Unfortunately, it is starting to get a bit chilly in the mornings up here in New York, and I’m starting to dread the arrival of winter. Actually, it is not winter so much as the indoor rides that go along with it that I really hate. The trainer is, in my mind, an odious and tortuous device, capable of driving the sanest of men crazy, to say nothing of those of us who already dance along that edge of athletic genius and madness. But the trainer can be a very valuable device, in large part because of what exactly it is that makes riding the trainer so different.

The trainer is, by definition, a “low inertia” (in layman’s terms there is not much weight moving) environment. Unlike on the road, where you have your body weight the weight of the bike moving at X mph, on the trainer, you have nothing but a little flywheel. Even on “deluxe” trainers, the heaviest flywheel commercially available weighs 6lbs.; this is the flywheel on the Kurt Kinetic road machine.

So, for an “average cyclist and rider” of ~180lbs. (this seems to be the industry standard), that means your flywheel is basically 1/30th the weight of your bike out on the road. The fluid or mag units in most trainers is designed to mimic air resistance on the road, so that as you go faster, it becomes exponentially harder to pedal.

Most good trainers do a pretty good job of mimicking the power required on the road to go a given speed, though you may feel a bit “slow” on the trainer if you are very light and/or have a very aerodynamic position. The trainer does not take into account your fancy aerobars, aerhelmet, skinsuit, etc.

But when people describe feeling “bogged down” on the trainer, it is not that their wheels are going slower for a given effort, it is that the SAME effort feels easier out on the road. And this is one case where perception actually matches reality. Because the trainer doesn\’t have much momentum behind it, it slows down very quickly.

There is a noticable slowdown even within each pedal stroke. So while you are outside, your momentum carries you through those little blips in your pedal stroke, those brief moments of inattention where you are coasting without realizing it, and those extended pauses to drink from your waterbottle, the trainer punishes you and reminds you to keep pedalling.

Obsessive cyclists, of which there are many, who seek a more roadlike feel on their trainer can replace the flywheel. A simple ratchet removes the wheel on most trainers, and any good machine shop can build a 20 or 30lb. flywheel to replace it. This, of course, is going to be very heavy and make your trainer very awkward to move, but it will make it feel much nicer, albeit at a bit of cost.

But you can use the low-inertia of the trainer to your advantage. A trainer workout can be very productive for doing interval work, where you want to be 100% on all the time. During interval workouts, you should not be soft pedaling, drinking from your waterbottle for extended periods, or stopping to take in the scenery.

Since the trainer is so harsh on these momentary lapses, it will encourage good cycling behavior, forcing you to keep on top of yourself even more than you would outside. Especially for riders without a powermeter, the trainer offers a repeatable and consistent environment that can help to weed out the imperfections in your cycling technique.

One other reason the trainer is feels so much more difficult is because there is no air movement except what your piddly little fan pushes over you. Outside, the cooling effect of cycling at even modest speeds is tremendous. Inside, your core temperature can skyrocket without the cooling effect of the breeze, limiting your ability to cool down, which is why it feels similar to riding outside in heavy winter gear. A good fan (or two or three or four…) can make a big difference in performance.

Since there doesn’t seem to be much benefit in training with a higher core temperature, it makes sense to improve the circulation in the room so that you can ride harder. It makes a lot more sense, training wise, to feel exhausted from pushing the pedals rather than overheating. Drink more (the bathroom is close at hand), and even change jerseys, during a longer session to keep wicking the sweat away.

Indoor riding is practically a different sport, so knowing why it is so different, and realizing how best to take advantage of those differences, can go a long way towards making those tortuous hours on the trainer more bearable.