One of the benefits of riding indoors is that it is a controlled environment; there are no hills, no wind, no traffic, no dogs or squirrels that might run in front of a cyclist. Riding a stationary trainer allows the rider to focus on technique and the main focus of the first few weeks of the indoor Cycling Centre program is to work on pedalling efficiency, increased rpms (revolutions per minute), and body position.
I've found that many athletes that begin riding feel they need to push big gears at a low cadence in order to keep up with their friends, and then wonder why they are getting dropped on the hills when they lead out the group for the first part of the ride, or get dropped completely from the group early on. The answer is that they are working too hard too soon. By riding an easier gear and increasing the cadence above 95 rpm, also known as spinning, the same speed can be maintained but the body is working more efficiently, lactic acid is being flushed out as it is produced, and energy is conserved that can later be used to power up the hills.
Think of it this way, if you have a 30 pound weight you may only be able to do 10 bicep curls, but if you have a 10 pound weight you may be able to do 30 reps before fatiguing. In both cases the total amount of weight lifted is the same, 300 pounds, it was just achieved in different ways. So if you are riding for 100 km and there is a big hill at the 60 km mark, your legs should be fresher when you get to the hill if you are riding 30 km/hr at 100 rpm versus riding in a bigger gear at 80 rpm - speed is the same, but leg speed and gearing are different.
We have been working on making the rider's "default" cadence close to 100 rpm, and 2 months in that goal has been achieved. Not only that, but the maximum cadence reached in our 10 second warm up sprints has greatly improved. Riders who were struggling to get up to 120 rpm are now well over 160 and can hold 120 rpm for a minute!