Should you train by miles, or by time? Which is the better way to train?

Personally, I\’m a by-miles type. Supposedly that makes sense for road riding. For mountain biking, going by time is said to make more sense. Here\’s the reason:

Maybe you\’ll ride an hour on a paved surface, using your road bike. You might cover 15 miles or more. Then the next day, you might ride an MTB for one hour on a difficult downhill track. You\’ll likely cover a considerably shorter distance, but the effort will be just as great; possibly greater.

Thus the miles or time debate. If you measure both of those rides using miles, it will seem that the second ride was much less of a workout; even though you might have been working much harder. And you don\’t want to shortchange yourself, right? Incidentally, here\’s where a power meter can be useful. X amount of effort is X amount of effort, regardless of mileage.

Even if you never ride a mountain bike, time could be a wiser way to train when your time available for riding is short; as it is for so many of us.

Are shorter, harder rides what I need during the week? Would that help me to improve my cruising speed? Even though I\’m a good deal better at pushing it up to 15, 16, or even 17 mph, I can\’t sustain it for nearly as long as I\’d like.

Keep trying, I guess. Maybe I need a time-management course?