Diminishing returns or just bad math?

Like all runners I dread the day when I’m gonna have to tell myself: “Yup. I’ve reached my potential, this is as good as I can get.” It has partly to do with aging and all that nastyness, but also another thing: At one point you reach the point of diminishing returns. Your added effort will at one point yield less effect. Because you approach the limit of your abilities, and you’re training as hard as you possibly can. Athletes are high up in this zone of course, they train as much as they have to. But for me, even before I get there I will reach the limit for how much time and energy I can use on running. Sad but true.

But before I get too deep in the glass, there is one thing that I, for one have gotten wrong: When you’re shaving minutes off your PB, not every minute is equal. There’s not a linear relation between speed and race times, or even speed and pace!

(If you count in miles and fathoms and such, the next bit will sound like gibberish. Sorry for that.)

For instance, I’ve improved my 5k race time from 25 minutes to about 20. Five minutes! Hooray! That’s a 3km/h increase in speed. Now if I increase by another 3km/h, will I get down to 15 minutes for a 5k? No, actually that will leave me at about 16:40. Not to be confused with diminishing returns. It’s the same increase in actual speed.

Likewise, the difference between a 30 and 25 minute 5k is a lot smaller than between a 25 and 20 minute one. So consider every minute you shave off your race time a bigger feat than the previous.

When it comes to regular pace, the difference in speed between 3 min/km and 4 min/km is 5km/h. Big. The difference between 4 min/km and 5 min/km. is 3km/h. And for the next step down, between 5 min/km and 6 min/km, it’s only two.

A graph would be nice here.

Anyway don’t expect to get your pace down from 5:00/km to 4:00/km as easily as you did from 6:00 to 5:00! Expect it to be 1,5 times as hard, and give yourself credit for that. Plus of course it’s also one step closer to…



Correct me if I’m wrong. ;-)


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