Why am I so tired after running my speed sessions

This is Ask Coach Parry, and today we have a short, sweet and simple question in from Alex Flemming. He says he is tired after his speed session, he can’t run properly for the rest of the week. Please can you help?

Lindsey Parry: That is a very basic question with very basic information. But it does lead me to believe he is running his speed session way too fast. We know that we recover much slower from high intensity sessions than we do to running easy.

But even really long easy runs which do take their toll, take less out of you than a really hard high intensity session.