If you're one of the athletes that I coach, you are no stranger to interval workouts. Why? Because they work! Even if you're an Ironman Triathlete and ride at a steady Tempo pace (for 5-6 hrs. during an event)..studies have shown that interval workouts improve race times.
Conversely, I believe that the road racer/cyclist (who normally enters races lasting 2-3 hrs.) would benefit from periodic long endurance rides.
What are intervals? Intervals are periods of high intensity work interspersed with periods of low intensity work (or rest intervals). Intervals are usually classified by the workload and rest period, or by the physiological fitness system that they stimulate. For example, I routinely prescribe a 3x5 or 5x3 @L5 interval workout, more commonly called VO2max interval workouts.
So, which interval training method works best? Well, it depends. It depends on how much time you have to devote to your interval workouts, your goals/objectives, your physical makeup, etc. And, to be honest with you..interval training methodology is just as much an art as it is science. If it was ALL science there would be books, articles, videos, etc. produced each year stating/claiming- do these interval workouts each year and we guarantee you'll be able to ride a sub-hour 40k Time Trial or win your local criterium. I don't think you'll see any of these claims published anytime soon.
The following are two important reasons why you should be doing Interval Workouts this Fall/Winter. I'm paraprhasing them from Arnie Baker, MDs e-book entitled, "High Intensity Training for Cyclists", which by the way is a MUST read:
a. Interval Training allows a greater volume of high quality work. (Afterall, with our busy work schedules, isn't this what we're looking for- the best bang for the buck?)
b. Interval Training allows for controlled high quality work. (It's easier to target a specific physiologic fitness system or evoke a physiological adaptation w/ a controlled stimulus)
I believe the most important reason for incorporating interval training into your weekly workouts is because interval training can simulate race-specific intensities. And, there is no substitute (in my opinion) for simulating race-specific intensities during training. You can ask any of the road racers I coach and the one thing I like to do is to look at a downloaded power file from a recent race. I'll break down the race into laps (intervals) and see where the accelerations occur (power demand), the frequency they occur, and how long they last. Then, I'll replicate the race in an interval training workout for that athlete- at a later time. When the body gets used to the stimulus (learns to adapt) it will respond more positively than before.
Remember, interval training can simulate race-specific intensities, be prescribed at appropriate frequencies to allow for adequate recovery and can be altered to progressively overload the cyclist in a manner that will result in improved performance. After all, isn't that the goal/objective- to improve performance? I think so.