Speed wins races. Session - 4 miles doing - 2 minutes at 3.45-50 per km - zone 2 - then 30 secs hard stride. Repeat for 4 miles. If your goal is sub 3 for a marathon, and your fastest pace for a hard 3 minutes effort is only a little quicker than sub 3 hour pace - the you’re not gonna break 3 hours for the marathon. 4.15 per km. If you improve your speed over a hard 3 minutes effort to say 3:45 per km, then of course it’s likely you’d stand a much better chance. If your max pace for 30 secs is 3