I’m going to be bold and say that Yasso 800’s really aren’t a great predictor of marathon times, in fact I’m not even sure they’re a great speed session for marathon training. I’m making this statement based on my extensive research of a grand total of 3 sessions and just the one athlete, me.
If you’ve never heard of Yasso 800’s then let me explain; the idea came from Bart Yasso who was an editor for Runners World and back in 2001 suggested that a test to know if you were in shape for your target marathon time was to run 10x800m at a pace fitting your target. So if you’re aiming for a 3 hour marathon you would do each rep in 3 minutes and then have an equal amount of rest in between.
In my quest to get some speed back for my autumn marathon this sounded like a perfect session so I headed out for the first time. I thought I’d be sensible and just try 5 first and see how I got on. That felt pretty easy but I stayed disciplined and didn’t do more. The following week I did 7 which also felt easy so in the 3rd week I did the full 10.