The simplest form of VO2 max training is three-minute intervals. To incorporate VO2 max training into your one-hour loop, start with 10 minutes of easy spinning and then complete three to six intervals of three minutes apiece at the maximum effort level you could sustain for 10 minutes in race conditions.
Spin for at least two minutes after each interval. Limit yourself to three intervals in your first VO2 max interval workout. Build to five intervals if you're moderately fit and competitive and six intervals if you're highly fit and competitive.
Again, pay no mind to turns, winds and hills and how these factors affect your speed. The point here is to make do with your favorite one-hour loop, not simulate laboratory conditions—after all, isn't this supposed to be fun?
3. One-hour Loop With Power Work
Power is the ability to apply force quickly. In cycling, it is the ability to turn big gears at a high cadence. Your maximum pedaling power is the greatest number of watts you can produce during a very short, all-out effort. There is a common misconception among triathletes and cyclists that maximum power is more or less irrelevant to endurance cycling performance, but it is not.
The best endurance cyclists typically have much greater maximum pedaling power than average endurance cyclists, and increasing your maximum power is an effective way for anyone to improve his or her performance in longer race efforts.
The best way to train your maximum power is to perform multiple short sprints. These can easily be incorporate into a one-hour loop ride. Cycling coach Hunter Allen recommends the following format: Start at a slow speed—five or eight miles an hour—and a middle gear in your small chainring.
Do a 10-second sprint with only one or two gear changes. Wind out the gear before you shift, like you do in a car. Go up to 120 RPM. Recover two minutes after each sprint. Start with just four sprints if you haven't done anything this intense recently (or ever!). Build up to six or eight sprints if you're moderately competitive or 10 or 12 if you're highly competitive.
Do make an effort to perform your sprints on a sensible stretch of road (no sharp turns, good pavement, relatively flat) within your one-hour loop.
4. One-hour Loop With Hill Work
Most hill workout formats require that you ride up and down the same hill multiple times. Obviously, that doesn't work with a one-hour loop. A radical but still effective alternative is to simply work with what you have by attacking any and all hills that exist on your one-hour loop.
If there are three hills, two of them short and steep and one of them long and moderate, then ride each as hard as you can without emptying your tank for the remainder of the ride. If there's just one big mountain to get over, attack that.
This approach is certainly not as systematic as your typical, structured hill interval session, but it beats the common alternative, which is to ride the hills a little harder than the rest the loop but certainly not to attack them. You will definitely gain additional climbing prowess by working with what you have on that favorite route, whatever it may be.