Most likely, your usual speed is derived from mostly
aerobic use of sugar (which is the norm for efforts that last 2 - 60 minutes, since it creates more power but lasts far less than aerobic use of fats).
Not exact matches
During long periods
of moderate exercise,
aerobic metabolism does most
of the work,
using oxygen to turn
sugar into energy, water, and CO2.
The solid
aerobic base will continue tapping into fat (and
sugar) and will be able to help
use lactate as energy as well as continue to generate ATP through the presence
of oxygen.