Miles or Minutes - How should runners measure their workouts?

With the increased popularity of fitness trackers has come the increased popularity of tracking workout statistics.  We can now track every mile, every footstep and even our sleep patterns with wearable devices.  It's true, as GI Joe used to tell us, that “Knowing is half the battle”, and it’s a good thing that more people have access to more data that can help them live healthier and longer lives. The challenge becomes identifying which numbers are truly meaningful.  Many runners (and walkers) track their lives in miles run, and I’m not sure it’s the best statistic out there.  Rather I recommend an approach that combines mileage for certain workouts and minutes for the bulk of your running. 

The argument for tracking miles is that the mile is a distance measurement most Americans understand.  Many roads and trails have mileage markers to tell us how far we have gone and how far we have to go.  Whether travel by car, plane or foot our travel is measured by the mile.  The mile is also a concrete unit to make comparisons from week to week or year to year.  A runner can say, “I ran 25 miles last week and 30 miles this week, therefore I had a better week of training.”  Or “I’m running 50 miles a week and my competition is only running 40 miles per week, therefore I’m working harder.”  These measurements give runners both sense of their physiological workload and also a potential mental/psychological boost.  In this way, it’s a logical, relatable tool for anyone to use to track performance and gauge fitness. 

The argument against tracking miles is that the mile is an unnatural distance and can potentially lead to some unhealthy behaviors.  According The Perfect Mile (by Neal Bascom), the idea of the mile was created by Roman soldiers based on using their strides to calculate the distance of their long marches:

“Roman soldiers calculated their long marches in mille passus (mille: one thousand; passus: a two-step stride).  Given that each stride was roughly two feet, five inches – shorter than average because the soldiers carried over fifty pounds of provisions and weapons – the earliest mile translated into roughly 1,611 yards.”

Clearly, not a distance created to calculate fitness since most of us are not carrying fifty pounds of provisions and weapons over long marches. 

This distance, the mile, means different things to different runners based on ability.  Running a mile can take a human being anywhere from three minutes and forty-three seconds (current men’s world record) to twenty-five minutes walking.  A ten-mile effort can take one hour for a very good runner and two and a half hours by another runner.  Two runners comparing mileage might be talking in the same language, but have very different emotional and physiological experiences when it comes to effort needed.  The American Heart Association gives their recommendation for exercise in minutes: 150 minutes per week.  The faster runner would need two and a half runs to reach the recommended 150 minutes, while the slower runner reaches the recommended 150 minutes in one run.  In addition, there is a common rule in increasing exercise workload that states that runner should not increase their workouts by more than 10% every week.  In this case, going from ten miles to eleven miles, both runners would increase the same amount of miles, but the slower runner’s activity time would increase by 2.5 times of the faster runner (6 minutes verses 15 minutes). 

Finally, tracking mileage leads to potentially harmful behaviors.  In my competitive years of running, it was an unstated, but understood contest of miles between myself and my running teammates and friends. A benchmark goal was running 100 miles in week, and we’d push ourselves, often to our detriment, to meet that goal with two (or even 3 runs) a day to reach it.  Or we’d run every run at the fastest pace we could handle in order to reach 100 miles in the shortest amount of time.  In doing so, we were robbing our bodies of much needed slower, recovery runs. The body doesn’t really understand the difference between 90, 95 or 100 miles, but the round number of 100 miles was a too easily identifiable goal.  Yes, we should have trained smarter.  Yes, we should have known better.  Yes, we probably would have come up with another potentially dangerous goal if we were counting minutes instead of miles.  However, I argue that a goal to run 100 of a distance set-up by Roman soldiers 2,000+ years ago is probably not the best science. 

When I coach runners, I use both methods. I use mileage for workouts that call for specificity.  For example, when I assign workouts on the track or where I am trying to attain a specific pace to reach aerobic or anaerobic thresholds. Otherwise, I use minutes: 15-30 minutes for short runs, 30-60 minutes for medium runs and one hour plus for longer runs.  My theory is that running for time strips away the need for running harder on easy days to hit a mileage goal.  On an easy/recovery day, I don’t care if my athletes run 2 miles or 5 miles, as long as they are out for 30 minutes.  It keeps the mileage down for the novice runner and allows for a natural increase in distance as the runner becomes more fit. I manage the 10% increase rule based on minutes as well.  I feel it’s a better way to manage relative increases in activity for runners of difference ability.

On a side note, I typically do not use heartrate training or V02 Max. This is due to practical considerations, not because I do not believe in the validity of those methods. My experience is that most people have not had their heartrate or V02 tested by an expert like a doctor or sports scientist.  What happens instead is that the athletes use the old method, for heartrate, of 220 – AGE = Max Heartrate and then based their training off that number.  My experience is that I have known athletes, elite and not, with max heartrates and resting heartrates that are naturally all over the map and 220-AGE method is way off. If you want to go this route, see your doctor or a local sports scientist that can give you accurate heartrate or V02 testing.  As a surrogate, I use the Jack Daniels Running Formula which is based off lots of good science and has a formula that individualizes results based on recent performance.