describes the various techniques. All it says about threshold is that sometimes "the aim is to stay aerobic and stay under the threshold", but he doesn't really explain why.
One thing weird about that book is that Carmichael says that if someones spends more than (i think) 45 mins aboive their threshold, they need at least 2 days recovery rides, but his 7 week program recommends hard days on Thurs, Sat and Sun, then 'spin' days Mon Tues Wed.
Haven't read it. Brilliant piece of marketting for the title, sounds just like one of those telemarketting ads that promise the world and a set of steak knives.
I can only guess that the "staying aerobic" statement relates to preservation of energy systems that can't be replenished easily or without rest. Ergo if you go anaerobic early in a race then you will burn out before you reach the end, or you will be beaten by someone who has more left in them. A key element relating to that statement is that with training you can raise the limit: ie you can go faster for longer without going anaerobic.
The second part is pure long term self preservation. Its not necessarily a hard and fast rule, but a bloody good rule of thumb. It can be adapted in any way you want, but the bottom line is you can't go hard forever. Without suitable rest/recovery your body can't make adaptation, in fact it will suffer badly. You don't make gains on the bike, you make them off the bike as tissues are rebuilt, restructured, or redeployed to suit the demands being placed on them.