And now here’s the important thing: Hold that new level for two or three weeks. Give your body time to adapt to the new stress. This is another area where the 10 percent formula falls short. As infinitesimal as some of the increases it can lead to are, they’re still increases. Your body never has a chance to adapt to the new workload before you throw another increase at it.
Let’s say you’re running 30 miles a week. Instead of going from 30 miles a week to 33.3 to 36.6 to 40.2, jump up immediately to 40, then hold at 40 a week for two or three weeks.