His comment read as follows:
"...Next year maybe going into my second season of racing. Right now capacity isn't the problem, recovering from 2-3 surges per lap in crits is. Riding steady at 10-15 beats over LT isn't a problem, but every crit in my area has a small hill on it leading into a corner at the top, and doing a hard 20 second surge every lap while otherwise riding tempo or right at LT seems difficult to recover from. Any thoughts other than the lame one that occurred to me, which was "improve your endurance base so you can ride at 24-25 in the endurance zone"?"
The single-most important factor in most endurance sports might be speed at threshold. In other words, your max speed without accumulating excess lactic acid. So, naturally, the question is: how to increase this speed?
There are three factors in this equation:
1. Max VO2
2. Threshold (% of Max VO2)
3. Efficiency / work economy
Although all these factors play a role, max VO2 may be the deciding one. Most literature agree that the limiting factor is the heart's ability to pump blood. In other words, the muscles (mitochondria) can process much more oxygen than they receive. So, since we have excess capacity in our muscles (they can utilize much more O2 than they receive), we need to increase the amount of blood (O2) pumped by the heart.
The ideal way to increase this capacity is to train the heart muscle. As you increase intensity, the heart will pump faster (work harder). This increase will continue up to about 95% of the individual's maximum heart rate. After that, we see a slight drop off, due to the fact that the heart is not able to completely fill with blood at max intensity. This leads us to conclude that the most efficient way to train max VO2 is to stress the heart muscle at about 90-95% of max.
We do this best by training intervals at the before mentioned intensity. Recommended length per repetition is 4-6 minutes x 5 times. No reps shorter than 4 minutes, since it takes the heart muscle about 2 minutes to work up to the recommend intensity. This leaves you with 2 minutes of "heart muscle training" per rep. If you can do 6 minute reps, then do that, but chances are 4 minutes is more than enough.
The challenge during these sessions is controlling the intensity. Most people go too hard and as a result, cannot complete the recommended amount of sets. Keep in mind that each rep will make you very "out of breath", but you shouldn't have completely stiff legs. Do the first rep a bit slower, so that you have enough energy to complete the last rep. You should feel as though can go 1 minute longer on each rep and that you could do one extra set when you are finished. Give yourself 3 minutes of active recovery (easy spinning) in between reps.
The hotly contended question these days, is how often do we have to do these? The easy answer is that well-training athletes need at least 2 sessions a week to maintain their current capacity. Any less and you lose performance. 3 sessions would show a slight increase. Individuals with a Max VO2 over 70ml/dl/kg might need 3 sessions per week to maintain their levels.
The good news is that the heart muscle is very "trainable" and responds extremely well to this training. Each session can give you a 0.5% increase in performance. When training hard and doing several such sessions a week - make sure you listen to your body. If you are tired, don't do these sessions. Recovery between sessions is vital.
So - by improving your heart muscle's ability to move blood - you will be able to hold a higher threshold speed and improve your race results. In other words, those hill climbs will not put you as far into the red zone as earlier. And remember that it's never the fastest rider that wins the sprint, it's the rider with the freshest legs. That is a very important distinction.