Run a ton of hard/long efforts - 30 min tempos, 50 min sub-tempos, etc. After you finish these, do a few hill sprints or 6x30 seconds fast. If it feels hard, it is. Over the course of your training block, mix in some harder long runs (90-100 minutes is fine), 2 or 3 vo2 max workouts, and 2 or 3 other workouts that feel hard (e.g. tempo in the middle of a longer run or the classic 10x400 hard with 400 jog for speed development), and there's your 1:12.
I don't think you'll find great cookie cutter stuff for sub-1:12. I like Daniels. You could check out his plans.
But you're going to want good mileage. 70-80+. 2 workouts/week. 1 threshold & 1 alternating some marathon paced stuff in your weekend long run (15-20 miles) or 1 under distanced workout. Do a medium long run mid-week. 12-15 miles easy. All easy runs, with a couple of doubles on the other days. Don't overthink it. Sequence the threshold workouts so you're doing your biggest sessions as you're approaching the race. Taper for 1-2 weeks.
Male, 32. PR's: 2:32; 1:14 (in a workout); 32:20 (time trial); 15:40 (time trial).
To hit the 2:32 I did some pretty hefty mileage (80 - 110 depending on the week) with consistently a track workout and a tempo each week.
I'm taking a break from the thon to lower my half and 5K times so that I'll be able to do a faster thon in the long run.
Well, all you need is to run your individual best paces in training and less mileage you could believe is necessary. You need to run 2 workouts per week and mostly a maxVO2 interval with shorter reps at 5 k race pace and a LT interval with reps of 400m - 3000m It looks to be too simple but it always functions great. The problem to many runners, and even some coaches, is that they seem to complicate something that is very simple if you have the knowledge and experience how to perform it.🧙♂️🇸🇪