← Thinking in Rates · Lesson 3 of 4
A longer race is slower
Nobody holds the same pace for ten kilometres as for five. In 1977 the engineer Peter Riegel noticed that race times grow a little faster than distance: roughly, time multiplies by the distance ratio raised to the power 1.06.
Doubling the distance therefore multiplies the time by about 2.08, not 2. A 30-minute 5 km suggests a 10 km of about 62 or 63 minutes, not 60.
It is a rough rule fitted to trained runners, and it gets worse the further you stretch it. Use it to pick a sensible first pace, not to make a promise.
Using the rough rule, a 30-minute 5 km suggests a 10 km of about how long?
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