There they are, prominent among countless undistinguished runs dutifully recorded within one’s physical or virtual training log, the workouts that tower above the rest like monuments. They are the long, long runs, or the special blocks, or the hardest track workouts you’ve ever done. They are the red-letter days in your own personal Running Book of Devotions.

I’ve been thinking a lot lately about these big days on the training calendar, and about their role in advancing fitness.

In working with Tyler, I’ve seen how he works “Red days” into his training blocks. Indeed, thinking about these mega-days and the days before and after is one of the main things we do when discussing training. And while I wouldn’t want to compare my own running to that of a professional runner, I’ve been trying to schedule a few red days for myself, too.

Back in March, when I started my latest mileage build-up, I had two main goals: run more often, and extend the duration of my weekly long run. It was about the simplest plan possible, but it was effective. All week long, I’d trudge out my 30 minutes a day, which brought no particular joy. And then, on the weekend, I’d try to run a little bit further. At first my long runs were only six miles. After a few weeks, I was able to run eight miles and not feel crippled. I was excited when my long run hit ten miles. The last three weekends, I’ve managed 11, 12, and 13 miles. My red-letter days.

I also tried to get in a workout on the track each week, but some weeks it never happened. I’m not embarrassed to say that it was tough to do workouts on my own, so if I wasn’t feeling up to it, I just substituted a normal run. This meant that the only thing in my training that was really pushing me out of my comfort zone was the weekly long run. At least there was one thing.  And amazingly, that one thing has worked. The longer runs have gotten longer and faster. I might not be progressing as fast as I’d like, but I’m clearly going in the right direction.

While I was making my slow return to something resembling consistent training, I was also coaching, and also thinking a lot about how to schedule hard workouts into the Spring track calendar. The distance runners had their own red-letter days, usually just one day per week that involved work that was long and hard enough to break them down and stimulate meaningful adaptation to the demands of the races to come.

I know other coaches might schedule more hard days per week. I don’t pretend to know the right formula for how hard to push kids each day. I do know that there’s a physical and psychological benefit to having key workouts that test one’s limits. I also believe that the recovery afterwards is crucial to obtaining the benefits. And that, in a nutshell, is the basic challenge of training: sufficient hard work to improve, avoiding excessive work that incurs longer-lasting damage. Such a schedule is naturally going to include patterns of easy, normal, hard, and really hard workouts.

The origins of the phrase “red-letter day” seem to be a bit in dispute. I had always read that the phrase originated with the red ink used in Ecclesiastical works like the Book of Common Prayer to mark special feast days. According to some sources, the phrase has been in use for longer than that, and has meaning in many cultures and across many cultures. Regardless of where it came from, the idea of such special days seems deeply ingrained in us. We circle them on the calendar, and feel them approach with a mixture of eagerness and perhaps apprehension.

Red-letter days, or red workouts, are not like all the other days.

They are when the awesome or awful magic happens.