Exactly. Same here. Don't care what running calculators say, I bet you would find more sub 5 miles than cannot run 60s 400 m than those who can, particularly as we get older.

On a separate note, not sure who suggested this, but whoever suggested 4,800 m worth of 400-600 m intervals at mile pace..that's a really hard and injury risky workout for anyone who is not a high school or college runner.

Thanks for the response; about to knock out my first baby run now. Bike volume has been low after being out of town a couple months, but I’m about 80kg, w/kg for xert threshold is around 3.5, peak wattage is a little over 20 w/kg, 2-minute power around 7.1 w/kg, 3-minute power a little over 6 w/kg, and 30-second w/kg is about 13ish.

If your 3 min wattage is is 6W per kilo, then according to RChung if you get your ability to the same level in running your 3 min run speed would be roughly 6 meters per second. This is 4:26 mile speed IF and only IF your 3 minute output can hold for 4.5 minutes which it cannot. 5 min mile is 5.33 meters per second, so basically if your running and biking were identical ability, your 5 min power should be 5.33 watts per kilo and your 5 min run speed should be 5.33 meters per second.

But you'll break your body really fast doing lots of 400m repeats at 75 second pace (5.33 meters per second or 5.33 watts per kilo rough equivalent). So you need time to prep your body. Best of luck.

Thanks for the help. Went back over my chart, and I was around 6.45 w/kg last summer For 3 minutes—having been a little lighter then. When I was focusing more on 1- and 2- minute stuff maybe two years ago, that may have been higher, but I don’t have any data from then.

Hope you don’t mind, but would love to follow up with you offline if I get serious about this sideshow.

I guess I wasn’t try to write the person a complete plan Just giving a range And a common workout basis. I didn’t just say 4800; I said 3000-4800 assuming they’d start at the low end and build up. And also assumed that they’d use their own common sense and listen to their body to know what works. 12x400 is hard but not unheard of. I’ve done it when I was training for some faster stuff post collegiate. I’d say if you can make it to 8 you have a shot and if you get to all 12 you know it should be easy to hold that pace.

The other way to do it is 12x400m with 200m jogging with the 400m being at a comfortably fast pace but not mile pace. More like 5km race pace. Then bring alternate 400's down a touch, and keep even 400's on 5000m pace (or 10,000 pace if you want). Keep bringing odd ones down closer to target mile pace over many weeks. Now do 2 on mile pace, one on 5km/10km pace. then 3 on, one at 10km pace. Do the entire set but make it cumulatively faster and faster over many weeks. Like you said, whatever pace you max out for 12x400m average for the work intervals with the 200m jog (whatever the average is for work) is a good guess for what we'll hold for 4x400m with zero rest.

I am a few months from 55 and having suffered a bad disc injury in 2015 and loss of use of my left leg for several years from running and biking (and crippled walking...docs said I would not walk and may need a wheelchair for life but whatever screw them because they never hear of the people who get OK) I just got back into running last March, did the 100/100 and now back to running a decent volume and may give the 7 minute mile a try.

I'll need to hold 105 seconds for the 12x400m. I think that is in my range of being doable. I did a 10:30 1.5 mile "test" back in April. Our military test "pass" was 10:15 which is 6:50 so really I would like to say I can still pass the old military run test given I was a 7:08 guy (4:43 mile split) at 20 now that I am running again. As a point of reference, I have swam 6 min for the 400m swim andd 6:55 for my 400IM so my engine is plenty good to go sub 7.

4 W per kilo ~ 4 m/s which is a 6 min mile. I was doing 6 min rowing erg intervals at 3.9W per kilo this spring and that is quite a bit lower than biking. So I think the engine is OK to go sub 7 on the mile run, its just the biomechanics that will get in the way. But it would be nice to pass the old armed forces fitness test run pass mark and only be 50 percent slower than 35 years ago LOL

I am 63 years old and ran a mile in 4:47.
But that was in high school in 1974 and it wasn't fast because we had many runners that were 4:30 and faster, around 4:10 being the fastest.
My coach in high school always made me run the 2 mile and told me I lacked "basic speed". He was probably right.
In my 30's I ran a 10K with the first mile at 5:05
Age is really against you, but it might be possible with a lot of speed work provided you do not get injured.
I know when I was 50 I would have been lucky to run 6:00

While I agree with all your points it should be added That mo’s 1500m times were run probably a few years before his HM. Different training - but talent no doubt!