Couch to 800m for a 43 year old

All the details you gave are for longer runs. What can you do for 400m right now?

You've had 43 years to build up PURE HATE. This should be easy.

Good catch. If I went out right now, I'm running a 400 in about 80-85 seconds.

I know, I know. It's an untapped reservoir at this point.

Not sure if it matters, but I do 100 in about 14-15 and 200 in about 29-30.

Beat it pops. Can’t you go play pickle ball or just whack off ? You’re old , and old people look funny trying to waddle down the bike paths. Maybe go to Tijuana and find some young girls to cure your ED. You suck 🖕🖕

Great, OK, here's a few suggestions.

Try running 8x200m, making 40 seconds feel very smooth and relaxed. Take 60 seconds between those reps. You can follow up 10 minutes later with 10x100yards on the grass, with 30 seconds rest, tall smooth on your toes, don't push too hard.

That should become an easy tempo workout. A much tougher one that targets 800m, is '200s on the minute'. You run 200m in about 43 seconds, gather yourself and start again on the minute (17 seconds rest). Do 4 reps, then rest 4 minutes, and repeat for 3 sets, a total of 12 reps. Run them evenly, don't start too fast. If you can do them all in 43, work down to 40.

If you can do 200 in 30, then your 80-85 400 indicates a lack of speed endurance lactate tolerance. A short term goal is 70 seconds for 400m. Try running 5x200m, each in 36 seconds, with 2 minutes rest. It will be incredibly hard the first time. Once you succeed, run a 400, pacing it 34+36=70.