The Yasso session was devised by Bert Yasso and as someone who has used it several times to gauge my fitness and marathon time it definitely works! There will be further 800m sessions over the coming weeks where you can run 8x800m and then 10x 800m to get a fix on your training progress and predict your marathon time! How does that work. Here goes!
You run 800m and then take a recovery jog for the same length of time as you took to run the 800m. Repeat this 6 times. In future session increase the number of 800m intervals to 8 and then 10. When you run the 10x800m aim to run each 800m in a similar time (maintaining jog recoveries for the same length of time). The time it takes you to run 800m in minutes and seconds is the same as the time it will take you to run the marathon in hours and minutes. For example, I run each of the 800m in 3 mins 50 secs so my predicted marathon time is 3 hours 50 minutes. It works whether you are a 3 hour marathon runner or 6 hour marathon runner.