MFR 38: Break Up Your Runs, Sometimes
It’s time to talk about breaking up your long run, at least sometimes. That’s right. Sometimes, it is advisable to break up your long run, but to still do the two runs close enough together for them to have the same, or nearly the same, or even a better, more advantageous effect.
Here is an excellent article by Patrick McCrann: “Should You Split Your Long Run“