Recently a fellow writer and runner got me–and several years earlier, half the nation–to thinking. Malcolm Gladwell, a bestselling author with an eye for the arbitrary (and a former 1500-meter hopeful and current recreational runner) put me in mind of an idea I first got hold of several years ago during a volume-padding run undertaken to build to my weekly mileage quota. Having made a very strong case in the book Outliers that something as arbitrary as the date on which an academic or athletic year begins can keep a culture from effectively spotting and subsequently grooming talent born in the second half of the calendar year, Gladwell emboldened me to speak out about my own crazy–if considerably less ambitious and important–idea.

Just as Gladwell’s revelation was right there under our noses, so is mine–every time we start a training journal or begin a training plan.

Virtually every running journal and every training program fits neatly into the seven tabular columns of the monthly calendar, one for each day of the week; taken conceptually, they stand like Doric columns atop which the pediment of Western athletic training rests, as revered a structure as the Parthenon. Every veteran runner knows by rote the blueprint for virtually all such plans: one day of intervals, one tempo run, and one long run per week, with easy or rest days between. The volume of such plans is almost invariably expressed in weekly miles.

Here’s where I–like the impertinent tourist on the scripted Acropolis walking tour–come in. I’m the wise guy who summons the gall to ask, ‘Why?” That is to say, why are the overwhelming majority of athletic training plans based on a calendar week?

From an exercise physiology perspective, is there really anything sacred–or even particularly special–about a calendar week? Or is it that we’re so used to breaking our lives into repeating weekly units that we’ve merely defaulted to weekly training cycles as the convention nearest to hand?

The anthropologist Roy Rappaport once said that, “To invest social conventions with sanctity is to hide their arbitrariness in a cloak of seeming necessity.” Bring up the term calendar reform in polite conversation, and observe the hush that follows: that’s how sacred we hold calendrical conventions like the magic 7. And no, I’m not suggesting calendar reform. No petition will follow. I’m instead suggesting that the organizational basis of our training should be informed (or is it constrained?) by more scientific considerations than conformation to the calendar.

Why should 21st century exercise physiology continue to take its cue from conventions first codified in ancient Greece? We wouldn’t think to measure a race course in stadia, and yet not an eyebrow is raised to the practice of basing our training on a unit no less Greek. Thoreau–a man whose heartening quotes would be the perfect inspirational margin-filler for a new kind of running journal–was certainly infected by the reforming spirit. “My days were not days of the week, bearing the stamp of any heathen deity,” he wrote, referring to the Odins and Thors for whom our Old English Wednesdays and Thursdays are named.

Speaking of Old English, what I suggest instead of weekly training is fortnightly training. Though it may sound antiquated, as a training matrix its architecture would be anything but foursquare. And if as ungainly a word as the Swedish fartlek can take root in running parlance, what is to bar the less foreign fortnight? Or why not use week and fortnight alternately. As runners, we take for granted the fact that we toggle between miles and kilometers with a laudable fluency to which most of the non-running world can’t begin to keep pace.

And as long as we’re on the subject of alternating, if you’ve ever tried to alternate running and rest or, say, running and swimming or cycling, you’ve quickly run into the dilemma of how to treat the extra day that occurs in the weekly round. Seven is not a multiple of two. Fourteen is. In fortnight training there is no difficulty because there is no extra day.

The idea behind fortnight training would not be to recreate another arbitrary unit of measurement merely twice as long as the first, but to use the concept to create a more expansive bracket in which to express a greater number of training variables. The idea behind the fortnight is greater freedom, more possibilities.

For the aging runner the fortnightly training cycle may better match his or her need for additional recovery. Nearly all coaches pay lip service to the master runner’s slower recovery rate. Yet nearly all training plans for masters runners continue to be based on a calendar week. If a 50-year-old runner requires more than a day of recovery from a quality session, how is he or she to work three such quality runs into a week? There simply are not enough days. But if that 50-year-old runner has 14 days with which to work, he or she may now insert two and sometimes three rest days between quality sessions, adapting to a less-harried rhythm that may also flow more naturally with the well-documented changing perception of time that aging adults experience. If, as one ages, weeks seem to fly by as if they contained far fewer hours, it may feel overwhelming not only to the body but to the mind to have to squeeze three quality sessions into what feels like an increasingly narrow space of time.

A brief scan of the Web reveals that there are a few scattered grumblings made sotto voce about the shortness of the training week, a few isolated musings advancing such heretical ideas as 10, 14 and 21-day cycles. Many is the paradigm shift that began as a heresy. Many is the revelation experienced in the instant of seeing something so obvious and so ubiquitous that it had remained invisible. Am I dismayed to find that others have had “my” idea? Not at all. That’s the way it’s supposed to work. When the time is ripe for something new under the sun, many will discover it simultaneously and independently.

For elite runners whose work week is their running, a weekly training schedule may serve them as well as any. Life may sometimes still get in the way of their work. But work will never get in the way of their work.

Then there’s the rest of us. As a mortal with a job and family life, can you imagine having 14 days in which to meet your volume quota? For a 56-mile-per-week runner, his average run is eight miles per day. Miss a single day due to work or life getting in the way and now he must run one 16-mile day or, say, two 12-mile days to make up the difference. But what if he were a 112-mile-a-fortnight runner and had 13 possible days over which to distribute that eight miles? Wouldn’t that take a load off? In this sense, a fortnight is more forgiving, better able to absorb the chaos liable to creep into even the most orderly of lives. And as long as one doesn’t race every weekend, one could spend the first half of a fortnight tapering for a race, only to make up the volume with several long slow runs over the second half. In fact one could systematically front load a fortnight with higher-quality, lower-volume work while back loading it with higher-volume, moderately-paced work, thus alternating and possibly reaping the rewards of both training modes simultaneously.

Still think the seven-day training cycle is unassailable? Remember, even the Parthenon is crumbling.