The following is another question sent my way by a somewhat discouraged-sounding athlete who must be in his early Base period. In fact, this is an extension of the same question I answered in my last Q&A blog post.
Question: I have a question about theory. If it is true that the body only adapts when there is a demand put on it, how does riding around lazily cause my body to adapt? How does it put a demand on my body? It makes some sense to me that I could continually increase the duration of my rides in an effort to increase the demands on my body, but I am already capable of riding 4 hours in zone 2 without being tired at the end, riding longer than 4 hours can be a drag (and hard on my butt, back, neck, hands, etc), and you have recommended not to increase the duration past the duration of the longest event.
Answer: Perhaps the easiest way to understand training is to think about it in terms of desired outcomes. I believe what you are asking about here has to do with aerobic endurance and is similar to the last question I answered on this topic. Aerobic endurance is the ability to ride (or run, swim, XC ski, etc) for a long time at a low to moderate effort. By doing this you promote more slow twitch (type 1a) characteristics in type 2a muscles, develop a more dense capillary network in your endurance muscles (types 1 and 2a), increase the activity of aerobic enzymes, improve the cardiovascular system’s capacity for transporting oxygen and fuel to the muscles, cause your body to become better at burning fat instead of sugar and more. The bottom line is that your endurance improves and you are also able to go faster for a longer time at what used to feel like a somewhat more difficult intensity.
You don’t want to ride around lazily unless you are recovering. To stress your aerobic endurance you are best advised to ride at or slightly above aerobic threshold. In my last post on this subject I suggested that both zones 2 and 3 may be the best way to do this. If you have already made great progress with 4-hour workouts in z2 then begin to include more z3 efforts as also explained in the previous post. I think this will boost your aerobic endurance even higher.
All the best for your training and racing!