20 to 30 minutes. The all-important purpose of T runs is to allow your body to improve its ability to clear blood lactate and keep it below a fairly manageable level. It is often best to think of the purpose of T runs as being to improve your endurance—teaching your body how to deal with a slightly more demanding pace for a prolonged period of time, or increasing the duration of time you can hold at a specific pace. Just as E and M runs improve your ability to press on mentally at a comfortable pace, T runs improve the speed you can keep up for a moderately prolonged time period.
