One big workout, three days rest

This approach never works. The body doesn't adapt.

The body does adapt though I would take only 2 days between the workouts and sometimes 3. I know this from personal experience.

I'd get fat on the days off. Lying on the couch like a beached Narwhal.

It assumes you have a healthy diet. Stop eating junk food and excessive carbs.

Post PR's from using this method for a substantial amount of time.

I would but you wouldn't believe them. People can try it for themselves.

Shocker

Can't believe Pre took 3 days off before a race...

Your idea of hard day followed by 3 easy, gives you basically 2 workouts a week (every 8 days)

I bet this could actually work, as you would definitely recover thoroughly.

Your idea though of putting all into 1 hard day won't work, however, as you would run out of energy to complete the hard day elements.

Plus 1 day work with 3 complete off days may have too little effect to build fitness.

This reminds me of some Canova stuff. He talks about “modulation” or the differences between hard and easy. As I understand it, the idea is to increase the modulation as you peak for a competitive effort.

To illustrate, in base phase it is probably ok if you run most of your runs at a moderate effort. As you get into the middle of your season you want to do some harder days interspaced by easier days, but not so easy that your volume drops. When you are in the specific (peaking) phase all that matters is the workouts, he has his runners blast incredibly hard long runs followed by as many “regenerations days” as they need.

I have good experiences with this system. My caveat is that this is a pretty intense way of training and I don’t think your body can handle it for very long. His specific phase is 6-8 weeks

You would be even more shocked if you knew some of my race results after several months of no running nor exercise. Maybe I'm just a freak of nature (which may explain who recruited me).

Ever hear of a man named Bill Bowerman? One of his claims to fame was his hard/easy method, which from an exercise physiology perspective was not discovered by him but he was perhaps the first coach to apply it to running.

Maybe at first, but before long you will adapt to be able to do full workouts.

The key is allowing yourself the recovery time to push the limit on a regular basis.

The poster asking about PRs is missing the point. This isn't going to maximize your performance at any one thing, but will quickly build a solid overall fitness base. You could do it that way though, for example an 800 runner could do drills, some volume, and intervals in a massive workout, then take full recovery

That depends on who you are.

Good point, you specifically said this is how you build base fitness, not how you train in season.