Power, Heart Rate, RPE

This is a big question. How do I train? What system do I use to structure my workouts? Do I just go out and ride, or do I use one of the standard metrics to gauge my daily workout? This is a tricky area, one where you will never get a unanimous answer for. Your options are 4:

1. Heart rate monitor (HRM)
2. Power meter (PM)
3. Rate of perceived exertion (RPE)
4. Nothing

I own an HRM that I don't use all the time. I wish I owned a PM (too expensive). I sometimes use RPE. On my weekend off-road ride, I use nothing, though it could be argued that I inherently use RPE since I know myself well enough at this stage to gauge my level of effort.

What's the difference between RPE and nothing? Well, RPE is a skill where you can tell how hard you're riding based on experience. If you're reading this you're not experienced enough to use RPE. Don't delude yourself, you're not the exception to this rule. Despite the fact that RPE has been shown to be highly accurate, you don't know how to use it, for now.

That's not to say that you couldn't learn in a short time. But unless you've been inwardly focusing for a good long time, RPE is not going to be that accurate for now. And if you're reading this at all, chances are that doesn't describe what you do when you ride. So what to do?

Heart Rate
Heart rate is probably the best way for a beginner to pick up the whole concept. An HRM is fairly inexpensive and allows you to really get a feeling for how your efforts correspond to your RPE. If you've been riding for a long time it can still help, but it probably won't be as beneficial. Still, HR allows you to put a cap on your efforts, especially for the long ones. Even those who have gone to power often still collect HR data.

Power
If you have the money go buy yourself a power meter. It's the so-called wave of the future and when a moderately reliable mid-range model comes out ($500 range), I'll probably get one. Power allows you to exactly measure what output you can maintain for how long. Software packages have made it a lot easier to sort out the data. Those who have converted to power never go back.

RPE
As mentioned before, RPE has been shown to be highly accurate. But you need to be in tune with yourself and it takes hard work as well as experience. This is a very cheap way to train and it allows you to not get caught up in the numbers. For my LT intervals, I'll put on my HRM and go. But for longer rides or shorter intervals, I leave the HRM at home and do my best with RPE.

Nothing
Just get out and ride. Good advice, but it only goes so far. If you use this technique you're probably not going to make huge strides in your biking. You'll feel better at the end of every season and then gain 10+ pounds and start all over when spring rolls around. This is great if it's your thing. But if you want to make gains and keep them over the winter, you'll need to be more dedicated than that.

What you choose is up to you, your wallet, and your aims. There is no right answer. But if you want to see sustainable growth you need to do more than just go out and ride your bike. If you want to structure a program it's going to help if you have some power or HR or at least RPE framework to exist in. Any book you buy will break down workouts by these parameters.